Saccharina latissima, Chorda filum and dense red seaweeds on shallow unstable infralittoral boulders or cobbles

Summary

UK and Ireland classification

Description

Seasonally disturbed unstable boulders and cobbles in very shallow water dominated by the fast-growing brown seaweed Chorda filum together with the kelp Saccharina latissima. The brown seaweed Desmarestia aculeata is also typical of this disturbed environment as well as encrusting coralline algae and brown crusts. Beneath the prolific growth of Chorda filum, red and brown seaweeds densely cover many of the boulders, cobbles and pebbles. Other sediment-tolerant seaweeds such as species from the Ectocarpales (brown filamentous seaweeds) and the red seaweeds Chondrus crispusPhyllophora pseudoceranoïdesDilsea carnosa and Corallina officinalis are normally present. Other red seaweeds which can be found here include Chondria dasyphyllaVertebrata byssoidesCarradoriella elongataCeramium nodolosum, Cystoclonium purpureum, Heterosiphonia plumosaRhodomela confervoides and Plocamium cartilagineum. The brown seaweeds Punctaria sp. and Cladostephus spongiosus are generally present. The faunal component of this biotope is typically sparse. The starfish Asterias rubens and the crabs Pagurus bernhardus and Necora puber are amongst the most conspicuous animals. The encrusting bryozoan Electra pilosa colonizes many of the algae along with the ascidian Botryllus schlosseri. Occasionally, the polychaete Lanice conchilega may occur in the sand between pebbles, and the anthozoan Urticina felina may be found amongst pockets of gravel along with the gastropod Steromphala cineraria. At some sites, the rock beneath the algae can be occupied by the tube-building polychaete Spirobranchus triqueter. This biotope is also present at other open coast sites around the UK where suitable shallow, seasonally stable boulders, cobbles and pebbles occur. Typical examples of this biotope occur on the shallowest areas of the Sarns in Cardigan Bay, Wales, where reef crests are formed by embedded and mobile boulders, together with cobbles and pebbles in between (typically at 2-3m depth).

This biotope occurs in shallow water, often on the crest of an infralittoral boulder/cobble bank and as such will not have any biotope 'above' it. More mobile areas of smaller boulders, cobbles and pebbles nearby may support dense ephemeral red seaweeds (EphR) or robust scour-tolerant red seaweeds on sand-covered rock (ProtAhn). The Halidrys siliquosa biotope XKHal also thrives under similar conditions, extending deeper than the shallow SlatChoR biotope. Deeper still in the circalittoral zone encrusting fauna is found on highly mobile mixed substrata (SpiB). At a few sites, this biotope can occur within more extensive maerl beds (SS.SMp.Mrl) but more commonly is surrounded by sandy sediments (SS.SSa). This biotope will change markedly with the seasons. During the winter months, boulders and cobbles will be storm-battered and overturned and much of the biota dislodged from the rocks. During more stable conditions in the late spring and summer months, the fast-growing seaweeds that characterize this biotope (Chorda filum and Saccharina latissima in particular) will be quick to re-establish, growing at a phenomenal rate. The seasonal disturbance of the substratum prevents a stable Laminaria hyperborea forest from developing. (Information from JNCC, 2015; 2022). 

Depth range

0-5 m

Additional information

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Listed By

Habitat review

Ecology

Ecological and functional relationships

The species present in this biotope thrive particularly in conditions of disturbance. They are mainly annual species with rapid growth or are perennial species that may die back in winter and persist as crusts or basal portions that survive abrasion during winter storms. Grazing species such as sea urchins do not survive well in conditions of abrasion and so seaweeds can thrive.

Seasonal and longer term change

It is expected that there will be considerable reduction in the abundance of foliose seaweeds especially following the summer. The reduction is partly because of grazing, partly seasonal disintegration of fronds and partly abrasion. Annual seaweeds start to colonize and perennial seaweeds to regrow in about April and can be expected to be fully grown by May.

Habitat structure and complexity

This is a complex habitat with semi-stable hard substratum supporting epibiota through to sediments supporting infauna. The fronds of seaweeds also provide significant surfaces especially for epibiota and for gastropods. The holdfasts of Saccharina latissima and, where present, of Saccorhiza polyschides provide a habitat for cryptic animal species.

Productivity

This biotope would appear to be productive of organic matter from seaweeds especially.

Recruitment processes

The dominant and characteristic species are recruited from planktonic larvae and spores. Other species such as fish and crustaceans are mainly transitory once settled.

Time for community to reach maturity

Providing that sources of larvae, spores and mobile animals are nearby, the biotope would develop rapidly on new substrata so that, in appearance based on visually dominant species, it would be likely to be established in a year. However, recruitment of a full range of species, especially molluscs and some algae would take longer so that a dynamic stability would probably be reached only after about three years.

Additional information

No information was available on the infauna associated with this biotope although it is expected that species will be tolerant of displacement.

Preferences & Distribution

Habitat preferences

Depth Range 0-5 m
Water clarity preferences
Limiting Nutrients No information
Salinity preferences Full (30-40 psu)
Physiographic preferences Open coast
Biological zone preferences Upper infralittoral
Substratum/habitat preferences Large to very large boulders, Small boulders, Cobbles, Pebbles, Gravel / shingle
Tidal strength preferences Moderately strong 1 to 3 knots (0.5-1.5 m/sec.)
Wave exposure preferences Moderately exposed
Other preferences

Additional Information

See Sanderson et al. (2001) for detailed descriptions of the biotope

Species composition

Species found especially in this biotope

    Rare or scarce species associated with this biotope

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    Additional information

    The biotope may be conspicuously characterized by dense red algae (often bleached by sunlight) in spring and summer. These algae are ephemeral and especially include Cystoclonium purpureum and Brongniartella byssoides as well as the brown alga Desmarestia aculeata.

    Sensitivity review

    Sensitivity characteristics of the habitat and relevant characteristic species

    IR.HIR.KSed.SlatChoR is within the sediment affected or disturbed kelp and seaweed communities (IR.HIR.KSed) habitat complex. Shallow boulders and cobbles are seasonally mobilised and the opportunistic brown seaweeds; Saccharina latissima (formerly Laminaria saccharina) and Chorda filum proliferate. The seasonal mobility of the substrata dislodges the resident community and inhibits the establishment of Laminaria hyperborea biotopes. As stability increases Laminaria hyperborea can become more abundant (Connor et al., 2004).

    Due to the disturbed nature of IR.HIR.KSed biotopes the understorey community can be locally variable and defined by scour tolerant or ephemeral seaweeds, such as; Brown filamentous seaweeds (Ectocarpales), Chondrus crispus, Corallina officinalis, Dilsea carnosa, encrusting coralline algae and Phyllophoras pseudoceranoides. Faunal diversity and abundance are also generally low and typically limited to; encrusting bryozoans, Spirobranchus triqueter and other scour tolerant fauna (Connor et al., 2004).

    In undertaking this assessment of sensitivity, an account is taken of knowledge of the biology of all characterizing species/taxa in the biotope. However, 'indicative species' are particularly important in undertaking the assessment because they have been subject to detailed research. For this sensitivity assessment the opportunistic brown seaweeds; Saccharina latissima & Chorda filum are the primary foci of research. Examples of other important species groups are mentioned where appropriate.

    Resilience and recovery rates of habitat

    Saccharina latissima (formerly Laminaria saccharina) and Chorda filum are opportunistic seaweeds which have relatively fast growth rates when compared to other perennial species, and can dominate in areas subject to recurrent disturbance. Saccharina lattisima is a perennial kelp which can reach maturity in 15-20 months ((Sjøtun, 1993) and has a life expectancy of 2-4 years (Parke, 1948). Saccharina lattisma is widely distributed in the north Atlantic from Svalbard to Portugal (Birket et al., 1998; Conor et al., 2004; Bekby & Moy 2011; Moy & Christie 2012). Chorda filum has a widely distributed across the northern hemisphere (Algae Base, 2015). In the North Atlantic specifically, Chorda filum is recorded from Svalbard (Fredriksen et al., 2014) to Northern Portugal (Araújo et al, 2009).  Chorda filum is an annual seaweed, completing it’s life cycle in a single season (Novaczek et al., 1986).

    Saccharina lattisma and Chorda filum have heteromorphic life strategies (Bikett et al., 1988). Mature sporophytes broadcast spawn zoospores from reproductive structures known as sori (South & Burrows, 1967; Birket et al., 1998). Zoospores settle onto rock and develop into gametophytes, which following fertilization germinate into juvenile sporophytes. Laminariale zoospores are expected to have a large dispersal range, however, zoospore density and the rate of successful fertilization decreases exponentially with distance from the parental source (Fredriksen et al., 1995). Hence, recruitment can be influenced by the proximity of mature kelp beds producing viable zoospores (Kain, 1979; Fredriksen et al., 1995). Saccharina lattisma recruits appear in late winter early spring beyond which is a period of rapid growth, during which sporophytes can reach a total length of 3m (Werner & Kraan, 2004), in late summer and autumn growth rates slow and spores are released from autumn to winter (Parke, 1948; Lüning, 1979; Birket et al., 1998). The overall length of the sporophyte may not change during the growing season due to marginal erosion but the growth of the blade has been measured at 1.1 cm/day, with a total length addition of ≥2.25m per year (Birket et al., 1998). Chorda filum recruits appear from February (South & Burrows, 1967), beyond which is a period of rapid growth during which sporophytes can reach a length of ≤6m (South & Burrows, 1967). In culture Chorda fillum can reach reproductive maturity and produce zoospores within 186 days (ca 6 months) of settlement, however, the time taken to reach maturity may be locally variable (South & Burrows, 1967). In nature sporophytes growth slows/stops from October and sporophytes may begin to die off (South & Burrows, 1967; Novaczek et al., 1986).

    Saccharina lattisma can be quite ephemeral in nature and appear early in algal succession. For example, Leinaas & Christie (1996) removed Strongylocentrotus droebachiensis from “Urchin Barrens” and observed a succession effect. Initially, the substratm was colonized by filamentous algae, after a couple of weeks these were out-competed and the habitat dominated by Saccharina latissima, however, this was subsequently out-competed by Laminaria hyperborea. In the Isle of Man, 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. Saccharina lattisma was an early colonizer, however within 2 years of clearance the blocks were dominated by Laminaria hyperborea.

    In 2002, a 50.7-83% decline of Saccharina latissima was discovered in the Skaggerak region, South Norway (Moy et al., 2006; Moy & Christie, 2012). Survey results indicated a sustained shift from Saccharina latissima communities to those of ephemeral filamentous algal communities. The reason for the community shift was unknown, low water movement in wave and tidally sheltered areas combined with the impacts of dense human populations, e.g. increased land run-off, was suggested to be responsible for the dominance of ephemeral turf macro-algae. Multiple stressors such as eutrophication, increasing regional temperature, increased siltation and overfishing may also be acting synergistically to cause the observed habitat shift.

    Resilience assessment. Saccharina latissima and Chorda filum are opportunistic species with rapid colonization and growth rates (South & Burrows, 1967; Birket et al., 1998). Chorda filum is an annual seaweed, completing it’s life cycle within a single season. Saccharina latissima has been shown to be an early colonizer within algal succession, appearing within 2 weeks of clearance. Resilience has therefore been assessed as ‘High’ for all levels of resistance.

    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

    The temperature isotherm of 19-20 °C has been reported as limiting Saccharina latissima geographic distribution (Müller et al., 2009). Gametophytes can develop in ≤23°C (Lüning, 1990) however the optimal temperature range for sporophyte growth is 10-15 °C (Bolton & Lüning, 1982). Bolton & Lüning (1982) experimentally observed that sporophyte growth was inhibited by 50-70% at 20 °C and following 7 days at 23 °C all specimens completely disintegrated. In the field Saccharina latissima has shown significant regional variation in its acclimation to temperature changes, for example Gerard & Dubois (1988) observed sporophytes of Saccharina latissima which were regularly exposed to ≥20 °C could tolerate these temperatures, whereas sporophytes from other populations which rarely experience ≥17 °C showed 100% mortality after 3 weeks of exposure to 20 °C. Therefore the response of Saccharina latissima to a change in temperatures is likely to be locally variable.

    In experiments, Lüning (1980) observed that Chorda filum could not reproduce at 15-20 °C but found that sporophytes could tolerate ≤26 °C.

    IR.HIR.KSed.Slat.ChoR 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 in the UK (Beszczynska-Möller & Dye, 2013). The effect of this pressure is likely to be regionally variable.

    Sensitivity assessment. Ecotypes of Saccharina lattisma have been shown to have different temperature optimums (Dubois, 1988). Both a 2 & 5 °C increase in temperature when combined with high UK summer temperatures in the south of the UK could cause large scale mortality of Saccharina lattisma and inhibit Chorda filum reproduction. Resistance has been assessed as ‘None’, Resilience as ‘High’. Sensitivity has been assessed as ‘Medium’.

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    Medium
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    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

    Saccharina lattissima and Chorda filum are widespread throughout the arctic. Saccharina lattissima has a lower temperature threshold for sporophyte growth at 0 °C (Lüning, 1990). Chorda filum sporophytes can also tolerate 0 °C, Novaczek et al., (1986) observed that 99% of newly settled zoospores died at 0 °C but sporophytes transferred from 5 °C to 0 °C remained healthy and continued to grow for a period of 2 months. Novaczek et al., (1986) therefore demonstrated that sporophytes could tolerate exposure to low (≥0°C) temperatures, but that exposure could have negative effects on larval survival and recruitment processes. Subtidal red algae can survive at -2°C (Lüning, 1990; Kain & Norton, 1990). The distribution and temperature tolerances of these species suggests they likely be unaffected by temperature decreases assessed within this pressure.

    Sensitivity assessment. Resistance has been assessed as ‘High’, resilience as ‘High’”. Sensitivity has been assessed as ‘Not Sensitive’.

     

    High
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    High
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    Not sensitive
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    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

    Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu. Saccharina latissima showed high photosynthetic ability at >80% of the control levels between 25-55 psu. However, Birkett et al. (1998) suggested that kelps are stenohaline and therefore long-term increases in salinity may be detrimental.

    Chorda filum can be found in rock pools (South & Burrows, 1967). High air temperatures cause surface evaporation of water from rock pools, so that salinity steadily increases. The extent of temperature and salinity change is affected by the frequency and time of day at which tidal inundation occurs. If high tide occurs in early morning and evening the diurnal temperature follows that of the air, whilst high water at midday suddenly returns the temperature to that of the sea (Pyefinch, 1943). It should be noted however that local populations may be acclimated to the prevailing salinity regime and may therefore exhibit different tolerances to other populations subject to different salinity conditions and therefore caution should be used when inferring tolerances. However, it is likely that Chorda filum is tolerant of short-term salinity increases.

    Sensitivity assessment. The evidence suggests that Saccharina latissima and Chorda filum can tolerate short-term exposure to hypersaline conditions (≥40‰-MNCR full salinity). An increase in salinity to ≥40‰ long-term may however be above the optima for characterizing species and cause a decline in growth, and possibly loss of red algae and a reduction in species diversity. Resistance has been assessed as ‘Medium’, resilience as ‘High’. The sensitivity of this biotope to an increase in salinity has been assessed as ‘Low’.

    Medium
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    High
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    Low
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    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

    Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu . Saccharina latissima showed high photosynthetic ability at >80% of the control levels between 25-55 psu. Hyposaline treatment of 10-20 psu led to a gradual decline of photosynthetic ability. After 2 days at 5 psu Saccharina latissima showed a significant decline in photosynthetic ability at approx. 30% of control. After 5 days at 5 psu Saccharina latissima specimens became bleached and showed signs of severe damage. The affect of long-term salinity changes (>5 days) or salinity >60 PSU on Saccharina latissima’ photosynthetic ability was not tested. The experiment was conducted on Saccharina latissima from the Arctic, and the authors suggest that at extremely low water temperatures (1-5°C) macroalgae acclimation to rapid salinity changes could be slower than at temperate latitudes. It is therefore possible that resident Saccharina latissima of the UK maybe be able to acclimate to salinity changes more effectively and quicker.

    Chorda filum is tolerant of low salinities (Hayren, I940; Norton & South, 1969), and has been recorded at Björnholm, Finland where salinity has been recorded as low as 5.15%o (Hayren, I940). Norton & South (1969) observed (experimentally) that Chorda filum could develop sporophytes at ≥5%o, however at low salinities the time taken to develop into sporophytes was slower than at full salinities (5%o=65 days, 35%o=16 days) and below 9% sporophytes did not grow above 2mm in length.

    Sensitivity assessment. A decrease in one MNCR salinity scale from “Full Salinity” (30-40psu) to “Reduced Salinity” (18-30 psu) may inhibit Saccharina lattissima photosynthesis and hence growth. Chorda filum is highly tolerant of low salinity and is unlikely to be affected. Resistance has been assessed as ‘Medium’ resilience as ‘High’. Sensitivity of this biotope to a decrease in salinity has been assessed as ‘Low’.

    Medium
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    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

    Peteiro & Freire (2013) measured Saccharina latissima growth from 2 sites, the 1st had maximal water velocities of 0.3 m/sec and the 2nd 0.1 m/sec. At site 1 Saccharina latissima had significantly larger biomass than at site 2 (16 kg/m to 12 kg/m respectively). Peteiro & Freire (2013) suggested that faster water velocities were beneficial to Saccharina latissima growth. However, Gerard & Mann (1979) measured Saccharina latissima productivity at greater water velocities and found Saccharina latissima productivity is reduced in moderately strong tidal streams (≤1 m/sec) when compared to weak tidal streams (<0.5 m/sec).

    Chorda filum sporophytes often grow on unstable objects, such as pebbles and shell. Owing to the typically unstable substratum which Chorda filum grows on, whole populations can be moved during storms and deposited in more sheltered locations where development will continue (South & Burrows, 1967). The survival of Chorda filum sporophytes following transport of their attached substrata indicates the species is relatively tolerant to changes in water flow or wave action.

    Sensitivity assessment. IR.HIR.KSed.SlatChoR is recorded from moderately strong (0.5-1.5m/sec)-weak tidal streams (<0.5m/sec).A change of 0.1m/s to 0.2m/s is not likely to dramatically affect biotope structure. Resistance has been assessed as ‘High’, resilience as ‘High’. Sensitivity has been assessed as ‘Not Sensitive’.

    High
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    Not sensitive
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    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

    IR.HIR.KSed.SlatChoR is recorded from 0-10m Below Chart Datum (BCD) (Connor et al., 2004). Both Saccharina latissima and Chorda filum can grow in the sub-littoral fringe (South & Burrows, 1967) and as such would likely be exposed during some low tides.

    An increase in emergence will result in an increased risk of desiccation and mortality of Saccharina latissima and Chorda filum. Removal of canopy forming seaweeds has also been shown to increase desiccation and mortality of the understorey macro-algae (Hawkins & Harkin, 1985). Providing that suitable substrata are present, the biotope is likely to re-establish further down the shore within a similar emergence regime to that which existed previously.

    Sensitivity assessment. Resistance has been assessed as ‘Medium’. Resilience as ‘High’. The sensitivity of this biotope to a change in emergence is considered as ‘Low’.

     

    Medium
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    High
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    Low
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    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

    IR.HIR.KSed.SlatChoR is recorded from extreme wave exposed-sheltered sites (Connor et al., 2004). Birket et al., (1998) suggested that Saccharina latissima is rarely present in areas of wave exposure, where it is out-competed by Laminaria hyperborea. However, the seasonal unstable nature of the substrata within IR.HIR.KSed.SlatChoR is likely to inhibit growth of Laminaria hyperborea and allow Saccharina latissima to opportunistically colonize rock particles. Chorda filum sporophytes often grow on unstable objects, such as pebbles and shell. Owing to typically unstable substrate which Chorda filum grows on, whole populations can be moved during storms and deposited in more sheltered locations where development will continue (South & Burrows, 1967). The survival of Chorda filum sporophytes following transport of their attached substrata indicates the species is relatively tolerant to changes in water flow or wave action.

    Sensitivity assessment. A large scale increase in local wave height may increase local sediment mobility, potentially increase dislodgment or relocation of sporophytes (South & Burrows, 1967; Birket et al., 1998). However, an increase in nearshore significant wave height of 3-5% is not likely to have a significant effect on biotope structure. Resistance has been assessed as ’High’, Resilience as ‘High’. Sensitivity has been assessed as ‘Not Sensitive’ at the benchmark level.

    High
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    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 al,. (1999) reported that Hg was very toxic to macrophytes. Similarly, Hopkin & Kain (1978) demonstrated sub-lethal effects of heavy metals on kelp 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). 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. Thompson & Burrows (1984) observed the growth of Saccharina latissima sporophyte growth was significantly inhibited at 50 µg Cu /l, 1000 µg Zn/l and 50 µg Hg/l. Zoospores were found to be more intolerant and significant reductions in survival rates were observed at 25 µg Cu/l, 1000 µg Zn/l and 5 µg/l.

    Not Assessed (NA)
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    Not assessed (NA)
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    Not assessed (NA)
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    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.

    The mucilaginous slime layer coating of laminariales 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 kelps. Similarly, surveys of subtidal communities at a number sites between 1-22.5m below chart datum showed no noticeable impacts of the Sea Empress oil spill and clean up (Rostron & Bunker, 1997) or during the experimental release of untreated oil in Baffin Island, Canada (Cross et al., 1987). Laboratory studies of the effects of oil and dispersants on several red algae species (Grandy 1984) concluded that they were all sensitive to oil/ dispersant mixtures, with little differences between adults, sporelings, diploid or haploid life stages.

    Not Assessed (NA)
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    Not assessed (NA)
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    Not assessed (NA)
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    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). Saccharina latissima has also been found to be sensitive to antifouling compounds. Johansson (2009) exposed samples of Saccharina latissima to several antifouing compounds, observing chlorothalonil, DCOIT, dichlofluanid and tolylfluanid inhibited photosynthesis. Exposure to Chlorothalonil and tolylfluanid, was also found to continue inhibiting oxygen evolution after exposure had finished, and may cause irreversible damage.

    Smith (1968) observed that epiphytic and benthic red algae were intolerant of dispersant or oil contamination during 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.

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

    Radionuclide contamination

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

    Evidence

    No evidence

    No evidence (NEv)
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    Not relevant (NR)
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    No evidence (NEv)
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    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)
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    Not assessed (NA)
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    Not assessed (NA)
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    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 can 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). 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).

    Sensitivity Assessment. Reduced oxygen levels are likely to inhibit photosynthesis and respiration but not cause a loss of the macroalgae population directly. Resistance has been assessed as ‘High’, Resilience as ‘High’. Sensitivity has been assessed as ‘Not sensitive’ at the benchmark level.

    High
    Medium
    High
    High
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    High
    High
    High
    High
    Help
    Not sensitive
    High
    High
    High
    Help
    Nutrient enrichment [Show more]

    Nutrient enrichment

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

    Evidence

    Conolly & Drew (1985) found Saccharina latissima sporophytes had relatively higher growth rates when in close proximity to a sewage outlet in St Andrews, UK when compared to other sites along the east coast of Scotland. At St Andrews, nitrate levels were 20.22µM, which represents an approx 25% increase when compared to other comparable sites (approx 15.87 µM). Handå et al. (2013) also reported Saccharina latissima sporophytes grew approx 1% faster per day when in close proximity to Salmon farms, where elevated ammonium can be readily absorbed.  Read et al. (1983) reported after the installation of a new sewage treatment  works which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent. Bokn et al. (2003) conducted a nutrient loading experiment on intertidal fucoids. Within 3 years of the experiment no significant effect was observed in the communities, however, 4-5 years into the experiment a shift occurred from perennials to ephemeral algae occurred. Although Bokn et al. (2003) focussed on fucoids the results could indicate that long-term (>4 years) nutrient loading can result in community shift to ephemeral algae species. Disparities between the findings of the aforementioned studies are likely to be related to the level of organic enrichment, however, could also be time dependant.

    Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009) however also highlighted that macroalgal communities are relatively tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009 and references therein).

    At the time of writing little direct evidence for the effects of nutrient enrichment on Chorda filum could be found. Bonsdorff et al., (2002) noted that chronic eutrophication in coastal areas can cause an increased abundance and dominance of filamentous algae, resulting in a decline of other resident algal communities. For example in Puck Bay, Poland Chorda filum, Fucus vesiculosus and Furcellaria

    Lumbricalis have been absent sine the 1970’s and the filamentous species Ectocarpus spp. and Pilayella spp. now dominates the area (Ciszewski et al., 1992).

    Sensitivity assessment. Although short-term exposure (<4 years) to nutrient enrichment may not affect seaweeds directly, indirect effects such as turbidity may significantly affect photosynthesis and result in reduced growth and reproduction and increased competition from fast growing but ephemeral species. However, this biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with good status as defined by the WFD.

    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

    Read et al. (1983) reported after the installation of a new sewage treatment  works which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent. Bokn et al. (2003) conducted a nutrient loading experiment on intertidal fucoids. Within 3 years of the experiment no significant effect was observed in the communities, however, 4-5 years into the experiment a shift occurred from perennials to ephemeral algae occurred. Although Bokn et al. (2003) focussed on fucoids the results could indicate that long-term (>4 years) nutrient loading can result in community shift to ephemeral algae species. Disparities between the findings of the aforementioned studies are likely to be related to the level of organic enrichment, however, could also be time dependent.

    Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009) however also highlighted that macroalgal communities are relatively tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009). Organic enrichment may also result in phytoplankton blooms that increase turbidity and, therefore, may negatively impact photosynthesis.

    Sensitivity assessment. Although short-term exposure (<4 years) to organic enrichment may not affect seaweeds directly, indirect effects such as turbidity may significantly affect photosynthesis. Resistance has been assessed as ‘Medium’, resilience as ‘High’. Sensitivity has been assessed as ’Low’.

    Medium
    Medium
    High
    High
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    High
    High
    Medium
    High
    Help
    Low
    Medium
    Medium
    High
    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
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    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 Saccharina latissima and Chorda filum would not be able to tolerate. 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
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    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 on hard rock substrata

    Not relevant (NR)
    NR
    NR
    NR
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    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 on hard rock substrata

    Not relevant (NR)
    NR
    NR
    NR
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    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

    Abrasion of the substratum e.g. from bottom or pot fishing gear, cable laying etc. may cause localised mobility of the substrata and mortality of the resident community. The effect would be situation dependent, however, if bottom fishing gear were towed over a site it may mobilise a high proportion of the rock substrata and cause high mortality in the resident community.

    Sensitivity assessment. Resistance has been assessed as ‘None’, Resilience as ‘High’. Sensitivity has been assessed as ‘Medium’.

     

    None
    Low
    NR
    NR
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    High
    High
    High
    High
    Help
    Medium
    Low
    Low
    Low
    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 substrata on the surface of the seabed”.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    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 positive linear relationship with subsurface light attenuation (Kd) (Devlin et al., 2008). Light availability and water turbidity are principal factors in determining depth range at which macro-algae can be found (Birkett et al., 1998b). Light penetration influences the maximum depth at which Laminarians 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 kelp is found may be reduced, or in some cases excluded completely (e.g. Severn Estuary), because of the alteration in light attenuation by suspended sediment (Lüning, 1990; Birkett et al. 1998b). Laminarians 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).

    Sensitivity Assessment. 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 is probably to this pressure is defined as ‘Medium’ at the benchmark. Hence, this biotope is regarded as having a sensitivity of ‘Medium ‘to this pressure.

    None
    High
    High
    High
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    Medium
    High
    Medium
    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 Saccharina latissima and Chorda filum sporophytes but may provide a physical barrier to zoospore settlement and, therefore, could negatively impact on recruitment processes (Moy & Christie, 2012). Laboratory studies showed that kelp and gametophytes can survive in darkness for between 6-16 months at 8°C and would probably survive smothering by a discrete event and once returned to normal conditions gametophytes resumed growth or maturation within 1 month (Dieck, 1993).

    IR.HIR.KSed.SlatChoR is recorded from extreme wave exposed-sheltered sites (Connor et al., 2004). In wave exposed biotopes deposited sediment is unlikely to remain for more than a few tidal cycles (due to water flow or wave action). In sheltered biotopes deposited sediment could remain however are unlikely to remain for longer than a year.

    Sensitivity assessment. Resistance has been assessed as ‘High’, resilience as ‘High’ and sensitivity assessed as ‘Not Sensitive’.

     

    High
    Low
    NR
    NR
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    High
    High
    High
    High
    Help
    Not sensitive
    Low
    NR
    NR
    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 mature Saccharina latissima and Chorda filum sporophytes but may provide a physical barrier to zoospore settlement and, therefore, could negatively impact on recruitment processes (Moy & Christie, 2012). The volume of sediment may also inundate juvenile sporophytes. Given the microscopic size of the gametophyte, 30cm of sediment could be expected to significantly inhibit growth. Laboratory studies showed that kelp and gametophytes can survive in darkness for between 6-16 months at 8°C and would probably survive smothering by a discrete event and once returned to normal conditions gametophytes resumed growth or maturation within 1 month (Dieck, 1993).

    IR.HIR.KSed.SlatChoR is recorded from extreme wave exposed-sheltered sites (Connor et al., 2004). In wave exposed biotopes deposited sediment is unlikely to remain for more than a few tidal cycles (due to water flow or wave action). In sheltered biotopes deposited sediment could remain, however, is unlikely to remain for longer than a year.

    Sensitivity assessment. Resistance has been assessed as ‘Medium’, resilience as ‘High’. Sensitivity has been assessed as ‘Low’.

     

    Medium
    Low
    NR
    NR
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    High
    Low
    NR
    NR
    Help
    Low
    Low
    Low
    Low
    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
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    Not assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    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

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

    Introduction of light or shading

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

    Evidence

    There is no evidence to suggest that anthropogenic light sources would affect Saccharina latissima or Chorda filum. Shading of the biotope (e.g. by the 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 seaweed abundance.

    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
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    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
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    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.

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

    There is little evidence for translocation of Saccharina latissima or Chorda filum over significant geographic distances. Nor is there any evidence regarding the genetic modification or effects of translocation of native kelp populations.

    Not relevant (NR)
    NR
    NR
    NR
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    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 although 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 San Juan Islands, Washington State, USA, showed that Sargassum muticum reduced the abundance of native macroalgae, including the kelp Laminaria bongardiana due to shadingHowever, 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; Kraan, 2017; Epstein & Smale, 2018; Epstein et al., 2019a,b; Tidbury, 2020). Undaria pinnatifida originates from Japan but is established currently 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 had become 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). De Leij et al. (2017) suggested that in natural substrata, Undaria pinnatifida can be inhibited by the presence of native competitors, such as large perennial species. Undaria pinnatifida species 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).

    In Torquay Marina, UK, Farrell & Fletcher (2006) completed a canopy removal experiment between 1996-2002. They reported that Saccharina latissima decreased in both control and treatment plots from ca 3 plants per 0.45 m² in 1996 to ca 1 plant per 0.45 m² in 1997 and had disappeared completely from pontoons by 2002. This coincided with a significant increase in Undaria pinnatifida from 0 plants per 0.45 m² in 1996 to ca 6 plants per 0.45 m² in 1997. However, there was a slight decrease in Undaria pinnatifida in both control and treatment plots between 1997 and 1998. By 2002, Undaria pinnatifida had recovered at control and treatment plots to ca 4-6 plants per 0.45 m² whereas Saccharina latissima had not.

    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 Saccharina latissima. However, they reported that Undaria pinnatifida biomass was negatively related to Saccharina latissima in both intertidal and subtidal habitats. This was only statistically significant in subtidal habitats, which suggested that there was some competition between the two species (Epstein et al., 2019b).

    Heiser et al. (2014) surveyed 17 sites within Plymouth Sound, UK and found that Saccharina latissima was significantly more abundant at sites with Undaria pinnatifida with ca 5 Saccharina latissima individuals per m² present, compared to ca 0.5 Saccharina latissima individuals per m² present at sites without Undaria pinnatifida.

    Epstein et al. (2019a) reported that when Undaria pinnatifida was removed from sites in Plymouth Sound, there was no difference in understorey assemblages. Surveys revealed that there was a high variation in the abundance and mean cover of understorey macroalgae, both between plots and survey months. For example, the mean cover of brown understorey algae followed the same trend for each removal treatment (0%, 50% and 100% removal of Undaria pinnatifida). Epstein et al. (2019a) observed an initial increase in mean percentage cover 0-5 months following the removal of Undaria pinnatifida, which peaked after 7 months. This then decreased 7-15 months post-removal and then slightly recovered after 16-20 months.

    Undaria pinnatifida was successfully eradicated on a sunken ship in Clatham 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 compete with Saccharina latissima depending on local conditions. For example, Undaria pinnatifida can out-compete Saccharina latissima in artificial habitats, such as in Torquay Marina. Undaria pinnatifida can co-exist with native kelp species within its depth range (-1 to 4 m), as shown in Plymouth Sound, UK. Also, Undaria pinnatifida is unlikely to cause changes in the abundance of brown understorey algae, such as Chorda filum.

    IR.HIR.KSed.LsacChoR is moderately exposed to wave action and has moderately strong tidal streams that result in seasonal disturbance. The disturbed nature of this biotope may result in vulnerability to colonization by Undaria pinnatifida. However, Undaria pinnatifida and Saccharina latissima may co-exist within this biotope as it has a depth range of 0-5 m but Undaria pinnatifida is unlikely to out-compete Saccharina latissima in wave exposed conditions.  Similarly, Sargassum muticum prefers wave sheltered conditions and is unlikely to out-compete Saccharina latissima or Chorda filum under the conditions that characterize this biotope. 

    Therefore, resistance is assessed as ‘Medium’ to represent the potential Undaria or Sargassum to colonize the biotope, forming a mixed canopy.  Resilience is assessed as ‘High’ as the biotope is disturbed and both the native and non-native species recolonize and/or regrow annually. Hence, sensitivity is assessed as ‘Low’.  Overall, confidence is assessed as ‘Low’ due to evidence of variation and site-specific nature of competition between native kelps and both Undaria pinnatifida and Sargassum muticum.

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

    Laminariales may be infected by the microscopic brown alga Streblonema aecidioides. Infected algae show symptoms of Streblonema disease, i.e. alterations of the blade and stipe ranging from dark spots to heavy deformations and completely crippled thalli Infection can reduce growth rates of host algae (Peters & Scaffelke, 1996). The marine fungi Eurychasma spp can also infect early life stages of Laminariales and Desmarestia viridis, however, the effects of infection are unknown (Müller et al., 1999).

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

    Low
    Low
    NR
    NR
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    High
    High
    High
    High
    Help
    Low
    Low
    Low
    Low
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    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

    There has been recent commercial interest in Saccharina lattisima as a consumable called “sea vegetables” (Birket et al., 1998). However, Saccharina lattissima sporophytes are typically matured on ropes (Handå et al 2013) and not directly extracted from the seabed, as with Laminaria hyperborea (Christie et al., 1998). No evidence has been found for commercial extraction of Chorda filum.  This pressure has therefore been assessed as not relevant.

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

    Low level disturbances (e.g. solitary anchors and scallop dredges) are unlikely to cause harm to the biotope as a whole, due to the impact’s small footprint.  Thus, evidence to assess the resistance of IR.HIR.KSed.SlatChoR to non-targeted removal is limited. It is assumed that incidental non-targeted catch will mobilise sediment and cause high mortality within the affected area.

    Sensitivity assessment. Resistance has been assessed as ‘None’, resilience as ‘High’, and sensitivity assessed as ‘Medium’.

    None
    Low
    NR
    NR
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    High
    High
    High
    High
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    Medium
    Low
    Low
    Low
    Help

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    Citation

    This review can be cited as:

    Hiscock, K., Stamp, T.E., Lloyd, K.A.,, Mardle, M.J., & Tyler-Walters, H., 2022. Saccharina latissima, Chorda filum and dense red seaweeds on shallow unstable infralittoral boulders or cobbles. 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 02-12-2023]. Available from: https://marlin.ac.uk/habitat/detail/363

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