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 percentage of plants of Rhodochorton purpureum sporulating was greatest at 10°C from Washington and Alaska, but greatest at 15°C in plants from California but plants from Chile sporulated between 10 and 15°C (West, 1972). But sporulation was 'strikingly' inhibited above or below these optima. Gametogenesis was greatest at 15°C but reduced below 10 (West, 1972). Tetrasporophytes survived at 25°C in the laboratory but exhibited aberrant growth (Stegenga, 1978). In the Shetland Isles, Conway & Knaggs (1966) recorded Rhodochorton purpureum along the top of cliffs 200 feet high, suggesting that it can tolerate supralittoral conditions, exposed to high summer temperatures and low winter temperatures.  It is also widely distributed in the North East Atlantic, and occurs in California, suggesting that it would be resistant of an increase in temperature at the benchmark level within the UK. In addition, the biotopes occur in the darker or shaded areas of caves, protected from strong sunlight and, in the presumably humid or moist areas of caves, protected from desiccation due to the sun and the wind.

Fortes & Lüning (1980) and Lüning (1984) reported that Cladophora rupetrsis from Helgoland were able to survive at temperatures between 0 -28°C (for a period of a week), so the species is likely to tolerate the benchmark acute increase in temperature, the species is also characteristic of upper shore rock pools, where water and air temperatures are greatly elevated on hot days. The biotope CvOv.AudPil also occurs on the upper littoral level of cliffs, where is could receive heating from sunlight. However, Pleurocladia lacustis is recorded from Devon Island in the Arctic, Greenland, Novaya Zemlya, south to the Baltic and the French Mediterranean (Wilce, 1966).

Overall, the important characterizing species are probably resistant of an increase in temperature at the benchmark level within the UK. Therefore, a resistance of High is recorded, so that resilience is also High and the biotope is assessed as Not sensitive.

Temperature decrease (local)

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

Evidence

The percentage of plants of Rhodochorton purpureum sporulating was greatest at 10°C from Washington and Alaska, but greatest at 15°C in plants from California but plants form Chile sporulated between 10 and 15°C (West, 1972). But sporulation was 'strikingly' inhibited above or below these optima. Gametogenesis was greatest at 15°C but reduced below 10 (West, 1972). In the Shetland Isles, Conway & Knaggs (1966) recorded Rhodochorton purpureum along the top of cliffs 200 feet high, suggesting that it can tolerate supralittoral conditions, exposed to high summer temperatures and low winter temperatures. It is also widely distributed in the North East Atlantic, and occurs in California, suggesting that it would be resistant of an increase in temperature at the benchmark level within the UK. In addition, the biotopes occur in the darker or shaded areas of caves, protected from strong sunlight and, in the presumably humid or moist areas of caves, protected from desiccation due to the sun and the wind.

Fortes & Lüning (1980) and Lüning (1984) reported that Cladophora rupetrsis from Helgoland were able to survive at temperatures between 0 -28°C (for a period of a week), so the species is likely to tolerate the benchmark acute increase in temperature, the species is also characteristic of upper shore rock pools, where water and air temperatures are greatly elevated on hot days. The biotope CvOv.AudPil also occurs on the upper littoral level of cliffs, where is could receive heating from sunlight. However, Pleurocladia lacustis is recorded from Devon Island in the Arctic, Greenland, Novaya Zemlya, south to the Baltic and the French Mediterranean (Wilce, 1966).  In addition, Wilce (1966) noted that it must be able to withstand the intense freezing and thawing associated with the start of the growing season in the Arctic.

Overall, the important characterizing species are probably resistant of a decrease in temperature at the benchmark level within the UK. Therefore, a resistance of High is recorded, so that resilience is also High and the biotope is assessed as Not sensitive.

Salinity increase (local)

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

Evidence

Rhodochorton purpureum is recorded as an epiphyte on laminarian stipes in the subtidal, and a lithophyte under fucoids in the littoral, in caves in the littoral or littoral fringe, on cliffs and cliff tops in the supralittoral, and in a freshwater waterfall in a shallow cave (Shetland) (Conway & Knaggs, 1966; Connor et al., 2004; Guiry & Guiry, 2015). In experiments, West (1972) noted that clones of Rhodochorton purpureum from the upper littoral showed little response to a change in salinity, and were able to sporulate at 10‰, and 20‰ but that clones from the mid-littoral showed the poorest ability to sporulate at the salinities tested (10, 20 and 30‰). Nevertheless, Rhodochorton purpureum found on cave walls is probably resistant of a wide range of salinities as it occupies a littoral fringe or supralittoral position on the shore.

Cladophora rupestris found in intertidal rock pools can withstand 5-30 psu (Jansson, 1974) and as the species is successful in the high intertidal zone it is likely that the species has a broad salinity tolerance (Dodds & Gudder, 1992). However, Thomas et al. (1988) found that, at extreme temperatures, Cladophora rupestris had a reduced salinity tolerance range, e.g. the most marked inhibition of photosynthesis occurred in conditions of low salinity (0 psu) and high temperatures (25 - 30°C). Pleurocladia lacustris was reported from the upper littoral of limestone shores, exposed to freshwater runoff and rainfall until the breakup of the ice sheet, after which conditions are fully marine (Wilce, 1966).  

Sensitivity assessment. The important characterizing species are typical of upper littoral and supralittoral habitats. Therefore, they are probably exposed to a wide range of salinities, from running freshwater and rainfall, for fully marine and salt deposited by spray and splash, especially on cliffs. The biotopes are probably resistant of a change in salinity from full to reduced or low. Therefore, resistance is assessed as High, so that resilience is High and the biotope assessed as Not sensitive.

Salinity decrease (local)

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

Evidence

Rhodochorton purpureum is recorded as an epiphyte on laminarian stipes in the subtidal, under fucoids in the littoral, in caves in the littoral or littoral fringe, on cliffs and cliff tops in the supralittoral, and in a freshwater waterfall in a shallow cave (Shetland) (Conway & Knaggs, 1966; Connor et al., 2004; Guiry & Guiry, 2015). In experiments, West (1972) noted that clones of Rhodochorton purpureum from the upper littoral showed little response to a change in salinity, and were able to sporulate at 10‰, and 20‰ but that clones from the mid-littoral showed the poorest ability to sporulate at the salinities tested (10, 20 and 30‰). Nevertheless, Rhodochorton purpureum found on cave walls is probably resistant of a wide range of salinities as it occupies a littoral fringe or supralittoral position on the shore.

Cladophora rupestris found in intertidal rock pools can withstand 5-30 psu (Jansson, 1974) and as the species is successful in the high intertidal zone it is likely that the species has a broad salinity tolerance (Dodds & Gudder, 1992). However, Thomas et al. (1988) found that, at extreme temperatures, Cladophora rupestris had a reduced salinity tolerance range, e.g. the most marked inhibition of photosynthesis occurred in conditions of low salinity (0 psu) and high temperatures (25 - 30°C). Pleurocladia lacustris was reported from the upper littoral of limestone shores, exposed to freshwater runoff and rainfall until the breakup of the ice sheet, after which conditions are fully marine (Wilce, 1966).  

Sensitivity assessment. The important characterizing species are typical of upper littoral and supralittoral habitats. Therefore, they are probably exposed to a wide range of salinities, from running freshwater and rainfall, for fully marine and salt deposited by spray and splash, especially on cliffs. The biotopes are probably resistant of a change in salinity from marine to reduced, or reduced to low. Therefore, resistance is assessed as High, so that resilience is High and the biotope assessed as Not sensitive.

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

Tidal influence in mid-littoral to supralittoral caves is probably is probably limited to the floor and sides of the caves, and the upper walls and ceilings only receive spray and splash. However, water movement, splash, spray in caves are probably wave mediated rather than due to tidal streams. Therefore, the biotope is unlikely to be affected by water flow as described by the benchmark and the pressure is Not relevant.

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

Rhodochorton purpureum (syn. Audouinella purpurea) is recorded from s recorded as an epiphyte on laminarian stipes in the subtidal, and a lithophyte under fucoids in the littoral, in caves in the littoral or littoral fringe, on cliffs and cliff tops in the supralittoral, and in a freshwater waterfall in a shallow cave (Shetland) (Conway & Knaggs, 1966; Connor et al., 2004; Guiry & Guiry, 2015). It is, therefore, found in a variety of emergence regimes.  Cladophora rupestris is also recorded from the sublittoral fringe to the supralittoral (Connor et al., 1997a) while Pleurocladia lacustris (syn Pilinia maritima) is primarily recorded from upper littoral or littoral fringe habitats (Wilce, 1966). However, the Rhodochorton purpureum dominated biotopes only occur in shaded areas of caves, sheltered from wave action, or on cliff faces, presumably moist and shaded enough to support the biotope. Changes in emergence will probably affect the degree of splash and spray, and, hence, moisture, desiccation and salinity experienced by the biotopes. Therefore, a change in wave exposure will probably affect the upper and lower extent of the biotopes, and result in loss of extent.  Therefore, a resistance of Low is recorded. Resilience is probably High (albeit at Low confidence), therefore, a sensitivity of Low is recorded.

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

These biotopes (CvOv.AudCla and CvOv.AudPil) occur on the entrances and inner reaches of upper to mid-shore caves that are partially sheltered from direct wave action, in moderately wave exposed to wave sheltered shores (Connor et al., 2004). Wave surge, splash and spray keep the rock surface moist while the cave habitat maintains the humidity. AudPil can also occur on upper littoral cliffs. Changes in wave action will probably affect the degree of splash and spray, and, hence, moisture, desiccation and salinity experienced by the biotopes. Therefore, a change in wave exposure will probably affect the upper and lower extent of the biotopes, and result in loss of extent. However, a 3-5% change in significant wave height is unlikely to be significant in wave exposed conditions. Therefore, the biotope is probably Not sensitive (resistance and resilience are High) at the benchmark level.

Transition elements & organo-metal contamination

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

Evidence

This pressure is Not assessed but evidence is presented where available.

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.

Smith (1968) reported Cladophora rupestris to be amongst algae of unhealthy appearance following exposure to oil dispersants. O'Brien & Dixon (1976) suggested that red algae were the most sensitive group of algae to oil or dispersant contamination. Laboratory studies of the effects of oil and dispersants on several red algal species concluded that they were all sensitive to oil/dispersant mixtures, with little difference between adults, sporelings, diploid or haploid stages (Grandy, 1984, cited in Holt et al., 1995). In addition, Cole et al. (1999) suggested that the herbicides Atrazine, Simazine, Diuron, Linuron and the insecticide Dimethoate were probably very toxic to algae.

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 littoral fringe and supralittoral and cave ceilings are rarely inundated and are, therefore, permanently exposed to the air. The biotope is unlikely to be exposed to deoxygenated conditions.

Nutrient enrichment

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

Evidence

Maritime cliff plant and algae communities are probably nutrient poor, i.e. lack nutrients. An increase in nutrients in the form of runoff from adjacent agricultural land may benefit the communities. The opportunistic filamentous algae such as Ulothrix sp. and Urospora sp. may overgrow these biotopes. However, no evidence concerning the effects of nutrient enrichment on these communities was found.

Organic enrichment

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

Evidence

Maritime cliff plant and algae communities are probably nutrient poor, i.e. lack nutrients. An increase in nutrients in the form of runoff from adjacent agricultural land may benefit the communities. The opportunistic filamentous algae such as Ulothrix sp. and Urospora sp. may overgrow these biotopes. However, no evidence concerning the effects of nutrient enrichment on these communities was found.

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

These biotopes require hard or soft rock substrata. A change to a sedimentary substratum, however unlikely, would result in the permanent loss of the biotope. Therefore, the biotope has a resistance of None, with a Very low resilience (as the effect is permanent) and, therefore, a sensitivity of 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 sediment type)

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

Evidence

Not Relevant on hard rock biotopes. Where present, it is unlikely that chalk would be replaced by sediment in the littoral fringe or supralittoral.  Therefore, this pressure is Not relevant. However, change in substratum type is address above.

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

Extraction of sediment, as described under this pressure, is not relevant in hard rock habitats. However, soft rocks could suffer extraction due to tunnelling, mining or construction. Therefore, removal of chalk from the cliff or caves would remove the surface resulting in loss of the biotope. Resistance would, therefore, be None where it occurs on chalk or other soft rocks. But if the existing substratum (chalk) remains in the same habitat (upper littoral fringe to supralittoral) then the biotope would recover rapidly and resilience is probably High, therefore, sensitivity to extraction is probably Medium.

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 characterizing species are filamentous, lithophytes, and probably fairly soft and fragile.  These algal communities are likely to be removed as a result of any abrasion, e.g. from vessel grounding, the abrasion from chains or cables, or recreational access and trampling, especially where the friable (e.g. chalk) rock surface is removed. Therefore, resistance is probably Low (depending on the scale of the impact). However, recovery is likely to be rapid if suitable substratum remains so that resilience is probably High and sensitivity is probably 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 by mobile fishing gear is unlikely to occur in caves or on vertical chalk cliffs. However, soft rock, by definition, can be damaged by other penetrative activities, for example during construction. Therefore, where these biotopes occur on chalk (e.g. CvOv.AudPil) resistance is probably Low (depending on the scale of the impact). However, recovery is likely to be rapid if suitable substratum remains so that resilience is probably High and sensitivity is probably Low.

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 occurs in mid to upper littoral and littoral fringe and reaches upper walls of caves, probably only exposed to wave splash and rarely inundated.  Therefore, an increase in turbidity due to suspended solids (at the benchmark) is unlikely to adversely affect the biotope and Not relevant is recorded.

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

The upper, vertical walls of caves are unlikely to be subject to smothering, but the inner reaches of caves with shallow slopes or horizontal ledges may be.  In the wave exposed conditions experienced by this biotope, 5 cm of sediment may be removed quickly from the entrance but may persist in the inner reaches of the cave, depending on the shape of the cave.  The fine 'velvety' mat of Rhodochorton purpureum, filaments of Cladophora rupestris or Pleurocladia lacustris may trap sediment and result in localised anoxia near the base of the plant. This may cause death, where the slope of the rock is sufficient for sediment to be deposited and the wave action so limited that sediment is not removed quickly.  It is possible, therefore, that a proportion of the biotope (on shallow sloping or horizontal surfaces) could be lost and a resistance of Medium is recorded. Resilience is probably High, so that a sensitivity of Low is suggested, albeit at Low confidence.

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

The upper, vertical walls of caves are unlikely to be subject to smothering, but the inner reaches of caves with shallow slopes or horizontal ledges may be.  In the wave exposed conditions experienced by this biotope, sediment may be removed quickly from the entrance but may persist in the inner reaches of the cave, depending on the shape of the cave.  The fine 'velvety' mat of Rhodochorton purpureum, filaments of Cladophora rupestris or Pleurocladia lacustris may trap sediment and result in localised anoxia near the base of the plant. This may cause death, where the slope of the rock is sufficient for sediment to be deposited and the wave action so limited that sediment is not removed quickly.  It is possible, therefore, that a proportion of the biotope (on shallow sloping or horizontal surfaces) could be lost and a resistance of Medium is recorded. Resilience is probably High, so that a sensitivity of Low is suggested, albeit at Low confidence.

Litter

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

Evidence

Not assessed. Caves, especially high on the shore, may accumulate litter blown into the cave by the wind. Large pieces of marine debris blown around by wind or wave action may cause abrasion of the cave wall communities (see above). However, No evidence on the effects of litter was found. 

Electromagnetic changes

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

Evidence

No evidence was found. 

Underwater noise changes

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

Evidence

No relevant

Introduction of light or shading

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

Evidence

Red algae are more shade tolerant than their green or brown equivalents. West (1972) noted that vegetative growth and gametogenesis of Rhodocorton purpureum was greatest in long day lengths (summer months), that sporulation and growth were greatest at highest light intensity tested (5000 lux), yet spermatangia and carpogonia production was greatest in short days (winter months), but concluded that the observations were not true photoperiodism. It may be that long summer days promote growth and asexual reproduction while short days and winter months promote sexual reproduction.  No evidence on the effects of light on the other characteristic species was found. 

These biotopes are characteristic of shaded or dark, moist caves, presumably because green algae would out-compete the dominant species at higher light levels. If artificial lighting was introduced to a cave where this biotope occurred, then it might adversely affect the biotopes by promoting green algal growth. Increased shaded might allow the biotope to increase in extent, or reduce light levels below those needed for the algae to survive. Therefore, a resistance of Medium is suggested at Low confidence. However, resilience is probably High, so that sensitivity is Low.

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

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

The pressure definition is not directly applicable to caves, so Not relevant has been recorded.  Collision via ship groundings or terrestrial vehicles is possible but the effects are probably similar to those of abrasion above.

Visual disturbance

Benchmark. The daily duration of transient visual cues exceeds 10% of the period of site occupancy by the feature. Further detail

Evidence

Not relevant has been recorded. 

Genetic modification & translocation of indigenous species

Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail

Evidence

No evidence was found to suggest that the macroalgae that characterize these biotopes were subject to translocation, nor that they were subject to genetic modification or hybridization with other similar species.

Introduction or spread of invasive non-indigenous species

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

Evidence

No evidence was found

Introduction of microbial pathogens

Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail

Evidence

No evidence was found.

Removal of target species

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

Evidence

The algal communities characteristic of these biotopes are unlikely to be targetted by any commercial or recreational fishery or harvest.

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

Incidental removal the dominant characteristic species would result in loss of the entire biotope. Where present, mobile invertebrate or gastropod fauna are probably not entirely dependent on the biotope for food or habitat and would forage elsewhere.  However, soft rock and hard rock cave communities are unlikely to be targetted by any commercial or recreational fishery or harvest. Accidental physical disturbance due to access (e.g. trampling) or grounding is examined under abrasion above.