Biodiversity & Conservation

LR.FLR.CvOv.ChrHap

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Removal of the substratum will result in the removal and loss of the biotope. Therefore, an intolerance of high has been recorded. Rock falls may be a natural dynamic feature of this biotope resulting in loss of areas of substratum and its associated biotopes but revealing new substratum for colonization. However, where the substratum is modified, e.g. by coastal defence structures, recovery may not be possible (see importance). The microalgae within this biotope can probably colonize new substratum and grow rapidly, probably within a year (see additional information below). Therefore a recoverability of high has been recorded.
Smothering
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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.
Increase in suspended sediment
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This biotope is unlikely to be affected by changes in suspended sediment since it is only exposed to wave splash or spray. Therefore, this factor is probably not relevant. However, it may be covered in silt due to heavy rainfall (see smothering above).
Decrease in suspended sediment
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This biotope is unlikely to be affected by changes in suspended sediment since it is only exposed to wave splash or spray. Therefore, this factor is probably not relevant. However, it may be covered in silt due to heavy rainfall (see smothering above).
Desiccation
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Risk of desiccation, high salt concentration due to evaporation and temperature change increase with increasing height above high tide. Anand (1937c) carried out a detailed, quantified study of the amount of spray, rates of drying, evaporation rates, capillarity and salinity changes in chalk cliff algal communities. Anand (1937c) made the following important observations:
  • the 'Chrysophyceae' belt received little spray, and in summer may suffer up to three days of drought, separated by only brief exposure to spray during calm weather;
  • the Pseudendoclonium submarinum belt was rarely wetted except in stormy weather, and was exposed to long periods of drought of up to three days;
  • the mucilaginous 'Chrysophyceae' belt retains more water and losses water by evaporation or drainage slower than the Ulva sp. belt beneath it, loosing only 6.8-11.3% of water by evaporation after 5hrs in the field or 15.7% after 12hrs in the laboratory;
  • however, prolonged high temperatures and direct sunlight n summer result in drying and cracking of the 'Chrysophyceae' mat (Anand, 1937b&c).
Anand (1937c) concluded that the 'Chrysophyceae' succeed in an inhospitable habitat, probably due to water retention by the mucilaginous mat, which also reduces their exposure to extremes of salt concentration and temperature. Tittley & Shaw (1980) also reported that chalk absorbed more water and released it more slowly on drying than concrete, suggesting that the water retention by the substratum was important for the development and height of the algal belts.
Overall, the 'Chrysophyceae' belt and Pseudendoclonium submarinum in particular are extremely tolerant of desiccation when compared to other intertidal organisms. However, the 'Chrysophyceae' belt inhabits a narrow habitat where a particular range of environmental conditions occurs (desiccation, sunlight, substratum and temperature) and is, therefore, probably highly intolerant of a change in desiccation at the level of the benchmark, especially during summer. An increase in the length of the time between spray events is likely to reduce the extent or duration of the population and reduce its height on the shore. However, physical removal from the effects of the sea (wave splash and spray) for long periods of time, e.g. by coastal defences, has been shown to result in loss of suitable environmental conditions and loss of the biotope (see importance: Fowler & Tittley, 1993; Anon, 1999e). Therefore, an intolerance of high has been recorded. Once prior conditions return, recovery is likely to be rapid (see additional information below).
Increase in emergence regime
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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 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 an intolerance of intermediate has been recorded at the benchmark level. However, physical removal from the effects of the sea (wave splay and spray) for long periods of time, e.g. by coastal defences has been shown to result in loss of suitable environmental conditions and loss of the biotope (see importance; Fowler & Tittley, 1993; Anon, 1999e). Once prior conditions return, recovery is likely to be rapid (see additional information below).
Decrease in emergence regime
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A decrease in emergence equivalent to a 1 hour change cover by the sea (see benchmark) 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. Therefore, an intolerance of low has been recorded.
Increase in water flow rate
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This biotope is never directly covered by the sea and is, therefore, not affected by water flow rates.
Decrease in water flow rate
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This biotope is never directly covered by the sea and is, therefore, not affected by water flow rates.
Increase in temperature
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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 and 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.
Overall, 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, an intolerance of intermediate has been recorded. Once prior conditions return, recovery is likely to be rapid (see additional information below).
Decrease in temperature
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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, not sensitive* has been recorded.
Increase in turbidity
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This biotope is never directly covered by the sea and is, therefore, not affected by changes in turbidity.
Decrease in turbidity
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This biotope is never directly covered by the sea and is, therefore, not affected by changes in turbidity.
Increase in wave exposure
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The height and extent of the supralittoral, and hence the communities it supports is dependant on wave wash, splash and spray, and therefore, wave exposure. Anand (1937b&c) noted that the Pseudendoclonium submarinum belt could reach up to 8-10m 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 supralittoral and increase the height and extent of the associated algal communities. Therefore, not sensitive* has been recorded. Increased spray may also allow a more diverse community to develop resulting in a rise in species richness.
Decrease in wave exposure
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The height and extent of the supralittoral, and hence the communities it supports is dependant on wave wash, splash and spray, and therefore, wave exposure. A decrease in wave exposure is likely to reduce the height of the supralittoral and hence the extent of its associated algal communities. Therefore, an intolerance of intermediate has been recorded. Once prior conditions return, recovery is likely to be rapid (see additional information below).
Noise
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Microalgae have no known sound receptors and are unlikely to respond to vibration.
Visual Presence
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Microalgae can orientate themselves to light when motile. However, visual acuity is probably non-existent and they are unlikely to respond to visual presence or periodic shading, especially when fixed to the substratum in the form of a thallus.
Abrasion & physical disturbance
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The 'Chrysophyceae' mat is very thin (a few millimetres) and the Pseudendoclonium submarinum belt exists as a thin coasting of the rock. These algal communities are likely to be removed as a result of any abrasion, e.g. from stranding or trampling, especially where the friable rock surface is removed. Therefore, an intolerance of intermediate has been recorded. However, recovery is likely to be rapid if suitable substratum remains (see additional information below).
Displacement
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Rock falls are probably a natural feature of soft rock communities. Any algal communities present on falling rocks will be deposited at the base of the cliff in the intertidal and will be lost. No information concerning displacement or transplantation was found, however, it is probable that any part of the 'Chrysophyceae' or Pseudendoclonium submarinum communities removed from the substratum is unlikely to be able to reattach to suitable substratum and will be lost. Therefore, an intolerance of high has been recorded. However, recovery is likely to be rapid if suitable substratum remains (see additional information below).

Chemical Factors

Synthetic compound contamination
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No information of 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 (19910 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. Hence an intolerance of intermediate has been recorded. However, recovery is likely to be rapid if suitable substratum remains (see additional information below).
Heavy metal contamination
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Cole et al. (1999) suggest that Pb, Zn, Ni and As were probably very toxic to algae. Therefore, in the absence of any specific studies an intolerance of intermediate has been recorded. However, recovery is likely to be rapid if suitable substratum remains (see additional information below).
Hydrocarbon contamination
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No information concerning the effects of hydrocarbons or oil spills on supralittoral algal communities was found.
Radionuclide contamination
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Insufficient information
Changes in nutrient levels
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Maritime cliff plant and algae communities are probably nutrient poor, i.e. lack nutrients. A 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 information concerning the effects of nutrient enrichment on these communities was found and no intolerance assessment was recorded.
Increase in salinity
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Although not covered by seawater, the supralittoral experiences 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 3 times that of seawater (Anand, 1937c). Therefore, since soft rock algal communities are also likely to be exposed to fresh water in the form of rain, this biotope is probably not intolerant of changes in salinity comparable to the benchmark.
Decrease in salinity
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See above.
Changes in oxygenation
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This biotope is exposed to the air and therefore unlikely to experience hypoxia or anoxia.

Biological Factors

Introduction of microbial pathogens/parasites
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No information found
Introduction of non-native species
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No information found
Extraction
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Soft rock algal communities are unlikely to be subject to extraction.

Additional information icon Additional information

Recoverability

Recovery will depend on regrowth from existing thallus or filaments and should be rapid. The 'Chrysophyceae' communities develop over winter, and several members of soft rock algal communities develop rapidly in spring.
Most members of these algal communities produce motile spores or have a motile pelagic stage in their life cycle (except Cyanobacteria) and have the potential to disperse widely with effectively high fecundity. Therefore, once suitable habitat or environmental conditions return recovery is likely to be rapid, probably taking a year at most. However, little direct evidence of recovery rates was found.

This review can be cited as follows:

Tyler-Walters, H. 2001. Chrysophyceae on vertical upper littoral fringe soft rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 24/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=121&code=2004>