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

Amphianthus dohrnii occurs in waters around the UK, south-western Europe and the Mediterranean. Over its range it experiences warmer air and sea temperatures than in the UK. Its range suggests that it is likely to be tolerant of warmer temperatures but it should be noted that local populations are likely to have adapted to local temperature regimes and assessments based on the range should be interpreted with caution. General observations on sea anemones show mortalities at raised temperatures. A short-term increase of 5°C is likely to kill some individuals of a population. A decrease in temperature may inhibit growth or reproduction. 

Eunicella verrucosa has been recorded in the Western Mediterranean and off north-west Africa (Wells et al., 1983 cited in Koomen & Helsdingen, 1996), and increase in temperature is not likely to negatively affect the species. However, during the last decades, mass mortality events related to high seawater temperature anomalies have been reported within the Western Mediterranean basin. A mass mortality event in 1999 affected many gorgonians, although Eunicella verrucosa near Gallinaria Island was ‘little affected’ (Cerrano et al. 2000).  ‘Occasional’ mortality was observed in the shallowest populations along the Provence coast (at 37-38 m) during a high temperature event in 1999 where sea temperature was 23-24 °C throughout the water column to 40m depth (Perez et al., 2000). In 2003, the pink sea fan populations were affected in the Gulf of Genoa but not along the Provence coast (Garrabou et al., 2009). Although total mortality was not explicitly reported for this species, a certain reduction in population size could be suspected, due to delayed mortality of colonies affected by high levels of injury, as observed in some other Mediterranean gorgonians (e.g. Linares et al., 2005; Coma et al., 2006).The  seafan  host, Eunicella verrucosa, may, therefore, not be impacted by this pressure.

Sensitivity assessment.  No direct evidence was found to assess the sensitivity of Amphianthus dohrnii to this pressure. This species occurs in the subtidal and compared with species from habitats which experience more variable temperatures such as the intertidal and estuaries is probably less tolerant of varying temperatures.  A chronic increase at the pressure benchmark is likely to fall within natural variation experienced by this species and as it occurs within warmer waters over its range is likely to be tolerated. An acute increase at the pressure benchmark (5^oC for a month) may exceed physiological tolerances, particularly if these occur when, or where, the anemones are acclimated to lower temperatures.  As a precaution, resistance is assessed as ‘Low’ and resilience as ‘Medium’ so that sensitivity is 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

No direct evidence was found to assess this pressure. Amphianthus dohrnii occurs in waters around the UK, south-western Europe and the Mediterranean. The UK represents the most northern part of its range and it is likely to be sensitive to a decrease in temperature.

The host species, Eunicella verrucosa may also be impacted by decreased temperatures.  Eunicella verrucosa is a southern species, distribution is generally limited to the south west of the British Isles (Hayward & Ryland, 1990; NBN, 2015).  A decrease in temperature is likely to result in mortality. However, a live specimen collected from shallow depths off North Devon in 1973 exhibited growth rings that demonstrated that the colony had survived the 1962/63 cold winter(Hiscock, pers comm.). Also, large colonies were collected from Lundy in the late 1960's suggesting no significant loss in 1962/63 (Hiscock, pers comm.).

Sensitivity assessment. No direct evidence was found to assess the sensitivity of Amphianthus dohrnii to this pressure. This species occurs in the subtidal and compared with species from habitats which experience more variable temperatures such as the intertidal and estuaries is probably less tolerant of varying temperatures.  A chronic decrease at the pressure benchmark is likely to fall within natural variation experienced by this specie and as it occurs within warmer waters over its range is likely to be tolerated. An acute decrease at the pressure benchmark (5^oC for a month) may exceed physiological tolerances, particularly if these occur when, or where, the anemones are acclimated to lower temperatures.  As a precaution, resistance is assessed as ‘Low’ and resilience as ‘Medium’ so that sensitivity is assessed as ‘Medium’. Readman & Hiscock (2017) assessed the sensitivity of Eunicella verrucosa to this pressure as ‘Medium’, suggesting that a proportion of seafans is likely to remain following decreased temperatures to support recruitment.

Salinity increase (local)

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

Evidence

No direct evidence was found to assess the sensitivity of Amphianthus dohrnii to this pressure. This species only lives in fully saline habitats. An increase in salinity to hyposaline conditions (>40 ppt) may impact both the anemone and its host seafan. Whilst no evidence for Eunicella verrucosa sensitivity was found, there is evidence of gorgonian mortality due to hypersaline effluent.  Chesher (1975) monitored the species surrounding a desalination outfall with brine effluent at 52‰ salinity, together with variable concentrations of copper and nickel.  As a group gorgonians were noted to survive brief exposure to 4-5% effluent, however, long-term survival decreased in relation to proximity to the outfall. 

Sensitivity assessment. An increase in salinity to hyposaline conditions may affect both Amphianthus dohrnii and its seafan hosts. Resistance is therefore probably ‘Low’, resilience ‘Medium’ and sensitivity is ‘Medium’.

Salinity decrease (local)

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

Evidence

Amphianthus dohrnii and its seafan hosts occur in full salinity (30-35 ppt), at the pressure benchmark, a change from full to variable salinity (18-30 ppt) is assessed. No direct evidence was found to assess this pressure but as no records from brackish or estuarine habitats were found for either the anemone or seafans, it is probable that Amphianthus dohrnii would be affected adversely by a decrease in salinity.

Sensitivity assessment. Whilst there is no specific evidence for sea fan anemone or seafans in low salinity conditions, it is probable that these species, which are typically found in circalittoral open water, would be affected adversely by a decrease in salinity at the benchmark level. Resistance is assessed as ‘Low’ (with low confidence), resilience as ‘Medium’ and sensitivity as ‘Medium’.

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

Based on diving records Amphianthus dohrnii is absent in shallower  sites around Plymouth with healthy sea fan populations that are exposed to greater levels of current and swell than preferred sites (Sharrock, 2012). Seafans are less sensitive and occur at shallower sites and those that are more exposed (Sharrock, 2012).

Sensitivity assessment. An increase in water flow at the pressure benchmark may result in less settlement of larvae but may enhance food supply to adult Amphianthus dohrnii. Resistance is assessed as ‘Medium’ and resilience as ‘Medium’ so that sensitivity is assessed as ‘Medium’.

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

This pressure is considered relevant only to species that inhabit the intertidal and sublittoral fringe and is, therefore, not relevant to Amphianthus dohrnii as it is found exclusively in subtidal habitats.

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

Amphianthus dohrnii prefer deeper habitats that are less exposed and are more senstive to wave action than its seafan hosts which occur at shallower and more wave exposed sites (Sharrock, 2012). At the pressure benchmark a change in wave height is unlikely to impact seafan anemones.

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.

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.

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.

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

No evidence was found to assess sensitivity.

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 pressure benchmark is set at compliance with Water Framework Directive (WFD) criteria for good status, based on nitrogen concentration (UKTAG, 2014).  A change in nutrient enrichment to comply with 'good' status is unlikely to lead to impacts on Amphianthus dohrnii or its sea fan hosts. Resistance and resilience are assessed as 'High' and the sea fan anemone is considered 'Not sensitive' at the benchmark level.

Organic enrichment

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

Evidence

No evidence was found on the diet of Amphianthus dohrnii but it may be able to consume organic matter. As Amphianthus dohrnii on sea fans may accumulate silt (Sharrock, 2012), the anemone is not considered sensitive to the deposition of organic matter at the pressure benchmark. Cocito et al. (2013) demonstrated the ability of Eunicella verrucosa and other gorgonians to feed on both suspended organic matter and zooplankton.

Sensitivity assessment. The input of organic matter at the pressure benchmark may provide food for the anemone and its sea fan hosts. Resistance was assessed as ‘High’, resilience as ‘High’ and sensitivity as ‘Not sensitive’.

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

Sea fans and thus sea anemones may colonize artificial hard substratum such as wrecks. A change to an artificial hard substratum does not, therefore, automatically result in loss of the population from a location. Recovery would depend on the colonization rate of sea fans. Artificial substratum may differ in character from natural habitats and may be associated with other pressures such as the presence of oil leaking from fuel tanks or the discharge of other chemicals from cargo or the presence of antifoulant.

A change to sediments would result in the loss of suitable substratum for the sea fan hosts and in turn lead to the loss of the Amphianthus dohrnii population. Based on the loss of suitable host species following a change to a sedimentary habitat, resistance to this pressure is assessed as ‘None’. Resilience is assessed as ‘Very low’ as the pressure benchmark refers to a permanent change. Sensitivity is, therefore ‘High’. This assessment is recorded with high confidence based on the clear habitat requirements of the sea fan hosts.

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 rock habitats.

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 sea fan hosts are epifaunal, 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’. (N.B. extraction of sea fans is assessed under the removal of target and non-target species pressures).

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

No specific evidence was found to assess the sensitivity of Amphianthus dohnrii to abrasion. Amphianthus dohrnii is epifaunal, soft bodied and highly likely to be killed by physical disturbance, however, where abrasion damages individuals they may recover through regrowth and the effect may be to produce more anemones via regrowth of fragments.

The host species sea fans are also likely to be intolerant of abrasion. Eunicella verrucosa has some resistance to some forms of abrasion.  Eno et al. (2001) conducted experimental potting on areas containing fragile epifaunal species in Lyme Bay, south west England. Divers observed that pink sea fan ‘flexed and bent before returning to an upright position under the weight of pots’. Although relatively resistant to a single event it was not clear whether repeated exposure could cause further damage or whether injuries had been inflicted that could lead to deterioration (Eno et al., 2001). Observation of pots suggested that they were dragged along the bottom when wind and tidal streams were strong, however, little damage to epifauna was observed.  Eunicella verrucosa were patchily distributed in areas subject to potting damage, but the study could not determine whether this was due to damage from potting (Eno et al., 2001). A further four year study on potting in the Lundy Marine Protected Area detected no significant differences in Eunicella verrucosa between areas subject to commercial potting and those where this activity was excluded.   Tinsley (2006) observed flattened sea fan that had continued growing, with new growth being aligned perpendicular to the current, so even colonies of Eunicella verrucosa that are damaged can survive. Healthy Eunicella verrucosa were able to recover from minor damage and scratches to the coenenchyme (Tinsley, 2006), and the coenenchyme covering the axial skeleton would re-grow over scrapes on one side of the skeleton in about one week (Hiscock, pers. comm.)  Hinz et al. (2011) reported that Eunicella verrucosa did not show a significant negative response (abundance or average body size) to scallop dredging intensity.

Sensitivity assessment. No evidence was found to assess the sensitivity of Amphianthus dohrnii, as it is dependent on its seafan host the sensitivity assessment is based on the seafan Eunicella verrucosa. Eunicella verrucosa is likely to be severely damaged by heavy gears, such as scallop dredging (MacDonald et al., 1996).  However,  some studies suggests that the species may be more resistant, particularly to low intensity lighter abrasion pressures, such as pots and associated anchor damage (Eno et al., 1996)  Taking all the evidence into account, a resistance of ‘Low’ is recorded, albeit with a low confidence value owing to the lack of consensus in the literature. Resilience is assessed as ‘Medium’ and sensitivity as ‘Medium’. Confidence is assessed as low as the evidence refers to the host seafan rather than Amphianthus dohrnii.

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 considered ‘Not Relevant’ to hard rock species and habitats.

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

Amphianthus dohrnii attached to sea fans often collect silts and some may be heavily silted (Sharrock, 2012), suggesting that they are tolerant of increases in siltation associated with increased sediments in the water column.  While siltation may inhibit feeding, colonies of the sea fan Eunicella verrucosa produce mucus to clear themselves of silt (Hiscock, pers. comm.) and is probably tolerant of increases in suspended sediment (Hiscock et al., 2004).  Bunker (1986) reported that Eunicella verrucosa were mostly observed on bedrock or boulders, but occurred at sites described as ‘moderately silted’.

Williamson et al. (2011) recorded responses in the gorgonian Leptogorgia virgulata over 14 days to sedimentation treatments up to 20,000 mg /l.  The gorgonians maintained healthy tissue and polyp feeding activity and did not show any symptoms or significant differences in tissue loss.

Sensitivity assessment. Amphianthus dohrnii and its sea fan hosts would probably tolerate an increase in suspended sediments and some siltation and a change at the benchmark level is unlikely to cause mortality although there may be some sub-lethal effects on feeding and hence growth and possibly reproduction.  Resistance is recorded as ‘High’, resilience as ‘High’ and the species is ‘Not sensitive’ at the benchmark level. A decrease in suspended inorganic solids is unlikely to lead to negative effects on the anemones or seafan hosts but a reduction in suspended organic matter may reduce food supply to anemones and sea fans may reduce food supply but this could be mitigated by enhanced phytoplankton productivity. 

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

Amphianthus dohrnii attached to sea fans often collect silts and some may be heavily silted (Sharrock, 2012), suggesting that they are tolerant of increases in siltation associated with sediment deposition.  At the pressure benchmark (deposition of 5cm of fine sediment) the anemone is unlikely to be directly smothered as it tends to occur on the top of sea fans (Sharrock, 2012) and will, therefore, be too high above the substratum to be covered.

While high levels of suspended sediment may inhibit feeding, colonies of the sea fan Eunicella verrucosa produce mucus to clear themselves of silt (Hiscock, pers comm.). Bunker (1986) reported that Eunicella verrucosa were mostly observed on bedrock or boulders but occurred at sites up to ‘moderately silted’.  

Sensitivity assessment. Amphianthus dohrnii tends to occur on the top of sea fans (Sharrock, 2012) and is therefore unlikely to be affected at the benchmark level.  Resistance is therefore assessed as 'High', resilience as 'High' and the species is 'Not sensitive'.

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 30 cm of sediment would likely bury the majority of sea fans and the associated Amphianthus dohrnii, with only those individuals on larger boulders and vertical surfaces escaping burial.  Amphianthus dohrnii appears to prefer sites without strong wave action and currents (Sharrock, 2012) and removal of sediments by water may require some time.  The damage to the anemones and sea fans would depend on the time taken for the deposited sediment to be removed. Resistance is assessed as ‘Low’ as there may be mortality of substantial numbers of sea fans and anemones, resilience is probably ‘Medium’ and sensitivity is 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

Neither Amphianthus dohrnii nor its host species are likely to react to noise vibrations and this pressure is considered to be ‘Not relevant’.

Introduction of light or shading

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

Evidence

Not relevant, neither Amphianthus dohrnii or Eunicella verrucosa are likely to be directly impacted by changes in light levels.

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: barriers and changes in tidal excursion are not relevant to species 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 and associated species.  NB. Collision by interaction with bottom towed fishing gears and moorings are 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

Neither Amphianthus dohrnii nor its host species are likely to react to visual disturbance and this pressure is considered to be ‘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

Amphianthus dohrnii and the sea fans they grow on are not cultivated or translocated. This pressure is therefore considered ‘Not relevant’ to this species.

Introduction or spread of invasive non-indigenous species

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

Evidence

No direct evidence was found for impacts of invasive non-indigenous species (INIS) on Amphianthus dohrnii. Non-indigenous species may have indirect effects on the sea fan anemone where they lead to mortality or changes in distribution of the seafan hosts.

Solidobalanus fallax is an invasive southern species barnacle only recently recorded in south west England (Southward et al., 2004) and, along with hydroids and bryozoans, have been observed fouling (primarily damaged or diseased) gorgonians (Hall-Spencer et al., 2007).  Fouling smothers the sea fan polyps and the membrane that covers the skeleton thus killing the live tissue of the sea fan. Eventually this can weaken the fan structure to the extent that fragmentation occurs. This can be accentuated by the weight of fouling turf and attracted silt associated with Amphianthus dohrnii (Sharrock, 2012). The barnacle may impact Amphianthus dohrnii either thorugh space pre-emption on seafans or through damage and loss of seafans.

Sensitivity assessment. Resistance is assessed as ‘Medium’, resilience as ‘Medium’ and sensitivity as ‘Medium’.  

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

No evidence was found to assess the sensitivity of Amphianthus dohrnii to microbial pathogens.

A number of diseases may affect the seafan hosts. The first recorded incidence of cold-water coral disease was noted in Eunicella verrucosa, in south west England in 2002 (Hall-Spencer et al., 2007).  Video surveys in south west England from 2003 to 2006 of 634 separate colonies at 13 sites revealed that disease outbreaks were widespread and 9% of colonies had tissue necrosis.  Coenenchyme became necrotic in diseased specimens, leading to tissue sloughing and exposing skeletal gorgonin to settlement by fouling organisms. Sites where necrosis was found had significantly higher incidences of fouling. No fungi were isolated from diseased or healthy tissue, but significantly higher concentrations of bacteria occurred in diseased specimens. Vibrio isolated from Eunicella verrucosa did not induce disease at 15°C, but, at 20°C, controls remained healthy and test gorgonians became diseased, regardless of whether Vibrio were isolated from diseased or healthy colonies. Bacteria associated with diseased tissue produced proteolytic and cytolytic enzymes that damaged Eunicella verrucosa tissue and may be responsible for the necrosis observed. Monitoring at the site where the disease was first noted showed new gorgonian recruitment from 2003 to 2006; 5 of the 18 necrotic colonies videoed in 2003 had died and become completely overgrown, whereas others had continued to grow around a dead central area (Hall-Spencer et al., 2007).

Sensitivity assessment. Based on evidence of mortality linked to disease in Eunicella verrucosa, resistance is assessed as ‘Medium’, resilience as ‘Medium’ sensitivity as ‘Medium’. Confidence is low as the impacts of diseases on seafan host habitat provision to Amphianthus dohrnii is not clear.

Removal of target species

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

Evidence

Amphianthus dohrnii is not targeted by commercial or recreational fishers or harvesters. This pressure is therefore considered ‘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

Amphianthus dohrnii may be indirectly impacted by commercial or recreational collecting or fishing activities that affect the sea fans that it occurs on leading to habitat loss.   Amphianthus dohrnii is likely to be removed if the sea fan it is associated with is removed.

Eunicella verrucosa has historically been harvested as a curio by divers and was collected in the British Isles (Bunker, 1986; Wells et al., 1983 cited in Koomen & Helsdingen, 1996), however it is now protected under schedule 5 of the Wildlife and Countryside Act 1981 and harvesting is illegal. 

Sensitivity assessment. The biogenic habitat provided by Eunicella verrucosa or Swiftia pallida would have no resistance to harvesting.  Resistance has been assessed as ‘None’, resilience as ‘Low’ and sensitivity is therefore ‘High’.