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

The important species in the biotope have wide geographic ranges and are likely to be tolerant of higher temperatures than those experienced in the British Isles. Although species ranges may not accurately describe their ability to withstand localized changes in temperature.  They may to some extent display the limits of the species genetic ability to acclimatize to temperatures. 

Furcellaria lumbricalis has a wide geographic range, occurring in Europe from northern Norway to the Bay of Biscay.  Novaczek & Breeman (1990) recorded that specimens of Furcellaria lumbricalis grew well in the laboratory from 0 - 25°C with optimal growth between 10 and 15°C.  Growth ceased at 25°C and 100% mortality resulted after 3 months exposure to 27 °C.  Similarly, Bird et al. (1979) recorded optimum growth at 15°C and cessation of growth at 25°C with associated necrosis of apical segments.

Polyides rotunda is found throughout the North Atlantic Ocean and have related populations in the North Pacific.  Growth and survival was tested over a temperature range of -5 to 30°C.  Polyides rotunda tolerated temperatures from -5 to 27°C, grew well from 5 to 25°C, and had a broad optimal range of 10-25°C.  Both Polyides rotunda and Furcellaria lumbricalis can tolerate three months in darkness at 0°C (Novaczek & Breeman, 1990).

Chondrus crispus also has a wide geographical range, occurring in Europe from northern Russia to southern Spain (Dixon & Irvine, 1977).  In New Hampshire, USA, Chondrus crispus grows abundantly in waters with an annual variation in surface temperature from -1 to +19°C (Mathieson & Burns, 1975).

Sensitivity assessment.  The ability of the characterizing species to tolerate a wide range of temperatures suggests that a change in this pressure at the benchmark is unlikely to have a negative effect on the biotope.  Both resistance and resilience have been assessed as ‘High’.  This results in a ‘Not sensitive’ assessment of the biotope.

Temperature decrease (local)

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

Evidence

The important species in the biotope have wide geographic ranges and are likely to be tolerant of higher temperatures than those experienced in the British Isles. Although species ranges may not accurately describe their ability to withstand localized changes in temperature.  They may to some extent display the limits of the species genetic ability to acclimatize to temperatures.

Furcellaria lumbricalis occurrs in Europe from northern Norway to the Bay of Biscay.  Novaczek & Breeman (1990) recorded that specimens of Furcellaria lumbricalis grew well in the laboratory from 0-25 °C with optimal growth between 10 and 15 °C.  Growth ceased at 25 °C and 100% mortality resulted after 3 months exposure to 27 °C. Similarly, Bird et al. (1979) recorded optimum growth at 15 °C.

Growth and survival of the key characterizing species, Polyides rotunda was tested over a temperature range of -5 to 30°C.  Polyides rotunda tolerated temperatures from -5 to 27°C, grew well from 5 to 25°C, and had a broad optimal range of 10-25°C (Novaczek & Breeman, 1990).  This species tolerated three months in darkness at 0°C (Novaczek & Breeman, 1990).

Dudgeon et al. (1990) investigated the effects of freezing on Chondrus crispus. Plants from Maine, USA, were frozen at -5°C for 3 hours a day for 30 days. Photosynthesis was reduced to 55% of control values, growth rates were reduced and fronds were eventually bleached and fragmented resulting in biomass losses. Additionally, fronds of Chondrus crispus which were frozen daily had higher photosynthetic rates following subsequent freezing events than unfrozen controls, indicating that the species is able to acclimate to freezing conditions (Dudgeon et al., 1990).

Sensitivity assessment.  The ability of the characterizing species to tolerate a wide range of temperatures suggests that a change in this pressure at the benchmark is unlikely to have a negative effect on the biotope.  Both resistance and resilience have been assessed as ‘High’.  This results in a ‘Not sensitive’ assessment of the biotope.

Salinity increase (local)

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

Evidence

IR.LIR.Lag.ProtFur typically occurs in areas of reduced or low salinity (Connor et al., 2004).  Furcellaria lumbricalis is a euryhaline species which occurs in a wide range of salinity conditions down to 6-8 psu (Bird et al., 1991).  In the Kattegat and the Gulf of St Lawrence, it is reported to compete well with other species at salinities ranging from 25-32 psu (see review by Bird et al., 1991).  Growth experiments in the laboratory revealed that optimum growth occurred at 20 psu, the species grew well at 10 psu and 30 psu, but that growth declined above 30 psu to negligible levels at 50 psu (Bird et al., 1979).  It is expected that an increase in salinity may cause reduced growth and fecundity but that mortality is unlikely.

No specific evidence was found for the salinity tolerance of the key characterizing species Polyides rotunda.  Polyides rotunda is a characterizing species within biotopes at full salinity e.g. IR.HIR.Ksed.ProtAhn (Connor et al., 2004).  Mathieson & Burns (1971) recorded maximum photosynthesis of Chondrus crispus in culture at 24 psu but rates were comparable at 8, 16 and 32 psu.  Photosynthesis continued up to 60 psu.  Bird et al. (1979) recorded growth of Canadian Chondrus crispus in culture between 10 and 50 psu, with a maximum at 30 psu.  The species would therefore appear to be extremely tolerant of hypersaline conditions.

Sensitivity assessment.  The characterizing species within this biotope would be tolerant of an increase in salinity at the pressure benchmark.  However, the removal of the biotope from the salinity regime will mean that the chemical characteristics of the biotope have changed.  The increase in salinity will also enable species which were previously excluded from the habitat to settle.  Therefore, changing the biological community.  The combination of these two factors would mean that the biotope would be lost.  Consequently the resistance has been assessed as ‘Low’.  On the return of the habitat to the previous salinity regime, the species which had taken advantage of the increase in salinity would disappear.  As the characterizing species would not have died due to the change in salinity the biological community of this biotope would quickly return.  Resulting in a resilience of ‘High’.  Consequently the biotope sensitivity is assessed ‘Low’.

Salinity decrease (local)

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

Evidence

IR.LIR.Lag.ProtFur typically occurs in areas of reduced or low salinity (Connor et al., 2004).  Furcellaria lumbricalis occurs in the lowest category on the salinity scale (Connor et al., 2004) and therefore probably relatively tolerant of decreases in salinity.  The species forms extensive populations in the main basin of the Baltic Sea where salinity is 6-8 psu in the upper 60-70 m and its extension into the Gulfs of Bothnia and Finland is limited by the 4 psu isohaline (see review by Bird et al., 1991).  However, if the salinity conditions within the habitat were to become freshwater Furcellaria lumbricalis would not be able to survive, as it is a marine species.  No information was found on the effect of low salinities on Polyides rotunda.  Chondrus crispus occurs in estuaries in New Hampshire, USA, where surface water salinity varies from 16-32 psu (Mathieson & Burns, 1975).  Mathieson & Burns (1971) recorded maximum photosynthesis of Chondrus crispus in culture at 24 psu, but rates were comparable at 8, 16 and 32 psu.

Sensitivity assessment.  A decrease in salinity at the pressure benchmark would create freshwater conditions for those biotopes already found in low salinity regimes.  The marine nature of the characterizing species would mean that a change in the pressure benchmark for a year would cause mortality of the characterizing species and the associated species.  Therefore, resistance is ‘None’.  The need for the biological community to recolonize the habitat from scratch when the salinity regime returns to ‘normal’ means that the resilience is ‘Low’.  This gives a sensitivity of ‘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

This biotope is only found in very weak water flow conditions (Connor et al., 2004).  Very little information was available on the effect of water flow on Furcellaria lumbricalis and Polyides rotunda.  However, these species are found in biotopes ranging from strong to negligible (Connor et al., 2004).  Therefore, these species may decrease in abundance if water flows were to increase above 6 knots (> 3 m/sec).

An increase in water flow at the benchmark is unlikely to have a significant negative effect on the biological composition of the biotope.  However, it must be assumed that if there is an increase in the water flow within the biotope there will also be an increase in the water flow around the lagoon.  This increase could have a detrimental effect on the structure of the lagoon through erosion.  This could consequently lead to the loss collapse of a lagoon wall and completely change the physical environment of the biotope, and lead to the loss of the lagoon biotope altogether.

Sensitivity assessment. A change in the water flow at the pressure benchmark is unlikely to cause the loss of the lagoon biotope.  However, an increase in this pressure above the given benchmark has the possibility of removing the lagoon completely.  Therefore, resistance and resilience are assessed as ‘High’, resulting in an assessment of ‘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

The infralittoral situation of this biotope means that it is permanently submerged.  For this reason an increase in emergence would change the physical conditions of the biotope, which would affect the biological community.  The biotope will be replaced by one where the biological community is better suited to the new emergence regime.  A decrease in emergence is not relevant to this biotope as it is already submerged all of the time.

Furcellaria lumbricalis can be found from the lower intertidal to 12 m subtidally (Bunker et al., 2012).  Bunker et al. (2012) notes that Polyides rotunda occurs from the mid shore down to 24 m depth.  Therefore, if examples of this biotope in were to experience an increase in emergence then the species are decrease in abundance, but not suffer complete mortality.

This biotope is recorded from 0 – 5 m (Connor et al., 2004).  A change in the emergence is unlikely to expose the substratum to 5m.  Therefore part of the biotope is likely to survive on the substratum which is still immersed.  This will allow the biotope to remain in part, and will provide a mature adult population from which repopulation can occur when the ‘normal’ emergence conditions return.

Sensitivity assessment.  The resistance to this pressure at the benchmark is ‘Medium’.  It is likely that the characterizing species in the upper part of the biotope will decrease in abundance.  The resilience is thought to be ‘Medium’ as it may take a while for the species to return to their previous abundances after a year at this pressure benchmark.  The sensitivity is therefore assessed to be ‘Medium’.

Wave exposure changes (local)

Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail

Evidence

This biotope is only found in very and extremely wave sheltered conditions (Connor et al., 2004).  Both of the characterizing species can be found in biotopes where wave exposure far exceeds that found within IR.LIR.Lag.ProtFur.  The benchmark increase would place the biotope in 'sheltered' conditions for one year.  A more severe increase in wave action would cause some damage to fronds resulting in reduced photosynthesis and compromised growth.  Furthermore, individuals may be damaged or dislodged by scouring from sand and gravel mobilized by increased wave action (Hiscock, 1983).  Austin (1960b) noted that Furcellaria lumbricalis from extremely exposed sites have smaller dimensions than individuals from semi-exposed sites and that fronds may be lost due to storm action.  Sharp et al. (1993) reported Furcellaria lumbricalis found cast ashore following storms. Dudgeon & Johnson (1992) noted wave induced disturbance of intertidal Chondrus crispus on shores of the Gulf of Maine during winter.  During one winter 25-30% of cover of large Chondrus crispus thalli was lost.  Increased wave action above the pressure benchmark would result in some mortality.  However, at this pressure benchmark the biological component of this biotope is unlikely to be affected.

An increase in wave exposure at the benchmark will not have a significant negative effect on the biological composition of the biotope.  However, it might be assumed that if there is an increase in the wave height within the biotope there will also be an increase in the water flow around the lagoon.  This increase could have a detrimental effect on the structure of the lagoon through erosion.  This could consequently lead to the loss collapse of a lagoon wall and completely change the physical environment of the biotope, and lead to the loss of the lagoon biotope altogether.  A decrease in wave exposure is not possible within this biotope, as it is already found in the most sheltered conditions.

Sensitivity assessment.  An increase in this pressure above the given benchmark has the possibility of removing the lagoon completely.  However, at the pressure benchmark it is very unlikely that the biotope will be affected.  Therefore, both the resistance and resilience have been assessed as ‘High’, resulting in a ‘Not sensitive’ assessment. 

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.

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.

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.

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

The effects of reduced oxygenation on the characterizing red algae are not well studied.  Lack of oxygen may impair both respiration and photosynthesis (see review by Vidaver, 1972).  No evidence is available to make a sensitivity assessment for the key characterizing algal species.  However, the presence of these species in rock pools suggests that they can tolerate some short-term oxygen depletion.

Aerobic organisms in the biotope are certain to be intolerant of anoxia to some degree, and it is expected that, at the very least, growth and reproduction would be compromised by the benchmark decrease in oxygen levels.

Sensitivity assessment.  The short-term exposure to de-oxygenation at this benchmark decreases the severity of the pressure.  However, the isolated nature of saline lagoons will mean that at low tide, when the lagoons are cut off, may become even more de- oxygenated.  This may increase the level of de-oxygenation and consequently the severity of the pressure.  The lack of evidence regarding the effect of low oxygen levels on the characterizing species within this biotope has led to an assessment of ‘No evidence’.

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 nutrient enrichment of a marine environment leads to organisms no longer being limited by the availability of certain nutrients.  The consequent changes in ecosystem functions can lead to the progression of eutrophic symptoms (Bricker et al., 2008), changes in species diversity and evenness (Johnston & Roberts, 2009) decreases in dissolved oxygen and uncharacteristic microalgae blooms (Bricker et al., 1999, 2008).

Johansson et al. (1998) suggested that one of the symptoms of large scale eutrophication is the deterioration of benthic algal vegetation in areas not directly affected by land-runoff or a point source of nutrient discharge. Altered depth distributions of algal species caused by decreased light penetration and/or increased sedimentation through higher pelagic production have been reported in the Baltic Sea (Kautsky et al., 1986; Vogt & Schramm, 1991).  Johansson et al. (1998) studied changes in the benthic algal community of the Skagerrak coast in the Baltic Sea, an area heavily affected by eutrophication, between 1960 and 1997. They noted the disappearance of the red alga, Polyides rotunda, but commented that problems existed in their sampling method. They also noted the increase of delicate red algae with foliaceous thalli, e.g. Delesseria sanguinea and Phycodrys rubens, and tougher red algae with foliaceous thalli, e.g. Phyllophora sp. Increases in the delicate algae were most pronounced at the more wave exposed sites, while increases in the tougher algae occurred at the more sheltered sites with high sedimentation. They commented that these results suggest that the increase of delicate species with large growth potential may have been caused by eutrophication, but that the effect is counteracted when eutrophication results in high sedimentation, in which case the tougher Phyllophora sp. thrive. Additionally, Chondrus crispus and Furcellaria lumbricalis, both species with tough thalli, decreased at the wave exposed sites, possibly due to competition from the more vigorous Phycodrys rubens and Delesseria sanguinea, but persisted at the sites with high sedimentation.  These findings suggest that the dominant red algal turf that characterizes the biotope is likely to decline following increases in nutrient levels and faster growing species are likely to proliferate.

In studies of Chondrus crispus from Prince Edward Island, Canada, Juanes & McLachlan (1992) concluded that primary production was limited by temperature during the autumn to the spring period and by nitrogen availability when production was maximal in the summer. They suggested that growth of Chondrus crispus became nutrient limited at approximately 14°C. To a certain degree, therefore, an increase in the level of nutrients would be likely to enhance growth of algae in the biotope

Johnston & Roberts (2009) undertook a review and meta analysis of the effect of contaminants on species richness and evenness in the marine environment.  Of the 47 papers reviewed relating to nutrients as a contaminants, over 75% found that it had a negative impact on species diversity, <5% found increased diversity, and the remaining papers finding no detectable effect.  None of the 47 papers considered the impact of nutrients on saline lagoons.  Yet this finding is still relevant as the meta analysis revealed that the effect of marine pollutants on species diversity were ‘remarkably consistent’ between habitats (Johnston & Roberts, 2009).  It was found that any single pollutant reduced species richness by 30-50% within any of the marine habitats considered (Johnston & Roberts, 2009).  Throughout their investigation there were only a few examples where species richness was increased due to the anthropogenic introduction of a contaminant.  These examples were almost entirely from the introduction of nutrients, either from aquaculture or sewage outfalls.  However, research into the impacts of nutrient enrichment from these sources on intertidal rocky shores often lead to shores lacking species diversity and the domination by algae with fast growth rates (Abou-Aisha et al., 1995, Archambault et al., 2001, Arévalo et al., 2007, Diez et al., 2003, Littler & Murray, 1975).

Nutrient enrichment alters the selective environment by favouring fast growing, ephemeral species such as Ulva lactuca and Ulva intestinalis (Berger et al., 2004, Kraufvelin, 2007).  Opportunistic algae such as these can’t store nutrients in the thallus (unlike larger, long-lived species) and are adapted to efficiently capture and utilise available nutrients in the water column (Pedersen et al., 2009).  A large body of field observations and experiments, surveys and laboratory experiments confirm that Ulva sp., can utilise high levels of nutrients for growth (Martínez et al., 2012) and that enhanced recruitment (Kraufvelin, 2007) and growth of this genus can occur in enriched areas (Kennison & Fong, 2013; Vaudrey et al., 2010).  In areas where nutrient availability is lower either naturally or through management to reduce anthropogenic inputs, Ulva sp. may be negatively affected through reduced growth rate and species replacement (Martínez et al., 2012; Vaudrey et al., 2010).  Rohde et al. (2008) found that both free growing filamentous algae and epiphytic microalgae can increase in abundance with nutrient enrichment.  This stimulation of annual ephemerals may accentuate the competition for light and space and hinder perennial species development or harm their recruitment (Berger et al., 2003; Kraufvelin et al., 2007).  Nutrient enrichment can also enhance fouling of Fucus fronds by biofilms (Olsenz, 2011).  Nutrient enriched environments can not only increase algae abundance, but the abundance of grazing species (Kraufvelin, 2007).

Changes in community composition on intertidal rocky shores can happen rapidly, and fast growing ephemeral species can become established quickly in the presence of higher concentrations of nutrients.  The establishment and growth of these species are not controlled by wave exposure (Kraufvelin, 2007).  However, even though these fast growing ephemeral species can become well established quickly, healthy communities on intertidal rocky shores can survive long periods of time, and maintain ecological function after these species have become established (Bokn et al., 2002, 2003; Karez et al.,2004; Kraufvelin, 2007; Kraufvelin et al., 2007).

Sensitivity assessment. A slight increase in nutrients may enhance growth rates but high nutrient concentrations could lead to the overgrowth of the algae by ephemeral green algae and an increase in the number of grazers.  However, if the biotope is well established and in a healthy state the biotope could have the potential to persist.  The effect of an increase in this pressure to the benchmark level will not have a negative impact on the biotope.  Therefore, the resistance and resilience of this biotope are assessed as ‘High’, giving the biotope an overall assessment of ‘Not sensitive’. 

Organic enrichment

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

Evidence

The organic enrichment of a marine environment at this pressure benchmark leads to organisms no longer being limited by the availability of organic carbon.  The consequent changes in ecosystem functions 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).

Johnston & Roberts (2009) undertook a review and meta analysis of the effect of contaminants on species richness and evenness in the marine environment.  Of the 49 papers reviewed relating to sewage as a contaminant, over 70% found that it had a negative impact on species diversity, <5% found increased diversity, and the remaining papers finding no detectable effect.  None of the 49 papers considered the impact of sewage on saline lagoons.  Yet this finding is still relevant as the meta analysis revealed that the effect of marine pollutants on species diversity were ‘remarkably consistent’ between habitats (Johnston & Roberts, 2009).  It was found that any single pollutant reduced species richness by 30-50% within any of the marine habitats considered (Johnston & Roberts, 2009).  Throughout their investigation there were only a few examples where species richness was increased due to the anthropogenic introduction of a contaminant.  These examples were almost entirely from the introduction of nutrients, either from aquaculture or sewage outfalls.  However, research into the impacts of organic enrichment from these sources on intertidal rocky shores, often lead to shores lacking species diversity and the domination by algae with fast growth rates (Abou-Aisha et al., 1995, Archambault et al., 2001, Arévalo et al., 2007, Diez et al., 2003, Littler & Murray, 1975).  This could also occur within saline lagoon habitats, where similar fast growing species such as Ulva are found.

Organic enrichment alters the selective environment by favouring fast growing, ephemeral species such as Ulva lactuca and Ulva intestinalis (Berger et al., 2004, Kraufvelin, 2007).  Rohde et al., (2008) found that both free growing filamentous algae and epiphytic microalgae can increase in abundance with nutrient enrichment.  This stimulation of annual ephemerals may accentuate the competition for light and space and hinder perennial species development or harm their recruitment (Berger et al., 2003; Kraufvelin et al., 2007).  Nutrient enrichment can also enhance fouling of fucoid fronds by biofilms (Olsenz, 2011).  Nutrient enriched environments can not only increase algae abundance, but the abundance of grazing species (Kraufvelin, 2007).  Bellgrove et al. (2010) found that coralline turfs out-competed fucoids at a site associated with organic enrichment caused by an ocean sewage outfall.

Changes in community composition on intertidal rocky shores can happen rapidly, and fast growing ephemeral species can become established quickly in the presence of higher concentrations of nutrients.  The establishment and growth of these species are not controlled by wave exposure (Kraufvelin, 2007).  However, even though these fast growing ephemeral species can become well established quickly, healthy communities on intertidal rocky shores can survive long periods of time, and maintain ecological function after these species have become established (Bokn et al., 2002, 2003, Karez et al.,2004, Kraufvelin, 2007, Kraufvelin et al., 2007).

Sensitivity assessment.  Little empirical evidence was found to support an assessment of this biotope at this benchmark.  Ulva sp. could easily increase in abundance, and this species could over grow the slower growing characterizing species.  However, when organic carbon returned to pre-pressure levels the niche for the conditions for the characterizing algae would return.  Resistance has been assessed as ‘Medium’ and resilience has been assessed as ‘Medium’. This gives an overall sensitivity score of ‘Medium’.

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’.  

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 characterized by a lagoon formed from bedrock, boulders and cobbles.  Removal of this substratum would remove the attachment surface for the macroalgae that characterize this biotope, significantly altering the character of the biotope.  Artificial hard substratum may also differ in character from natural hard substratum, so that replacement of natural surfaces with artificial may lead to changes in the biotope through changes in species composition, richness and diversity (Green et al., 2012; Firth et al., 2014) or the presence of non-native species (Bulleri & Airoldi, 2005).

The change in substratum also has the potential to de-stabilize the lagoon structure.  This change in structure could make the lagoon more susceptible to erosion from other physical factors at work within the environment.

Sensitivity assessment. A change to a sedimentary habitat would reduce habitat suitability for this biotope, resistance is assessed as ‘None’ and resilience as ‘Very Low’ as the change is considered to be permanent. Sensitivity is therefore 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 for bedrock biotopes.

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 occur 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

No studies of the effects of trampling or netting on lagoons were found but studies of the effects on emergent algal communities are probably indicative.  For example, moderate (50 steps per 0.09 sq. metre) or more trampling on intertidal articulated coralline algal turf in New Zealand reduced turf height by up to 50%, and the weight of sand trapped within the turf to about one third of controls (Schiel & Taylor, 1999).  This resulted in declines in densities of the meiofaunal community within two days of trampling.  Although the community returned to normal levels within 3 months of trampling events, it was suggested that the turf would take longer to recover its previous cover (Brown & Taylor, 1999).  Similarly, Schiel & Taylor (1999) noted that trampling had a direct detrimental effect on fucoid algae and coralline turf species on the New Zealand rocky shore.  Low trampling intensity (10 tramples) reduced fucoid cover by 25%, while high intensity (200 tramples) reduced fucoid cover by over 90%, although over 97% cover returned within 21 months after spring trampling; autumn treatments took longer to recover due to the delay in recruitment.  Coralline bases were seen to peel from the rocks (Schiel & Taylor, 1999) due to increased desiccation caused by loss of the algal canopy.  Brosnan & Cumrie (1994) demonstrated that foliose species (e.g. fucoids and Mastocarpus papillatus) were the most susceptible to trampling disturbance, while turf forming species were more resistant.  Boalch et al. (1974) and Boalch & Jephson (1981) noted a reduction in fucoid cover (especially of Ascophyllum nodosum) at Wembury, Devon, when compared with the same transects surveyed 43 years previously.  They suggested that the reduction in fucoid cover was due to the large number of visitors and school groups received by the site.

The Furcellaria lumbricalis and Polyides rotunda red algal turf is likely to be tolerant of abrasion as the fronds are flexible and cartilaginous.  The plants' point of attachment to the substratum, the holdfast, is a potential point of weakness.  For example, Taylor (1970) (cited in Sharp et al., 1993) stated that clumps of fronds of Furcellaria lumbricalis were easily removed from the substratum by drag raking, but only where the plant had a sufficient number of dichotomies (usually more than 3) to snag in the rake. It is likely therefore that the benchmark level of abrasion would cause detachment and/or damage. Sharp et al. (1993) noted that, following detachment, Furcellaria lumbricalis plants were capable of reattachment. 

Worm & Chapman (1998) suggested that Chondrus crispus was highly resistant to intense physical and herbivore induced disturbance, ensuring competitive dominance on the lower shore. However, the benchmark level of abrasion, for example, a scallop dredge, would be expected to remove or damage some fronds, although the holdfasts are likely to escape unscathed.  Chondrus crispus is capable of regenerating from its holdfasts (e.g. Dudgeon & Johnson, 1992) and so no mortality is expected, although growth and reproduction of the algae would be compromised during regeneration.  However, a proportion of the fronds would be removed, together with any associated mesoherbivores, meiofauna, and epiphytes.

Sensitivity assessment.  The impact of surface abrasion will depend on the footprint, duration and magnitude of the pressure.  Based on evidence from the step experiments and the relative robustness of the algal turf found within this biotope, resistance, to a single abrasion event is assessed as ‘Medium’ (loss of <25% cover/abundance) and resilience is also assessed as ‘Medium’.  Therefore, the sensitivity is assessed as ‘Medium’.

Penetration or disturbance of the substratum subsurface

Benchmark. Damage to sub-surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

The species characterizing this biotope group are epifauna or epiflora occurring on hard rock, which is resistant to subsurface penetration.  Therefore, ‘penetration’ is 'Not relevant'. The assessment for abrasion at the surface only is, therefore, considered to equally represent sensitivity to this pressure’. Please refer to ‘abrasion’ above.

Changes in suspended solids (water clarity)

Benchmark. A change in one rank on the WFD (Water Framework Directive) scale e.g. from clear to intermediate for one year. Further detail

Evidence

Both of the characterizing species, Furcellaria lumbricalis and Polyides rotunda within this biotope are tolerant to sand cover and scour.  Therefore, the algal species that characterize the biotope are not likely to be affected directly by an increase in scour which could be caused by a change in suspended sediment. However, increased suspended sediment will decrease light availability.  Furcellaria lumbricalis often occurs in relatively turbid waters. Laboratory experiments by Bird et al. (1979) revealed that Furcellaria lumbricalis was growth saturated at very low light levels (ca 20µE/m²/s) compared to other algae such as Chondrus crispus (50-60 µE/m²/s).  They suggest that this may be an explanation why Furcellaria lumbricalis is able to proliferate in relatively deep and turbid waters.  Similarly, in their review, Bird et al. (1999) comment that in all studies, saturation and inhibition radiances were low for Furcellaria lumbricalis compared to other macroalgae indicating good competitive ability in the attenuated light of deeper or more turbid waters.  Increases in turbidity may provide the species with a competitive advantage over other macroalgae.

No direct evidence was found on the ability of Polyides rotunda to cope with low light environments.  However, Bunker et al. (2012) state that Polyides rotunda can be found as deep at 24 m. 

Sensitivity assessment.  The negligible water flows and the very sheltered to extremely wave sheltered conditions within this biotope mean that an increase in suspended sediment would not cause an increase in the level of scour within this biotope.  Both of the characterizing species are scour tolerant and are found in conditions where scour is far more severe than what would occur in this biotope.  A change in light attenuation would be unlikely to cause any significant issue to the characterizing species as they can both be found in deeper waters than those typical of this biotope.  This suggests that they would tolerate a decrease in light attenuation.  Both resistance and resilience have been assessed as ‘High’, resulting in a ‘Not sensitive’ assessment. 

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

Furcellaria lumbricalis is tolerant of sand cover (Dixon & Irvine, 1977) and Furcellaria lumbricalis persisted in areas of the Baltic Sea where eutrophication resulted in high sediment loads (Johansson et al., 1998). However, recently settled propagules and small developing plants would be buried by 5 cm of sediment and be unable to photosynthesise. For example, Vadas et al. (1992) stated that algal spores and propagules are adversely affected by a layer of sediment, which can exclude up to 98% of light.

No direct evidence could be found on the effect of sediment inundation could be found on Polyides rotunda.  However, this species is known to be a scour tolerant species.

Seapy & Littler (1982) reported a decrease in macroalgal cover from 47.3 to 37.5% on a Californian rocky shore due to sediment deposition on the mid to lower shore following rain and flooding.  Corallina sp. and Pelvetia sp. were the most affected macroalgal species, while associated red algae were only slightly affected by the resultant scour.  Macroinvertebrates declined in cover from 15.8% to 6.5%, particularly barnacle species.  Daly & Mathieson (1977) examined intertidal zonation on a shore affected by sand scour, and noted that fucoids were reduced to small or young plants, while sand tolerant species dominated on areas affected by sediment.  Smothering by 5 cm of sediment is likely to increase scour and be detrimental to the characterizing red algae species.  Red algae whose fronds are long enough not to be smothered by 5 cm of sediment could be negatively impacted by the increase in scour.  However, all of the characterizing red algae within this biotope are noted for their tolerance to scour and could, therefore, tolerate an increase in this pressure at the benchmark.  Germlings are more likely to be smothered and killed and are inherently most susceptible to this pressure.  Indeed, all early life stages are smaller in size than adults and are thus most vulnerable to this pressure as even a small load of added sediment will lead to the complete burial.  Sediment deposition can reduce macroalgal recruitment by (1) reducing the amount of substratum available for attachment of propagules; (2) scour, removing attached juveniles and (3) burial, altering the light and/or the chemical microenvironment (Devinny & Volse, 1978, Eriksson & Johansson, 2003).

The saline lagoon environment is likely to be more vulnerable to smothering as sediment is likely to accumulate in and be retained by the lagoon itself.  This effectively increases the depth of the sediment layer in the pool.  The very sheltered and extremely wave sheltered conditions in which this biotope is found means that sediment may be retained for longer than indicated by the benchmark.  Overall, while the biotope will remain, smothering is likely to reduce the diversity, exclude grazing littorinids, and smother small epifaunal species such as sponges, bryozoans and ascidians.

Sensitivity assessment.  Based on the tolerance of the characterizing red algae to sediment inundation and scour, the resistance of the characterizing algae to this pressure at the benchmark is likely to be high.  However, the grazing littorinids are not tolerant of sediment inundation and an increase in the pressure at the benchmark could reduce the number of these gastropods and a number of the other small epiphytic species within this biotope .  The resistance is assessed as 'Medium' and resilience is assessed as ‘High’ resulting in a ‘Low’ sensitivity.

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

No evidence was found to assess this pressure at the benchmark.  A deposit at the pressure benchmark would cover all species with a thick layer of fine materials. Species associated with this biotope such as littorinids would not be able to escape and would likely suffer mortality (see evidence for light siltation).  Sensitivity to this pressure will be mediated by site-specific hydrodynamic conditions and the footprint of the impact.  Where a large area is covered sediments may be shifted by water currents rather than removed.  Mortality will depend on the duration of smothering; where wave action rapidly mobilises and removes fine sediments, survival of the characterizing and associated species may be much greater.

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

Species characterizing this habitat do not have hearing perception but vibrations may cause an impact, however, no studies exist to support an assessment.

Introduction of light or shading

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

Evidence

In general, subtidal red algae are able to exist at relatively low light levels (Gantt, 1990).  Canopy removal experiments in a rocky subtidal habitat in Nova Scotia, Canada by Schmidt & Scheibling (2007) did not find a shift in understorey macroalgal turfs (dominated by Corallina officinalis, Chondrus crispus and Mastocarpus stellatus) to more light-adapted species over 18 months.

Furcellaria lumbricalis often occurs in relatively turbid waters.  Laboratory experiments by Bird et al. (1979) revealed that Furcellaria lumbricalis was growth saturated at very low light levels (ca 20 µE/m²/s) compared to other algae such as Chondrus crispus (50 - 60 µE/m²/s) and Fucus serratus (100 µE/m²/s).  They suggest that this may be an explanation why Furcellaria lumbricalis is able to proliferate in relatively deep and turbid waters.  Similarly, in their review, Bird et al. (1999) comment that in all studies, saturation and inhibition radiances were low for Furcellaria lumbricalis compared to other macroalgae indicating good competitive ability in the attenuated light of deeper or more turbid waters.

Sensitivity assessment.  The characterizing species colonize a broad range of light environments from intertidal to deeper subtidal and shaded understorey habitats the biotope is considered to have ‘High’ resistance and, by default, ‘High’ resilience and therefore is ‘Not sensitive’ to this pressure.

Barrier to species movement

Benchmark. A permanent or temporary barrier to species movement over ≥50% of water body width or a 10% change in tidal excursion. Further detail

Evidence

Not relevant – this pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit propagule dispersal.  But propagule dispersal is not considered under the pressure definition and benchmark.

Death or injury by collision

Benchmark. Injury or mortality from collisions of biota with both static or moving structures due to 0.1% of tidal volume on an average tide, passing through an artificial structure. Further detail

Evidence

Not relevant 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

Key characterizing species within this biotope are not cultivated or translocated.  This pressure is therefore considered not relevant to this biotope.

Introduction or spread of invasive non-indigenous species

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

Evidence

The brown seaweed Sargassum muticum is a non native species which could potentially invade the biotope.  Sargassum muticum is a non-native macroalgae spreading around the coasts of Britain and Europe (see Eno et al., 1997) and can be found in a range of intertidal and shallow subtidal biotopes.  Although, no studies on its effects on saline lagoons were found, studies of its effect on shallow sublittoral macroalgae suggest that it can out-compete fucoids and kelps (Stæhr et al., 2000).  An increase in the abundance of Sargassum muticum in the Limfjorden (Denmark) from 1990 to 1997 was accompanied by a decrease in the abundance of thick, slow growing macroalgae such as Saccharina latissima (studied as Laminaria saccharina), Codium fragile, Halidrys siliquosa, Fucus vesiculosus, and Fucus serratus, together with other algae such as Ceramium virgatum(as rubrum) and Dictyota dichotoma.  In Sargassum muticum removal experiments on the coast of Washington State, Britton-Simmonds (2004) concluded that Sargassum muticum reduced the abundance of native canopy algae (especially kelps) by 75% and native understorey algae by 50% probably as a result of shading.  However, Viejo (1999) noted that mobile epifauna (e.g. amphipods, isopods) successfully colonized Sargassum muticum which provided additional habitat.  It is likely that Sargassum muticum could successfully invade saline lagoons, and would probably out-compete resident fucoids and kelp species, and some red algae.  Although the results of studies of feeding preferences for Sargassum muticum over native macroalgae vary, Littorina littorea does feed on this species so shoreline colonization by this species would mean that food was still available (Withers et al. 1975).  Littorina littorea also grazes on degraded or stressed Didemnum vexillem individuals (Valentine et al., 2007) and Codium fragile sp. tomentosoides (Schiebling et al., 2008), so gains some benefit from the presence of these species.

A number of invasive red algae have been recorded in the UK, including Bonnemaisonia hamifera and Grateloupia turuturu.  There are no reports of these species invading saline lagoon habitats.  However, it is possibly they could, with possible consequences for the biological community found within this biotope.

Sensitivity assessment.  There is a chance that the highly successful non-native Sargassum muticum might be able to invade this biotope.  The biotope may remain, but with a reduced species richness due to the loss of some species of macroalgae.  Resistance is ‘Medium’ and resilience could also be ‘Medium’, but assumes removal of Sargassum muticum, which is unlikely.  Hence, a resilience of 'Very low' has been recorded since the biotope is likely to change, although a viable community will remain, therefore, the sensitivity of the biotope is assessed as ‘Medium’.  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

Barton (1901) noted that Furcellaria lumbricalis may become infested with nematode worms and reacts by gall formation.  Pathogenic infections have the potential to cause mortality in red algae and so intolerance is assessed as intermediate. As some portion of the population is likely to remain for vegetative regrowth, recovery is likely to occur within 18 months (see additional information below) and recoverability is, therefore assessed as high.  No information is available on the impact of microbial pathogens on Polyides rotunda.  Parasitism by trematodes may cause sterility in Littorina littorea.  Littorina littorea are also parasitized by the boring polychaete, Polydora ciliate and Cliona sp, which weakens the shell and increases crab predation (Stefaniak et al., 2005).

Sensitivity assessment.  Based on the lack of evidence for the characterizing red algae species within this biotope an assessment of ‘No Evidence’ has been given.

Removal of target species

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

Evidence

The harvesting of Furcellaria lumbricalis is due to the gelling properties of its extracted structural polysaccharide, furcellaran (Bird et al., 1991). Extraction of Furcellaria lumbricalis was reviewed by Guiry & Blunden (1991).  Plinski & Florczyk (1984) noted that over-exploitation of Furcellaria lumbricalis resulted in severe depletion of stocks.  However, no commercial harvest as yet occurs in Britain or Ireland. Overall, while saline lagoons in areas subject to commercial harvesting may be directly affected, most examples of the biotope are unlikely to be affected by commercial harvesting in the UK. However, due to the relative small size of the community, even small scale hand collecting may have a significant effect.

Littorinids are one of the most commonly harvested species of the rocky shore.  Large scale removal of Littorina littorea may allow a proliferation of opportunistic green algae, such as Ulva sp., on which it preferentially feeds.  The community structure within the biotope is likely to be altered but some individuals are likely to remain.  Experiments designed to test the effects of harvesting by removing individuals at Strangford Lough found that there was no effect of experimental treatments (either harvesting or simulated disturbance) on Littorina littorea abundance or body size over a 12 week period (Crossthwaite et al. 2012).  This suggests that these animals are generally abundant and highly mobile; thus, animals that were removed were quickly replaced by dispersal from surrounding, un-affected populations.

A broad scale study of harvesting in Ireland using field studies and interviews with wholesalers and pickers did suggest that some areas were over harvested but the lack of background data and quantitative records make this assertion difficult to test (Cummins et al., 2002).

Sensitivity assessment.  This biotope is considered to have 'Low' resistance to removal of targeted species by hand-gatherers and 'Medium' resilience and is therefore, considered to have a ‘Medium’ sensitivity to this pressure.  However, intense collection of the species Littorina littorea (the species present in high enough quantities within this biotope to be collected commercially) over extended periods of time could lead to the degradation of the biotope and consequent loss of the biotope.

Removal of non-target species

Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Direct, physical impacts from harvesting are assessed through the abrasion and penetration of the seabed pressures.  The characterizing species Furcellaria lumbricalis and Polyides rotunda are also the dominant species within this biotope.  The dominance of these characterizing species means that they could easily be incidentally removed from this biotope as by-catch when other species are being targeted.  The loss of these species and other associated species would decrease species richness and negatively impact on the ecosystem function.

Sensitivity assessment. Removal of a large percentage of the characterizing species would alter the character of the biotope. The resistance to removal is ‘Low’ due to the easy accessibility of the biotopes location and the inability of these species to evade collection. The resilience is ‘Medium’, with recovery only being able to begin when the harvesting pressure is removed altogether. This gives an overall sensitivity score of ‘Medium’.