The Marine Life Information Network

Temperature increase (local)

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

Evidence

Churchill & Moeller (1972) suggested the minimum temperature for the formation of reproductive structures in Codium fragile was 12-15°C. Haniask (1979) experimentally measured Codium fragile thalli and sporeling growth over a range of environmental conditions. Maximal thalli growth was recorded at 24°C.  The upper temperature threshold has been recorded at 30°C and no detectable growth occurs at <6°C.

Mortensen (1927) reported Psammechinus miliaris was found in Limfjorden, Denmark where winter water temperatures are regularly just above 0°C (Ursin, 1960). At Psammichinus miliaris southern range edge, Morocco and the Azores (Mortensen, 1927), winter-summer temperatures range from17-21°C (Seatemperature, 2015). The optimal temperature tolerances are therefore likely to be between 0-21°C. Furthermore, Psammichinus miliaris reproduces in waters around the Faeroes where the summer temperatures seldom exceed 11°C (Ursin, 1960).

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.

Andersen et al. (2011) transplanted Saccharina latissima in the Skagerrak region, Norway and from 2006-2009. There was annual variation however high mortality occurred from August-November within each year of the experiment. In 2008 of the original 17 sporophytes 6 survived from March-September (approx. 65 % mortality rate). All surviving sporophytes were heavily fouled by epiphytic organisms (estimated cover of 80 & 100%). Between 1960 and 2009, sea surface temperatures in the region have regularly exceeded 20°C and so has the duration which temperatures remain above 20 °C. High sea temperatures have been linked to the slow growth of Saccharina latissima which is likely to decrease the photosynthetic ability of, and increase the vulnerability of Saccharina latissima to epiphytic loading, bacterial and viral attacks (Anderson et al., 2011). These factors combined with the establishment of annual filamentous algae in Skagerrak, Norway are likely to prevent the establishment of self-sustaining populations in the area (Anderson et al., 2011; Moy & Christie, 2012).

Phyllophora crispa and Phyllophora pseudoceranoides are sensitive to large changes in temperature. Through culture experiments, 30°C was found lethal to Phyllophora pseudoceranoides within 4-12 weeks. At 27°C plants were severely damaged after 3 months but were able to recover when returned to lower temperatures.  Furthermore, temperature was found to control the time at which Phyllophora pseudoceranoides begins sporulation. For example, ≥15°C sporulation occurred at 30 months were as 10 °C sporulation occurred at 8 months (Molenaar & Breeman, 1994).

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are 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)

Sensitivity assessment. A 2°C increase for one year may impair Saccharina latissima sporophyte growth but otherwise not affect the characterizing species.  A 5°C increase for one month combined with high UK summer temperatures may cause mortality in Saccharina latissima populations that are not acclimated to >20°C. Resistance has been assessed as ‘None’, to reflect the potential mass mortality effect of sudden temperature increases on Saccharina latissima, and resilience as ‘Medium’. Sensitivity has been assessed as ‘Medium’.

Temperature decrease (local)

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

Evidence

During winter Codium spp. thalli reduce to a small holdfast and biological activity is reduced (Haniask, 1979). Mortensen (1927) reported Psammechinus miliaris was found in Limfjorden, Denmark where winter temperatures are regularly just above 0°C. Saccharina lattissima has a lower temperature threshold for sporophyte growth at 0°C (Lüning, 1990). Phyllophora pseudoceranoides can tolerate temperatures of -2 and 0°C 3 months (Molenaar & Breeman, 1994).  None of the characterizing species are likely to be adversely affected by a temperature decrease at the benchmark level.

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

Salinity increase (local)

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

Evidence

Haniask (1979) reported Codium fragile salinity tolerances are variable, and dependant on temperature. At 24°C thalli growth occurred from 12-42‰, with an optimum from 24-30‰. Gezelius (1962) reported the littoral growth form of Psammechinus miliaris had an optimal salinity range of 20-32 ppt, and the sub-littoral growth form had an optimal salinity tolerance of 26-38 ppt.

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. The affect of long-term salinity changes (>5 days) or salinity >60 PSU on Saccharina latissima’ photosynthetic ability was not tested.

Phyllophora crispa and Phyllophora pseudoceranoides are widely distributed around the UK in full marine conditions (Bunker et al., 2012).

Sensitivity assessment. IR.LIR.KVS.Cod, IR.LIR.KVSSlatPsaVS & IR.LIR.KVS.SlatPhyVS are only recorded from reduced or low salinity conditions (<18-30 psu). An increase to full salinity (30-40‰) may cause declines in Codium fragile growth. Phyllophora is recorded within full marine salinity, however, it may not be sufficiently abundant or be out-competed by other red seaweeds in full salinity. Therefore, a long-term change to full salinity (30-40‰) may change the character of the biotope, so that they are replaced by more diverse sheltered rock Saccharina latissima biotopes (e.g. IR.LIR.K.Slat). Resistance has been assessed as ‘None’, resilience as ‘Medium’. The sensitivity of this biotope to an increase in salinity has been assessed as ‘Medium’.

Salinity decrease (local)

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

Evidence

Haniask (1979) reported that at 24°C Codium fragile thalli growth could occur from 12-42‰, with an optimum from 24-30‰. 100% mortality occurred at 6‰ and at 12‰ growth was reduced. At the extremes of Codium fragile temperature tolerance (6 & 30°C) salinity tolerances were restricted, thalli grown at 6°C had a tolerance of 18-36‰, and thalli grown at 30°C had a salinity tolerance of 18-48 ‰ (Haniask, 1979). Codium fragile sporelings had narrower salinity and thresholds than mature thalli; Spores did not germinate at <18‰.

Lindahl and Runnström (1929) showed (experimentally) that Psammechinus miliaris from the littoral (Z form) and sub-littoral (S form) had different salinity optima. Gezelius (1962) reported the littoral growth form had an optimal salinity range of 20-32 ppt, whereas the sub-littoral growth form 26-38ppt. Mature examples of the littoral growth form tolerated 15 ppt for a period of 27 days, however, were not able to produce gametes at this salinity.

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 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.

Sensitivity assessment. IR.LIR.KVS.Cod is recorded in full salinity but probably exposed to reduced (18-30 ppt) conditions (Connor et al., 2004). A salinity decrease to “Low” (<18 ppt) may cause declines in Codium spp. growth and detriment the biotope. As a result, the Codium abundance could fall resulting in the SlatPhyVS biotope. IR.LIR.KVS.SlatPsaVS and IR.LIR.KVS.SlatPhyVS are recorded in ‘reduced’ and ‘low’ salinity, A further reduction in salinity would result in close to freshwater conditions and, however unlikely, would result in loss of the biotopes.  Resistance has been assessed as ‘Low’ and resilience as ‘High’. Therefore, the sensitivity of this biotope to a decrease in salinity has been assessed as ‘High’.

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

Information concerning the effects of increased water flow on Codium spp. or Psammechinus miliaris is limited. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are predominantly recorded from sites with very weak to weak tidal streams (Connor et al., 2004).

Peteiro & Freire (2013) measured Saccharina latissima growth from 2 sites, the first had maximal water velocities of 0.3m/sec and the second 0.1m/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) found Saccharina latissima productivity is reduced in moderately strong tidal streams (≤1 m/sec) when compared to weak tidal streams (<0.5 m/sec). Despite the results published in Gerard & Mann (1979) Saccharina latissima can characterize or be a dominant in the tide swept biotopes IR.MIR.KT.XKTX & IR.MIR.KT.SlatT, which have been recorded from very strong (>3 m/sec) to moderately strong tidal streams (≤1 m/sec) (Connor et al., 2004), indicating Saccharina latissima can tolerate greater tidal streams than <1m/sec.

Sensitivity assessment. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are classed as low energy biotopes, restricted to only weak tidal streams. Many of the characteristic species are found in a range of tidal regimes so that a change in flow velocities of between 0.1-0.2 m/sec would not cause a significant effect on most species present. In SlatCod an increase in water flow at the benchmark may be enough to remove the silt that characterizes the biotope, and allow the abundance of Saccharina latissima to increase. In SlatPsa, an increase in water flow to moderately strong or strong would probably reduce the abundance of Echinus esculentus and to a lesser extent Psammechinus miliaris and favour a change from SlatPsaVS to SlatPhyVS. However, at the benchmark level, there is only likely to be slight changes in the character of the biotope and the KVS complex would remain. Therefore, resistance has been assessed as ‘Medium’, resilience as ‘High’, and sensitivity has been assessed as ‘Low‘ at the benchmark level.

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.LIR.KVS.Cod , IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are predominantly shallow biotopes recorded from 0-10 m BCD An increase in emergence will result in an increased risk of desiccation and mortality of the macro-algae of the biotope.  Removal of canopy-forming kelps, through desiccation, has also been shown to increase desiccation and mortality of the understorey macroalgae (Hawkins & Harkin, 1985). Thomsen & McGlathery (2007) demonstrated that Codium fragile biomass declined if artificially placed at higher tidal elevations, and would therefore likely be sensitive to changes in emergence regime. Many of the dominant species an also occur in the lower intertidal, however, the biotope would probably be replaced by a lower shore equivalent.  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 ‘Low’ and resilience  as ‘Medium’. The sensitivity of this biotope to a change in emergence is considered to be ‘Medium’.

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.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS are classed as low energy biotopes, recorded from sheltered-ultra wave sheltered sites (Connor et al., 2004). Therefore, a large scale increase in wave exposure is likely to have a fundamental effect on the characterizing species. However, evidence that specifically relates to the tolerance of the characterizing species to increases in wave exposure is limited.

Bulleri & Airoldi (2005) recorded the seasonal abundance of Codium fragile on the wave exposed and sheltered faces of breakwaters (coastal defence structures) built in the Adriatic sea. Codium fragile density was similar across both the exposed and sheltered sides in spring-early summer, however as summer progressed Codium fragile density declined on the exposed side of the breakwater. Codium fragile thalli also attained greater sizes (>14 cm) were more branched and had higher biomass on the sheltered faces of the breakwater. Indicating, that wave exposure has an impact on the density of Codium spp. thalli.

At the time of writing there is limited evidence for the effect of wave exposure on Psammechinus miliaris or Saccharina latissima other than they are predominantly recorded in wave sheltered locations (Birkett et al., 1998b; Kelly, 2000).

Sensitivity assessment. Wave exposure is one of the principal defining features of rock biotopes, and large changes in wave exposure are likely to alter the relative abundance of the dominant macro-algae, grazing and understorey community, and hence, the biotope. However, a change in near shore significant wave height of 3-5% is unlikely to have any significant effect on IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS or IR.LIR.KVS.SlatPsaVS. Resistance has been assessed as ‘High’, resilience as ‘High’ and sensitivity as ‘Not Sensitive’ at the benchmark level.

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. The effects of copper, zinc and mercury on Saccharina latissima have been investigated by Thompson and Burrows (1984). They observed that the growth of sporophytes 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.

At the time of writing, little is known about the effects of heavy metals on echinoderms. Bryan (1984) reported that early work had shown that echinoderm larvae were intolerant of heavy metals, e.g. the intolerance of larvae of Paracentrotus lividus to copper (Cu) had been used to develop a water quality assessment. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu). Sea-urchins, especially the eggs and larvae, are used for toxicity testing and environmental monitoring (reviewed by Dinnel et al. 1988). Taken together with the findings of Gommez & Miguez-Rodriguez (1999) above it is likely that echinoderms are intolerant of heavy metal contamination.

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.

Saccharina latissima fronds, being predominantly subtidal, would not come into contact with freshly released oil but only to sinking emulsified oil and oil adsorbed onto particles (Birkett et al., 1998). 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 kelp forests. Similarly, surveys of subtidal communities at a number sites between 1-22.5 m below chart datum 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 (Somerfield & Warwick, 1999).

Echinoderms seem especially sensitive to the toxic effects of oil, likely because of the large amount of exposed epidermis (Suchanek, 1993). Schäfer & Köhler (2009) found 20 day exposure to sub-lethal concentrations of phenanthrene resulted in severe ovarian lesions of Psammechinus miliaris limiting the production of gametes.

Following the Torrey Canyon incident, large numbers of dead Psammechinus miliaris were found in the vicinity of Sennen, UK possibly due to exposure to the oil spill and the heavy spraying of hydrocarbon based dispersants in that area (Smith, 1968). Other significant effects have been observed in other species of urchins. For example, mass mortality of the echinoderm Echinocardium cordatum was observed shortly after the Amoco Cadiz oil spill (Cabioch et al., 1978) and reduced abundance of the species was detectable up to >1000 m away one year after the discharge of oil-contaminated drill cuttings in the North Sea (Daan & Mulder, 1996). In the Mediterranean around Naples, urchins were absent from areas which had visible signs of massive pollution of both sewage and oil. 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) (Gommez & Miguez-Rodriguez, 1999). But the observed effects may have been due to a single contaminant or synergistic effects of all present.

Cullinane et al. (1975) found large quantities of Codium fragile washed up on Relane, Bantry Bay, USA shortly after a large oil spill. No other evidence could be located for the effect of hydrocarbon & PAH contamination on Codium spp.

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.

Johansson (2009) exposed samples of Saccharina latissima to several antifouling 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) 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. Considerable observations and work, mainly on Echinus esculentus but also on Psammechinus miliaris (Smith, 1968; Gommez & Miguez-Rodriguez, 1999; Dinnel et al., 1988) indicate high intolerance to synthetic contaminants. Newton & McKenzie (1995) state that echinoderms tend to be very intolerant of various types of marine pollution, but there is little more detailed information than this. Following the Torrey Canyon incident, large numbers of dead Psammechinus miliaris in the vicinity of Sennen, UK presumably due to the heavy spraying of dispersants in that area and exposure to the oil spill (Smith, 1968).

Radionuclide contamination

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

Evidence

No evidence.

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.

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 2 mg/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. Therefore, resistance has been assessed as ‘High’ and resilience as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

Nutrient enrichment

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

Evidence

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)  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).

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 20.22 µM, 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 Norwegian 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.

Haniask (1979) observed that Codium fragile growth rate increased when exposed to elevated nitrogen (Nitrate, Nitrite, Ammonium and Urea). After 21 day nitrogen enrichment treatments Codium fragile grew on average 23-25 mm, whereas in the no enrichment treatment Codium fragile grew 4.8 mm. Conversely Thomsen & McGlathery (2006) observed that short-term nutrient enrichment did not increase the biomass of Codium fragile, however, the authors suggested that Codium spp. store excess Nitrogen to sustain growth if nutrients become depleted. Despite disagreement between the authors on the effect of enrichment, in both examples, enrichment did not have a detectable negative impact on Codium spp.

Sensitivity assessment. The evidence suggests that enrichment would not negatively impact on Codium spp. growth or directly affect Saccharina latissima. However indirectly nutrient enrichment may increase turbidity which may decrease water clarity and, therefore, macro-algae photosynthesis. Nevertheless, this biotope is considered to be Not sensitive at the pressure benchmark that assumes compliance with good status as defined by the WFD.

Organic enrichment

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

Evidence

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).

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 20.22 µM, 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 Norwegian 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.

Sensitivity assessment. The evidence suggests that enrichment would not negatively impact on Codium spp. growth or directly affect Saccharina latissima. However, indirect organic enrichment may increase turbidity, which may decrease water clarity and therefore negatively effect macroalgal photosynthesis and growth. Resistance has therefore been assessed as ‘Medium’, resilience as ‘High’. Sensitivity has been assessed as ’Low’.

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.

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

This biotope forms on hard rock substrata, i.e. bedrock, boulders and cobbles.  A change from hard rock to sedimentary substrata would result in permanent loss of the biotope. Therefore, resistance is assessed as None, resilience as Very low and sensitivity as High. confidence is assessed as 'High' due to the incontrovertible nature of the pressure.

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.

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.

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’.

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

Penetration is unlikely to be relevant to hard rock substrata. Therefore, the pressure is Not relevant.  However, physical disturbance of the surface is assessed under 'abrasion' above.

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 negative linear relationship with sub-surface 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 depth range at which kelp can be found (Birkett et al., 1998). 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 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., 1998).

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 decrease the photosynthetic ability of, abundance and density of Saccharina latissima.

Codium fragile is photosynthetically efficient at low light levels (Ramus et al., 1976). Thomsen & McGlathery (2006) also demonstrated that Codium fragile gained biomass in both low and high light conditions, and found no apparent negative effect of shading on Codium fragile biomass.

Psammechinus miliaris is omnivorous, feeding directly on live and dead algae but also on an array attached fauna (Kelly, 2000). The feeding plasticity of Psammechinus miliaris is likely to ameliorate some of the effects of diminished kelp growth as a result of decreased light availability, however, a decrease in Saccharina latissima may cause some declines in Psammechinus miliaris abundance.

Many red algal species are scour tolerant, and occur in turbid waters and in general algal turfs replace fucoids and kelps in areas where turbidity and sedimentation increase (Airoldi, 2003). Furthermore, many red algal species occur beneath canopies of larger macroalgae (e.g. IR.HIR.KFaR.LhypR) and are tolerant of low light levels (Gantt, 1990).

Sensitivity Assessment. A decrease in turbidity is likely to support enhanced growth (and possible habitat expansion) and is therefore not considered in this assessment. However, an increase in turbidity is likely to result in the loss of Saccharina latissima at the deeper extent of the biotope. Codium spp., Psammechinus miliaris and red algal species are resistant to decreases in water clarity. To represent the potential decline in Saccharina latissima resistance to this pressure has been defined as ‘Medium’ and resilience to this pressure is defined as ‘High’ at the benchmark level due to the scale of the impact. Hence, this biotope is regarded as having a sensitivity of ‘Low‘.

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 sporophytes but may affect holdfast fauna, gametophyte survival, interfere with zoospore settlement and, therefore, recruitment processes (Moy & Christie, 2012). Given the short life expectancy of Saccharina latissima (2-4 years-(Parke, 1948)), IR.LIR.KVS.SlatPhyVS is likely to be dependent on annual Saccharina latissima recruitment (Moy & Christie, 2012). Given the microscopic size of the gametophyte, 5 cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that kelp 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.

Mature Codium tomentosum thalli can grow up to 30 cm long (Pizzolla, 2007). Therefore, during summer when thalli are erect light deposition of sediment is unlikely to inundate thalli, however if sediment is deposited during winter when the thalli are fragmented and reduced to the holdfast (Haniask, 1979) then Codium spp. thalli will become inundated. It is unknown whether retained sediment would inhibit growth if the holdfast was inundated the following spring.

Psammechinus miliaris is quite small (typically up to 4 cm) and is likely to be inundated by 5 cm of sediment (Jackson, 2008). If unable to 'dig out' of the sediment, deposited sediment may cause mortality.

The effect of deposition of 5cm sediment Phyllophora crispa and Phyllophora pseudoceranoides is likely to be seasonally variable. As highlighted within the resilience section, Phyllophora sp. can lose fronds during winter. Phyllophora crispa fronds can grow to a length of 15cm and Phyllophora pseudoceranoides can grow to a length of 10cm (Bunker et al., 2012). Therefore, if plants are complete deposition is not likely to completely inundate mature individuals. However if sediment deposition occurs during periods of early seasonal thalli growth then this could affect Phyllophora sp. growth.

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are classed as low energy habitats, and are therefore unlikely to experience >moderate tidal streams (>0.5 m/sec) or wave action.

Sediment could, therefore, remain within the host habitat and recovery rate would be related to sediment retention but will probably be dissipated within a year. Deposited sediments could affect kelp recruitment (Birkett et al., 1998) and the survival of Psammechinus miliaris.

Sensitivity assessment. SlatCod is a heavily silted biotope (Connor et al., 2004) so an addition of 5 cm of fines may not have a significant effect on the biotope. In SlatPsaVS and SlatPhyV, the deposit of fine sediment may remain for some time (depending on local conditions) and result in the smothering of small invertebrates, and smothering of short turf forming red algae and encrusting corallines.  Smothering would inhibit photosynthesis, growth for algae, and possibly lead to mortality of germlings.  Therefore, a resistance of ‘Medium’ is suggested. Resilience as ‘High’. Sensitivity has been assessed as ‘Low’.

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 Saccharina latissima sporophytes but may affect holdfast fauna, gametophyte survival, interfere with zoospore settlement and, therefore, recruitment processes (Moy & Christie, 2012). Given the short life expectancy of Saccharina latissima (2-4 years (Parke, 1948)), IR.LIR.KVS.SlatPhyVS is likely to be dependent on annual Saccharina latissima recruitment (Moy & Christie, 2012). Given the microscopic size of the gametophyte, 30cm of sediment could be expected to significantly inhibit growth. However, laboratory studies showed that kelp 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.

Mature Codium tomentosum thalli can grow up to 30 cm long (Marlin, 2015). 30cm of deposited sediment is likely to inundate mature thalli. During winter, thalli fragment and individuals are reduced to a holdfast. It is unknown whether retained sediment would inhibit growth if the holdfast was inundated the following spring. 

Psammechinus miliaris is quite small (typically up to 40 mm) and is likely to be inundated by 30 cm of sediment (Jackson, 2008). If unable to 'dig out' of the sediment, deposited sediment may cause mortality.

Phyllophora crispa fronds can grow to a length of 15 cm and Phyllophora pseudoceranoides can grow to a length of 10cm (Bunker et al., 2012). Deposition of 30 cm sediment is likely to completely inundate Phyllophora crispa and Phyllophora pseudoceranoides.

IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are classed as low energy habitats, and are therefore unlikely to experience >moderate tidal streams (>0.5 m/sec) or wave action.

Sediment could, therefore, remain within the host habitat and recovery rate would be related to sediment retention but will probably be dissipated within a year. Deposited sediments could affect macroalgae recruitment (Birkett et al., 1998) and the survival of Psammechinus miliaris.

Sensitivity assessment Deposition of 30 cm of sediment is likely to inundate all but large macroalgae, e.g. mature Saccharina lattisima, and cause mortality in Codium spp. and understorey red seaweeds. As the deposit may remain for some time (depending on local conditions) and mortality is likely. Resistance has been assessed as of ‘None’; resilience has been assessed as ‘Medium’. Sensitivity has been assessed as ‘Medium’.

Litter

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

Evidence

Not assessed.

Electromagnetic changes

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

Evidence

No evidence.

Underwater noise changes

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

Evidence

No evidence.

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 macro-algae. Shading (e.g. by the construction of a pontoon, pier etc) could adversely affect IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS 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.

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.

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.

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.

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

Saccharina latissima has shown significant regional acclimation to environmental conditions. Gerard & Dubois (1988) found Saccharina latissima sporophytes which were regularly exposed to ≥20°C could tolerate these high temperatures whereas sporophytes from other populations which rarely experience ≥17°C showed 100% mortality after 3 weeks of exposure to 20°C. It is, therefore, possible that transplanted eco-types of Saccharina latissima may react differently to environmental conditions that differ from those of their origin.

However, there was little evidence for translocation of any other characteristic species over significant geographic distances. Nor was there any evidence regarding the genetic modification or effects of translocation.

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 (de Bettignies et al., 2021).  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 shading.  However, 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 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).  It 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).  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 canopy disturbance was not always required (De Leij et al., 2017; Epstein & Smale, 2018).

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).

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 can inhibit a broad range of habitats including – reefs; coastal brackish/saline lagoons; large shallow inlets and bays; estuaries; estuarine rocky habitats; natural or near-natural estuary; coastal lagoons; and tidal rivers, estuaries, mudflats, sandflats and lagoons (James, 2017).  Undaria pinnatifida prefers 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).  Undarai sporophytes were also reported to survive at salinities down to 11 psu (Epstein & Smale, 2018).

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 present per m², compared to ca 0.5 Saccharina latissima individuals per m² present at sites without Undaria pinnatifida.

Undaria pinnatifida has been reported to both co-exist with and out-compete Saccharina latissima (Farrell & Fletcher, 2006; Heiser et al., 2014; Epstein et al., 2019b). For example, 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 zero 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.

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.

The proliferation of Undaria pinnatifida and competition with native species may cause a reduction in local biodiversity (Valentine & Johnson, 2003; Vaz-Pinto et al., 2014; Arnold et al., 2016; Teagle, 2017; Tidbury, 2020).  A shift towards Undaria pinnatifida dominated beds could result in diminished epibiotic assemblages and lower local biodiversity compared with assemblages associated with native perennial kelp species, such as Laminaria spp. and Saccharina latissima (Arnold et al., 2016; Teagle et al., 2017).  In Plymouth, UK, Arnold et al. (2016) found that Undaria pinnatifida supported less than half the number of taxa and had no unique epibionts compared to Laminaria ochroleuca and Saccharina latissima (Arnold et al., 2016).

Sensitivity assessment.  The above evidence suggests that both Sargassum muticum and Undaria pinnatifida can both compete with and co-exist with Saccharina latissima, depending on local conditions.  For example, Undaria pinnatifida can out-compete Saccharina latissima in artificial habitats, such as in Torquay Marina, but within natural habitats, it can co-exist with native kelp species within its depth range (-1 to 4 m), as shown in Plymouth Sound, UK.  Similarly, Sargassum muticum out-competed Saccharina latissima in theLimfjorden but coexisted in the Dorn in Strangford Lough.

This Saccharina latissima dominated biotope (IR.LIR.KVS.SlatPhyVS) is found from 0 to 10 m in depth (JNCC, 2015, 2022) in reduced or low salinity with weak or very weak tidal streams and wave sheltered or very sheltered conditions.  The evidence above suggests that Undaria prefers sheltered conditions, with low tidal flow, in the shallow subtidal and sublittoral fringe (ca +1 to 4 m in depth), while Sargassum also prefers wave sheltered conditions and shallow water (ca 1 to 4 m depth). Both species are reported to survive in estuarine conditions and low salinities. Therefore, Undaria pinnatifida and Sargassum muticum are only likely to threaten the most shallow (e.g. 0-5 m) examples of this biotope, where suitable hard substrata are available.  They may either co-exist with or out-compete Saccharina latissima, resulting in a potentially significant (25-75%) reduction in the abundance or extent of the native kelp and a possible decrease in the diversity of other macroalgae.  Therefore, resistance is assessed as ‘Low’ for shallow, wave sheltered examples of the biotope, i.e. above 5 m in depth.  Both Sargassum and Undaria may colonize at 5-10 m but in low numbers so Saccharina will probably dominate.  Recovery after invasion by Sargassum or Undaria, although rapid, would require direct intervention (removal) so that resilience is assessed as ‘Very low’.  Hence, the sensitivity of shallow, sheltered, examples of the biotope is assessed as ‘High’.  Overall, confidence is assessed as ‘Low’ due to evidence of variation and site-specific nature of competition between native kelps, Sargassum muticum, and Undaria pinnatifida.

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

Saccharina latissima 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 (Peters & Scaffelke, 1996). Infection can reduce growth rates of host algae.

Psammechinus miliaris 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 (Maes et al., 1986). It is thought to be caused by the bacteria Vibrio anguillarum and Aeromonas salmonicida. This disease has been recorded from Psammechinus miliaris from the French Atlantic coast. Although associated with mass mortalities of Strongylocentrotus franciscanus in California and Paracentrotus lividus in the French Mediterranean there is no evidence of mass mortalities of Psammechinus miliaris associated with this disease around Britain and Ireland.

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’.

Removal of target species

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

Evidence

Targeted removal of characterizing species IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS & IR.LIR.KVS.SlatPsaVS would likely have a fundamental effect on the character of the biotopes. Saccharina latissima is commercially cultivated, however, typically sporophytes are matured on ropes (Handå et al., 2013) and not directly extracted from the seabed, as is the case with Laminaria hyperborea (see Christie et al., 1998).  As a consequence related literature on which to assess the “resistance” of Saccharina latissima to targeted harvesting is sparse. Similarly, at the time of writing, no evidence could be found to suggest that Codium spp. was extracted for commercial or recreational l purposes.  Psammechinus miliaris is targeted as a potential aquaculture species. When fed a nutritious diet in culture, the gonad biomass rapidly proliferates which can then be marketed as urchin “roe” (Kelly et al., 1998; 2000). However, Kelly (2000) concluded that there was no viability in a Psammechinus miliaris commercial fishery because of the low gonad content of wild populations. While some extraction of Psammechinus miliaris may conceivably develop for roe-enhancement through feeding artificial or nutrient enriched diets (Dr Maeve Kelly pers comm, 2000), this is currently not in practice within the UK.

Sensitivity assessment.  None of the characterizing species are commercially extracted from the seabed. If extracted in the future resistance would need to be re-assessed. This pressure has been assessed as ‘Not relevant’.

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

Direct, physical impacts from harvesting are assessed through the abrasion and penetration of the seabed pressures. The sensitivity assessment for this pressure considers any biological/ecological effects resulting from the removal of non-target species on this biotope.  Incidental removal of the key characterizing species and associated species would alter the character of the biotope. IR.LIR.KVS.Cod, IR.LIR.KVS.SlatPhyVS and IR.LIR.KVS.SlatPsaVS are characterized by a canopy of Saccharina lattisima. Saccharina lattisima provides a canopy under which a variety of red seaweeds grow, including,  Phyllophora sp. (as in IR.LIR.KVS.SlatPhyVS).The loss of the canopy due to incidental removal as by-catch would, therefore, alter the character of the habitat and result in the loss of species richness. The ecological services such as primary and secondary production provided by these species would also be lost. Codium spp. is also a key/characterizing species that may be removed through incidental/accidental by-catch. Removal Codium spp. would by definition also change biotope structure

Psammechinus miliaris may suffer as a result of trawling or dredging for other benthic species. Species with fragile tests such as urchins have been reported to be particularly sensitive to damage from mobile fishing gear (see Jennings & Kaiser, 1998; Bergman & van Santbrink, 2000). Kaiser & Spencer (1994) reported a ca 20 – 50% mortality in Psammechinus miliaris as a result of a single pass of an experimental 4 m beam trawl.

Sensitivity assessment. For this assessment, it has been assumed that incidental removal would result in complete removal of the characterizing species. Resistance has been assessed as Low resilience as High and sensitivity as Low.