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

Limited evidence was found on the effect of changes in temperature and resistance is inferred from the species range. As with other marine species, changes in temperature may influence timing of reproduction and, therefore, long-term recruitment.

Hesionura elongata occurs in the Canary Islands and Caribbean, which suggests a resistance of higher water temperatures than around UK and Irish seas (Brito et al., 2005; Miloslavich et al., 2010). Similarly, Microphthalmus similis occurs in warmer waters along the west coast of Portugal (Carvalho et al., 2005). Protodrilus spp.  such as Protodrilus corderoi, Protodrilus ovarium and Protodrilus pythonius also occur in warmer waters and are reported from beaches in southern and south eastern Brazil (Di Domenico et al., 2013).

Turbellaria spp. occur in high abundance with records of up to 115 000 per m² recorded (Murina, 1981). Although Turbellaria spp. occur globally there is limited evidence available on the range of species that occur in UK and Irish seas. There is limited evidence on the temperature range occupied by these species. This limits interpretation of resistance to increases in temperature. Turbellaria spp. display life history strategies of larger meiofauna, with planktonic development, dispersal in larval stages and continuous growth. Generation times are of no more than one year and the species feed indiscriminately on particles, these traits suggest faster recolonization and adaptability to conditions, aiding resilience and recovery times (Warwick, 1984, Martens & Schockaert, 1986).

Sensitivity assessment. This assessment relies on limited evidence and utilises global species distribution records and so confidence is low. As all characterizing species occur in water temperatures greater than they are likely to experience in the UK. Resistance and Resilience are assessed as ‘High’ and Sensitivity as ‘Not Sensitive’. There is low confidence associated with this assessment as limited evidence was available.

Temperature decrease (local)

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

Evidence

Limited evidence was returned on the effect of changes in temperature and resistance is inferred from the species range. Hesionura elongata has been identified in samples from water ranging from 7.3-24°C (OBIS, 2016).

Microphthalmus similis is recorded in locations with water temperatures ranging from 6.05 to 11.62°C (OBIS, 2016). Protodrilus spp.  also show a similar lower temperature preference of 7.34 °C from distribution maps of species records (OBIS, 2016).

Turbellaria spp. occur throughout colder regions than UK and Irish seas, including circumpolar seas, which suggests the species is likely to be resistant to lower temperatures (Ax & Armonies, 1990; Ax, 1993).

Sensitivity assessment. Limited evidence was available and this assessment is based on non-peer reviewed literature on species range. A 5°C decrease in temperature for one month period is likely to impact the characterizing species in winter months and therefore Resistance is ‘Medium’, Resilience is ‘High’ and Sensitivity is ‘Low’. 

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 conditions. An increase in one MNCR salinity category to hypersaline conditions is likely to cause mortality of characterizing species. Resistance is ‘None’, Resilience is ‘Medium’ and Sensitivity is ‘Medium’. There is limited evidence associated with this assessment and confidence is therefore low.

Salinity decrease (local)

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

Evidence

A decrease from full/variable to reduced (18-30‰) is considered in this assessment.

Degraer et al. (2006) report that Hesionura elongate was found in greatest abundance outside the near coastal zone (in samples from across the Belgium part of the North Sea). This suggests that the species is likely to occur in greater abundance in habitats with full salinity compared to variable salinity or reduced. Moulaert et al. (2008) also found that species communities in which Hesionura elongate was an indicator species were only present >16 km from the coast and displayed a positive correlation with increasing salinity.

Microphthalmus similis were a dominant species in the Weser estuary, suggesting resistance to the benchmark pressure although the species was most abundant in polyhaline conditions (18-30‰) but not in lower salinities (Witt, 2004). Limited evidence was found on Protodrilus spp.

Procerodes littoralis, a common triclad turbellarian that occurs along the Atlantic coast of Europe, has been shown to be exceptionally tolerant of short-term salinity changes ranging from completely freshwater to undiluted seawater (McAllen et al. 2002).

Travisia forbesii is restricted to a narrow range of clean medium sands (d50: 250 - 500 µm) under fully marine conditions. In reduced salinity waters (5-19‰), the species was found also in clean fine sands with a lower limit of about 100 µm. No occurrence was reported from coarse sediments in low salinity waters (Zettler et al., 2013).

Sensitivity assessment. Resistance is assessed as ‘Medium’ as Hesionura elongate may decrease in abundance, although confidence is limited in this assessment and all other species would have higher resistance. Resilience is assessed as ‘High’ and sensitivity is assessed as ‘Low’.

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

The biotope occurs most often in weak or strong tidal streams (JNCC comparative tables) suggesting the species characterizing the biotope can adapt to a range of tidal currents, aided by each species traits, burrowing or living interstitially.

The hydrographic regime is an important structuring factor in sedimentary habitats. The most damaging effect of a change in flow rate could be the erosion of the substratum (an increase in flow rate), or deposition of fine grain sized sediment (decrease in flow rate) as this could eventually lead to loss of the habitat. Increased peak flow may cause an increase in sediment movement and this is to be prohibitive to substantial interstitial fauna colonisation due to sediment movement and the potential for the gaps in the sediment to be disturbed (Nybakken, 2001; Alexander, 2013).

The species community appears to have low resistance to changes to finer sediment grain sizes. The characterizing species Hesionura elongata and Microphthalmus similis are found in greater abundance in sediments with larger grain sizes, and decreasing abundance in fine sediments. Moulaert & Hostens (2007) found that higher gravel content and sediment grain size was a dictating environmental factor for communities in which Hesionura elongate was an indicator species for. Resilience is likely to be high for Hesionura elongate as the species showed the highest increase following cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007). Microphthalmus similis was the principal characterizing species in medium and coarse grain sediments on Belgium coastal sandbanks, but was not present in other regional species communities that inhabited sediments with very low % coarse grain size (<10%) (Degraer et al., 1999).

The deposition of fine sediment re-suspended by scour processes may alter this biotope and should be considered. Longer term deposition of fine material (e.g. continuous deposition) would be expected to lead to a decrease in abundance of the characterizing species and higher densities of other macrobenthic organisms. For example, in the North Sea (Belgium) deposition of fine particle sediment, disturbed by scour around the base of a wind farm tower led to higher macrobenthic densities and created a shift in macrobenthic communities around the wind farm tower (influenced by the  direction fine material had settled) (Coates et al., 2014).

Sensitivity assessment. The biotope occurs most often in weak or moderately strong tidal currents suggesting the characterizing species are resistant to changes in spring bed flow velocity. The effects on sediment transport characteristics at a site or case specific level are important. A decrease in flow velocity may increase deposition of fine material which may lead to a decrease in occurrence of characterizing species. As the biotope occurs across weak to strong categories Resistance is assessed as ‘High’ as species abundance may decrease but if gravel content is still high characterizing species will still occur. Resilience is assessed as ‘High’ and Sensitivity is assessed as ‘Not sensitive’.

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 biotope does not occur in the intertidal, and consequently an increase in emergence is considered not relevant to this biotope.

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

The biotope occurs on sandbanks permanently covered by seawater (5-10 m depth and 10-20 m depth) and species communities are unlikely to be affected by wave action directly.  However, increased wave action results in increased water flow in the shallow subtidal. Wave mediated water flow tends to be oscillatory, i.e. move back and forth (Hiscock, 1983), and may result in suspension of fine sediments and deposition in the direction of dominant water currents. In areas where fine sediment is deposited impacts will be similar to those under the section below on ‘smothering and siltation changes’ (light deposition).

The species community appears to have low resistance to changes to finer sediment grain sizes. The characterizing species Hesionura elongata and Microphthalmus similis are found in greater abundance in sediments with larger grain sizes, and decreasing abundance in fine sediments. Moulaert & Hostens (2007) found that higher gravel content and sediment grain size was a dictating environmental factor for communities in which Hesionura elongate was an indicator species for. Resilience is likely to be high for Hesionura elongate as the species showed the highest increase following cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007). Microphthalmus similis was the principal characterizing species in medium and coarse grain sediments on Belgium coastal sandbanks, but was not present in other regional species communities that inhabited sediments with very low % coarse grain size (<10%) (Degraer et al., 1999).

Protodrilus spp. have been reported to thrive in the swash zone of reflective beaches, where turbulence is far greater than would be experienced under the pressure at baseline levels (Di Domenico et al. 2009; McLachlan 1985, 1990). The presence of adhesive glands as well as special epidermal glandular or skeletal structures provides these species with adaptations to such extremely turbulent environments (Bush, 1968; Delamare & Deboutteville, 1960; Boaden, 1995; Giere, 2009; Jouin, 1970).

Sensitivity assessment. The abundance of characterizing species is likely to be unaffected or increase in areas where fine sediment is removed and coarse sediment is present. However, abundance is likely to decrease in areas where fine sediment is deposited. Under pressure benchmark levels which consider <5% change, Resistance is ‘High’ and Resilience ‘High’. Sensitivity is assessed as ‘Not Sensitive’.

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. Although contamination at levels greater than the pressure benchmark may adversely affect the biotope.

Hydrocarbon & PAH contamination

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

Evidence

This pressure is Not assessed but evidence is presented where available. The following review discusses impacts at higher concentrations than the pressure benchmark.

Suchanek (1993) reviewed the effects of oil spills on marine invertebrates and concluded that, in general, on soft sediment habitats, infaunal polychaetes, bivalves and amphipods were particularly affected. The 1969 West Falmouth Spill of Grade 2 diesel fuel, documented by Sanders (1978), illustrates the effects of hydrocarbons in a sheltered habitat with a soft mud/sand substrata (Suchanek, 1993). The entire benthic fauna was eradicated immediately following the spill and remobilization of oil that continued for a period >1 year after the spill contributed to much greater impact upon the habitat than that caused by the initial spill. Effects are likely to be prolonged as hydrocarbons incorporated within the sediment by bioturbation will remain for a long time, owing to slow degradation under anoxic conditions. Oil covering the surface and within the sediment would prevent oxygen transport to the infauna and promote anoxia as the infauna utilise oxygen during respiration. Although this study investigates impacts on an estuarine biotope the impact on benthic infauna communities is likely to be similar in shallow sandbank biotopes.

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. The following review discusses impacts at higher concentrations than the pressure benchmark.

Limited evidence was available on the response of characterizing species to synthetic compound contamination. For instance, the Turbellaria species Giardia tigrina displayed 100% mortality when exposed to 50 ppm concentrations of diazepam and ivermectin, 60% mortality at concentrations of 25 ppm, and 20% mortality after 24 hours exposure to 1 ppm (Alves & De Melo, 2013).

Radionuclide contamination

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

Evidence

Limited evidence is available on other infauna species. Beasley & Fowler (1976) and Germain et al., (1984) examined the accumulation and transfers of radionuclides in Hediste diversicolor from sediments contaminated with americium and plutonium derived from nuclear weapons testing and the release of liquid effluent from a nuclear processing plant. Both concluded that the uptake of radionuclides by Hediste diversicolor was small. Beasley & Fowler (1976) found that Hediste diversicolor accumulated only 0.05% of the concentration of radionuclides found in the sediment. Both also considered that the predominant contamination pathway for Hediste diversicolor was from the interstitial water.

Sensitivity assessment: There is insufficient information available on the biological effects of radionuclides to comment further upon the intolerance of characterizing species to radionuclide contamination. Assessment is given as ‘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.

Some, all be it limited evidence was retuned by searches on activated carbon (AC). AC is utilised in some instances to effectively remove organic substances from aquatic and sediment matrices. Lillicrap et al. (2015) demonstrate that AC may have physical effects on benthic dwelling organisms at environmentally relevant concentrations at remediated sites.

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

Limited evidence was returned on effects of decreased dissolved oxygen concentrations on the characterizing species.

All meiofauna have some sensitivity to extended hypoxia, although more mobile nematode species are able to emigrate into the water column in high numbers where they survive (Wetzel et al., 2013). Emigration is likely to increase predation risk. Although evidence on characterizing species is lacking, densities of meiofauna populations are likely to be lower under prolonged anoxia (Moodley et al., 1997).  

A turbellarian, Macrostomum lignano was found to be a species that is tolerant of a wide range of oxygen concentrations (being able to maintain aerobic metabolism from extremely low P-O2 up to hyperoxic conditions), and is thought to be resistant to the drastic environmental oxygen variations that occur within intertidal sediments (Rivera-Ingraham et al., 2013).

As the biotope occurs in high energy areas strong water flow occurs and deoxygenation is likely to be short lived.

Sensitivity assessment. Due to the limited evidence confidence in this assessment is low. A reduction in meiofauna populations is likely if deoxygentaion persisted for long periods, but this is unlikely due to high water flow. As some species are likely to emigrate or maintain aerobic metabolism under low dissolved oxygen conditions, Resistance is assessed as ‘Medium’, Resilience is ‘High’ and Sensitivity is assessed as ‘Low’.

Nutrient enrichment

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

Evidence

Meiofauna respond to nutrient enrichment. The distribution of different meiofauna assemblages has been identified as a good tool for detecting short-term responses of the benthic domain to nutrient enrichment from sources such as river discharge (Semprucci et al., 2015). In the Bay of Cadiz, Spain, abundance of meiofauna was seven times higher in the presence of macroalgae (Bohorquez et al., 2013).

Limited evidence is available on response of characterizing species of this biotope, although Semprucci et al. (2015) identified that platyhelminthes (Turbellaria spp.) responded positively to nutrient enrichment.  

Sensitivity assessment. As the benchmark levels comply with WFD criteria for good status, Resistance is ‘High’, Resilience is ‘High’ and the biotope is 'Not sensitive' at the benchmark level, which assumes compliance with environmental standards. Confidence is limited as evidence was only available for higher taxonomic levels and study sites within warmer, coastal European locations than UK and Irish seas.

Organic enrichment

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

Evidence

Limited evidence was returned on individual characterizing species. Microphthalmus similis occurred in the area of a coastal lagoon characterized by sandy sediment and low organic content (Carvalho et al., 2005).  However, case studies for other individual species were lacking. At higher taxonomic levels meiofauna have been utilised in studies investigating their role as indicators of organic enrichment. Bianchelli et al. (2016) identified that meiofauna diversity increased when sediment organic contents increased.

Bianchelli et al. (2016) identified that meiofauna can be used as a descriptor of environmental quality, indicating conditions from sufficient to moderately impacted, in relation to organic enrichment. In the investigated sediments, characterized by oligo- and mesotrophic conditions, increasing richness of meiofaunal taxa was linked to the increase in sediment organic contents and the protein to carbohydrate content ratio (Bianchelli et al., 2016). Further evidence on other conditions such as mesotrophic to eutrophic was not available.

Sensitivity assessment. Evidence was limited on individual species responses and confidence in the assessment is low. Although studies identified that meiofauna diversity increased at hogher taxonomic levels this may not include characterizing species . Resistance is 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

This biotope is only found in infralittoral sandbanks and sandwaves and other areas of mobile medium-coarse sand, and characterizing species  burrow or live interstitially within the sediment and would not be able to survive if the substratum type was changed to either a soft rock or hard artificial type. Consequently, the biotope would be lost altogether if such a change occurred. 

Sensitivity assessment.  The Resistance to this change is ‘None’, and the Resilience is assessed as ‘Very low’, due to the long-term nature of a change in substratum.  The biotope is assessed to have a ‘High’ Sensitivity to this pressure at the benchmark. 

Physical change (to another sediment type)

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

Evidence

The biotope is recorded from; medium to coarse sand, loosely packed, forming waves up to several metres high often with gravel, or occasionally silt, in the troughs of the waves. The most relevant folk class is ‘medium fine coarse sand’.  An, increase in gravel content within the Folk classes is unlikely to negatively impact the characterizing species. An increase in finer sand or silt is likely to reduce the abundance of the characterizing species as Hesionura elongata and Microphthalmus similis, which are found in greater abundance in sediments with larger grain sizes, and decreasing abundance in fine sediments. Moulaert & Hostens (2007) found that higher gravel content and sediment grain size was a dictating environmental factor for communities where Hesionura elongata was an indicator species. Resilience is likely to be high for Hesionura elongata as the species showed the highest increase following the cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007). Microphthalmus similis was the principal characterizing species in medium and coarse grain sediments on Belgium coastal sandbanks but was not present in other regional species communities that inhabited sediments with very low % coarse grain size (<10%) (Degraer et al., 1999).  Variants of this biotope with more coarse or mixed substrata may lack Hesionura elongata, probably due to the increase in fine particulates in mixed sediment, but still include the interstitial polychaetes characteristic of this biotope. 

Sensitivity assessment. A decrease in gravel and sand content and a change to ‘muddy sand’ or 'mud and sandy muds' is considered in this assessment as the biotope and characterizing species are unlikely to be impacted by an increase in coarse sediment. As silt is occasionally encountered in the troughs of the sand waves and coarser sediment is most likely to be found on the ridges of sand waves, the biotope and its variants contain a range of sediment classes. However, characterizing species show a preference for coarse sediment and are likely to reduce in abundance as the percentage of finer sediments increases. Therefore, resistance is assessed as ‘Low’, resilience as ‘Very low ’(the pressure is a permanent change) and sensitivity is assessed as ‘High’.

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 substratum of this biotope consists of infralittoral sandbanks and sandwaves and other areas of mobile medium-coarse sand (Conner et al., 2004). The characterizing species burrow into the sediment, tunnel to depths not exceeding 30 cm or live in the interstices between the grains of sediment. The process of extraction is considered to remove all biological components of the biotope group.  If extraction occurred across the entire biotope, loss of the biotope would occur. Recovery would require substratum to return to mobile medium-coarse sand.

Sensitivity assessment. Resistance to the pressure is considered ‘None’, and resilience ‘Medium’. Sensitivity has been assessed as ‘Medium’. Although no specific evidence is described, confidence in this assessment is high, due to the incontrovertible nature of this pressure.  

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

The spatial scale and duration are important to consider in utilizing this assessment. For instance, spatially the whole biotope or just a smaller area may be affected. Also different sediment types and associated species communities will occur in the surface layers, at the site of aggregate extraction or scouring (where coarser sediment grain sizes prevail) and areas where finer sediment is deposited within the prevailing currents. The species characterizing this biotope are likely to colonize areas where extraction or scour has occurred and not the areas of deposition. For instance, Vanaverbeke et al. (2007) found Hesionura elongata, Polygordius appendiculatus and Microphthalmus spp. represented a more important proportion of the density in very intensively extracted dredging sites in the Belgium North Sea. Resilience is likely to be high for Hesionura elongate as the species showed the highest increase following cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007).

Collie et al. (2000) suggest that bottom towed fishing gears are likely to cause a shift from communities dominated by relatively high biomass species towards dominance by high abundances of small-sized organisms, such as the characterizing species in this biotope; Hesionura elongata and Microphthalmus similis. This suggests that,  even though initial resistance to physical damage from contact with fishing gears is likely to be ‘Low’, resilience is ‘High’ given the physical traits of the species and species life history.

Boat moorings were demonstrated to impact species communities close to the mooring buoy in a case study in the Fal and Helford estuaries (south west UK). Coarser sediment was exposed close to mooring buoys, caused by suspension of fine sediments by movement of the chain (Latham et al., 2012). Abrasion from anchors and anchor chains may have similar impacts on this biotope. However, the highly mobile nature of sediments in the biotope are likely to result in the sediment providing high resistance to such abrasion over small spatial scales and the biotope will only be impacted if a high density of vessels are at anchor.

Turbellarian abundance is likely to be decreased by deposition of fine material as the species live relatively shallowly in the sediment. Being mobile, individuals may be able to relocate to preferred depths. In the long-term, however, populations are likely to show a preference for sites with lower deposition of material. In the Fladen Ground area. Faubel et al. (1983) only found turbellarians below 4 cm occasionally. Huys et al. (1984) found 5 – 10 ind/10cm² in 19 stations of a shallow subtidal dumping site but on average Turbellarians accounted for only 3.6% of the total meiofauna in the samples.

Sensitivity assessment. Different sediment types and associated species communities will occur in association with aggregate extraction, scouring around renewable energy device bases and anchoring sites. Where coarser sediment is exposed abundance of characterizing species will display limited impact. Where deposition of fine sediment occurs, typically further away from an obstruction such as a wind farm tower, or from deposition of aggregate or drilling waste will be likely to lead to reduction in abundance of characterizing species. Resistance to damage to seabed surface features is assessed as ‘Medium’. The species community displays high recoverability and Resilience is ‘High’ and Sensitivity is assessed as ‘Low.’

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 and or disturbance of the substratum would result in similar effects as ‘abrasion’ or ‘extraction’ of this biotope (see evidence in those sections).  As the characterizing species are burrowing species the impact from damage to the sub-surface sea bed would be greater than damage to the sea bed surface. Resistance has been assessed as '​Low' ​and resilience as ​Medium​, s​ensitivity is Medium.

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

This biotope is probably exposed to water flow rates that will re-suspend sediements when it occurs in areas with moderately strong tidal streams. Therefore, the resident species are probably adapted to high suspended sediment levels.

The characterizing species live infaunally. Microphthalmus similis and Travisia forbesii along with protodrilid polychaetes such as Protodrilus spp. and Protodriloides spp. are deposit feeders, therefore relying on a supply of nutrients at the sediment surface. An increased rate of siltation may result in an increase in food availability and therefore growth and reproduction of characterizing species. However, food availability would only increase if the additional suspended sediment contained a significant proportion of organic matter and the population would only be enhanced if food was previously limiting. A decrease in the suspended sediment would result in a decreased rate of deposition on the substratum surface and therefore a reduction in food. This would be likely to impair growth and reproduction.

Sensitivity assessment. Changes in light penetration or attenuation associated with this pressure are not relevant to the characterizing species. As the species live in the sediment they are also likely to be adapted to increased suspended sediment (and turbidity). However, alterations in the availability of food or the energetic costs in obtaining food or changes in scour could either increase or decrease habitat suitability for these characterizing species.

The following sensitivity assessment relies on expert judgement, utilizing evidence of species traits and distribution and therefore confidence has been assessed as low. Resistance is ‘High’ as no significant negative effects are identified and potential benefits from increased food resources may occur. Resilience is also ‘High’ as no recovery is required under the likely impacts. Sensitivity of the biotope is therefore assessed as ‘Not Sensitive’.

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

Evidence is assessed for deposits of fine material from sources such as dredge waste spoil, re-suspended sediment from scouring around wind farm tower bases and recovery from aggregate dredging.

The biotope consists of mobile medium-coarse sand and the characterizing species typically occur in coarser grain size sediments, and are not found in finer grain size habitats. Moulaert & Hostens (2007) found that higher gravel content and sediment grain size was a dictating environmental factor for communities in which Hesionura elongate was an indicator species for. Resilience is likely to be high for Hesionura elongate as the species showed the highest increase following cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007).

Turbellarian abundance is likely to be decreased by heavy deposition of fine material as the species live relatively shallowly in the sediment. Being mobile, individuals may be able to relocate to preferred depths. In the long-term, however, populations are likely to show a preference for sites with lower deposition of material. In the Fladen Ground area Faubel et al. (1983) only occasionally found turbellarians below 4 cm. Heap 1990 and Huys et al. (1984) found 5 – 10 ind/10cm² in 19 stations of a shallow subtidal dumping site but on the average turbellarians accounted for only 3.6% of the total meiofauna in the samples.

Species of Protodrilus occur in a greater range of sediment sizes but are restricted to the interstitial environment of marine sediments, spanning from sand to gravel (Von Nordheim 1989), suggesting the finest sediment grain sizes are likely to provide unsuitable habitats.

The species community appears to have low resistance to changes to finer sediment grain sizes. The deposition of fine sediment re-suspended by scour processes as a result of presence of wind farm towers and other renewable energy device bases may alter this biotope and should be considered. Longer term deposition of fine material (e.g. continuous deposition) would be expected to lead to decrease in abundance of the characterizing species and higher densities of other macrobenthic organisms. For example, in the North Sea (Belgium) deposition of fine particle sediment, disturbed by scour around the base of a wind farm tower led to higher macrobenthic densities and created a shift in macrobenthic communities around the wind farm tower (influenced by the  direction fine material had settled) (Coates et al., 2014).

The species characterizing this biotope are likely to colonize areas where extraction or scour has occurred and not the areas of deposition. For instance, Vanaverbeke et al. (2007) found Hesionura elongata, Polygordius appendiculatus and Microphthalmus spp. represented a more important proportion of the density in very intensively extracted dredging sites in the Belgium North Sea. 

Sensitivity assessment. Where deposition of fine sediment occurs, typically further away from an obstruction such as a wind farm tower, or from deposition of aggregate or drilling waste will be likely to lead to reduction in abundance of characterizing species. Resistance to deposition of fine sediment is assessed as ‘Medium’. The species community displays high recoverability due to inhabiting mobile sediments and resilience is ‘High’. Sensitivity is 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

Limited evidence was found on responses of characterizing species to a deposition of up to 30cm of fine material. Evidence is assessed for deposits of fine material from sources such as dredge waste spoil and recovery from aggregate dredging.

The biotope consists of mobile medium-coarse sand and the characterizing species typically occur in coarser grain size sediments, and are not found in finer grain size habitats. Moulaert & Hostens (2007) found that higher gravel content and sediment grain size was a dictating environmental factor for communities in which Hesionura elongate was an indicator species for. Resilience is likely to be high for Hesionura elongate as the species showed the highest increase following cessation of sediment extraction in the Belgium part of the North Sea (Moulaert & Hostens, 2007).

Turbellarian abundance is likely to be decreased by heavy deposition of fine material as the species live relatively shallowly in the sediment. Being mobile, individuals may be able to relocate to preferred depths. In the long-term, however, populations are likely to show a preference for sites with lower deposition of material. In the Fladen Ground area, Faubel et al. (1983) only occasionally found turbellarians below 4 cm. Heap (1990) and Huys et al. (1984) found 5 – 10 ind/10cm² in 19 stations of a shallow subtidal dumping site but on the average turbellarians accounted for only 3.6% of the total meiofauna in the samples.

Species of Protodrilus occur in a greater range of sediment sizes but are restricted to the interstitial environment of marine sediments, spanning from sand to gravel (Von Nordheim, 1989), suggesting the finest sediment grain sizes are likely to provide unsuitable habitats.

The species community appears to have low resistance to changes to finer sediment grain sizes. The deposition of fine sediment re-suspended by scour processes as a result of presence of wind farm towers and other renewable energy device bases may alter this biotope and should be considered. Longer term deposition of fine material (e.g. continuous deposition) would be expected to lead to decrease in abundance of the characterizing species and higher densities of other macrobenthic organisms. For example, in the North Sea (Belgium) deposition of fine particle sediment, disturbed by scour around the base of a wind farm tower led to higher macrobenthic densities and created a shift in macrobenthic communities around the wind farm tower (influenced by the direction fine material had settled) (Coates et al., 2014).

Sensitivity assessment. Deposition of fine sediment, typically occurring further away from an obstruction such as a wind farm tower, or deposition of aggregate or drilling waste will be likely to lead to a change in the species community. The species community will return to that charcaterizing mobile medium-coarse sand if physical processes such as sediment transport provide a return to that habitat. Resistance is assessed as ‘Low’, Resilience to a single discrete event (given conditions are likely to return to coarser material over time) is ‘Medium’ and Sensitivity is ‘Medium.’

The spatial scale and duration are important to consider in utilizing this assessment. For instance, spatially the whole biotope or just a smaller area may be affected. Also different sediment types and associated species communities will occur at the site of aggregate extraction or scouring (where coarser sediment grain sizes prevail) and areas where finer sediment is deposited within the prevailing currents. The species characterizing this biotope are likely to colonize areas where extraction or scour has occurred and not the areas of deposition. For instance, Vanaverbeke et al. (2007) found Hesionura elongata, Polygordius appendiculatus and Microphthalmus spp. represented a more important proportion of the density in very intensively extracted dredging sites in the Belgium North Sea.  

Litter

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

Evidence

No evidence was returned on the impact of litter on characterizing species for this biotope, although studies show impacts from ingestion of micro plastics by sub surface deposit feeding worms (Arenicola marina) and toxicants present in cigarette butts have been shown to impact the burrowing times and cause DNA damage in ragworms Hediste diversicolor.

Litter, in the form of cigarette butts has been shown to have an impact on Ragworms. Hediste diversicolor showed increased burrowing times, 30% weight loss and a  >2 fold increase in DNA damage when exposed to water with toxicants (present in cigarette butts) in quantities 60 fold lower than reported from urban run-off (Wright et al., 2015). Studies are limited on impacts of litter on infauna and this UK study suggests health of infauna populations are negatively impacted by this pressure.

Studies of sediment dwelling, sub surface deposit feeding worms, a trait shared by species abundant in this biotope, showed negative impacts from ingestion of micro plastics. For instance, Arenicola marina ingests micro plastics that are present within the sediment it feeds within. Wright et al. (2013) carried out a lab study that displayed presence of micro plastics (5% UPVC) significantly reduced feeding activity when compared to concentrations of 1% UPVC and controls. As a result, Arenicola marina showed significantly decreased energy reserves (by 50%), took longer to digest food, and decreased bioturbation levels. These effects would be likely to impact colonisation of sediment by other species, reducing diversity in the biotopes the species occurs within. Wright et al. (2013) also present a case study based on their results, that in the intertidal regions of the Wadden Sea, where Arenicola marina is an important ecosystem engineer, Arenicola marina could ingest 33mᵌ; of micro plastics a year.

Sensitivity assessment. ‘Not assessed’ as there is no defined benchmark for this pressure, however, both microplastics and the toxicants present in cigarette butts are likely to have negative impacts on the characterizing species.

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 on effects of electric and magnetic fields on the characterizing species.

Electric and magnetic fields generated by sources such as marine renewable energy device/array cables may alter behaviour of predators and affect infauna populations. Evidence is limited and occurs for electric and magnetic fields below the benchmark levels, confidence in evidence of these effects is very low.

Field measurements of electric fields at North Hoyle wind farm, North Wales recorded 110µ V/m (Gill et al., 2009). Modelled results of magnetic fields from typical subsea electrical cables, such as those used in the renewable energy industry produced magnetic fields of between 7.85 and 20 µT (Gill et al., 2009; Normandeau et al., 2012). Electric and magnetic fields smaller than those recorded by in field measurements or modelled results were shown to create increased movement in thornback ray Raja clavata and attraction to the source in catshark Scyliorhinus canicular (Gill et al., 2009).

Flatfish species which are predators of many polychaete species including dab Limanda limanda and sole Solea solea have been shown to decrease in abundance in a wind farm array or remain at distance from wind farm towers (Vandendriessche et al., 2015; Winter et al., 2010). However, larger plaice increased in abundance (Vandendriessche et al., 2015). There have been no direct causal links identified to explain these results.

Sensitivity assessment. ‘No evidence’ was available to complete a sensitivity assessment, however, responses by flatfish and elasmobranchs suggest changes in predator behaviour are possible. There is currently no evidence but effects may occur on predator prey dynamics as further marine renewable energy devices are deployed, these are likely to be over small spatial scales and not impact the biotope.

Underwater noise changes

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

Evidence

Species within the biotope can probably detect vibrations caused by noise and in response may retreat in to the sediment for protection. However, at the benchmark level the community is unlikely to be sensitive to noise and this pressure is ‘Not relevant’.

Introduction of light or shading

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

Evidence

All characterizing species live in the sediment and do not rely on light levels directly to feed or find prey so limited direct impact is expected.  Most species will respond to the shading caused by the approach of a predator, however, their visual acuity is probably very low. Even then, additional disturbance, such as an electronic flash, caused the retraction of palps and cirri and cessation of all activity for some minutes. Visual disturbance, in the form of direct illumination during the species' active period at night, may therefore result in loss of feeding opportunities, which may compromise growth and reproduction.

As this biotope is not characterized by the presence of primary producers it is not considered that shading would alter the character of the habitat directly. More general changes to the productivity of the biotope may, however, occur. Beneath shading structures there may be changes in microphytobenthos abundance, which would affect food resources (Tait & Dipper, 1998).

Shading will prevent photosynthesis leading to death or migration of sediment microalgae altering sediment cohesion and food supply to higher trophic levels. The impact of these indirect effects is difficult to quantify.

Sensitivity assessment. Based on the direct impact, biotope Resistance is assessed as ‘High’ and Resilience is assessed as ‘High’ (by default). The biotope Sensitivity is considered to be ‘Not sensitive’.

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 that reduce the degree of tidal excursion may alter larval supply to suitable habitats from source populations. Barriers may also act as stepping stones for larval supply over greater distances (Adams et al., 2014). Conversely, the presence of barriers at brackish waters may enhance local population supply by preventing the loss of larvae from enclosed habitats to environments, which are unfavourable, reducing settlement outside of the population. If a barrier (such as a tidal barrier) incorporated renewable energy  devices such as tidal energy turbines, these devices may affect hydrodynamics and therefore migration pathways for larvae into and out of the biotope (Adams et al., 2014). Evidence on this pressure is limited.

Sensitivity assessment. Resistance to this pressure is assessed as 'High' and resilience as 'High' by default. This biotope is therefore considered to be 'Not sensitive'.

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 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

Characterizing species may have some, limited, visual perception. As they live in the sediment the species will most probably not be impacted at the pressure benchmark and this pressure is ​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

Not relevant. Key, characterizing species are not cultiviated or translocated.

Introduction or spread of invasive non-indigenous species

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

Evidence

There is limited evidence of the impact of the introduction of one or more invasive non-indigenous species on this biotope or the characterizing species. There are limited studies on meiofauna at a higher taxonomic level which suggests total meiofauna numbers have increased in the presence of the invasive polychaete, Marenzelleria spp., as the burrowing of the polychaete extended the vertical distribution of meiofauna in a lagoon in the southern Baltic Sea (Urban-Malinga et al., 2013). In addition, Marenzelleria spp. had a positive impact on the survival of turbellarians (Urban-Malinga et al., 2013). 

Globally, examples from tropical ecosystems show similar effects of an invasive species on meiofauna abundance, with meiofauna abundance being significantly greater in an area colonized by invasive seaweed Spartina alterniflora in comparison with neighbouring vegetation and non-vegetated sand flats (Lin et al., 2015).

The American slipper limpet Crepidula fornicata was introduced to the UK and Europe in the 1870s from the Atlantic coasts of North America with imports of the eastern oyster Crassostrea virginica. It was recorded in Liverpool in 1870 and the Essex coast in 1887-1890. It has spread through expansion and introductions along the full extent of the English Channel and into the European mainland (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Hinz et al., 2011; McNeill et al., 2010; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015). 

Crepidula fornicata is recorded from shallow, sheltered bays, lagoons and estuaries or the sheltered sides of islands, in variable salinity (18 to 40) although it prefers ca 30 (Tillin et al., 2020). Larvae require hard substrata for settlement. It prefers muddy gravelly, shell-rich, substrata that include gravel, or shells of other Crepidula, or other species e.g., oysters, and mussels. It is highly gregarious and seeks out adult shells for settlement, forming characteristic ‘stacks’ of adults. But it also recorded in a wide variety of habitats including clean sands, artificial substrata, Sabellaria alveolata reefs and areas subject to moderately strong tidal streams (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Hinz et al., 2011; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015; Tillin et al., 2020). 

High densities of Crepidula fornicata cause ecological impacts on sedimentary habitats. The species can form dense carpets that can smother the seabed in shallow bays, changing and modifying the habitat structure. At high densities, the species physically smothers the sediment, and the resultant build-up of silt, pseudofaeces, and faeces is deposited and trapped within the bed (Tillin et al., 2020, Fitzgerald, 2007, Blanchard, 2009, Stiger-Pouvreau & Thouzeau, 2015). The biodeposition rates of Crepidula are extremely high and once deposited, form an anoxic mud, making the environment suitable for other species, including most infauna (Stiger-Pouvreau & Thouzeau, 2015, Blanchard, 2009). For example, in fine sands, the community is replaced by a reef of slipper limpets, that provide hard substrata for sessile suspension-feeders (e.g., sea squirts, tube worms and fixed shellfish), while mobile carnivorous microfauna occupy species between or within shells, resulting in a homogeneous Crepidula dominated habitat (Blanchard, 2009). Blanchard (2009) suggested the transition occurred and became irreversible at 50% cover of the limpet. De Montaudouin et al. (2018) suggested that homogenization occurred above a threshold of 20-50 Crepidula /m². 

Impacts on the structure of benthic communities will depend on the type of habitat that Crepidula colonizes. De Montaudouin & Sauriau (1999) reported that in muddy sediment dominated by deposit-feeders, species richness, abundance and biomass increased in the presence of high densities of Crepidula (ca 562 to 4772 ind./m²), in the Bay of Marennes-Oléron, presumably because the Crepidula bed provided hard substrata in an otherwise sedimentary habitat. In medium sands, Crepidula density was moderate (330-1300 ind./m²) but there was no significant difference between communities in the presence of Crepidula. Intertidal coarse sediment was less suitable for Crepidula with only moderate or low abundances (11 ind./m²) and its presence did not affect the abundance or diversity of macrofauna. The presence of Crepidula as an ecosystem engineer has created a range of new niche habitats, reducing biodiversity as it modifies habitats (Fitzgerald, 2007). De Montaudouin et al. (1999) concluded that Crepidula did not influence macroinvertebrate diversity or density significantly under experimental conditions, on fine sands in Arcachon Bay, France. De Montaudouin et al. (2018) noted that the limpet reef increased the species diversity in the bed, but homogenised diversity compared to areas where the limpets were absent. In the Milford Haven Waterway (MHW), the highest densities of Crepidula were found in areas of sediment with hard substrata, e.g., mixed fine sediment with shell or gravel or both (grain sizes 16-256 mm) but, while Crepidula density increased as gravel cover increased in the subtidal, the reverse was found in the intertidal (Bohn et al., 2015). Bohn et al. (2015) suggested that high densities of Crepidula in high-energy environments were possible in the subtidal but not the intertidal, suggesting the availability of this substrata type is beneficial for its establishment. Hinz et al. (2011) reported a substantial increase in the occurrence of Crepidula off the Isle of Wight, between 1958 and 2006, at a depth of ca 60 m, on hard substrata (gravel, cobbles, and boulders), swept by strong tidal streams. Presumably, Crepidula is more tolerant of tidal flow than the oscillatory flow caused by wave action which may be less suitable (Tillin et al., 2020). 

Sensitivity assessment. The sediments characterizing this biotope are likely to be too mobile or otherwise unsuitable for most of the invasive non-indigenous species currently recorded in the UK. However, the above evidence suggests that Crepidula fornicata could colonize coarse sediment habitats in the subtidal, typical of this biotope. Bohn et al. (2015) demonstrated that Crepidula had a preference for gravelly habitats, while De Montaudouin & Sauriau (1999) and Bohn et al. (2015) noted that Crepidula densities were low in intertidal coarse sediments. Therefore, Crepidula has the potential to colonize, and modify the habitat and its associated community due to the introduction of Crepidula shell biomass, silt, pseudofaeces and faeces (Blanchard, 2009; Tillin et al., 2020), as occurs in maerl gravels (Grall & Hall-Spencer, 2003) resulting in the loss of the biotope. This is an exposed to sheltered energy habitat, in which wave action and storms may mobilise the sediment (JNCC, 2022), which may mitigate or prevent colonization by Crepidula at high densities, although it has been recorded from areas of strong tidal streams (Hinz et al., 2011). Therefore, the habitat may be more suitable for Crepidula in wave sheltered areas of the biotope and where water movement is meditated by tidal flow rather than wave action, e.g., the deeper examples of the biotope. However, Crepidula reduced the density of suspension feeders and mobile Crustacea in coarse sediment even at low densities (De Montaudouin & Sauriau, 1999). 

Therefore, resistance is assessed as 'Medium' in examples where wave action is high and subject to storms but 'Low', in wave sheltered areas dominated by tidal flow. Resilience is assessed as 'Very low' as it would require the removal of Crepidula probably by artificial means. Hence, sensitivity is assessed as 'High' based on the worst-case scenario. Crepidula has not yet been reported to occur in this biotope so the confidence in the assessment is 'Low' and further evidence is required. 

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

Limited evidence was returned on individual characterizing or abundant species and the effect of introduction of pathogens or disease vectors.

At higher taxonomic levels meiofauna and in particular bacteria feeding nematodes, present in a Mediterranean case study were found to possibly limit the abundance of pathogenic Vibrio species. In this case study top down control through nematode grazing was suggested (Vezzulli et al., 2009).

Sensitivity assessment. Due to insufficient evidence the assessment is ‘No evidence’.

Removal of target species

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

Evidence

No characterizing species are targeted directly by fishing activities at a commercial or recreational scale, this pressure is therefore ‘Not relevant’. The biotope is more likely to be impacted by disturbance to substratum as discussed in sections above on ‘removal’ or ‘abrasion’ of sediment. As small polychaete species, living infaunally and capable of burrowing rapidly, Hesionura elongata and Microphthalmus similis are likely to withstand physical disturbance caused by bottom towed fishing gears (such as otter or beam trawls) (Vanosmael et al., 1982; Bolam et al., 2014 cited in Walmsley et al., 2015). As discussed in sections on ‘abrasion’ and sediment deposition, the characterizing species occur in mobile sediments and exposed regions where sediment redistribution occurs and are likely to be resistant to some disturbance of the habitat (Elliot et al., 1998).

Sensitivity assessment. As characterizing species are not targeted by commercial or recreational fisheries the assessment is ‘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

Due to their small size, the characterizing species are unlikely to be removed through by-catch. But removal of features, such as the characterizing mobile medium-coarse sand sediment may occur. Bottom towed fishing gears such as trawls and dredges as well as suction dredging for shellfish will disturb or remove the sediment up to 10 cm depth. Due to the mobile nature of the substratum and existing exposure of this biotope recovery of substratum characteristics is likely to be rapid. Disturbance to substratum, relative to bottom towed fishing activity, is discussed in sections above on ‘extraction’ or ‘abrasion’ of sediment. As small polychaete species, living infaunally, Hesionura elongata and Microphthalmus similis are likely to withstand physical disturbance caused by bottom towed fishing gears (such as otter or beam trawls) (Vanosmael et al. 1982; Bolam et al. 2014 cited in Walmsley et al. 2015). The possibility for some physical damage to a small number of the population and the habitat alteration caused by settlement of re-suspended fine grain size sediment are likely to have an impact on the populations of characterizing species. In a global analysis of the effect of fishing activities on benthic communities in sand habitats, initial impacts occurred in relation to beam trawling but recovery was considered rapid. Otter trawling had limited initial impact but there was some evidence of a small delayed effect (Kaiser et al. 2006).

Sensitivity assessment. The initial impact of bottom towed fishing activity, in particular beam trawl and dredges may cause some mortality through direct damage to characterizing species. The action of the dredge or trawl may also move buried organisms to the surface or suspend them in the water column, potentially increasing predation risk. The physical effects of physicla disturbance ar addressed under 'abrasion' and 'penetration' above.  However, the incidental removal of a proportion of the population may change the character of the biotope temperaility. Therefore, resistance is  assessed as ‘Medium’.  As resilience is probably ‘High’ sensitivity is assessed as ’Low’.