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

Anand (1937c) examined the range of temperatures experienced by chalk cliff algal communities. The Pseudendoclonium submarinum belt was exposed to temperatures slightly less than air (since the cliff face heats up slowly) but similar variability in temperature to that of the air. The mucilaginous Chrysophyceae belt was consistently lower in temperature than the air, was least affected by changes in air temperature and showed no marked variation over several hours. Anand (1937c) concluded that its water content and retention acted as a buffer against temperature change. Curiously, in contrast, the Ulva sp. and Fucus sp. belts of the lower shore showed a much greater range of temperatures, especially in bright sunlight. However, Anand (1937b&c) also noted that prolonged exposure to high temperatures during summer in desiccating conditions resulted in death, cracking and peeling off of the 'Chrysophyceae' belt. The mat was seldom seen to crack in areas sheltered from direct sunlight and/or wind.

Sensitivity assessment.  Therefore, an increase in annual temperatures (at the benchmark level) is likely to increase the risk of desiccation and exposure to high temperatures during summer, resulting in loss of the proportion of the population depending on its shelter and aspect. Hence, a resistance of Low has been recorded. Once prior conditions return, recovery is likely to be rapid  and resilience is probably High. Hence, sensitivity is likely to be Low.

Temperature decrease (local)

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

Evidence

Anand (1937b&c) reported that light brown or white patches appeared in the 'Chrysophyceae' mat during winter due to frost. However, little other information concerning low temperatures was found. A decrease in annual winter temperatures is likely to increase the risk of frost, however, a reduction in average summer temperatures will reduce the risk of desiccation. Since the Chrysophyceae communities are best developed in winter and the associated Cyanobacteria communities develop in spring and summer the biotope as a whole may benefit from a reduction in average summer temperatures. Therefore, resistance is probably High, so that resilience is also High and Not sensitive has been recorded.

Salinity increase (local)

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

Evidence

Although not covered by seawater, the upper littoral fringe and supralittoral experience a wide range of salinities due to the evaporation of wave splash and spray, resulting in high salt concentrations, and exposure to rain and freshwater runoff. Anand (1937c) showed that the salt concentration in the 'Chrysophyceae' belt was higher than in the Ulva sp. belt (lower on the shore) but (due to water retention) did not experience as great an increase in salt concentration once the tide fell. However, in the 'Chrysophyceae' belt the salt concentration may be approximately three times that of seawater (Anand, 1937c). Therefore, since soft rock algal communities are also likely to be exposed to freshwater in the form of rain, this biotope is probably resistant to changes in salinity comparable to the benchmark (i.e. >40 PSU).  Therefore, a resistance of High is suggested, so that resilience is also High and Not sensitive is recorded.

Salinity decrease (local)

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

Evidence

Although not covered by seawater, the upper littoral fringe and supralittoral experience a wide range of salinities due to the evaporation of wave splash and spray, resulting in high salt concentrations, and exposure to rain and freshwater runoff. Anand (1937c) showed that the salt concentration in the 'Chrysophyceae' belt was higher than in the Ulva sp. belt (lower on the shore) but (due to water retention) did not experience as great an increase in salt concentration once the tide fell. However, in the 'Chrysophyceae' belt the salt concentration may be approximately three times that of seawater (Anand, 1937c). Therefore, since soft rock algal communities are also likely to be exposed to freshwater in the form of rain, this biotope is probably resistant to changes in salinity comparable to the benchmark (i.e. full to reduced).  Therefore, a resistance of High is suggested, so that resilience is also High and Not sensitive is recorded.

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 upper littoral fringe and supralittoral are rarely if ever inundated. Therefore, the biotope is unlikely to be affected by water flow as described by the benchmark. Runoff due to heavy rainfall is possible but is outside the scope of the pressure. Therefore, 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

Anand (1937c) examined the volumes of water and spray received by the littoral fringe and supralittoral on chalk cliffs.  He concluded that the Chrysophyceae belt received occasional spray and rarely very much. In calm weather in summer drought periods the belt was subject to periods of drought of up to three days occasionally separated by brief periods of spray. The Endocladia belt was rarely wetted by spray except in rough weather at spring tides and experienced periods of drought of up to three days and yet still extended to high levels (8-10 m). The Endocladia belts showed more conspicuous growth in tunnels and recesses where waves break and spray reached higher levels (Annand, 1937c). It should be remembered that chalk retains moisture and may offset the desiccation experienced at different shore height.  Anand (1937c) also noted that rainfall contributed to moisture but did not influence zonation (height on the shore) as it affected the entire shore.

A decrease in emergence equivalent would expose the habitat to an increased level of spray. However, decreased emergence will allow the algal communities to colonize further up the shore so that the entire zonation (see habitat complexity) will probably move up the shore.

An increase in emergence will result in a reduction in the height reached by wave splash and spray. Hence, the height of the algal communities in the littoral fringe and supralittoral will also be reduced, resulting in the biotope effectively moving down the shore. Some species particularly abundant in more moist conditions may be lost. Therefore, the extent or abundance of the biotope is likely to be reduced and a resistance of Low has been recorded at the benchmark level.  Once prior conditions return, recovery is likely to be rapid so that resilience is probably High and sensitivity Low.

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 height and extent of the littoral fringe and supralittoral, and hence the communities they support is dependent on wave wash, splash and spray, and therefore, wave exposure. Anand (1937b&c) noted that the Pseudendoclonium submarinum belt could reach up to 8-10 m above high water but in caves or recesses where waves break and create more spray the algal communities could extend higher up the shore. Similarly, Lewis (1964) noted that the supralittoral could reach 50-60 ft above mean high water springs on wave exposed North Atlantic headlands. Increased wave exposure is likely to increase the overall height of the littoral fringe or supralittoral and increase the height and extent of the associated algal communities. Increased spray may also allow a more diverse community to develop resulting in a rise in species richness. A decrease in wave exposure is likely to reduce the height of the littoral fringe or supralittoral and hence the extent of its associated algal communities. However, as the biotope is typical of moderately wave exposed conditions, a 3-5% change in significant wave height (the benchmark) is unlikely to have a significant effect. Therefore, resistance and resilience are considered High, and the biotope is probably Not sensitive at the benchmark level.

Transition elements & organo-metal contamination

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

Evidence

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

Cole et al. (1999) suggested that Pb, Zn, Ni and As were probably very toxic to algae but no direct evidence of the effects on this biotope was found.

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 . No evidence concerning the effects of hydrocarbons or oil spills on chalk cliff algal communities was found.

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.

No information on the effects of synthetic chemicals on soft rock algal communities was found. However, 1µg/l TBT was shown to significantly reduce growth of the diatoms Pavlova lutheri and Dunaliella tertiolecta and Skeletonema costatum would not grow at 100 ng/l TBT. All species died at 5 µg/l TBT (Beaumont & Newman, 1986; Bryan & Gibbs, 1991). Bryan & Gibbs (1991) reported that TBT suppressed growth of the Skeletonema costatum (EC₅₀ 350ng/l) and Thalassiosira pseudonana (EC₅₀ 1.15 µg/l). Cole et al. (1999) reported that TBT impaired the development of motile spores of green macroalgae (5 day EC₅₀ of 1 ng/l TBT), which were considered the most intolerant phase of their life cycle. In addition, Cole et al. (1999) suggested that the herbicides Atrazine, Simazine, Diuron, Linuron and the insecticide Dimethoate were probably very toxic to algae.

Therefore, it is probable that soft rock algal communities are intolerant of synthetic chemicals, in particular, herbicides that may be contained in runoff (during heavy rains) from adjacent agricultural land.

Radionuclide contamination

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

Evidence

No evidence was found.

Introduction of other substances

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

Evidence

This pressure is Not assessed.

De-oxygenation

Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail

Evidence

The littoral fringe and supralittoral 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. However, the opportunistic filamentous algae such as Ulothrix sp. and Urospora sp. and even Pseudendoclonium submarinum may overgrow the 'Chrysophyceae' belt, resulting in the dominance of a few species at the expense of a more diverse community. 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. However, the opportunistic filamentous algae such as Ulothrix sp. and Urospora sp. and even Pseudendoclonium submarinum may overgrow the 'Chrysophyceae' belt, resulting in the dominance of a few species at the expense of a more diverse community. 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

Urban and industrial development in south east UK, resulted in a need for coastal defence works to stabilise cliffs and reduce coastal erosion. The construction of sea walls at the base of cliffs cuts off caves and tunnels from the inundation by the sea and prevents sea wash or spray reaching the cliff face. The cliff face may also be scarped and straightened to reduce falls and gullies torn down, resulting in loss of substratum (Fowler & Tittley, 1993). The resultant sea walls do not support the 'Chrysophyceae' algal communities, although limestone and brick structures support similar communities but with a reduced range of chalk species and communities (Tittley & Shaw, 1980; Fowler & Tittley, 1993). Tittley et al. (1998) surveyed chalk cliffs throughout England and revealed that 56% of coastal chalk in Kent and 33% in Sussex had been modified by coastal defence and other works. On the Isle of Thanet, this increased to 74% and had resulted in the loss of a wide range of microhabitats on the upper shore and the removal of splash-zone communities. Elsewhere in England, coastal chalk remains in a largely natural state (Anon, 1999e, Tittley et al., 1998). Fowler & Tittley (1993) noted that the brown algae Kuetzingiella holmesii, characteristic of cave communities and Pleurocladia lacustris had not been re-recorded since the 1930s.

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

Soft rock, such as chalk, is liable to split and wave action and frost can result in loss of the surface of the rock, and localised landslides. However, this would free up new substratum for colonization, and the biotope would probably recover quickly.  It is unlikely that chalk cliffs would be replaced by sedimentary substrata. But the replacement of soft chalk with man-made structures, e.g. of concrete or hard rock has resulted in the loss of the chalk cliff algal communities.

Urban and industrial development in south east UK, resulted in a need for coastal defence works to stabilise cliffs and reduce coastal erosion. The construction of sea walls at the base of cliffs cuts off caves and tunnels from the inundation by the sea and prevents sea wash or spray reaching the cliff face. The cliff face may also be scarped and straightened to reduce falls and gullies torn down, resulting in loss of substratum (Fowler & Tittley, 1993). The resultant sea walls do not support the 'Chrysophyceae' algal communities, although limestone and brick structures support similar communities but with a reduced range of chalk species and communities (Tittley & Shaw, 1980; Fowler & Tittley, 1993). Tittley et al. (1998) surveyed chalk cliffs throughout England and revealed that 56% of coastal chalk in Kent and 33% in Sussex had been modified by coastal defence and other works. On the Isle of Thanet, this increased to 74% and had resulted in the loss of a wide range of microhabitats on the upper shore and the removal of splash-zone communities. Elsewhere in England, coastal chalk remains in a largely natural state (Anon, 1999e, Tittley et al., 1998). Fowler & Tittley (1993) noted that the brown algae Kuetzingiella holmesii, characteristic of cave communities and Pleurocladia lacustris had not been re-recorded since the 1930s.

Sensitivity assessment. Therefore, the resistance is assessed as None, resilience as Very low (as it is a permanent change) and sensitivity as High.

Physical change (to another sediment type)

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

Evidence

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 soft rock habitats. However, soft rocks could suffer extraction due to tunnelling, mining or construction. Therefore, removal of chalk from the cliff would remove the surface Chrysophyceae and Haptophyceae belt, resulting in loss of the biotope. Resistance would, therefore, be None. 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 'Chrysophyceae' mat is very thin (a few millimetres) and the Pseudendoclonium submarinum belt exists as a thin coating of the rock. These algal communities are likely to be removed as a result of any abrasion, e.g. from vessel grounding or recreational access and trampling, especially where the friable 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 on vertical chalk cliffs. However, soft rock, by definition, can be damaged by other penetrative activities, for example during construction.  The 'Chrysophyceae' mat is very thin (a few millimetres) and the Pseudendoclonium submarinum belt exists as a thin coating of the rock. These algal communities are likely to be removed as a result of any abrasion or penetration,  especially where the friable 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.

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

The upper littoral fringe or supralittoral are rarely inundated. It is, therefore, unlikely to be exposed to changes in water clarity due to changes in suspended sediment.

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

Smothering could occur as a result of rainwater runoff of silt and soil from the tops of the cliffs. However, the slope of the cliff would preclude the build up of significant deposits (except on crevices and pits) sufficient to block the algal communities access to sunlight. Therefore, the factor is probably Not relevant at the level of the benchmark. Smothering by impermeable materials or by other hard construction materials, however, would result in loss of the biotope (see physical loss above).

Smothering and siltation rate changes (heavy)

Benchmark. ‘Heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

Smothering could occur as a result of rainwater runoff of silt and soil from the tops of the cliffs. However, the slope of the cliff would preclude the build up of significant deposits (except on crevices and pits) sufficient to block the algal communities access to sunlight. Therefore, the factor is probably Not relevant at the level of the benchmark. Smothering by impermeable materials or by other hard construction materials, however, would result in loss of the biotope (see physical loss above).

Litter

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

Evidence

Not assessed.

Electromagnetic changes

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

Evidence

No evidence was found.

Underwater noise changes

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

Evidence

Not relevant.  The biotope is rarely underwater and microalgae are not known to respond to noise.

Introduction of light or shading

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

Evidence

An increase in artificial light might be beneficial but shading is likely to result in loss of the biotope.  Anand (1937b&c) reported that the Chrysophyceae belt was restricted to the entrance and mouth of caves and out-competed in tunnels.  In the two caves examined, the Chrysophyceae belt was restricted to the 9m from the cave mouth where light intensity was reduced to 10% of incident light. In caves where light could not penetrate, the Chrysophyceae belt was replaced in shaded areas.  Resistance to shading is probably Low.  However, the Chrysophyceae belt would probably recover rapidly once the shading activity is removed, and resilience is probably High. Therefore, the sensitivity to change in light is probably 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. This pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit the dispersal of spores. But spore 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

The pressure definition is not directly applicable to the littoral fringe 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. Microalgae respond to light intensity but are unlikely to respond to 'visual' cues.

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 Chrysophyceae and Haptophyceae that characterize the green algal mats in this biotope were subject to translocation, nor that they were subject to genetic modification or hybridization with other similar species.  Several species of Chrysophyceae and Haptophyceae may be cultured as a food source or for research but no evidence was found to suggest that genetically modified or laboratory stocks were released into the wild.

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

Viruses are thought to play a part in the control of phytoplankton populations (Brussaard, 2004). However, no evidence specific to these chalk cliff communities 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

Soft-rock algal communities 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 of the Chrysophyceae and Haptophyceae 'belt' would probably remove the entire belt rather than specific characteristic species. The Cyanobacteria probably depend on the mucilaginous 'belt' for substratum but are otherwise not closely associated with any other species. Similarly, the mobile invertebrate fauna are probably not entirely dependent on the 'belt' for food or habitat and would forage elsewhere. 

However, soft-rock 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.