Grazed Laminaria hyperborea forest with coralline crusts on upper infralittoral rock

Summary

UK and Ireland classification

Description

Exposed to moderately exposed Laminaria hyperborea forest is in some areas intensely grazed by the urchin Echinus esculentus. The rock surface lacks a significant turf of foliose seaweeds and generally looks bare, though encrusting algae cover the rock. In addition to these encrusting coralline algae, non-calcareous crusts such as Cruoria pellita and brown algal crusts also occur. The kelp stipes may or may not be grazed; in the most extremely grazed areas, the stipes are also devoid of seaweeds. More usually, however, the stipes offer a refuge from grazing and are characterised by dense turfs of red seaweeds, especially Phycodrys rubens, Metacallophyllis laciniata, Plocamium cartilagineum and Delesseria sanguinea. The hydroid Obelia geniculata and the bryozoan Membranipora membranacea colonize the kelp fronds. On the rock itself, certain brown seaweeds such as Cutleria multifida may persist in this grazed environment. Fast-growing species such as the kelp Saccharina latissima may be present at sites recovering from grazing, opportunistically colonising the rock surfaces that have been cleared by grazing. The fauna within a grazed kelp forest is also relatively sparse and is mostly confined to cracks, crevices and under-boulders. Species such as the ascidian Clavelina lepadiformis can often be found on vertical rock. Also found on the rock surface are the anthozoans Urticina felina and Alcyonium digitatum. Encrusting species such as the tube-building polychaete Spirobranchus triqueter are resistant to grazing and may occur in abundance. The grazers present include the echinoderm Echinus esculentus and the gastropods Calliostoma zizyphinum and Steromphala cineraria. Other echinoderms present include Asterias rubens and Antedon bifida which can be abundant in the north-west. Moderate grazing occurs within many kelp forests; records should only be assigned to this biotope where the community has been intensively grazed leaving algal-encrusted rock with very few epilithic algae. With increasing depth, the kelp forest grades into a grazed kelp park (IR.MIR.KR.Lhyp.GzPk), the lower limit of which is often abrupt, representing the balance point between urchin-grazing pressure and kelp growth capabilities. In wave-exposed steep rocky areas, the shallowest water may be characterised by a forest of kelp with red seaweeds (IR.HIR.KFaR.LhypR.Ft), with a grazed kelp forest beneath. This effect may be a result of the increased wave action in shallower water, which regularly dislodges the urchins thereby reducing their grazing impact. IR.MIR.KR.Lhyp.GzFt is prevalent in the north of the UK where Echinus esculentus populations reach high densities. Although Echinus esculentus is widely distributed around the UK it occurs in greatest abundance in Scotland and north-east England where urchin grazing can substantially affect infralittoral communities. Fluctuations in Echinus esculentus numbers may give foliose seaweeds a chance to re-grow periodically. Further information is required on the temporal variation within these grazed forests and the changes in community structure when grazing pressure decreases. (Information taken from JNCC, 2022).

Depth range

0-5 m, 5-10 m, 10-20 m

Additional information

Survey results are most often referred to one of the sub-biotopes: MIR.LhypGz.Ft (Grazed Laminaria hyperborea forest with coralline crusts on upper infralittoral rock), or MIR.LhypGz.Pk (Grazed Laminaria hyperborea park with coralline crusts on lower infralittoral rock); both of which have been included in research here.

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Habitat review

Ecology

Ecological and functional relationships

Kelps are major primary producers. Up to 90% of kelp production enters the detrital food web and kelp is probably a major contributor of organic carbon to surrounding communities (Birkett et al., 1998b). Kelp beds are diverse species rich habitats and over 1,800 species have been recorded in the UK kelp biotopes (Birkett et al., 1998b). Kelp communities and the interaction between kelp, urchins and predators has been studied in Nova Scotia, Norway, southern California and the UK (Kain, 1979; Mann, 1982; Schiel & Foster, 1986; Elner & Vadas, 1990; Vadas & Elner, 1992; Sivertsen, 1997). The following are important ecological relationships.

  • Sea-urchins graze rock surfaces including juvenile kelp sporophytes, together with epiphytes and epifauna on laminarian stipes. It is sea urchin grazing that gives the rocks their bare appearance below the kelp. Grazing may prevent potentially dominant species from becoming established and therefore facilitate species richness. Vost (1983) examined the effect of removing grazing Echinus esculentus and found that after 6-10 months the patchiness of the understorey algae had decreased and the species richness and biomass of epilithic species increased. Strongylocentrotus droebachiensis and Paracentrotus lividus also graze kelp beds but are less common in the British Isles than Echinus esculentus. Echinus esculentus grazing probably controls the lower limit of Laminaria hyperborea distribution in some locations, e.g. in the Isle of Man (Jones & Kain, 1967; Kain et al., 1975; Kain, 1979).
  • Epifauna is more developed on vertical surfaces, under overhangs or boulders and in crevices inaccessible to grazing sea urchins.
  • grazes epiphytes and the kelp tissue directly, forming pits similar to the home scars of intertidal limpets (see Kain & Svendsen, 1969 for photographs). The larger, Patella pellucida laevis form excavates large cavities in laminarian holdfasts. This tissue damage weakens the adult plant and contributes to its loss due to wave action and storms (Kain, 1979, Birkett et al., 1998b). Infestation with Patella pellucida varies between sites and decreases with depth, e.g. infestation may reach up to 50 % on mature plants in shallow water in the Isle of Man, whereas <20 % was found (on kelps of any age group and depth) in England and Scotland (Kain, 1979).
  • Laminaria hyperboreais grazed directly by Lacuna vincta in Norway, the individuals forming deep pits in the lamina (Kain, 1979).
  • Kelp fronds, stipes and holdfasts provide substrata for distinct communities of species, some of which are found only or especially on kelp plants. Kelp holdfasts provide both substrata and refugia (see Habitat complexity).
  • Epiphytes and understorey algae are grazed by a variety of amphipods, isopods and gastropods, e.g. Littorina spp., Acmaea spp., Haliotis tuberculata, Aplysia spp. and rissoid gastropods (Birkett et al., 1998b).
  • Predators within kelp beds have not been well studied in the UK. Lobsters (e.g. Homarus gammarus), crabs and some fish species (e.g. the wolf fish Anarhichas lupus) and perhaps otters are known to consume gastropod and echinoderm grazers.
  • Birkett et al. (1998b) suggest that juveniles of animals present in kelp beds as adults probably use the habitat as a nursery and unknown numbers of species are likely to use the habitat during their life cycle. Rinde et al. (1992, cited in Birkett et al., 1998b) state that Norwegian kelp beds are nurseries for gadoid species.

Seasonal and longer term change

The most conspicuous changes are likely to be in the abundance of algae and of associated species such as encrusting Bryozoa in the biotope. New blades of Laminaria hyperborea grow in winter between the meristem and the old blade, which is shed in early spring or summer together with associated species growing on its surface. Larger and older kelp plants become liable to removal by wave action and storms due to their size and weakening by grazers such as Patella pellucida. There is therefore likely to be a reduced abundance of kelps following the winter. Red algae show significant variability in abundance through the year with fresh growths appearing in spring, growing rapidly and being degraded by herbivores and by growths of animals such as hydroids and encrusting Bryozoa through the summer. Hiscock (1986c) demonstrated significant changes in red algae on pebble communities and it is likely that similar changes occur on bedrock.

Many of the species within the community demonstrate seasonal changes in abundance and reproduction. In temperate waters most bryozoan species tend to grow rapidly in spring and reproduce maximally in late summer, depending on temperature, day length and the availability of phytoplankton (Ryland, 1970). Several species of bryozoans and hydroids demonstrate seasonal cycles of growth in spring/summer and regression (die back) in late autumn/winter, overwintering as dormant stages or juvenile stages (see Ryland, 1976; Gili & Hughes, 1995; Hayward & Ryland, 1998). For example, the fronds of Bugula species are ephemeral, surviving about 3-4 months but producing two frond generations in summer before dying back in winter, although, the holdfasts are probably perennial (Eggleston, 1972a; Dyrynda & Ryland, 1982). Similarly, Bicellaria ciliata produces 2 generation per year, larvae from the second generation producing small overwintering colonies (Eggleston, 1972a; Hayward & Ryland, 1998). The uprights of the hydroid Nemertesia antennina die back after 4-5 months and exhibit three generations per year (spring, summer and winter) (see MarLIN reviews; Hughes, 1977; Hartnoll, 1998; Hayward & Ryland, 1998). Many of the bryozoans and hydroid species are opportunists (e.g. Bugulina flabellata) adapted to rapid growth and reproduction (r-selected), taking advantage of the spring/summer phytoplankton bloom and more favourable (less stormy) conditions (Dyrynda & Ryland, 1982; Gili & Hughes, 1995). Some species such as the ascidians Ciona intestinalis and Clavelina lepadiformis are effectively annual (Hartnoll, 1998). Therefore, the biotope is likely to demonstrate seasonal changes in the abundance or cover of the dominant bryozoans and hydroids.

Some species may vary in abundance from year-to-year for no apparent reason. For instance, the sea squirt Clavelina lepadiformis may be abundant in some years but not others (Hiscock, 1994). Other species may lose condition or otherwise change in appearance. For instance, from February through to July colonies of the soft coral Alcyonium digitatum expand and feed regularly. However, from late July through to December colonies remain contracted, during which time they do not feed and assume a shrunken appearance and become colonized by hydroids, algae and tube amphipods (Hartnoll, 1985). Fish populations that inhabit the biotope (especially wrasse, pollock and gobies) may show seasonal changes that reflect migration to deeper and therefore calmer water in winter and possibly mortality following adverse autumn conditions.

Habitat structure and complexity

Habitat complexity is the result of both substratum architecture and the organisms that characterize this biotope. Rock surfaces may be smooth or broken and may include fissures, crevices and, where composed of boulders, refugia for a wide range of mobile and sessile species under the boulders. Species such as squat lobsters, Galathea spp., may be present in fissures emerging only at night whilst sea cucumbers such as Pawsonia saxicola and brittle stars such as Ophiopholis aculeata may live in crevices with only feeding arms protruding.

Kelp plants themselves provides a variety of habitats and refugia in a similar way to terrestrial forests. Kelps also reduce current flow and their canopy shades the understorey vegetation and substrata producing a particular microclimate depending on the depth and density of the kelp plants. In kelp forest (e.g. EIR.LhypR.Ft) the kelp density produces a canopy which excludes up to 90% of incident light encouraging the presence of shade tolerant algae, mainly reds and animals to occur where they can escape grazing. In deeper water, as light intensity decreases, the kelp density decreases forming a kelp park. Kelp beds are patchy and dynamic with areas devoid of kelp (due to storms, wave surge or grazing) in the process of expansion or recolonization in different stages of succession. Species diversity changes with depth, between forest & park, with exposure, substratum and turbidity (Norton et al. 1977; Erwin et al. 1990; Birkett et al. 1998b). Erwin et al. (1990) noted that species richness increased in the kelp park (as lower infralittoral and upper circalittoral species overlapped) and was higher in boulder fields in which sand-scour and substratum heterogeneity provided more niches for colonization. Kelp beds exhibit a series of stratified habitats, and a patchwork of species depending on the substratum, light, water flow and exposure.

  • Planktonic: Spores and larvae from algae and benthic organisms within the bed, as well as from the surrounding area, probably form an import food source given the number of suspension feeding organisms in kelp beds
  • Nekton: wrasse and pollock have been observed associated especially with kelp forests and epibenthic predatory or herbivorous fish are also found, e.g. blennies, gobies and wolf fish (Anarhichas lupus).
  • Kelp blades support microalgal epiphytes or endophytes such as Pogotrichum filiforme, Chilionema sp. and Myrionema corunnae which is only found on Laminaria blades, as well as Patella pellucida and opportunistic hydroids (e.g. Obelia geniculata) and bryozoans (e.g. Membranipora membranacea).
  • The stipes may support a diverse fauna and flora, especially foliose red algae, depending on age of the stipe, kelp density (stipes in close proximity may abrade each other) and degree of grazing. Epiphytes show greater biomass on the top 10-20 cm of stipe and exhibit a zonation pattern down the stipe which changes with depth (Birkett et al., 1998b). Norton et al. (1977) found the greatest biomass at 3m depth near Lough Ine. Whittick (1983) showed that epiphyte biomass was significantly greater in plants over 5yrs old, with Palmaria palmata(dulse) dominating the top of the stipe from 1-2m, being replaced by Ptilota plumosa between 6-10m, while Membranoptera alata and Phycodrys rubens dominate below 12m or are present at lower parts of the stipe.
  • . Hiscock & Mitchell (1980) list 15 species of algae associated with kelp stipes in the UK. The stipes also supports epifaunal bryozoans and hydroids (Norton et al., 1977).
  • Holdfasts support a diverse fauna that represents a sample of the surrounding mobile fauna and crevice dwelling organisms, e.g., polychaetes, small crabs, gastropods, bivalves, and amphipods. Jones (1971) lists 53 macrofaunal invertebrates in holdfasts and Moore (1973b) reports 389 species from holdfasts collected in the north east coast of Britain. A useful account of holdfast fauna is given by Hayward (1988).
  • The composition of the holdfast fauna has been show to vary with turbidity (natural and anthropogenic in origin), between kelp species (due to holdfast architecture and volume), and with location around the coast of the British Isles (Moore, 1973a&b; Moore, 1978; Edwards, 1980; Sheppard et al., 1980). Moore (1973a&b) identified groups of species that were found in most cases, or restricted to either turbid or clear waters. Moore (1978) noted that species diversity or amphipods decreased with increasing turbidity, partly due to the increased dominance of a few species. Edwards (1980) noted that holdfast fauna in south-west Ireland were numerically dominated by suspension feeders with decreasing numbers of omnivores and carnivores respectively. Edwards (1980) noted that holdfasts were dominated by Spirobranchus triqueter in the most turbid sites, although theses were not as turbid as sites examined by Moore (1973a&b). Sheppard et al. (1980) examined 35 sites around the Britain Isles and demonstrated a correlation between heavy metal pollution, turbidity and location. Along the North Sea coast species number and diversity increased with increased clarity, however where heavy metals were a factor species number and diversity decreased with increasing heavy metal pollution. They were able to distinguish groups of species characteristic of all sites, or clear or turbid sties. Along the west coast both heavy metals and turbidity were important. Where turbidity and heavy metals increased suspension feeders increased in abundance while other trophic groups decreased. However, along the south coast longitude was the most important factor, and they suggested that natural variation in temperature, salinity and water flow were responsible for variation between holdfast communities (Sheppard et al., 1980). Moore (1985) also demonstrated that the amphipod fauna varied with water flow rate (resulting from wave action and currents); for example sites of increased exposure were dominated by Amphithoe rubricata, Lembos websteri and Jassa falcata whereas Gitana sarsi, Dexamine thea and Corophium bonnellii flourish in wave sheltered environments.
  • A few meiofaunal species may burrow into kelp tissue, e.g. the nematode Monohystera disjuncta (Birkett et al., 1998b).
  • The benthic fauna varies with depth, exposure, location and substratum, however, no species are specific to kelp forest. Norton et al. (1977) demonstrate the zonation of 22 epibenthic species. However, many species, both fixed and mobile, are present and probably under recorded (Birkett et al., 1998b).

Productivity

No specific information found has been found but the communities in this biotope are likely to be highly productive. The biotope occurs in shallow depths where both high light intensity will result in high primary productivity. Kelps are the major primary producers in UK marine coastal waters producing nearly 75% of the net carbon fixed annually on the shoreline of the coastal euphotic zone (Birkett et al., 1998b). Kelp plants produce 2.7 times their standing biomass per year. Kelp detritus, as broken plant tissue, particles and dissolved organic material supports soft bottom communities outside the kelp bed itself. The kelps reduce ambient levels of nutrients, although this may not be significant in exposed sites, but increase levels of particulate and dissolved organic matter within the bed.

Recruitment processes

The characterizing species in this biotope all have planktonic spores or larvae and are fairly short-lived (five to ten years). There is therefore high recruitment and high turnover. Recruitment processes of key characteristic or dominant species are described here.

  • Laminaria hyperborea produces vast numbers of spores, however they need to settle and form gametophytes within about 1 mm of eachother to ensure fertilization and therefore may suffer from dilution effects over distance. Gametophytes can survive darkness and develop in the low light levels under the canopy.
  • Recruitment of epiphytes and epiflora are dependant on dispersal and settlement of algal spores and survival of early post-settlement stages. Norton (1992) suggests that spore dispersal is primarily dependant on currents and eddies. Settlement of algal spores is partly dependant on their motility (if any) and adhesive properties together with preferences for topography (surface roughness), the chemical nature of the substratum and water movement (Norton, 1992; Fletcher & Callow, 1992). For the foliose red alga Delesseria sanguinea (which is probably representative of many of the species in the biotope), Dickinson (1963) suggested a lifespan of 5-6 years but Kain (1979) estimated that 1 in 20 specimens may attain 9 -16 years of age. The spores of red algae are non-motile (Norton, 1992) and therefore entirely reliant on the hydrographic regime for dispersal. Norton (1992) reviewed dispersal by macroalgae and concluded that dispersal potential is highly variable. Spores of Phycodrys rubens, another species found in the biotope, were suggested to travel up to 5 km before settlement.
  • For Lithophyllum incrustans , representing the encrusting Corallinacea in the biotope, it has been calculated that 1 mm x 1mm of reproductive thallus produces 17.5 million bispores per year with average settlement of only 55 sporelings/year (Edyvean & Ford, 1984). Dispersal is likely to be in excess of 5 km and spores will settle and new colonies will arise rapidly on bare substratum although growth rate is slow (2-7 mm per annum - see Irvine & Chamberlain, 1994).
  • For Echinus esculentus, planktonic development is complex and takes between 45 -60 days in captivity (MacBride, 1914) enabling dispersion over a large area. Recruitment may be sporadic or variable depending on locality; e.g. Millport populations showed annual recruitment whereas few recruits were found in Plymouth populations during studies between 1980-1981 (Nichols, 1984). Bishop & Earll (1984) suggested that the population of Echinus esculentus at St Abbs had a high density and recruited regularly whereas the Skomer population was sparse, ageing and had probably not successfully recruited larvae in the previous 6 years. Bearing in mind that MLR.LhypGz is a northern biotope, the apparent higher recruitment success of Echinus esculentus in the north may be important in creating this biotope.
  • Some of the animal species that characterize the biotope may recruit readily and from considerable distances away. For instance, in Alcyonium digitatum, actively swimming lecithotrophic planulae are likely to have an extended pelagic life of several days or weeks (see MarLIN review for full details) before they eventually settle and metamorphose to polyps (Matthews, 1917; Hartnoll, 1975).
  • The embryos of Antedon bifida hatch as free-swimming larvae which, after a short pelagic phase, attach to the substratum and develop a short stalk (Chadwick, 1907, cited in Nichols, 1991).

Kelp beds also provide nurseries for larvae and fish species (see above).

Time for community to reach maturity

MIR.LhypGz is a dynamic biotope in which the maintenance of bare Corallinacea covered rock is dependant on grazing. Experimental studies as well as observations of the impacts of urchin grazing in natural communities provide significant information. Experimental clearance experiments in the Isle of Man (Kain, 1975; Kain, 1979) showed that Laminaria hyperborea out-competed other opportunistic species (e.g. Alaria esculenta, Saccorhiza polyschides and Desmarestia spp.) and returned to near control levels of biomass within 3 years at 0.8 m but that recovery was slower at 4.4m (see above). Studies of the effects of harvesting in Norway (Svendsen, 1972, cited in Birkett et al., 1998b) showed that kelp biomass returned 3-4 years after harvesting, although the plants were small (about 1m) and the age class was shifted towards younger plants. Sivertsen (1991, cited in Birkett et al., 1998b), showed that kelp populations stabilise about 4-5 years after harvesting. Current advice suggests that kelp forest should be left 7-10 years for kelp and non-kelp species to recover (Birkett et al., 1998b). Detailed studies in Norway by Rinde et al. (1992, cited in Birkett et al., 1998b) examined recovery of non-kelp species. The epiphyte community in control areas about 10 years old was richer and more extensive than on replacement plants in harvested areas. Of the epifauna, Halichondria sp. were only found on 10 year old plants and tunicates on plants 6 years post harvesting. Holdfast fauna was more abundant richer in 10 year old plants in control areas than younger plants in previously harvested area. Overall his results suggest that full biological recovery, or maturation, may take at least 10 years.

Additional information

MIR.LhypGz is a dynamic biotope in which the maintenance of bare Corallinacea covered rock is dependant on grazing. In the absence of significant grazing, the biotope would switch to another such as EIR.LhypR.

Preferences & Distribution

Habitat preferences

Depth Range 0-5 m, 5-10 m, 10-20 m
Water clarity preferencesNo information
Limiting Nutrients No information
Salinity preferences Full (30-40 psu)
Physiographic preferences Open coast
Biological zone preferences Upper infralittoral
Substratum/habitat preferences Bedrock, Large to very large boulders
Tidal strength preferences Moderately strong 1 to 3 knots (0.5-1.5 m/sec.), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferences Exposed, Moderately exposed
Other preferences Urchin grazing

Additional Information

None entered.

Species composition

Species found especially in this biotope

Rare or scarce species associated with this biotope

-

Additional information

The MNCR recorded 227 species within this biotope, although not all species occurred in all records of the biotope (JNCC, 1999).

Sensitivity review

Sensitivity characteristics of the habitat and relevant characteristic species

IR.MIR.KR.Lhyp.GzFt/Pk are defined by the kelp Laminaria hyperborea which is grazed to varying extent by the urchin Echinus esculentus. At high densities, Laminaria hyperborea forms a canopy over infralittoral rock. Beneath the canopy an understorey community grows, typically defined by a red seaweed turf although faunal species dominate in tide swept and/or wave surged conditions. Grazing by the urchins Echinus esculentus and Paracentrotus lividus can also define the biotope and reduce the biomass of Laminaria hyperborea and understorey flora. The abundance of Laminaria hyperborea is determined by light availability, which decreases with an increase in water depth. Therefore, depth and water clarity determines the density of Laminaria and hence the distribution of kelp forest (high density kelp) and park (low density kelp) sub-biotopes.

Kelp biotopes are a major source of primary productivity, and support magnified secondary productivity within North Atlantic coastal waters (Smale et al., 2013, Brodie et al., 2014). In Scotland, alone kelp biotopes are estimated to cover 8000 km2 (Walker, 1953), and account for ca 45% of primary production in UK coastal waters (Smale et al., 2013). Therefore kelp biotopes, of which Laminaria hyperborea is dominant within UK subtidal rocky reefs (Birkett et al., 1998), make a substantial contribution to coastal primary production in the UK (Smale et al., 2013). Laminaria hyperborea is grazed directly by species such as Patella pellucida, however approximately 80% of primary production is consumed as detritus or dissolved organic material (Krumhansl, 2012) which is both retained within and transported out of the parent kelp forest, providing valuable nutrition to potentially low productivity habitats such as sandy beaches (Smale et al., 2013).

Laminaria hyperborea also acts as an ecosystem engineer (Jones et al., 1996; Smale et al., 2013) by altering; light levels (Sjøtun et al., 2006), physical disturbance (Connell, 2003), sedimentation rates (Eckman et al., 1989) and water flow (Smale et al., 2013), profoundly altering the physical environment for fauna and flora in close proximity. Laminaria hyperborea biotopes increase the three dimensional complexity of unvegetated rock (Norderhaug, 2004, Norderhaug et al., 2007, Norderhaug & Christie, 2011, Gorman et al., 2012; Smale et al., 2013) and support high local diversity, abundance and biomass of epi/benthic species (Smale et al., 2013), and serve as a nursery ground for a number of commercial important species, e.g. Gadidae (The taxonomic family that contains many commercially important marine fish species, including the Atlantic Cod and Pollack) (Rinde et al., 1992).

In undertaking this assessment of sensitivity, an account is taken of knowledge of the biology of all characterizing species/taxa in the biotope. For this sensitivity assessment Echinus esculentus and Laminaria hyperborea are the primary focus of research, however, it is recognized that the understorey community, typically red seaweeds, also define the biotope. Examples of important species groups are mentioned where appropriate.

Resilience and recovery rates of habitat

A number of review and experimental publications have assessed the recovery of Laminaria hyperborea kelp beds and the associated community. If environmental conditions are favourable Laminaria hyperborea can recover following disturbance events reaching comparable plant densities and size to pristine Laminaria hyperborea beds within 2-6 years(Kain, 1979; Birkett et al., 1998b; Christie et al., 1998). Holdfast communities may recover in 6 years (Birkett et al., 1998b). Full epiphytic community and stipe habitat complexity regeneration require over 6 years (possibly 10 years). These recovery rates were based on discrete kelp harvesting events.  Recurrent disturbance occurring frequently within 2-6 years of the initial disturbance is likely to lengthen recovery time (Birkett et al., 1998b, Burrows et al., 2014). Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared, however within 2 years of clearance the blocks were dominated by Laminaria hyperborea (Kain, 1975).

In south Norway, Laminaria hyperborea forests are harvested, which results in large scale removal of the canopy-forming kelps.  Cristie et al., (1998) found that in south Norwegian Laminaria hyperborea beds a pool of small (<25cm) understorey Laminaria hyperborea plants persist beneath the kelp canopy for several years. The understorey Laminaria hyperborea sporophytes had fully re-established the canopy at a height of 1m within 2-6 years after kelp harvesting. Within 1 year following harvesting, and each successive year thereafter, a pool of Laminaria hyperborea recruits had re-established within the understorey beneath the kelp canopy. Cristie et al., (1998) suggested that Laminaria hyperborea bed re-establishment from understorey recruits (see above) inhibits the colonization of other kelps species and furthers the dominance of Laminaria hyperborea within suitable habitats, stating that Laminaria hyperborea habitats are relatively resilient to disturbance events.

Laminaria hyperborea has a heteromorphic life strategy, A vast number of zoospores (mobile asexual spores) are released into the water column between October-April (Kain & Jones, 1964). Zoospores settle onto rock substrata and develop into dioecious gametophytes (Kain, 1979) which, following fertilization, develop into sporophytes and mature within 1-6 years (Kain, 1979; Fredriksen et al., 1995; Christie et al., 1998).  Laminaria hyperborea zoospores have a recorded dispersal range of ~200m (Fredriksen et al., 1995). However zoospore dispersal is greatly influenced by water movements, and zoospore density and the rate of successful fertilization decreases exponentially with distance from the parental source (Fredriksen et al., 1995). Hence, recruitment following disturbance can be influenced by the proximity of mature kelp beds producing viable zoospores to the disturbed area. (Kain, 1979, Fredriksen et al., 1995).

Laminaria hyperborea biotopes are partially reliant on low (or no) populations of sea urchins, primarily the species; Echinus esculentus, Paracentrotus lividus and Strongylocentrotus droebachiensis, which graze directly on macroalgae, epiphytes and the understorey community.  Multiple authors(Steneck et al., 2002; Steneck et al., 2004; Rinde & Sjøtun, 2005; Norderhaug & Christie, 2009; Smale et al., 2013) have reported dense aggregations of sea urchins to be a principal threat to Laminaria hyperborea biotopes of the North Atlantic. Intense urchin grazing creates expansive areas known as ‘urchin barrens’, in which a shift can occur from Laminaria hyperborea dominated biotopes to those characterized by coralline encrusting algae, with a resultant reduction in biodiversity (Leinaas & Christie, 1996; Steneck et al., 2002; Norderhaug & Christie, 2009). Continued intensive urchin grazing pressure on Laminaria hyperborea biotopes can inhibit the Laminaria hyperborea recruitment (Sjøtun et al., 2006) and cause urchin barrens to persist for decades (Cristie et al., 1998; Stenneck et al., 2004; Rinde & Sjøtun, 2005). The mechanisms that control sea urchin aggregations are poorly understood but have been attributed to anthropogenic pressure on top down urchin predators (e.g. cod or lobsters). While these theories are largely unproven a number of studies have shown that removal of urchins from grazed areas coincide with kelp re-colonization (Leinaas & Christie, 1996; Norderhaug & Christie, 2009). Leinaas & Christie, (1996) removed Strongylocentrotus droebachiensis from ‘urchin barrens’ and observed a succession effect, in which the substratum was initially colonized by filamentous macroalgae and Saccharina latissima.  However, after 2-4 years Laminaria hyperborea dominated the community.

Reports of large scale urchin barrens within the North East Atlantic are generally limited to regions of the North Norwegian and Russian Coast (Rinde & Sjøtun, 2005, Norderhaug & Christie, 2009). Within the UK, urchin grazed biotopes (IR.MIR.KR.Lhyp.GzFt/Pk, IR.HIR.KFaR.LhypPar, IR.LIR.K.LhypSlat.Gz & IR.LIR.K.Slat.Gz) are generally localised to a few regions in North Scotland and Ireland (Smale et al., 2013; Stenneck et al., 2002; Norderhaug & Christie 2009; Connor et al., 2004). IR.MIR.KR.Lhyp.GzFt/Pk, IR.HIR.KFaR.LhypPar, IR.LIR.K.LhypSlat.Gz & IR.LIR.K.Slat.Gz are characterized by a canopy-forming kelp. However, urchin grazing decreases the abundance and diversity of understorey species. In the Isle of Man. Jones & Kain (1967) observed low Echinus esculentus grazing pressure can control the lower limit of Laminaria hyperborea in the and remove Laminaria hyperborea sporelings and juveniles. Urchin abundances in ‘urchin barrens’ have been reported as high as 100 individuals/m2 (Lang & Mann, 1976). Kain (1967) reported urchin abundances of 1-4/m2 within experimental plots of the Isle of Man. Therefore, while ‘urchin barrens’ are not presently an issue within the UK, relatively low urchin grazing has been found to control the depth distribution of Laminaria hyperborea, negatively impact on Laminaria hyperborea recruitment and reduce the understorey community abundance and diversity.

Other factors that are likely to influence the recovery of Laminaria hyperborea biotopes is competitive interactions with Invasive Non-Indigenous Species  (INIS), e.g. Undaria pinnatifida (Smale et al., 2013; Brodie et al., 2014; Heiser et al., 2014), and/or the Lusitanian kelp Laminaria ochroleuca (Brodie et al., 2014; Smale et al., 2015). A predicted sea temperature rise in the North and Celtic seas of between 1.5-5°C over the next century (Philippart et al., 2011) is likely to create northward range shifts in many macroalgal species, including Laminaria hyperborea. Laminaria hyperborea is a northern (Boreal) kelp species, thus increases in seawater temperature is likely to affect the resilience and recoverability of Laminaria hyperborea biotopes with southerly distributions in the UK (Smale et al., 2013; Stenneck et al., 2002). Evidence suggests that the Lusitanian kelp Laminaria ochroleuca (Smale et al., 2015), and the INIS Undaria pinnatifida (Heiser et al., 2014) are competing with Laminaria hyperborea along the UK south coast and may displace Laminaria hyperborea from some subtidal rocky reef habitats. The wider ecological consequences of Laminaria hyperborea’ competition with Laminaria ochroleuca and Undaria pinnatifida are however as of yet unknown.

Echinus esculentus is a sea urchin found within Northeast Atlantic, recorded from Murmansk Coast, Russia to Portugal (Hansson, 1998). Echinus esculentus, along with other urchins, is an important algal grazer in the North East Atlantic. (Connor et al., 2004). Echinus esculentus is estimated to have a lifespan of 8-16 years (Nichols, 1979; Gage, 1992a & b) and reach sexual maturity within 1-3 years (Tyler-Walters, 2008). Maximum spawning occurs in spring although individuals may spawn over a protracted period throughout the year. Gonad weight is at it’s maximum in February/March in English Channel (Comely & Ansell, 1989) but decreases during spawning in spring and then increases again through summer and winter until the next spawning season. Spawning occurs just before the seasonal rise in temperature in temperate zones but is probably not triggered by rising temperature (Bishop, 1985). Echinus esculentus is a broadcast spawner, with a complex larval life history which includes a blastula, gastrula and a characteristic 4 armed echinopluteus stage that forms an important component of the zooplankton. MacBride (1914) observed planktonic larval development could take 45-60 days in captivity. Recruitment is sporadic or variable depending on locality, e.g. Millport populations showed annual recruitment, whereas few recruits were found in Plymouth populations during Nichols studies between 1980-1981 (Nichols, 1984). Bishop & Earll (1984) suggested that the population of Echinus esculentus at St Abbs had a high density and recruited regularly whereas the Skomer population was sparse, ageing and had probably not successfully recruited larvae in the previous 6 years (Bishop & Earll, 1984). Comely & Ansell (1988) noted that the largest number of Echinus esculentus occurred below the kelp forest.

Echinus esculentus is a mobile species (Tyler-Walters, 2008) and could, therefore, migrate and re-populate an area quickly if removed. For example, Lewis & Nichols (1979) found that adults were able to colonize an artificial reef in small numbers within 3 months and the population steadily grew over the following year. If completely removed from a site and local populations are naturally sparse then recruitment may be dependent on larval supply which can be highly variable. As suggested by Bishop & Earll (1984) the Skomer, Wales Echinus esculentus population had most likely not successfully recruited for 6 years which would suggest the mature population would be highly sensitive to removal and may not return for several years. On 19th November 2002, the Prestige oil tanker spilled 63 000t of fuel 130 nautical miles off Galicia, Spain. High wave exposure and strong weather systems increased mixing of the oil to ‘some’ depth within the water column, causing sensitive faunal communities to be effected. Preceding and for nine years following the oil spill, the biological community of Guéthary, France was monitored. Following the oil spill taxonomic richness decreased significantly from 57 recorded species to 41, which included the loss of Echinus esculentus from the site. 2-3 years after the oil spill taxonomic richness had increased to pre-spill levels and Echinus esculentus had returned (Castège et al., 2014).

Resilience assessment.  The evidence suggests that beds of mature Laminaria hyperborea can regenerate from disturbance within a period of 1-6 years, and the associated community within 7-10 years. However, other factors such as competitive interactions with Laminaria ochroleuca and Undaria pinnatifida may limit recovery of Laminaria hyperborea biotopes following disturbance. The recovery of Laminaria hyperborea biotopes to disturbance from commercial harvesting in south Norway suggests that Laminaria hyperborea beds and the associated community could recover from a significant loss of canopy cover within 10 years. Echinus esculentus can reportedly reach sexual maturity within 1-2 years (Tyler-Walters, 2008), however as highlighted by Bishop & Earll (1984) and Castège et al., (2014) recovery may take 2-6 years (possibly more if local recruitment is poor). Resilience has therefore been assessed as Medium.

Please note* as in Northern Norway urchin grazing pressure could extend recovery/resilience of the Laminaria hyperborea biotopes >25 years, If intensive urchin grazing (as seen in Northern Norway) occurs in the UK resilience would be re-assessed as Very Low. However, because of the limited/localised incidence of urchin grazing within the UK, urchin grazing on large scales (as in Northern Norway) has not been included in this general resilience assessment. The introduction of Invasive Non-Indigenous Species  (INIS) will also inhibit the recovery of Laminaria hyperborea biotopes for an indeterminate amount of time, in these cases resilience would need to be re-assessed as Very Low. Another factor that is beyond the scope of this sensitivity assessment is the presence of multiple concurrent synergistic or cumulative effects, which Smale et al., (2013) suggests could be a more damaging than the individual pressures.

Hydrological Pressures

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ResistanceResilienceSensitivity
Temperature increase (local) [Show more]

Temperature increase (local)

Benchmark. A 5°C increase in temperature for one month, or 2°C for one year. Further detail

Evidence

Kain (1964) stated that Laminaria hyperborea sporophyte growth and reproduction could occur within a temperature range of 0 - 20°C. Upper and lower lethal temperatures have been estimated at between 1-2°C above or below the extremes of this range (Birkett et al., 1988). Above 17°C gamete survival is reduced (Kain, 1964 & 1971) and gametogenesis is inhibited at 21°C (Dieck, 1992). It is, therefore, likely that Laminaria hyperborea recruitment will be impaired at a sustained temperature increase of above 17°C. Sporophytes, however, can tolerate slightly higher temperatures of 20°C. Temperature tolerances for Laminaria hyperborea are also seasonally variable and temperature changes are less tolerated in winter months than summer months (Birkett et al., 1998).

Subtidal red algae are less tolerant of temperature extremes than intertidal red algae, surviving between -2°C and 18-23 °C (Lüning 1990; Kain & Norton, 1990).  Temperature increase may affect growth, recruitment or interfere with reproduction processes. For example, there is some evidence to suggest that blade growth in Delesseria sanguinea is delayed until ambient sea temperatures fall below 13 °C. Blade growth is also likely to be intrinsically linked to gametangia development (Kain, 1987), and maintenance of sea temperatures above 13 °C may affect recruitment success.

Increases in sea temperature are also likely to create a northward range contraction of Laminaria hyperborea (Brodie et al., 2014), and may inhibit competitive ability at the southern edge of Laminaria hyperborea’ range. Laminaria hyperborea may be out-competed by the Invasive Non-Indigenous Species (INIS) Undaria pinnatifida (Brodie et al., 2014; Heiser et al., 2014) and/or its’ Lusitanian competitor-Laminaria ochroleuca (Smale et al., 2014) along the south coast of the UK (see sub-biotopes IR.HIR.KFaR.LhypR.Loch & IR.LIR.K.LhypLoch). The ecological impacts of such invasions could fundamentally alter Laminaria hyperborea habitat structure and limit recovery, however at the time of writing these effects are largely unknown (Brodie et al., 2014; Smale et al., 2014).

Bishop (1985) suggested that Echinus esculentus cannot tolerate high temperatures for prolonged periods due to increased respiration rate and resultant metabolic stress. Ursin (1960) reported Echinus esculentus occurred at temperatures between 0-18°C in Limfjord, Denmark. Bishop (1985) noted that gametogenesis occurred at 11-19°C however, continued exposure to 19°C disrupted gametogenesis. Embryos and larvae developed abnormally after 24hr exposure to 15°C but normally at 4, 7 and 11°C (Tyler & Young 1998).

Sensitivity assessment. This biotope is distributed throughout the UK (Connor et al., 2004). Northern to southern Sea Surface Temperature (SST) ranges from 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013). Overall, a chronic change (2°C for a year) outside the normal range for a year may reduce Laminaria hyperborea recruitment and growth, resulting in a minor loss in the population of kelp, especially in winter months or in southern examples of the biotope. However, an acute change (5°C for a month; e.g. from thermal effluent) may result in loss of abundance of kelp or extent of the bed, especially in winter. An increase in sea surface temperature of 2°C for a period of 1 year combined with high temperatures may approach the upper temperature threshold of Echinus esculentus. Therefore, resistance to the pressure is considered ‘Medium’, and resilience ‘Medium’. The sensitivity of this biotope to increases in temperature has been assessed as ‘Medium’.

Medium
High
High
High
Help		Medium
High
High
High
Help		Medium
High
High
High
Help
Temperature decrease (local) [Show more]

Temperature decrease (local)

Benchmark. A 5°C decrease in temperature for one month, or 2°C for one year. Further detail

Evidence

Kain (1964) stated that Laminaria hyperborea sporophyte growth and reproduction could occur within a temperature range of 0 - 20°C. Upper and lower lethal temperatures have been estimated at between 1-2 °C above or below the extremes of this range (Birkett et al., 1988). Subtidal red algae can survive at temperatures between -2 °C and 18-23 °C (Lüning, 1990; Kain & Norton, 1990). Laminaria hyperborea is a boreal northern species with a geographic range from mid-Portugal to Northern Norway (Birket et al., 1998), and a mid range within southern Norway (60°-65° North)(Kain, 1971).

Echinus esculentus has been recorded from the Murmansk Coast, Russia. Due to the high latitude at which Echinus esculentus can occur it is unlikely to be affected at the pressure benchmark. 

Sensitivity assessment. This biotope is distributed throughout the UK (Connor et al., 2004). Northern to southern Sea Surface Temperature (SST) ranges from 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013). The available information suggests the key characterizing species of this biotope  would not be affected. Resistance to the pressure is considered ‘High’, and resilience ‘High’. The sensitivity of this biotope to decreases in temperature has been assessed as ‘Not Sensitive’.

High
High
High
High
Help		High
High
High
High
Help		Not sensitive
High
High
High
Help
Salinity increase (local) [Show more]

Salinity increase (local)

Benchmark. A increase in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

Lüning (1990) suggest that ‘kelps’ are stenohaline, their general tolerance to salinity as a phenotypic group covering 16 - 50 PSU over a 24 hr period. Optimal growth probably occurs between 30-35 PSU (MNCR category- 'Full' salinity) and growth rates are likely to be affected by periodic salinity stress. Birkett et al, (1998) suggested that long-term increases in salinity may affect Laminaria hyperborea growth and may result in loss of affected kelp, and, therefore, loss of the biotope.

Echinoderms are generally stenohaline and possess no osmoregulatory organ (Boolootian, 1966). Therefore, an increase in salinity may cause Echinus esculentus mortality. Alcyonium digitatum’ distribution and the depth at which it occurs also suggest it would not likely experience regular salinity fluctuations and therefore not tolerate significant increases in salinity

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’.  The sensitivity of this biotope to an increase in salinity has been assessed as ‘Medium’.

Low
Low
NR
NR
Help		Medium
High
Medium
High
Help		Medium
Low
NR
NR
Help
Salinity decrease (local) [Show more]

Salinity decrease (local)

Benchmark. A decrease in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

Lüning (1990) suggest that ‘kelps’ are stenohaline, their general tolerance to salinity as a phenotypic group covering 16 - 50 PSU over a 24 hr period. Optimal growth probably occurs between 30-35 PSU (MNCR category-Full Salinity) and growth rates are likely to be affected by periodic salinity stress. Birkett et al. (1998) suggest that long-term changes in salinity may result in loss of affected kelp and, therefore, loss of this biotope.

Hopkin & Kain (1978) tested Laminaria hyperborea sporophyte growth at various low salinity treatments. The results showed that Laminaria hyperborea sporophytes could grow ‘normally’ at 19 PSU, growth was reduced at 16 PSU and did not grow at 7 PSU. A decrease in one MNCR salinity scale from 'Full' salinity (30-40psu) to 'Reduced' salinity (18-30 PSU) would result in a decrease of Laminaria hyperborea sporophyte growth.

Echinoderms are generally unable to tolerate low salinity (stenohaline) and possess no osmoregulatory organ (Boolootian, 1966). At low salinity, urchins gain weight, and the epidermis loses its pigment as patches are destroyed; prolonged exposure is fatal. However, within Echinus esculentus, there is some evidence to suggest intracellular regulation of osmotic pressure due to increased amino acid concentrations. Furthermore, as highlighted the Marine Nature Conservation Review (MNCR) records of 23rd Oct 2014 show Echinus esculentus is found within a number of variable and reduced salinity biotopes, e.g. IR.LIR.KVS.SlatPsaVS.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’.  The sensitivity of this biotope to decreases in salinity has been assessed as ‘Medium’.

Low
Medium
Medium
Medium
Help		Medium
High
Medium
High
Help		Medium
Medium
Medium
Medium
Help
Water flow (tidal current) changes (local) [Show more]

Water flow (tidal current) changes (local)

Benchmark. A change in peak mean spring bed flow velocity of between 0.1 m/s to 0.2 m/s for more than one year. Further detail

Evidence

Kregting et al. (2013) measured Laminaria hyperborea blade growth and stipe elongation from an exposed and a sheltered site in Strangford Lough, Ireland, from March 2009-April 2010. Maximal significant wave height (Hm0) was 3.67 & 2m at the exposed and sheltered sites, and maximal water velocity (Velrms) was 0.6 & 0.3m/s at the exposed and sheltered sites respectively. Despite the differences in wave exposure and water velocity, there was no significant difference in Laminaria hyperborea growth between the exposed and sheltered sites. Therefore, water flow was found to have no significant effect on Laminaria hyperborea growth at the observed range of water velocities.

Biotope structure is, however, different between wave exposed and sheltered sites. Pedersen et al. (2012) observed Laminaria hyperborea biomass, productivity and density increased with an increase in wave exposure. At low wave exposure, Laminaria hyperborea canopy forming plants were smaller, had lower densities and had higher mortality rates than at exposed sites. At low wave exposure Pedersen et al. (2012) suggested that high epiphytic loading on Laminaria hyperborea impaired light conditions, nutrient uptake, and increased the drag on the host Laminaria hyperborea during extreme storm events.

The morphology of the stipe and blade of kelps vary with water flow.  In wave exposed areas, for example, Laminaria hyperborea develops a long and flexible stipe and this is probably a functional adaptation to strong water movement (Sjøtun et al, 1998). In addition, the lamina becomes narrower and thinner in strong currents (Sjøtun & Fredriksen, 1995). However, the stipe of Laminaria hyperborea is relatively stiff and can snap in strong currents. Laminaria hyperborea is usually absent from areas of high wave action or strong currents, although it is found  in the Menai Strait, Wales, where tidal velocities can exceed 4 m/s (NBN, 2015) and in tidal rapids in Norway (J. Jones, pers. comm.)  Laminaria hyperborea growth can persist in very strong tidal streams (>3 m/s).

Increase water flow rate may also remove or inhibit grazers including Patella pellucida and Echinus esculentus and remove epiphytic algae growth (Pedersen et al., 2012). The associated algal flora and suspension feeding faunal populations change significantly with different water flow regimes. Increased water flow rates may reduce the understorey epiflora, to be replaced by an epifauna dominated community (e.g. sponges, anemones and polyclinid ascidians) as in the biotope IR.HIR.KFaR.LhypFa. The composition of the holdfast fauna may also change, e.g. energetic or sheltered water movements favour different species of amphipods (Moore, 1985).

IR.HIR.KFaR.LhypR, IR.HIR.KFaR.LhypFa, IR.MIR.KR.Lhyp, and their associated sub-biotopes are found within strong (1.5-3 m/s)-moderate (0.5-1.5 m/s) tidal streams. A change in peak mean spring bed flow velocity which does not result in a change in tidal streams above or below 0.5-3 m/s is not likely to affect the dominance of Laminaria hyperborea within the community, but may cause changes in the understorey community. The prominent understorey filter feeding community within IR.HIR.KFaR.LhypFa is reliant on high water movement. A decrease in tidal streams may result in a decline of filter feeding fauna and an increase in red seaweeds within the understorey community or vice versa with an increase in tidal streams

Echinus esculentus occurred in kelp beds on the west coast of Scotland in currents of about 0.5 m/sec. Outside the beds specimens were occasionally seen being rolled by the current (Comely & Ansell, 1988), which may have been up to 1.4 m/sec. Urchins are removed from the stipe of kelps by wave and current action. Echinus esculentus are also displaced by storm action. After disturbance Echinus esculentus migrates up the shore, an adaptation to being washed to deeper water by wave action (Lewis & Nichols, 1979). Therefore, increased water flow may remove the population from the affected area; probably to deeper water although individuals would probably not be killed in the process and could recolonize the area quickly.

Sensitivity assessment. A change in peak mean spring bed flow velocity of between 0.1m/s to 0.2m/s for more than 1 year is not likely to affect the dominance of Laminaria hyperborea, however, subtle differences in tidal regime may influence the understorey community. Echinus esculentus may become dislodged but are unlikely to be killed and may recolonize quickly Resistance to the pressure is considered ‘High’, and resilience ‘High’. Hence, the sensitivity of this biotope to changes in peak mean spring bed velocity has been assessed as ‘Not Sensitive’.

High
High
High
High
Help		High
High
High
High
Help		Not sensitive
High
High
High
Help
Emergence regime changes [Show more]

Emergence regime changes

Benchmark.  1) A change in the time covered or not covered by the sea for a period of ≥1 year or 2) an increase in relative sea level or decrease in high water level for ≥1 year. Further detail

Evidence

The upper limit of the Laminaria hyperborea bed is determined by wave action and water flow, desiccation, and competition from the more emergence resistant Laminaria digitata. Laminaria hyperborea exposed at extreme low water are very intolerant of desiccation, the most noticeable effect being bleaching of the frond and subsequent death of the meristem and loss of the plant. An increase in wave exposure (see below- water flow), as a result of increased emergence, has been found to exclude Laminaria hyperborea from shallow waters due to dislodgement of the sporophyte or snapping of the stipe (Birket et al., 1998). Hence, an increase in emergence is likely to lead to mortality of exposed Laminaria hyperborea and the associated habitat.

An increase in water depth/decreased emergence (at the benchmark level) may increase the upper depth restriction of Laminaria hyperborea forest biotope variants. However, limited light availability at depth will decrease the lower extent of Laminaria hyperborea, and may, therefore, result in a shift from forest to park biotope variants at depth. Further increases in depth will cause a community shift to that characterized by circalittoral faunal species, however, this is beyond the scope of the benchmark.

Several mobile species such as sea urchins, brittle stars and feather stars are likely to move away. However, providing that suitable substrata are present, the biotope could re-establish further down the shore within a similar emergence regime to that which existed previously. Similarly, a decrease in emergence may allow the biotope to extend its extent up the shore, however, completion from other species would probably erode its lower extent.

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’. The sensitivity of this biotope to changes in tidal emergence has been assessed as ‘Medium’.

Low
Low
NR
NR
Help		Medium
High
Low
High
Help		Medium
Low
Low
Low
Help
Wave exposure changes (local) [Show more]

Wave exposure changes (local)

Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail

Evidence

Kregting et al. (2013) measured Laminaria hyperborea blade growth and stipe elongation from an exposed and a sheltered site in Strangford Lough, Ireland from March 2009-April 2010. Wave exposure was found to be between 1.1. to 1.6 times greater between the exposed and sheltered sites. Maximal significant wave height (Hm0) was 3.67 & 2 m at the exposed and sheltered sites. Maximal water velocity (Velrms) was 0.6 & 0.3 m/s at the exposed and sheltered sites. Despite the differences in wave exposure and water velocity, there was no significant difference in Laminaria hyperborea growth between the exposed and sheltered site.

Biotope structure is, however, different between wave exposed and sheltered sites. Pedersen et al. (2012) observed Laminaria hyperborea biomass, productivity and density increased with an increase in wave exposure. At low wave exposure, Laminaria hyperborea canopy forming plants were smaller, had lower densities and had higher mortality rates than at exposed sites. At low wave exposure high epiphytic loading on Laminaria hyperborea was theorised to impair light conditions, nutrient uptake, and increase the drag of the host Laminaria hyperborea during extreme storm events.

The morphology of the stipe and blade of kelps vary with water flow. In wave exposed areas, for example, Laminaria hyperborea develops a long and flexible stipe and this is probably a functional adaptation to strong water movement (Sjøtun, 1998). In addition, the lamina becomes narrower and thinner in strong currents (Sjøtun & Fredriksen, 1995). However, the stipe of Laminaria hyperborea is relatively stiff and can snap in strong currents. Lamiaria hyperborea is usually absent from areas of extreme wave action and can be replaced by Alaria esculenta. In extreme wave exposures Alaria esculenta can dominate the shallow sub-littoral to a depth of 15m (Birket et al., 1998b).

Increase water flow rate may also remove or inhibit grazers including Patella pellucida and Echinus esculentus and remove epiphytic algae growth (Pedersen et al., 2012). The associated algal flora and suspension feeding faunal populations change significantly with different water flow regimes. Increased water flow rates may reduce the understorey epiflora, to be replaced by an epifauna dominated community (e.g. sponges, anemones and polyclinid ascidians) as in the biotope IR.HIR.KFaR.LhypFa. The composition of the holdfast fauna may also change, e.g. energetic or sheltered water movements favour different species of amphipods (Moore, 1985).

IR.HIR.KFaR.LhypR, IR.HIR.KFaR.LhypFa, IR.MIR.KR.Lhyp, and their associated sub-biotopes are found between extremely exposed to moderate wave exposure. Changes in local wave height above or below that experienced in extremely exposed to moderately exposed sites will affect the dominance of Laminaria hyperborea. Smaller changes in local wave height have the potential to cause changes to the understorey community. The prominent understorey filter feeding community within IR.HIR.KFaR.LhypFa is reliant on wave surge currents. A decrease in wave surge may result in a decline of filter feeding fauna and an increase in red seaweeds within the understorey community or vice versa.

Echinus esculentus occurred in kelp beds on the west coast of Scotland in currents of about 0.5 m/sec. Outside the beds specimens were occasionally seen being rolled by the current (Comely & Ansell, 1988), which may have been up to 1.4 m/sec. Urchins are removed from the stipe of kelps by wave and current action. Echinus esculentus are also displaced by storm action. After disturbance Echinus esculentus migrates up the shore, an adaptation to being washed to deeper water by wave action (Lewis & Nichols, 1979). Keith Hiscock (pers. comm.) reported Echinus esculentus occurred in significant numbers as shallow as 15m below low water at the extremely wave exposed site of Rockall, Scotland. Therefore, localised increases in wave height may remove the population from the affected area; probably to deeper water although individuals would probably not be killed in the process and could recolonize the area quickly.

Sensitivity assessment. A change in nearshore significant wave height >3% but <5% is, however, unlikely to have a significant effect. Resistance to the pressure is considered ‘High’, and resilience ‘High’. Hence, the sensitivity of this biotope to changes in local wave height has been assessed as ‘Not Sensitive’.

High
High
High
High
Help		High
High
High
High
Help		Not sensitive
High
High
High
Help

Chemical Pressures

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ResistanceResilienceSensitivity
Transition elements & organo-metal contamination [Show more]

Transition elements & organo-metal contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

Bryan (1984) suggested that the general order for heavy metal toxicity in seaweeds is: Organic Hg > inorganic Hg > Cu > Ag > Zn > Cd > Pb. Cole et a,. (1999) reported that Hg was very toxic to macrophytes. Similarly, Hopkin & Kain (1978) demonstrated sub-lethal effects of heavy metals on Laminaria hyperborea gametophytes and sporophytes, including reduced growth and respiration. Sheppard et al., (1980) noted that increasing levels of heavy metal contamination along the west coast of Britain reduced species number and richness in holdfast fauna, except for suspension feeders which became increasingly dominant. Gastropods may be relatively tolerant of heavy metal pollution (Bryan, 1984). Echinus esculentus recruitment is likely to be impaired by heavy metal contamination due to the intolerance of its larvae. Echinus esculentus are long-lived and poor recruitment may not reduce grazing pressure in the short-term. Although macroalgae species may not be killed, except by high levels of contamination, reduced growth rates may impair the ability of the biotope to recover from other environmental disturbances.

Little is known about the effects of heavy metals on echinoderms. Bryan (1984) reported that early work had shown that echinoderm larvae were sensitive to heavy metals contamination, for example Migliaccio et al. (2014) reported exposure of Paracentrotus lividis larvae to increased levels of cadmium and manganese caused abnormal larval development and skeletal malformations. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu).

Not Assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help
Hydrocarbon & PAH contamination [Show more]

Hydrocarbon & PAH contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

Laminaria hyperborea fronds, being almost exclusively subtidal, would not come into contact with freshly released oil, but only to sinking emulsified oil and oil adsorbed onto particles (Birket et al., 1998). The mucilaginous slime layer coating of laminarians may protect them from smothering by oil. Hydrocarbons in solution reduce photosynthesis and may be algicidal. However, Holt et al. (1995) reported that oil spills in the USA and from the Torrey Canyon had little effect on kelp forests. Similarly, surveys of subtidal communities at a number sites between 1-22.5m below chart datum, including Laminaria hyperbora communities, showed no noticeable impacts of the Sea Empress oil spill and clean up (Rostron & Bunker, 1997). An assessment of holdfast fauna in Laminaria showed that although species richness and diversity decreased with increasing proximity to the Sea Empress oil spill, overall the holdfasts contained a reasonably rich and diverse fauna, even though oil was present in most samples (Sommerfield & Warwick, 1999). Laboratory studies of the effects of oil and dispersants on several red algae species, including Delesseria sanguinea (Grandy 1984; cited in Holt et al., 1995) concluded that they were all sensitive to oil/ dispersant mixtures, with little differences between adults, sporelings, diploid or haploid life stages. Holt et al. (1995) concluded that Delesseria sanguinea is probably generally sensitive of chemical contamination. Overall the red algae are likely to be highly intolerant to hydrocarbon contamination. Loss of red algae is likely to reduce the species richness and diversity of the biotope and the understorey may become dominated by encrusting corallines; however, red algae are likely to recover relatively quickly.

Echinus esculentus is subtidal and unlikely to be directly exposed to oil spills. However, as with the Prestige’oil spill rough seas can cause mixing with the oil and the seawater, and therefore subtidal habitats can be affected by the oil spill. Castège et al. (2014) recorded the recovery of rocky shore communities following the Prestige oil spill which impacted the French Atlantic coast. Rough weather at the time of the spill increased mixing between the oil and seawater, causing sub-tidal communities/habitats to be affected. The urchin Echinus esculentus was reported absent after the oil spill however returned after 2-5 years. Large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen cove, presumably due to a combination of wave exposure and heavy spraying of dispersants following the Torrey canyon oil spill (Smith 1968). Smith (1968) also demonstrated that 0.5 -1 ppm of the detergent BP1002 resulted in developmental abnormalities in its echinopluteus larvae. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999).

Not Assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help
Synthetic compound contamination [Show more]

Synthetic compound contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed but evidence is presented where available.

O'Brian & Dixon (1976) suggested that red algae were the most sensitive group of macrophytes to oil and dispersant contamination (see Smith, 1968). Although Laminaria hyperborea sporelings and gametophytes are intolerant of atrazine (and probably other herbicides) overall they may be relatively tolerant of synthetic chemicals (Holt et al., 1995). Laminaria hyperborea survived within >55m from the acidified halogenated effluent discharge polluting Amlwch Bay, Anglesey, albeit at low density. These specimens were greater than 5 years of age, suggesting that spores and/or early stages were more intolerant (Hoare & Hiscock, 1974). Patella pellucida was excluded from Amlwch Bay by the pollution and the species richness of the holdfast fauna decreased with proximity to the effluent discharge; amphipods were particularly intolerant although polychaetes were the least affected (Hoare & Hiscock, 1974). The richness of epifauna/flora decreased near the source of the effluent and epiphytes were absent from Laminaria hyperborea stipes within Amlwch Bay. The red alga Phyllophora membranifolia was also tolerant of the effluent in Amlwch Bay. Smith (1968) also noted that epiphytic and benthic red algae were intolerant of dispersant or oil contamination due to the Torrey Canyon oil spill; only the epiphytes Crytopleura ramosa and Spermothamnion repens and some tufts of Jania rubens survived together with Osmundea pinnatifida, Gigartina pistillata and Phyllophora crispa from the sublittoral fringe. Delesseria sanguinea was probably to most intolerant since it was damaged at depths of 6m (Smith, 1968). Holt et al., (1995) suggested that Delesseria sanguinea is probably generally sensitive of chemical contamination. Although Laminaria hyperborea may be relatively insensitive to synthetic chemical pollution, evidence suggests that grazing gastropods, amphipods and red algae are sensitive. Loss of red algae is likely to reduce the species richness and diversity of the biotope and the understorey may become dominated by encrusting corallines; however, red algae are likely to recover relatively quickly.

Large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen, presumably due to a combination of wave exposure and heavy spraying of dispersants in that area following the Torrey Canyon oil spill (Smith 1968). Smith (1968) also demonstrated that 0.5 -1ppm of the detergent BP1002 resulted in developmental abnormalities in echinopluteus larvae of Echinus esculentus. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999).

Not Assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help
Radionuclide contamination [Show more]

Radionuclide contamination

Benchmark. An increase in 10µGy/h above background levels. Further detail

Evidence

No evidence was found

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		No evidence (NEv)
NR
NR
NR
Help
Introduction of other substances [Show more]

Introduction of other substances

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

This pressure is Not assessed.

Not Assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help
De-oxygenation [Show more]

De-oxygenation

Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail

Evidence

Reduced oxygen concentrations have been shown to inhibit both photosynthesis and respiration in macroalgae (Kinne, 1977). Despite this, macroalgae are thought to buffer the environmental conditions of low oxygen, thereby acting as a refuge for organisms in oxygen depleted regions especially if the oxygen depletion is short-term (Frieder et al., 2012).  In addition, the biotope occurs in areas of moderate to extreme wave action, so is likely to be continuously aerated. A rapid recovery from a state of low oxygen is expected if the environmental conditions are transient. If levels do drop below 4 mg/l negative effects on these organisms can be expected with adverse effects occurring below 2mg/l (Cole et al., 1999).

In August 1978 a dense bloom of a dinoflagellate, Gyrodinium aureolum occurred surrounding Geer reef in Penzance Bay, Cornwall and persisted until September that year. Observations by local divers indicated a decrease in underwater visibility (<1 m) from below 8 m Below Sea Level. It was also noted that many of the faunal species appeared to be affected, e.g. no live Echinus esculentus were observed whereas on surveys prior to August were abundant, Alcyonium sp. and Bryozoans were also in an impoverished state. During follow-up surveys conducted in early September, Alcyonium sp. were noted to be much healthier and feeding. It was suggested the decay of Gyrodinium aureolum either reduced oxygen levels or physically clogged faunal feeding mechanisms. Adjacent reefs where also surveyed during the same time period and the effects of the Gyrodinium aureolum bloom were less apparent. It was suggested that higher water agitation in shallow water on reefs more exposed to wave action were less effected by the phytoplankton bloom (Griffiths et al., 1979).

Sensitivity Assessment.  Reduced oxygen levels are likely to inhibit photosynthesis and respiration but not cause a loss of the macroalgae population directly. Furthermore, wave exposure is likely to constantly aerate the affected area. While de-oxygenation may not directly affect Laminaria hyperborea, small invertebrate epifauna may be lost, causing a reduction in species richness. Therefore, resistance has been assessed as ‘Medium’ is recorded.  Resilience is likely to be ‘High’, and the biotopes is probably ‘Low’ at the benchmark level. 

Medium
High
Medium
High
Help		High
High
Medium
High
Help		Low
High
Medium
High
Help
Nutrient enrichment [Show more]

Nutrient enrichment

Benchmark. Compliance with WFD criteria for good status. Further detail

Evidence

This biotope is considered to be 'Not sensitive' at the pressure benchmark that assumes compliance with good status as defined by the WFD.

Holt et al. (1995) suggest that Laminaria hyperborea may be tolerant of nutrient enrichment since healthy populations are found at ends of sublittoral untreated sewage outfalls in the Isle of Man. Increased nutrient levels e.g. from sewage outfalls, has been associated with increases in abundance, primary biomass and Laminaria hyperborea stipe production but with concomitant decreases in species numbers and diversity (Fletcher, 1996).

Increased nutrients may result in phytoplankton blooms that increase turbidity (see water clarity pressure). Increased nutrients may favour sea urchins, e.g. Echinus esculentus, due their ability to absorb dissolved organics, and result in increased grazing pressure leading to loss of understorey epiflora/fauna, decreased kelp recruitment and possibly 'urchin barrens'. Therefore, although nutrients may not affect kelps directly, indirect effects such as turbidity, siltation and competition may significantly affect the structure of the biotope.

It was suggested by Comely & Ansell (1988) that Echinus esculentus could absorb dissolved organic material for the purposes of nutrition. Nutrient enrichment may encourage the growth of ephemeral and epiphytic algae and therefore increase sea-urchin food availability. Lawrence (1975) reported that sea urchins had persisted over 13 years on barren grounds near sewage outfalls, presumably feeding on dissolved organic material, detritus, plankton and microalgae, although individuals died at an early age.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not sensitive
NR
NR
NR
Help
Organic enrichment [Show more]

Organic enrichment

Benchmark. A deposit of 100 gC/m2/yr. Further detail

Evidence

Holt et al. (1995) suggest that Laminaria hyperborea may be tolerant of organic enrichment since healthy populations are found at ends of sublittoral untreated sewage outfalls in the Isle of Man. Increased nutrient levels e.g. from sewage outfalls, has been associated with increases in abundance, primary biomass and Laminaria hyperborea stipe production, but with concomitant decreases in species numbers and diversity (Fletcher, 1996). Increase organic enrichment has also been found to increase the abundance and dominance of suspension feeding fauna within Laminaria hyperborea holdfasts (Sheppard et al., 1980). Increase in ephemeral and opportunistic algae are associated with reduced numbers of perennial macrophytes (Fletcher, 1996). Increased nutrients may also result in phytoplankton blooms that increase turbidity. Therefore, although nutrients may not affect kelps directly, indirect effects such as turbidity and the increased abundance of suspension feeding fauna may affect the structure of Laminaria hyperborea biotopes (se

Medium
Medium
Medium
Medium
Help		High
High
Medium
High
Help		Low
Medium
Medium
Medium
Help

Physical Pressures

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ResistanceResilienceSensitivity
Physical loss (to land or freshwater habitat) [Show more]

Physical loss (to land or freshwater habitat)

Benchmark. A permanent loss of existing saline habitat within the site. Further detail

Evidence

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’).  Sensitivity within the direct spatial footprint of this pressure is, therefore ‘High’.  Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

None
High
High
High
Help		Very Low
High
High
High
Help		High
High
High
High
Help
Physical change (to another seabed type) [Show more]

Physical change (to another seabed type)

Benchmark. Permanent change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa. Further detail

Evidence

If rock substrata were replaced with sedimentary substrata this would represent a fundamental change in habitat type, which Laminaria hyperborea would not be able to tolerate (Birket et al., 1998). The biotope would be lost.

Sensitivity assessment. Resistance to the pressure is considered ‘None’, and resilience ‘Very Low’ or ‘None’. The sensitivity of this biotope to change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa is assessed as ‘High’.

None
High
High
High
Help		Very Low
High
High
High
Help		High
High
High
High
Help
Physical change (to another sediment type) [Show more]

Physical change (to another sediment type)

Benchmark. Permanent change in one Folk class (based on UK SeaMap simplified classification). Further detail

Evidence

Not relevant

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Habitat structure changes - removal of substratum (extraction) [Show more]

Habitat structure changes - removal of substratum (extraction)

Benchmark. The extraction of substratum to 30 cm (where substratum includes sediments and soft rock but excludes hard bedrock). Further detail

Evidence

Not relevant to rock substrata.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Abrasion / disturbance of the surface of the substratum or seabed [Show more]

Abrasion / disturbance of the surface of the substratum or seabed

Benchmark. Damage to surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

Christie et al. (1998) observed Laminaria hyperborea habitat regeneration following commercial Laminaria hyperborea trawling in south Norway. Within the study area, trawling removed all large canopy-forming adult Laminaria hyperborea, however, sub-canopy recruits were largely unaffected. In 2-6 years of harvesting, a new canopy had formed 1m off the seabed. The associated holdfast communities recovered in 6 years, however, the epiphytic stipe community did not fully recover within the same time period. Christie et al., (1998) suggested that kelp habitats were relatively resistant to direct disturbance/removal of Laminaria hyperborea canopy.

Recurrent disturbance occurring at a smaller time scale than the recovery period of 2-6 years (stated above) could extend recovery time. Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared however within 2 years of clearance the blocks were dominated by Laminaria hyperborea (Kain, 1975). Leinaas & Christie (1996) also observed Laminaria hyperborea re-colonization of ‘urchin barrens’, following removal of urchins. The substratum was initially colonized by filamentous macroalgae and Saccharina latissima however after 2-4 years Laminaria hyperborea dominated the community.

Species with fragile tests, such as Echinus esculentus were reported to suffer badly as a result of scallop or queen scallop dredging (Bradshaw et al., 2000; Hall-Spencer & Moore, 2000a & b). Kaiser et al. (2000) reported that Echinus esculentus were less abundant in areas subject to high trawling disturbance in the Irish Sea. Jenkins et al. (2001) conducted experimental scallop trawling in the North Irish sea and recorded the damage caused to several conspicuous megafauna species, both when caught as bi-catch and when left on the seabed. The authors predicted 16.4% of Echinus esculentus were crushed/dead, 29.3% would have >50% spine loss/minor cracks, 1.1% would have <50% spine loss and the remaining 53.3% would be in good condition. Sea urchins can rapidly regenerate spines, e.g. Psammechinus miliaris were found to re-grow all spines within a period of 2 months (Hobson, 1930).

Sensitivity assessment. Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’. The sensitivity of this biotope to damage to seabed surface features is assessed as ‘Medium’.

Low
High
High
High
Help		Medium
High
High
High
Help		Medium
High
High
High
Help
Penetration or disturbance of the substratum subsurface [Show more]

Penetration or disturbance of the substratum subsurface

Benchmark. Damage to sub-surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

Not Relevant, please refer to pressure “Abrasion/disturbance of the substratum on the surface of the seabed”.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Changes in suspended solids (water clarity) [Show more]

Changes in suspended solids (water clarity)

Benchmark. A change in one rank on the WFD (Water Framework Directive) scale e.g. from clear to intermediate for one year. Further detail

Evidence

Suspended Particle Matter (SPM) concentration has a linear relationship with subsurface light attenuation (Kd) (Devlin et al., 2008). An increase in SPM results in a decrease in sub-surface light attenuation. Light availability and water turbidity are principal factors in determining the depth range of Laminaria hyperborea’ (0-47 m Below Sea Level) (Birkett et al., 1998b). Light penetration influences the maximum depth at which kelp species can grow and it has been reported that Laminarians grow at depths at which the light levels are reduced to 1 percent of incident light at the surface. Maximal depth distribution of laminarians, therefore, varies from 100 m in the Mediterranean to only 6-7 m in the silt-laden German Bight. In Atlantic European waters, the depth limit is typically 35 m. In very turbid waters the depth at which Laminaria hyperborea is found may be reduced to 2.5m (Birkett et al. 1998), or in some cases excluded completely (e.g. Severn Estuary), because of the alteration in light attenuation by suspended sediment (Birkett et al. 1998; Lüning, 1990).

Laminaria spp. show a decrease of 50% photosynthetic activity when turbidity increases by 0.1/m (light attenuation coefficient =0.1-0.2/m; Staehr & Wernberg, 2009). An increase in water turbidity will likely affect the photosynthetic ability of Laminaria hyperborea and decrease Laminaria hyperborea abundance and density (see sub biotope-IR.HIR.KFaR.LhypR.Pk). Kain (1964) suggested that early Laminaria hyperborea gametophyte development could occur in the absence of light. Furthermore observations from south Norway found that a pool of Laminaria hyperborea recruits could persist growing beneath Laminaria hyperborea canopies for several years, indicating that sporophytes growth can occur in light limited environments (Christe et al., 1998). However in habitats exposed to high levels of suspended silts Laminaria hyperborea is out-competed by Saccharina latissima, a silt tolerant species, and thus, a decrease in water clarity is likely to decrease the abundance of Laminaria hyperborea in the affected area (Norton, 1978). An absence of this biotope in silt rich environments is therefore expected.

Moore (1977) suggested that Echinus esculentus was unaffected by turbid conditions. Echinus esculentus is an important grazer of red macro-algae within CR.MCR.EcCr. Increased turbidity and resultant reduced light penetration is likely to negatively affect algal growth. However, Echinus esculentus can feed on alternative prey, detritus or dissolved organic material (Lawrence, 1975, Comely & Ansell, 1988)

Sensitivity Assessment. Echinus esculentus is unlikely to be affected. However, an increase in water clarity from clear to intermediate (10-100mg/l) represent a change in light attenuation of ca 0.67-6.7 Kd/m, and is likely to result in a greater than 50% reduction in photosynthesis of Laminaria spp. Therefore, the dominant kelp species will probably suffer a severe decline, and resistance to this pressure is assessed as ‘None’.  Resilience to this pressure is assessed as ‘Medium’ at the benchmark. Hence, this biotope is regarded as having a sensitivity of ‘Medium ‘to this pressure.

None
High
High
High
Help		Medium
High
High
High
Help		Medium
High
High
High
Help
Smothering and siltation rate changes (light) [Show more]

Smothering and siltation rate changes (light)

Benchmark. ‘Light’ deposition of up to 5 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

Smothering by sediment e.g. 5 cm material during a discrete event is unlikely to damage Laminaria hyperborea sporophytes but is likely to affect gametophyte survival as well as holdfast fauna, and interfere with zoospore settlement.  Given the microscopic size of the gametophyte, 5 cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that gametophytes can survive in darkness for between 6 - 16 months at 8 °C and would probably survive smothering by a discrete event.  Once returned to normal conditions the gametophytes resumed growth or maturation within 1 month (Dieck, 1993). Intolerance to this factor is likely to be higher during the peak periods of sporulation and/or spore settlement.

If inundation is long lasting then the understorey epifauna/flora may be adversely affected, e.g. suspension or filter feeding fauna and/or algal species.  This biotope occurs in high wave exposures and, therefore, deposited sediments are unlikely to remain for more than a few tidal cycles, except in the deepest of rock-pools. Therefore, the effects of depositing 5cm of fine sediment in a discrete event are likely to be transient.

Comely & Ansell (1988) recorded large Echinus esculentus from kelp beds on the west coast of Scotland in which the substratum was seasonally covered with "high levels" of silt. This suggests that Echinus esculentus is unlikely to be killed by smothering, however, smaller specimens and juveniles may be less resistant. A layer of sediment may interfere with larval settlement.  If retained within the host biotope for extended periods a layer of 5cm of the sediment may negatively affect successive recruitment events.

Sensitivity assessment. Resistance to the pressure is considered ‘High’, and resilience ‘High’. The sensitivity of this biotope to light deposition of up to 5cm of fine material added to the seabed in a single discreet event is assessed as ‘Note Sensitive’.

High
Medium
High
High
Help		High
High
High
High
Help		Not sensitive
Medium
Medium
High
Help
Smothering and siltation rate changes (heavy) [Show more]

Smothering and siltation rate changes (heavy)

Benchmark. ‘Heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

Smothering by sediment e.g. 30 cm material during a discrete event is unlikely to damage Laminaria hyperborea plants but is likely to affect gametophyte survival, holdfast communities, epiphytic community at the base of the stipe, and interfere with zoospore settlement. Given the microscopic size of the gametophyte, 30 cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that gametophytes can survive in darkness for between 6 - 16 months at 8 °C and would probably survive smothering within a discrete event. Once returned to normal conditions the gametophytes resumed growth or maturation within 1 month (Dieck, 1993). Intolerance to this factor is likely to be higher during the peak periods of sporulation and/or spore settlement.

If clearance of deposited sediment occurs rapidly then understorey communities are expected to recover quickly. If inundation is long lasting then the understorey epifauna/flora may be adversely affected, e.g. suspension or filter feeding fauna and/or algal species.  While this  biotope occurs in high to moderate energy habitats (due to water flow or wave action) deposition of 30cm of sediment represents a large volume of material that would likely remain for a number of tidal cycles and is expected to damage understorey flora/fauna as well as juvenile Laminaria hyperborea.

Comely & Ansell (1988) recorded large Echinus esculentus from kelp beds on the west coast of Scotland in which the substratum was seasonally covered with "high levels" of silt. This suggests that Echinus esculentus is unlikely to be killed by smothering, however, smaller specimens and juveniles may be less resistant. A layer of sediment may interfere with larval settlement.  If retained within the host biotope for extended periods a layer of 5cm of the sediment may negatively affect successive recruitment events.

Sensitivity assessment. Resistance to the pressure is considered ‘Medium’, and resilience ‘High’. The sensitivity of this biotope to heavy deposition of up to 30cm of fine material added to the seabed in a single discreet event is assessed as ‘Low’.

Medium
Medium
High
High
Help		High
Low
Medium
High
Help		Low
Medium
Medium
High
Help
Litter [Show more]

Litter

Benchmark. The introduction of man-made objects able to cause physical harm (surface, water column, seafloor or strandline). Further detail

Evidence

Not assessed.

Not Assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help		Not assessed (NA)
NR
NR
NR
Help
Electromagnetic changes [Show more]

Electromagnetic changes

Benchmark. A local electric field of 1 V/m or a local magnetic field of 10 µT. Further detail

Evidence

No evidence was found

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		No evidence (NEv)
NR
NR
NR
Help
Underwater noise changes [Show more]

Underwater noise changes

Benchmark. MSFD indicator levels (SEL or peak SPL) exceeded for 20% of days in a calendar year. Further detail

Evidence

Not relevant

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Introduction of light or shading [Show more]

Introduction of light or shading

Benchmark. A change in incident light via anthropogenic means. Further detail

Evidence

Shading of the biotope (e.g. by construction of a pontoon, pier etc) could adversely affect the biotope in areas where the water clarity is also low, and tip the balance to shade tolerant species, resulting in the loss of the biotope directly within the shaded area, or a reduction in laminarian abundance from forest to park type biotopes.

Sensitivity assessment. Resistance is probably 'Low', with a 'Medium' resilience and a sensitivity of 'Medium', albeit with 'low' confidence due to the lack of direct evidence.

Low
Low
NR
NR
Help		Medium
Low
NR
NR
Help		Medium
Low
Low
Low
Help
Barrier to species movement [Show more]

Barrier to species movement

Benchmark. A permanent or temporary barrier to species movement over ≥50% of water body width or a 10% change in tidal excursion. Further detail

Evidence

Not relevant. This pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit the dispersal of spores.  But spore dispersal is not considered under the pressure definition and benchmark.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Death or injury by collision [Show more]

Death or injury by collision

Benchmark. Injury or mortality from collisions of biota with both static or moving structures due to 0.1% of tidal volume on an average tide, passing through an artificial structure. Further detail

Evidence

Not relevant. Collision from grounding vessels is addressed under abrasion above.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help
Visual disturbance [Show more]

Visual disturbance

Benchmark. The daily duration of transient visual cues exceeds 10% of the period of site occupancy by the feature. Further detail

Evidence

Not relevant

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help

Biological Pressures

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ResistanceResilienceSensitivity
Genetic modification & translocation of indigenous species [Show more]

Genetic modification & translocation of indigenous species

Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail

Evidence

No evidence regarding the genetic modification or effects of translocation of native kelp populations was found.

Not relevant (NR)
NR
NR
NR
Help		Not relevant (NR)
NR
NR
NR
Help		No evidence (NEv)
NR
NR
NR
Help
Introduction or spread of invasive non-indigenous species [Show more]

Introduction or spread of invasive non-indigenous species

Benchmark. The introduction of one or more invasive non-indigenous species (INIS). Further detail

Evidence

Competition with invasive macroalgae may be a potential threat to this biotope. Potential invasives include Undaria pinnatifida and Sargassum muticum. Sargassum muticum is a circumglobal invasive species (Engelen et al., 2015). It is recorded (2015) from Norway to Morocco and into the Mediterranean in the eastern Atlantic and from Alaska to Baja California in the eastern Pacific and from southern Russia to southern China in the western Pacific (Engelen et al., 2015). It colonizes a variety of habitats and can tolerate -1°C to 30°C and survive salinities below 10 ppt. Although fertilization does not occur below 15 ppt and growth of germlings is limited below 10°C it can complete its life cycle as long as temperatures are over 8°C for at least four months of the year (Engelen et al., 2015). However, its distribution is limited by the availability of hard substratum (e.g., stones >10 cm) and light (Staeher et al., 2000; Strong & Dring 2011; Engelen et al., 2015). It is most abundant between 1 and 3 m below mean water. But it has been recorded at 18 m or 30 m in the clear waters of California. However, it is a poor competitor under low light and only develops dense canopies in shallow areas (Engelen et al., 2015). 

Sargassum muticum was shown to replace and out-compete leathery, canopy-forming macroalgae such as Saccharina latissima, Halidrys siliquosa, and Fucus spp. and, to a lesser degree, understorey species such as Codium fragile, Chondrus crispus and Dictyota dichotoma in Limfjorden, Denmark between 1984 and 1997 (Staehr et al., 2000; Engelen et al., 2015; de Bettignies et al., 2021). The invasion in Limfjorden had stabilized by 2005 although many of the native macroalgal species continued to decline (Engelen et al., 2015). In Limfjorden, the distribution of Sargassum muticum was limited to areas with hard substratum, in particular stones >10 cm in diameter, while smaller stones, gravel and sand were unsuitable. It was most abundant between 1 and 4 m in depth but had low cover at 0-0.5 m or 4-6 m, in the turbid waters of the Limfjorden. Limfjorden is wave sheltered but wave exposure has been reported to restrict the growth and survival of Sargassum muticum (Staehr et al., 2000). Viejo et al. (1995) reported that Sargassum muticum transplanted to wave exposed shores in Spain experienced >80% breakages within a month and that the growth of undamaged plants was significantly lower than that of plants on sheltered shores. Similarly, Andrew & Viejo (1998) noted that Sargassum muticum was restricted to intertidal rockpools in wave exposed sites in the Bay of Biscay. 

Strong & Dring (2011) used canopy removal experiments to investigate inter- and intra-species competition between Sargassum muticum and Saccharina latissima in the Dorn, Strangford Lough, N. Ireland. The Dorn consists of tidal pools, very sheltered from wave action but with moderately strong tidal streams (1-2 knots). Sargassum muticum grew better in mixed stands with Saccharina latissima than in the highest density monospecific stands examined. However, the growth of Saccharina was not affected by the proportion of Sargassum in mixed stands. They concluded that Saccharina was not impacted significantly by the alien species while Sargassum benefited from growth in mixed stands. Experimental manipulation of subtidal algal canopies in the San Juan Islands, Washington State, USA, showed that Sargassum muticum reduced the abundance of native macroalgae, including the kelp Laminaria bongardiana due to shading. However, the experimental removal of Sargassum resulted in the recovery of native species within about one year (Britton-Simmons, 2004; Engelen et al., 2015). The negative effects of Sargassum muticum on native macroalgae are mainly due to competition for light, rather than changes in nutrient availability, sedimentation or water flow (Britton-Simmons, 2004; Engelen et al., 2015).    

Undaria pinnatifida (Wakame or Asian kelp) is a large brown seaweed and an Invasive Non-Indigenous Species (INIS) that could out-compete native UK kelp species (see Farrell & Fletcher, 2006; Thompson & Schiel, 2012; Brodie et al., 2014; Hieser et al., 2014; Arnold et al., 2016; Epstein & Smale, 2017; Epstein & Smale, 2018; Kraan, 2017; Epstein et al., 2019a,b; Tidbury, 2020). Undaria pinnatifida originates from Japan but is currently established on the coastlines of New Zealand, Australia, Northern France, Spain, Italy, the UK, Portugal, Belgium, Holland, Argentina, Mexico, and the USA (De Leij et al., 2017). Undaria pinnatifida was first recorded in the UK in the Hamble Estuary in 1994 (Macleod et al., 2016) and has since proliferated along UK coastlines. One year after its discovery at the Queen Anne Battery marina, Plymouth, it became a major fouling plant on pontoons (Minchin & Nunn, 2014). Although initially restricted to artificial habitats, such as marinas and ports, it is now widespread in natural habitats in several areas, including Plymouth Sound. 

Undaria pinnatifida seems to settle better on artificial substrata (e.g., floats, marinas or piers) than on natural rocky shores among local kelps (Vaz-Pinto et al., 2014). It is found predominantly in low intertidal to shallow subtidal habitats (Epstein et al., 2019b) and is significantly more abundant on artificial substrata compared to natural rocky substrata (Heiser et al., 2014; Epstein & Smale, 2018). James (2017) suggested that Undaria pinnatifida could out-compete native species on artificial substrata (such as marinas and wharf structures). In Plymouth, UK, De Leij et al. (2017) found that natural habitats with dense native macroalgal canopies, such as Laminaria hyperborea, Laminaria ochroleuca, Laminaria digitata and Saccharina latissima had more resistance to Undaria pinnatifida invasion than disturbed or sparse canopies, due to limited space and light availability for Undaria pinnatifida recruits. However, the dense canopies did not always prevent the invasion of Undaria pinnatifida as sporophytes were still recorded within dense Laminaria canopies, so that canopy disturbance was not always required (De Leij et al., 2017; Epstein & Smale, 2018). 

Undaria behaves as a winter annual, and recruitment occurs in winter followed by rapid growth through spring, maturity and then senescence through summer, with only the microscopic life stages persisting through autumn. It exhibits multiple dispersal strategies, such as short-range spore dispersal, and long-range dispersal as whole drift plants or fragments. Undaria pinnatifida has spread rapidly across the UK and Europe, resulting in community-wide responses and impacts (Vaz-Pinto et al., 2014; Epstein & Smale, 2017). Its impacts are complex and context-specific, depending on space, time, and taxa present in the introduced location (Epstein & Smale, 2017; Teagle et al., 2017; Tidbury, 2020). 

Undaria pinnatifida has a wide physiological niche meaning it can occur in both coastal and estuarine environments showing tolerance for varying salinities, turbidity and siltation (Heiser et al., 2014; Epstein & Smale, 2018). Undaria pinnatifida has a greater preference for sites sheltered with low wave exposure and weak tidal streams (Heiser et al., 2014; Epstein & Smale, 2018). In natural habitats, Undaria pinnatifida was not recorded if the wave fetch was greater than 642 km but increased in abundance and cover in very sheltered sites (Epstein & Smale, 2018). 

In St Malo, France, there was evidence that Undaria pinnatifida co-existed with Laminaria hyperborea under certain conditions (Castric-Fey et al., 1993). Epstein & Smale (2018) also observed that Undaria pinnatifida was relatively common (abundance of >70 individuals per 25 m transect) at three sites in Devon, UK (Jennycliff, Bovisand and Beacon Cove) where Laminaria spp. were abundant (40-79%) or superabundant (>80%), which suggested that Undaria pinnatifida could co-exist within refugia amongst areas with dense Laminaria spp..

In Plymouth Sound, UK, Heiser et al. (2014) observed that Laminaria hyperborea was significantly less abundant at sites with the presence of Undaria pinnatifida, with only ca 0.5 Laminaria hyperborea individuals per m2 present compared to ca 8 individuals per m2 at sites without the presence Undaria pinnatifida. However, the results from their correlation study only showed that the species were not found together (pers. comm., Epstein 2021). Whereas exclusion and succession experiments on reefs tell us that Laminaria spp. exclude Undaria pinnatifida, not the other way around. Epstein & Smale (2018) reported that in Devon, UK, persistent, dense, and intact Laminaria spp. canopies in rocky reef habitats exerted a strong influence over the presence/absence, abundance, and percentage cover of Undaria pinnatifida. A dense canopy of native kelp restricts the proliferation of Undaria pinnatifida and disturbance of the canopy is often the key to the recruitment of Undaria pinnatifida. Epstein et al. (2019b) reported that Undaria pinnatifida density and biomass were significantly negatively correlated with the sum of all Laminaria spp. in Plymouth, UK. The evidence indicated that native Laminaria spp. canopies in the UK inhibited Undaria pinnatifida and implied that Undaria pinnatifida was opportunistic but competitively inferior (Farrell & Fletcher, 2006; Heiser et al., 2014; Minchin & Nunn, 2014; De Leij et al., 2017; Epstein & Smale, 2018; Epstein et al., 2019b). However, Epstein et al. (2019b) also noted that Laminaria hyperborea had a non-significant positive relationship with Undaria pinnatifida due to low densities of Laminaria hyperborea across the study area, resulting in insufficient data.

In Plymouth Sound (UK), Epstein et al. (2019b) found that within its depth range (+1 to –4 m), Undaria pinnatifida co-existed with seven species of canopy-forming brown macroalgae, including Laminaria hyperborea. De Leij et al. (2017) found that natural habitats with dense native macroalgal canopies, such as Laminaria hyperborea had more resistance to Undaria pinnatifida invasion than disturbed or sparse canopies, due to limited space and light availability for Undaria recruits. However, the dense canopies will not prevent the invasion of Undaria, as sporophytes were still recorded within dense Laminaria canopies, and this suggests that canopy disturbance is not always required.

Undaria pinnatifida was successfully eradicated on a sunken ship in Chatham Islands, New Zealand, by applying a heat treatment of 70°C (Wotton et al., 2004). However, numerous other eradication attempts have failed and as noted by Fletcher & Farrell (1998), once established Undaria pinnatifida resists most attempts at long-term removal. 

Sensitivity Assessment. The above evidence suggests that Undaria pinnatifida can co-exist with Laminaria hyperborea where sites are suitable e.g., Laminaria hyperborea in Plymouth Sound, UK. A dense kelp canopy may restrict or slow the proliferation of Undaria pinnatifida, however, there is mixed evidence of its colonization with Laminaria hyperborea beds and in some areas, a lower abundance of Laminaria hyperborea may result in increased Undaria pinnatifida growth.  

This Laminaria hyperborea dominated biotope (IR.MIR.KR.Lhyp.GzFt) is found within the upper infralittoral with moderately strong to weak tidal streams and moderate exposure to wave action. The evidence above suggests that Sargassum muticum prefers wave sheltered, shallow sites in the sublittoral fringe. It was reported to out-compete and replace Saccharina latissima in the Limfjorden and achieve maximum abundance at 1-4 m (Staehr et al., 2000; Engelen et al., 2015) but no evidence of the effects of Sargassum on Laminaria hyperborea beds was found. However, Sargassum is unlikely to survive either the grazing pressure or the wave exposed conditions that characterize this biotope. 

Undaria has the potential to colonize and co-exist in refugia within Laminaria sp. dominated habitats, especially in shallow examples of their biotopes, sheltered from wave action. However, it is unlikely to survive either the grazing pressure or the wave exposure that characterizes this biotope. A reduction in grazing pressure, e.g., due to storms, will allow colonization by opportunistic algae such as Sargassum and Undaria in shallow, wave sheltered examples of the biotope, probably together with other native opportunistic kelps (e.g., Saccharina). However, the Laminaria hyperborea would probably outcompete the opportunists and the biotope would return to a Laminaria hyperborea dominated biotope. However, while grazing persists it is unlikely that either Sargassum or Undaria would gain foot-hold.  Therefore, resistance to Sargassum or Undaria is assessed as ‘High’, resilience as 'High', and sensitivity is assessed as ‘Not Sensitive’. Overall, confidence is assessed as ‘Low’ due to evidence of variation and the site-specific nature of competition between native kelps and Undaria pinnatifida. 

High
Low
NR
NR
Help		High
High
High
High
Help		Not sensitive
Low
NR
NR
Help
Introduction of microbial pathogens [Show more]

Introduction of microbial pathogens

Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail

Evidence

Galls on the blade of Laminaria hyperborea and spot disease are associated with the endophyte Streblonema sp. although the causal agent is unknown (bacteria, virus or endophyte). The resultant damage to the blade and stipe may increase losses in storms. The endophyte inhibits spore production and, therefore, recruitment and recoverability (Lein et al., 1991).

Echinus esculentus is susceptible to 'Bald-sea-urchin disease', which causes lesions, loss of spines, tube feet, pedicellariae, destruction of the upper layer of skeletal tissue and death. It is thought to be caused by the bacteria Vibrio anguillarum and Aeromonas salmonicida. Bald sea-urchin disease was recorded from Echinus esculentus on the Brittany Coast. Although associated with mass mortalities of Strongylocentrotus franciscanus in California and Paracentrotus lividus in the French Mediterranean it is not known if the disease induces mass mortality (Bower, 1996).

Sensitivity assessment. Resistance to the pressure is considered ‘Medium’, and resilience ‘High’. The sensitivity of this biotope to the introduction of microbial pathogens is assessed as ‘Low’.

Medium
Medium
High
High
Help		High
High
Low
High
Help		Low
Medium
High
Low
Help
Removal of target species [Show more]

Removal of target species

Benchmark. Removal of species targeted by fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Christie et al. (1998) observed Laminaria hyperborea habitat regeneration following commercial Laminaria hyperborea trawling in south Norway. Within the study area trawling removed all large canopy-forming adult Laminaria hyperborea, however, sub-canopy recruits were unaffected. Within 2-3 years of harvesting, a new canopy had formed 1 m off the seabed. The associated holdfast communities recovered in 6 years however the epiphytic stipe community did not fully recover within the same time period. Christie et al., (1998) suggested that kelp habitats were relatively resistant to direct disturbance of Laminaria hyperborea canopy.

Recurrent disturbance occurring at a smaller time scale than the recovery period of 2-6 years (stated above) could extend recovery time. Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared however within 2 years of clearance the blocks were dominated by Laminaria hyperborea (Kain, 1975). Leinaas & Christie (1996) also observed Laminaria hyperborea re-colonization of ‘urchin barrens’, following removal of urchins. The substratum was initially colonized by filamentous macroalgae and Saccharina latissima however after 2-4 years Laminaria hyperborea dominated the community.

Following disturbance or in areas were recurrent rapid disturbance occurs Laminaria hyperborea recruitment could also be affected by interspecific competitive interactions with Invasive Non-Indigenous Species or ephemeral algal species (Smale et al., 2013; Brodie et al., 2014), however, evidence for this is limited and thus not included within this assessment. Removal of kelp canopies can also result in the decline of the associated epiphytic and understorey red algal species (Hawkins & Harkin, 1985). Removal of Echinus esculentus from IR.MIR.KR.Lhyp.GzFt/Pk could also reduce grazing pressure and change the character of the biotope.

Sensitivity assessment.  Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’.  The sensitivity of this biotope to damage to seabed surface features is assessed as ‘Medium’.

Low
High
High
High
Help		Medium
High
High
High
Help		Medium
High
High
High
Help
Removal of non-target species [Show more]

Removal of non-target species

Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Incidental/accidental removal of Laminaria hyperborea from extraction of other marine resources, e.g. fisheries or aggregates, is likely to cause similar effects to that of direct harvesting of Laminaria hyperborea; hence, the same evidence has been used for both pressure assessments.

Christie et al. (1998) observed Laminaria hyperborea habitat regeneration following commercial Laminaria hyperborea trawling in south Norway. Within the study area trawling removed all large canopy-forming adult Laminaria hyperborea, however, sub-canopy recruits were unaffected. Within 2-6years of harvesting, a new canopy had formed 1m off the seabed. The associated holdfast communities recovered in 6 years however the epiphytic stipe community did not fully recover within the same time period. Christie et al., (1998) suggested that kelp habitats were relatively resistant to direct disturbance of Laminaria hyperborea canopy.

Recurrent disturbance occurring at a smaller time scale than the recovery period of 2-6 years (stated above) could extend recovery time. Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared however within 2 years of clearance the blocks were dominated by Laminaria hyperborea (Kain, 1975). Leinaas & Christie (1996) also observed Laminaria hyperborea re-colonization of ‘urchin barrens’, following removal of urchins. The substratum was initially colonized by filamentous macroalgae and Saccharina latissima however after 2-4 years Laminaria hyperborea dominated the community.

Following disturbance or in areas were recurrent rapid disturbance occurs Laminaria hyperborea recruitment could also be affected by interspecific competitive interactions with Invasive Non-Indigenous Species or ephemeral algal species (Smale et al., 2013; Brodie et al., 2014), however, evidence for this is limited and thus not included within this assessment. Removal of kelp canopies can also result in the decline of the associated epiphytic and understorey red algal species (Hawkins & Harkin, 1985). Removal of Echinus esculentus from IR.MIR.KR.Lhyp.GzFt/Pk could also reduce grazing pressure and change the character of the biotope.

Sensitivity assessment.  Resistance to the pressure is considered ‘Low’, and resilience ‘Medium’.  The sensitivity of this biotope to damage to seabed surface features is assessed as ‘Medium’.

Low
High
High
High
Help		Medium
High
High
High
Help		Medium
High
High
High
Help

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Citation

This review can be cited as:

Stamp, T.E. & Hiscock, K., Tyler-Walters, H., & Burdett, E.G. 2023. Grazed Laminaria hyperborea forest with coralline crusts on upper infralittoral rock. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25-11-2024]. Available from: https://marlin.ac.uk/habitat/detail/333

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Last Updated: 19/10/2023