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

Berman et al. (2013) monitored sponge communities off Skomer Island, UK over three years with all characterizing sponges for this biotope assessed.  Seawater temperature, turbidity, photosynthetically active radiation and wind speed were all recorded during the study. It was concluded that, despite changes in species composition, primarily driven by the non-characterizing Hymeraphia, Stellifera and Halicnemia patera, no significant difference in sponge density was recorded in all sites studied.  Morphological changes most strongly correlated with a mixture of water visibility and temperature. In addition, Goodwin et al. (2013) found little evidence to suggest that rising seawater temperatures (ca 1-2°C) had an effect on subtidal benthic assemblages in Northern Ireland between pre-1986 and post-2006 surveys. However, significant effects were noted in rarer species at the edge of the biogeographic ranges (Goodwin et al., 2013).

Whilst Dercitus bucklandi is found from the Celtic Sea to southern Europe (Ackers et al., 1992), the sponge is recorded as far north as the Outer Hebrides.  Chelonaplysilla noevusis is found from the British Isles to the Mediterranean and the Canary Isles. Stryphnus ponderosus is found from Norway to southern Europe (Ackers et al., 1992). Parazoanthus anguicomus is found across many parts of the north-east Atlantic and is probably widespread in deep water off the continental shelf.  In the British Isles, it is found from western Ireland to northern Scotland (Manuel, 1988), with scattered records across the south-west of England (NBN, 2015).  Parazoanthus axinellae is a more southerly distributed species and is found from the south-west coasts of the British Isles to the Mediterranean (Manuel, 1988). Leptopsammia pruvoti is commonly found in sea caves and under overhangs throughout the Mediterranean basin and along European coasts from Portugal to southern England (Goffredi et al., 2006), while, Hoplangia durotrix is found from north and south coasts of Devon to Mediterranean and Canary Isles (Manuel, 1988).

Sensitivity assessment. All the characterizing sponges have been reported from the north to the south of the British Isles (NBN, 2015). A number of the characterizing species have a southerly distribution.  Given the variety of characterizing species, decline or loss of some species may not have a significant effect on the nature of the biotope.  Resistance is assessed as ‘High’, resilience as ‘High’ and the biotope is ‘Not sensitive’ at the benchmark level.

Temperature decrease (local)

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

Evidence

Berman et al. (2013) monitored sponge communities off Skomer Island, UK over three years with all characterizing sponges for this biotope assessed.  Seawater temperature, turbidity, photosynthetically active radiation and wind speed were all recorded during the study. It was concluded that, despite changes in species composition, primarily driven by the non-characterizing Hymeraphia, Stellifera and Halicnemia patera, no significant difference in sponge density was recorded in all sites studied.  Morphological changes most strongly correlated with a mixture of water visibility and temperature.  In addition, Goodwin et al. (2013) found little evidence to suggest that rising seawater temperatures (ca 1-2°C) had an effect on subtidal benthic assemblages in Northern Ireland between pre-1986 and post-2006 surveys. However, significant effects were noted in rarer species at the edge of the biogeographic ranges (Goodwin et al., 2013).

All the characterizing sponges have been reported from the north to the south of the British Isles (NBN, 2015). Whilst Dercitus bucklandi is found from the Celtic Sea to southern Europe (Ackers et al., 1992), Records exists of the sponge being found as far north as the Outer Hebrides.  Chelonaplysilla noevusis is found from the British Isles to the Mediterranean and the Canary Isles.  Stryphnus ponderosus is found from Norway to southern Europe (Ackers et al., 1992). Parazoanthus anguicomus is found across many parts of the north-east Atlantic and is probably widespread in deep water off the continental shelf.  In the British Isles, it is found from western Ireland to northern Scotland (Manuel, 1988), with scattered records across the south-west of England (NBN, 2015).  Parazoanthus axinellae is a more southerly distributed species and is found from the south-west coasts of the British Isles to the Mediterranean (Manuel, 1988). Leptopsammia pruvoti is commonly found in sea caves and under overhangs throughout the Mediterranean basin and along European coasts from Portugal to southern England (Goffredi et al., 2006).  Hoplangia durotrix is found from north and south coasts of Devon to Mediterranean and Canary Isles (Manuel, 1988)

Sensitivity assessment.  There is evidence of sponge mortality at extremely low temperatures in the British Isles.  Combined with evidence that a number of the species in this biotope have a mainly southern distribution, some mortality is likely.  The circalittoral nature of the biotope may afford some resistance to short-lived temperature events.  Therefore, resistance is assessed as ‘Medium’ with a resilience of ‘Medium’ and sensitivity is assessed as ‘Medium’ at the benchmark level.

Salinity increase (local)

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

Evidence

The biotope occurs in full salinity, circalittoral environments and an increase at the benchmark level (40 ppt or greater) is unlikely.  However, hypersaline water is likely to sink to the seabed and the biotope could be affected by hypersaline effluents (brines).  Ruso et al. (2007) reported that changes in the community structure of soft sediment communities due to desalinisation plant effluent in Alicante, Spain. In particular, in close vicinity to the effluent, where the salinity reached 39 psu, the community of polychaetes, crustaceans and molluscs was lost and replaced by one dominated by nematodes. Roberts et al. (2010b) suggested that hypersaline effluent dispersed quickly but was more of a concern at the seabed and in areas of low energy where widespread alternations in the community of soft sediments were observed. In several studies, echinoderms and ascidians were amongst the most sensitive groups examined (Roberts et al., 2010b).

Nevertheless, ‘No evidence’ for the characterizing species in hypersaline conditions was found.

Salinity decrease (local)

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

Evidence

The biotope occurs in full salinity, circalittoral environments and a decrease at the benchmark level to variable salinity (18-35 ppt) is unlikely. The sponges Stryphnus ponderosus, Dercitus bucklandi, Chelonaplysilla noevus and the anthozoans Parazoanthus anguicomus, Parazoanthus axinellae, Leptopsammia pruvoti and Hoplangia durotrix have only been recorded as occurring in full salinity biotopes (Connor et al., 2004). Therefore, whilst there is no specific evidence for salinity tolerance in the characterizing species, resistance is likely to be ‘Low’. Hence, resilience is assessed as  ‘Low' and sensitivity 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

Riisgard et al. (1993) discussed the low energy cost of filtration for sponges and concluded that passive current-induced filtration may be insignificant for sponges.  Pumping and filtering occur in choanocyte cells that generate water currents in sponges using flagella (De Vos et al., 1991). In flume experiments, Hiscock (1983) noted that the tentacles of Caryophyllia smithii were displaced by currents over ca 0.5 m/s but withdrawn at 0.75 m/s and took several hours to re-emerge after cessation of strong flow. Hiscock (1983) noted that Caryophyllia smithii was most abundant is semi-exposed and sheltered habitats. The other cup corals (Balanophyllia regia, Hoplangia durotrix and Leptopsammia pruvoti) were recorded from weak and very weak tidal streams in cave and overhang biotopes (Connor et al., 2004). 

Sensitivity assessment. The biotope (CR.FCR.Cv) and its sub-biotope (CR.FCR.Cv.SpCup) are characterized by low energy (moderate to negligible tidal flows (0-1.5 m/sec) and a significant increase would probably result in a fundamental change to the nature of the community, such as an increase in the abundance of bryozoan and hydroid turfs, and hence reclassification would be required.  A decrease in water flow is probably 'not relevant' as the biotopes occur in weak or negligible flow. However, an increase in the flow of 0.1-0.2 m/s (the benchmark level) may increase the abundance of bryozoan turfs and reduce the abundance of cup corals, especially in caves and overhangs that otherwise experience negligible flow. Therefore, a precautionary resistance of 'Medium' is suggested to represent minor changes in the community.  Hence, resilience is assessed as 'Medium' and sensitivity as 'Medium' at the benchmark level. Nevertheless, Connor et al. (2004) noted that the species composition varies between records of the biotope, which may imply subtle differences in community with local environmental parameters such as water flow and turbidity.

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

Changes in emergence are ‘Not relevant’ to this biotope as it is restricted to fully subtidal/circalittoral condition. The pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.

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

This biotope is defined as occurring in caves and gullies that are not subject to wave surge. Wave action is attenuated with depth, and the depth at which the biotopes occur and their aspect to incoming waves offer resistance to wave effects.  For example, these biotopes (CR.FCR.Cv and CR.FCR.CV.SpCup) occur in a range of wave exposures from very exposed to sheltered conditions, and yet, are not subject to wave surge.  Therefore, they probably occur in areas of circalittoral rock and caves protected from the direct effect of wave action.

A significant increase in wave action in their locality may result in a fundamental change to the nature of the biotope and hence reclassification. However, an increase in wave exposure at the benchmark level (a 3-5% change in significant wave height) is unlikely to alter the biotope. Therefore, resistance is as ‘High’, resilience as ‘High’, and the biotope is assessed 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

Whilst some sponges, such as Cliona spp. have been used to monitor heavy metals by looking at the associated bacterial community (Marques et al., 2007; Bauvais et al., 2015), no literature on the effects of transition element or organo-metal pollutants on the characterizing sponges could be found.

Nevertheless, this pressure is Not assessed but evidence is presented where available.

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.

Oil pollution is mainly a surface phenomenon its impact upon circalittoral turf communities is likely to be limited. However, as in the case of the Prestige oil spill off the coast of France, high swell and winds can cause oil pollutants to mix with the seawater and potentially negatively affect sub-littoral habitats (Castège et al., 2014). Filter feeders are highly sensitive to oil pollution, particularly those inhabiting the tidal zones which experience high exposure and show correspondingly high mortality, as are bottom dwelling organisms in areas where oil components are deposited by sedimentation (Zahn et al., 1981).

Zahn et al. (1981) found that Tethya lyncurium concentrated BaP (benzo[a ]pyrene )to 40 times the external concentration and no significant repair of DNA was observed in the sponges, which, in higher animals, would likely lead to cancers. As sponge cells are not organized into organs the long-term effects are uncertain (Zahn et al., 1981).

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.

Radionuclide contamination

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

Evidence

‘No evidence’ was found.

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

In general, respiration in most marine invertebrates does not appear to be significantly affected until extremely low concentrations are reached. For many benthic invertebrates, this concentration is about 2 ml/l (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995). Cole et al. (1999) suggested possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l.

Hiscock & Hoare (1975) reported an oxycline forming in the summer months (Jun-Sep) in a quarry lake (Abereiddy, Pembrokeshire) from close to full oxygen saturation at the surface to <5% saturation below ca 10 m.  No sponges were recorded at depths below 10 - 11 m.  Demosponges maintained under laboratory conditions can tolerate hypoxic conditions for brief periods, (Gunda & Janapala, 2009) investigated the effects of variable dissolved oxygen (DO) levels on the survival of the marine sponge, Haliclona pigmentifera. Under hypoxic conditions (1.5-2.0 ppm O₂), Haliclona pigmentifera with intact ectodermal layers and subtle oscula survived for 42 ± 3 days.  Sponges with prominent oscula, foreign material, and damaged pinacoderm exhibited poor survival (of 1-9 days) under similar conditions. Complete mortality of the sponges occurred within 2 days under anoxic conditions (<0.3 ppm O₂).  Shiaparelli et al. (2007) described the decline of Leptopsammia pruvoti by 85% of specimens following an anoxic event caused by decomposing mucilage.  Bell (2002) reported that an oxycline at Lough Hyne (<5% surface concentration) limited vertical colonization by Caryophillia smithii.

Sensitivity assessment. Whilst some sponges have demonstrated tolerance to short-term hypoxic events, it is likely that significant mortality to the biotope community would occur.  Given the low energy nature of biotope, recovery to typical oxygen levels is likely to be protracted.  Therefore, resistance is assessed as  ‘Low’, resilience as ‘Low’ and sensitivity assessed as ‘High’ at the benchmark level.

Nutrient enrichment

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

Evidence

This pressure relates to increased levels of nitrogen, phosphorus and silicon in the marine environment compared to background concentrations.  The benchmark is set at compliance with WFD criteria for good status, based on nitrogen concentration (UKTAG, 2014). 

‘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

Organic enrichment leads to organisms no longer being limited by the availability of organic carbon.  The consequent changes in ecosystem function can lead to the progression of eutrophic symptoms (Bricker et al., 2008), changes in species diversity and evenness (Johnston & Roberts, 2009) and decreases in dissolved oxygen and uncharacteristic microalgae blooms (Bricker et al., 1999, 2008).  Indirect adverse effects associated with organic enrichment include increased turbidity, increased suspended sediment and the increased risk of deoxygenation.  Rose & Risk (1985) described an increase in the abundance of the sponge Cliona delitrix in an organically polluted section of Grand Cayman fringing reef affected by the discharge of untreated faecal sewage. De Goeij et al. (2008) used ¹³C to trace the fate of dissolved organic matter in the coral reef sponge Halisarca caerulea.  Biomarkers revealed that the sponge incorporated dissolved organic matter through both bacteria mediated and direct pathways, suggesting that it feeds, directly and indirectly, on dissolved organic matter.

Sensitivity assessment.  The above evidence suggests that resistance to this pressure is 'High'.  Therefore, resilience is assessed as 'High' and the biotope is assessed as 'Not sensitive' at the benchmark level.

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

If rock were replaced with sediment, this would represent a fundamental change to the physical character of the biotope and the species would be unlikely to recover. The biotope would be lost. Therefore, resistance to the pressure is considered ‘None’, and resilience ‘Very low’. Sensitivity has been assessed as ‘High’.

Physical change (to another sediment type)

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

Evidence

‘Not relevant’ to biotopes occurring on bedrock.

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

The species characterizing this biotope are epifauna or epiflora occurring on rock and would be sensitive to the removal of the habitat. However, extraction of rock substratum is considered unlikely and this pressure is considered to be ‘Not relevant’ to hard substratum habitats.

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

Van Dolah et al. (1987) studied the effects on sponges and corals of one trawl event over a low-relief hard bottom habitat off Georgia, US.  The densities of individuals taller than 10 cm of three species of sponges in the trawl path and in adjacent control area were assessed by divers and were compared before, immediately after and 12 months after trawling.  Of the total number of sponges remaining in in the trawled area, 32% were damaged.  Most of the affected sponges were the barrel sponges Cliona spp., whereas Haliclona oculta and Ircina campana were not significantly affected. The abundance of sponges had increased to pre-trawl densities, or greater, 12 months after trawling.

Tilmant (1979) found that, following a shrimp trawl in Florida, the US, over 50% of sponges, including Neopetrosia, Spheciospongia, Spongia and Hippiospongia, were torn loose from the bottom.  Highest damage incidence occurred to the finger sponge Neopetrosia longleyi. Size did not appear to be important in determining whether a sponge was affected by the trawl.  Recovery was ongoing, but not complete 11 months after the trawl, although no specific data relating to the sponges are provided. Freese (2001) studied deep cold-water sponges in Alaska a year after a trawl event.  46.8% of sponges exhibited damage with 32.1% having been torn loose.  None of the damaged sponges displayed signs of regrowth or recovery.  This was in stark contrast to early work by Freese (1999) on warm shallow sponge communities, with impacts of trawling activity being much more persistent due to the slower growth/regeneration rates of deep, cold-water sponges. Given the slow growth rates and long lifespans of the rich, diverse fauna, it is likely to take many years for deep sponge communities to recover if adversely affected by physical damage.

Boulcott & Howell (2011) conducted experimental Newhaven scallop dredging over a circalittoral rock habitat in the sound of Jura, Scotland and recorded the damage to the resident community. Whilst the faunal crusts were surprisingly resistant to abrasion, the sponge Pachymatisma johnstoni was highly damaged by the experimental trawl. Picton & Goodwin (2007) noted that in their survey of sponges in Northern Ireland, that dredge damage was associated with a decline in sponge community and biomass.  Coleman et al. (2013) described a 4 year study on the differences between a commercially potted area in Lundy with a no-take zone.  No significant difference in Axinellid populations was observed.  The authors concluded that the study indicated that lighter abrasion pressures, such as potting, were far less damaging than heavier gears, such as trawls.

Murillo et al. (2012) monitored sponge communities over 3 years, primarily composed of Geoda spp. and the characterizing Stryphnus ponderosus.  It was noted that the average biomass per hectare swept was 2.7 times greater in lightly and untrawled grounds than in moderately trawled grounds and more than 100 times greater than the sponge biomass on heavily trawled grounds.

Sensitivity assessment. Whilst some of the characterizing sponges can be quite elastic, abrasion pressures, especially by heavy gears, have been shown to cause significant damage to the sessile epifaunal sponges.  The presence of these biotopes (CR.FCR.CV and Cv.SpCup) on cave walls and ceiling, and overhangs may protect the habitat from trawling, it may be impacted by mooring chains or abraded by anthropogenic debris. Therefore, a precautionary resistance of Low is suggested.  Hence, resilience is assessed as 'Low' and sensitivity as 'High'.

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

The species characterizing this biotope group are epifauna or epiflora occurring on rock, which is resistant to subsurface penetration.  The assessment for abrasion at the surface only is, therefore, considered to equally represent sensitivity to this pressure. This pressure is thought ‘Not Relevant’ to hard rock biotopes

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

Whilst many sponges are disadvantaged by sedimentation (as would be expected, being sessile filter feeders), many examples exist of sponges adapting to sediment presence (Bell et al., 2015; Schönberg, 2015) and many encrusting sponges appear to be able to survive in highly sedimented conditions, and, in fact, many species prefer such habitats (Bell & Barnes, 2001; Bell & Smith, 2004). Castric-Fey & Chassé (1991) conducted a factorial analysis of the subtidal rocky ecology near Brest, France and rated the distribution of species in varying turbidity (corroborated by the depth at which laminarians disappeared). Cliona celata and Stelligera rigida were classed as indifferent to turbidity, Tethya citrina, Pachymatisma johnstonia and Polymastia boletiformis (as Polymastia robusta) had a slight preference for clearer water, while Dysidea fragilis, Polymastia mamillaris, and Raspailia ramosa had a strong preference for turbid water. 

Bell & Turner (2000) studied populations of Caryophyllia smithii at three sites of differing sedimentation regime in Lough Hyne, Ireland. Calyx size was largest at the site of least sedimentation and smallest at the site of most sedimentation. In contrast, the height of individuals was greatest at the site of most sedimentation and smallest at the site of least sedimentation. The height of individuals correlated with the level of surrounding sediment. High density was correlated with high sedimentation and depth (Bell & Turner, 2000). 

Sensitivity assessment.  CR.FCR.Cv occurs on bedrock in the circalittoral and is unlikely to experience highly turbid conditions.  From the evidence presented above, the characterizing species tolerate some siltation and a change at the benchmark level is unlikely to cause mortality.  Resistance is recorded as ‘High’, resilience as ‘High’ and the biotope is ‘Not sensitive’ at the benchmark level.

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

Despite sediment being considered to have a negative impact on suspension feeders (Gerrodette & Flechsig 1979), many encrusting sponges appear to be able to survive in highly sedimented conditions, and, in fact, many species prefer such habitats (Bell & Barnes, 2001; Bell & Smith, 2004). However, Wulff (2006) described mortality in three sponge groups following four weeks of complete burial under sediment;  16% of Amphimedon biomass died compared with 40% and 47% in Iotrochota and Aplysina respectively. The complete disappearance of the ‘sponges associated’ with the sea squirt Ascidiella aspersa in the Black Sea near the Kerch Strait was attributed to siltation (Terent'ev, 2008 cited in Tillin & Tyler-Walters, 2014). It should also be noted that some of the characterizing sponges are likely to be buried in 5 cm of sediment deposition.

The cup corals tend to be small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “light” sedimentation event. However, Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7 mm ± 0.5 mm) in Lough Hyne. It is, therefore, possible that the cup corals would have some resistance to periodic sedimentation.  Bell (2002) reported that juvenile Caryophyllia smithii are morphologically variable and initially undergo rapid growth with tall and thin forms in deeper, sheltered, relatively sedimented conditions near Lough Hyne, Ireland.  It was concluded that this was to escape the thin layer of sediment present.  

Sensitivity assessment. Whilst the biotope experiences negligible water movement and smothering would likely damage a number of characterizing species, CR.FCR.Cv and CR.FCR.Cv.SpCup occur on shaded overhanging rock, cave walls and ceilings and would, therefore, be protected from burial.  The biotope is defined as being protected from wave surge and, being low energy, increased scour is unlikely to occur.  Resistance at the benchmark has been assessed as ‘High’, resilience as ‘High’ and the biotope is assessed as ‘Not sensitive’ at the benchmark level.

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

Despite sediment being considered to have a negative impact on suspension feeders (Gerrodette & Flechsig 1979), many encrusting sponges appear to be able to survive in highly sedimented conditions, and, in fact, many species prefer such habitats (Bell & Barnes, 2001; Bell & Smith, 2004). However, Wulff (2006) described mortality in three sponge groups following four weeks of complete burial under sediment;  16% of Amphimedon biomass died compared with 40% and 47% in Iotrochota and Aplysina respectively. The complete disappearance of the ‘sponges associated’ with the sea squirt Ascidiella aspersa in the Black Sea near the Kerch Strait was attributed to siltation (Terent'ev, 2008 cited in Tillin & Tyler-Walters, 2014). It should also be noted that some of the characterizing sponges are likely to be buried in 5 cm of sediment deposition.

The cup corals tend to be small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “light” sedimentation event. However, Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7 mm ± 0.5 mm) in Lough Hyne. It is, therefore, possible that the cup corals would have some resistance to periodic sedimentation.  Bell (2002) reported that juvenile Caryophyllia smithii are morphologically variable and initially undergo rapid growth with tall and thin forms in deeper, sheltered, relatively sedimented conditions near Lough Hyne, Ireland.  It was concluded that this was to escape the thin layer of sediment present.  

Sensitivity assessment.  Whilst the biotope experiences negligible water movement and smothering would likely damage a number of characterizing species, CR.FCR.Cv and CR.FCR.Cv.SpCup occur on shaded overhanging rock, cave walls and ceilings and would, therefore, be protected from burial, except in examples at the base of walls. The biotope is defined as being protected from wave surge and, being low energy, increased scour is unlikely to occur. Therefore, resistance at the benchmark has been assessed as ‘High’, resilience as ‘High’ and the biotope is assessed as ‘Not sensitive’ at the benchmark level.

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’ was found.

Underwater noise changes

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

Evidence

Whilst no evidence could be found for the effect of noise or vibrations on the characterizing species of these biotopes, it is unlikely that these species have the facility for detecting or noise vibrations. The pressure is considered to be 'Not relevant' to this biotope.

Introduction of light or shading

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

Evidence

Jones et al. (2012) compiled a report on the monitoring of sponges around Skomer Island and found that many sponges, particularly encrusting species, preferred vertical or shaded bedrock to open, light surfaces.  However, it is possible that this relates to decreased competition with algae.  Whilst no evidence could be found for the effect of light on the characterizing species of these biotopes, it is unlikely that these species would be impacted.  As a circalittoral biotope, a decrease in light is unlikely to be important, and an increase at the benchmark level is unlikely to be significant, as growth ceases for a number of red algae (such as Chrondrus crispus)  below ca 1.0 μmol m^-2l^-1 (ca 50 Lux).

Sensitivity assessment: Resistance to this pressure is assessed as 'High' and resilience as 'High'. This biotope is therefore considered to be 'Not sensitive' at the benchmark level.

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

Barriers and changes in tidal excursion are 'Not relevant' to biotopes restricted to open waters.

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' to seabed habitats.  NB. Collision by grounding vessels is addressed under ‘surface abrasion’.

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

‘No evidence’ was found.

Introduction or spread of invasive non-indigenous species

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

Evidence

‘No evidence’ of Invasive Non-Indigenous Species (INIS) was found for this biotope.  Due to the constant risk of new invasive species, the literature for this pressure should be revisited.

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

Cerrano et al. (2006) described ‘severe reduction’ of the zoanthid Parazoanthus axinellae in the Ligurian Sea from an average colony size of 14.24 ± 5.79 cm² to 1.97±0.27 cm² over three years, with greatest loss attributed to a ‘summer disease’ associated with warm water and the massive proliferation of a cyanobacterium of the genus Porphyrosiphon.  The encrusting sponge Crambe crambe rapidly colonized the abandoned substrata.

Gochfeld et al. (2012) found that diseased sponges hosted significantly different bacterial assemblages compared to healthy sponges, with diseased sponges also exhibiting a significant decline in sponge mass and protein content.  Sponge disease epidemics can have serious long-term effects on sponge populations, especially in long-lived, slow-growing species (Webster, 2007).  Numerous sponge populations have been brought to the brink of extinction including cases in the Caribbean with 70-95% disappearance of sponge specimens (Galstoff,1942), the Mediterranean (Vacelet,1994; Gaino et al.,1992).  Decaying patches and white bacterial film were reported in Haliclona oculata and Halichondria panicea in North Wales, 1988-89, (Webster, 2007).  Specimens of Cliona spp. have exhibited blackened damage since 2013 in Skomer. Preliminary results have shown that clean, fouled and blackened Cliona all have very different bacterial communities. The blackened Cliona are effectively dead and have a bacterial community similar to marine sediments. The fouled Cliona have a very distinct bacterial community which may suggest a specific pathogen caused the effect (Burton, pers comm; Preston & Burton, 2015). 

Whilst evidence of sponge and anthozoan mortality due to disease exists, ‘No evidence’ for the characterizing species in the British Isles was found.

Removal of target species

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

Evidence

No evidence of targeted removal (i.e. by commercial activties) of the characterizing species could found and the pressure is ‘Not relevant’ to this biotope group.

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

The characteristic species probably compete for space within the biotope, so that loss of one species would probably have little if any effect on the other members of the community. However, it should be noted that several of the characteristic species can be epibiotic.  Removal of the characteristic epifauna due to by-catch, while unlikely, could remove a proportion of the biotope and change the biological character of the biotope. These direct, physical impacts 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.  Whilst a large proportion of the sponge community is likely to be affected by abrasion events, there is some debate as it the level of effects depending on the size of the sponge and the type of abrasion effect (see Freese et al., 1999, 2001; Coleman et al., 2013). 

Sensitivity assessment. Therefore, if a proportion of the resident community is removed as by-catch, resistance is assessed as ‘Low’, resilience as ‘Low’ and sensitivity assessed as ‘High’.