Biodiversity & Conservation

IR.SIR.Lag.FChoG

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
(View Benchmark)
The biotope is a macroalgae community so almost all species are attached directly to the substratum and will be lost if substratum is removed. Any other species that are present, such as the snail Littorina littorea, will either be lost along with the algae or will be indirectly affected by the loss of algal cover through increased risk of predation. Thus the overall effect of substratum loss is the loss of the biotope and intolerance is, therefore, reported to be high. See additional information for recovery of the biotope.
Smothering
(View Benchmark)
A 5cm layer of sediment or debris on beds of algae will reduce photosynthesis and may cause some plants to rot. Sediment will have an especially adverse effect on young germling algae. The suspension feeding structures of the occasional mussels are likely to become clogged and may be killed by smothering. In the extremely sheltered conditions found in the SIR.FChoG lagoonal habitat, there is not likely to be enough wave action to mobilise sediment and alleviate the effects of smothering and so most plants and animals are likely to die. Intolerance is therefore recorded to be high. For recovery see additional information.
Increase in suspended sediment
(View Benchmark)
Fucus serratus, Fucus vesiculosus and the other macroalgal species in the biotope, are not likely to be directly intolerant of an increase in suspended sediment because they are primary producing species. Settlement out of the sediment may cover some surfaces of the plants, reducing photosynthesis rates which may reduce growth and in the sheltered conditions in which the biotope is found will probably not be removed by wave action. However, the direct effects of increased suspended sediment (see turbidity for indirect effects of light attenuation) on photosynthesising plants are not expected to be significant. Other species in the biotope, such as suspension feeding mussels, are likely to be more intolerant because an increase in suspended sediment may interfere with feeding, increase cleaning costs and result in lower growth rates. However, the impact on the biotope as a whole will be sublethal effects on growth etc. and for a period of a month will be minimal so intolerance has been assessed as low. There may be a loss of a few very intolerant species. On return to pre-impact suspended sediment levels feeding rates of affected species and photosynthetic rates will return to normal very rapidly.
Decrease in suspended sediment
(View Benchmark)
The biotope is likely to be not sensitive to a decrease in suspended sediment because most of the key characterizing species are primary producers and do not require particles for feeding or tube building. The mussels, if present, are likely to be more intolerant because a decrease in suspended sediment may also result in a decrease in food supplies so growth may be affected. However, the impact on the biotope as a whole will be sublethal effects (i.e. growth, fecundity etc.) so intolerance has been assessed as low. On return to pre-impact suspended sediment levels feeding of affected species and photosynthetic rates will return to normal very rapidly.
Desiccation
(View Benchmark)
The fucoids present in the SIR.FChoG biotope are permanently submerged and so not normally subject to desiccation. However, almost all the macroalgae species are predominantly intertidal and can tolerate a degree of desiccation so the benchmark increase will have little effect. Chorda filum however, is an entirely subtidal or rockpool species, with high intolerance to an increase in desiccation and is likely to be lost if the factor increases. Therefore, because one of the key species would be lost, altering the species composition of the biotope, intolerance is considered to be intermediate. Recovery is expected to be high - see additional information below.
Increase in emergence regime
(View Benchmark)
The fucoids in the biotope are permanently submerged and so not normally subject to emersion. However, the fucoid plants Fucus serratus and Fucus vesiculosus and many of the other macroalgae are intertidal and so can tolerate a degree of emergence and are not likely to be adversely affected by one additional hour emergence in each tidal cycle. Chorda filum however, is an entirely subtidal or rockpool species, with high intolerance to an increase in emergence and may be lost if subjected to an increase. Therefore, because one of the key species would be lost intolerance of the biotope is considered to be intermediate. Recovery is expected to be high - see additional information below.
Decrease in emergence regime
(View Benchmark)
The biotope is subtidal and so a decrease in emergence is not relevant.
Increase in water flow rate
(View Benchmark)
Significant increases in water flow rate may cause some of the macroalgal populations to be torn off the substratum. However, the key algal species in the biotope are also found in strong tidal streams so should survive the benchmark increase. Increased water movement also favours filter feeding faunal groups so a cover of other species such as sponges and ascidians may develop. However, since the nature of the biotope is not expected to change significantly intolerance is considered to be low. On return to normal conditions recovery will be rapid.
Decrease in water flow rate
(View Benchmark)
The biotope is found in areas of very weak tidal streams so a decrease is unlikely and so a rank of not relevant is reported.
Increase in temperature
(View Benchmark)
The key species in the biotope, Fucus serratus, Fucus vesiculosus and Chorda filum, as well as Ulva, are well within their temperature limits being distributed further north and south of Britain and Ireland and so are not likely to be highly intolerant to increases in temperature. Also, the habitats in which the species are found, lagoons, rockpools and the intertidal, are subject to wide variations in temperature and so have low intolerance to an increase in temperature. For example, growth of Fucus serratus is optimal at 20 °C so British and Irish populations are more likely to benefit from increases in temperature. Fucus vesiculosus has been observed to tolerate temperatures as high as 30°C (Lüning, 1990) although the populations in Scottish lochs are subject to lower temperatures and would probably die if temperatures rapidly increased to 30°C. However, the biotope is likely to be able to tolerate both a short term increase of 5°C and a longer term increase of 2°C. The only effects are likely to be changes in growth rates and reproductive timings and periods and so intolerance is considered to be low. Return of normal metabolic processes will resume very rapidly if original temperatures return.
Decrease in temperature
(View Benchmark)
The key species in the biotope, Fucus serratus, Fucus vesiculosus and Chorda filum, as well as Ulva, are well within their temperature limits being distributed further north and south of Britain and Ireland. Also, the habitats in which the species are found, lagoons, rockpools and the intertidal, are subject to wide variations in temperature. Many of the species have low intolerance to a decrease in temperature. For example, in Helgoland Fucus serratus and Fucus vesiculosus can survive at 0°C for a week (Lüning, 1990) and so are likely to be able to tolerate a drop of 5°C. Therefore, the biotope is likely to be able to tolerate both a short term decrease of 5°C and a longer term decrease of 2°C. The only effects are likely to be changes in growth rates and reproductive timings and periods and so intolerance is considered to be low. Return of normal processes will resume very rapidly.
Increase in turbidity
(View Benchmark)
An increase in turbidity would reduce the light available for photosynthesis during immersion which could result in reduced biomass of plants and may reduce the depth to which the algae can grow. However, since the effects of increased turbidity are only expected to be sublethal impacts intolerance of the biotope is reported to be low. Upon return to previous turbidity levels, the photosynthesis rate would return immediately to normal.
Decrease in turbidity
(View Benchmark)
A decrease in turbidity would increase the light available for photosynthesis during immersion which may increase growth rates of all the algae in the biotope. Upon return to previous turbidity levels the photosynthesis rate would return immediately to normal.
Increase in wave exposure
(View Benchmark)
Chorda filum is most commonly found at sheltered locations. An increase in wave exposure above 'sheltered' (see benchmarks) could tear plants off the substratum or move the substratum with the plants attached. Fucus serratus only occurs on coasts with moderate exposure or less. Increases above this level of wave action will cause damage to individual plants, breaking fronds and removing entire plants from the substratum. Fucus serratus is more intolerant of wave exposure than Fucus vesiculosus. As wave exposure increases the density of fucoids falls and eventually on exposed coasts the community becomes dominated by grazers and barnacles at the expense of fucoids. At the level of the benchmark an increase in wave exposure is likely to remove Chorda filum and reduce abundance and biomass of the fucoids so intolerance is reported to be intermediate. On return to normal conditions recovery should be high - see additional information below.
Decrease in wave exposure
(View Benchmark)
As the biotope is naturally found in extremely sheltered conditions a reduction in wave exposure is not relevant.
Noise
(View Benchmark)
Algae have no known noise perception so the biotope is not sensitive to noise disturbance.
Visual Presence
(View Benchmark)
Algae have no visual perception so the biotope is not sensitive to visual disturbance.
Abrasion & physical disturbance
(View Benchmark)
Although the algal species in the biotope are flexible, abrasion is likely to cause damage to and removal of fronds and even removal of entire plants from the substratum. A proportion of the biotope is likely to be removed or damaged so the intolerance of the biotope is considered intermediate. In the intertidal fucoid algae are very intolerant of abrasion caused by trampling. Recovery by regrowth will be rapid and recolonization of plants will probably occur in one to two years. Note that, if present, Ascophyllum nodosum is a notable except and may take many years to recover.
Displacement
(View Benchmark)
Some algae in the biotope could survive being displaced, if the substratum moves with the plants attached to cobbles and pebbles. Stormy weather can transport plants attached to sediment to more sheltered locations where they continue growing. However, for plants attached to bedrock or boulders once displaced cannot reattach, are likely to be washed away and so intolerance of the biotope is high. Recovery is likely to be high - see additional information below.

Chemical Factors

Synthetic compound contamination
(View Benchmark)
Adult fucoids are generally quite tolerant of chemical pollutants. However, Cole et al. (1999) suggested that herbicides such as Simazina and Atrazine were very toxic to macrophytic algae. For instance, Fucus serratus was found to be intolerant of three biocides likely to be found in the marine environment (Scanlan & Wilkinson, 1987). Also, fucoids in general are reported to exhibit high intolerance to chlorate and pulp mill effluents containing chlorate (Kautsky, 1992). In the Baltic for example, fucoids have disappeared in the vicinity of pulp mill discharge points and are affected even at immediate and remote distances (Kautsky, 1992). However, such chemicals are no longer used in UK paper production. The growth of fucoids, and to a lesser extent Ulva sp., was adversely affected by an acidified, halogenated effluent discharge in Amlwch Bay in Wales (Hoare & Hiscock, 1974). The biotope may be particularly susceptible as it occurs in enclosed areas where water exchange is low and chemicals will not be rapidly flushed away. Intolerance of the biotope is recorded to be high. On return to normal conditions recovery should be good - see additional information.
Heavy metal contamination
(View Benchmark)
Fucoids accumulate heavy metals and may be used as indicators to monitor these. It is generally accepted that adult plants are relatively tolerant of heavy metal pollution (Holt et al., 1997). However, local variation exists in the tolerance to copper. Plants from highly copper polluted areas can be very tolerant, while those from unpolluted areas suffer significantly reduced growth rates at 25 µ/l. Heavy metals may therefore reduce growth rate, so intolerance is reported as low, although early life stages of the species may be more intolerant. Recovery is likely to be very rapid.
Hydrocarbon contamination
(View Benchmark)
Fucus vesiculosus shows limited intolerance to oil. After the Amoco Cadiz oil spill it was observed that Fucus vesiculosus suffered very little (Floc'h & Diouris, 1980). Indeed, Fucus vesiculosus, may increase significantly in abundance on a shore where grazing gastropods have been killed by oil. However, very heavy fouling could reduce light available for photosynthesis and in Norway a heavy oil spill reduced fucoid cover. In such sheltered conditions as lagoonal type habitats, where oil persists, effects are likely to be more significant. In investigations into the long-term effects of water-accommodated fraction of diesel oil on rocky shores Bokn et al. (1993) found no difference in the abundance patterns of the algae Fucus serratus, Fucus vesiculosus, Cladophora rupestris and Ulva spp. in oil contaminated mesocosms compared with controls. Intolerance of the biotope is therefore reported to be low. Recovery occurred within two years in moderately exposed conditions and four years in shelter (Holt et al., 1997). Oil spills are often followed by a flush of green algae, such as Ulva spp. as growth accelerates as grazers are killed by oil pollution.
Radionuclide contamination
(View Benchmark)
Insufficient information.
Changes in nutrient levels
(View Benchmark)
An increase in nutrients will increase the productivity of algae as nitrogen is very often considered to be the major limiting nutrient for plant growth in coastal waters. However, higher nutrient levels can exert a major influence on the composition of plant communities. Typically a decline in the number of perennial macroalgae such as fucoids and an increase in many green algae, such as Ulva spp. and Cladophora spp. are associated with eutrophic waters (Fletcher, 1996), sometimes leading to 'green tides' that can smother many other species. Therefore, the impact of a 50% increase in nutrients on the biotope is likely to be a decrease in fucoid algae and an increase in green algae and so intolerance is reported to be intermediate. Recovery is high - see additional information.
Increase in salinity
(View Benchmark)
The biotope is found in areas of low salinity and species such as Saccharina latissima are thought to be excluded by the low salinity conditions. A frequent member of the biotope, the three-spined stickleback, Gasterosteus aculeatus, is also found in conditions of reduced salinity and may not be present if salinity increases. Therefore, an increase in salinity is likely to change the species composition of the biotope with the addition of kelp plants in particular. The fucoids in the biotope are also found in full salinity so are likely to remain if salinity increases but the abundance of some of the green algal species would probably fall and some may completely disappear. Therefore, an increase in salinity is likely to lead to the development of a different biotope and so intolerance is reported to be high. See additional information for recovery.
Decrease in salinity
(View Benchmark)
The biotope is found in areas of low salinity and consists of many low salinity tolerant species. Fucus vesiculosus tolerates a wide range of salinities, as evidenced by it's penetration into the middle reaches of the Teign Estuary where salinity falls as low as 8psu (Laffoley & Hiscock, 1993). Below this the species is replaced by Fucus ceranoides (Suryono & Hardy, 1997). For Fucus serratus, growth rate is maximal at a salinity of 20 psu and salinity affects the photosynthetic rate and hence growth rate of seaweed. In the Teign Estuary Cladophora rupestris did not penetrate below 18psu. Therefore, a decrease in salinity may reduce the productivity of some of the algal species but it is also likely to lead to an increase in the abundance of very low salinity tolerant species such as Ulva sp., Chorda filum and possibly Fucus ceranoides. Thus, green algae may increase in abundance in the biotope but species composition could still include fucoids and so not be significantly different and so intolerance has been assessed as intermediate. See additional information for recovery.
Changes in oxygenation
(View Benchmark)
The biotope occurs in areas where relatively still water conditions do occur and so some species may be tolerant of a small degree of deoxygenation. The effects of deoxygenation on macroalgae are poorly studied. Kinne (1972) reports that reduced oxygen concentrations inhibit both photosynthesis and respiration although macroalgae may not be very intolerant of slight deoxygenation since they can produce their own oxygen. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l so some very intolerant species may be affected and an intolerance rank of intermediate is reported. On return to oxygenated conditions, rapid recovery is likely.

Biological Factors

Introduction of microbial pathogens/parasites
(View Benchmark)
There were no reported occurrences found of the fucoid algae or the biotope being affected by any diseases or infestations so intolerance is reported to be low. However, there is always the potential for this to occur so intolerance may change.
Introduction of non-native species
(View Benchmark)
The Japweed Sargassum muticum may have displaced Chorda filum from unstable habitats (Hill et al., 1998). There are no other reports of invasive species affecting the biotope.
Extraction
(View Benchmark)
Fucoids are harvested in many habitats for the production of alginates and are widely used in the pharmaceutical and cosmetics industries. Recovery of the fucoids in the biotope is likely to be rapid because fucoids recruit readily to cleared areas. Ulva intestinalis is used in the far east as 'green nori' but is not harvested in Britain and Ireland. However, if extracted, it is likely to recovery quickly because it is an opportunistic and early colonizing species. Little evidence has been found on the impact of extraction of Chorda filum although the species is harvested in Japan. However, if removed, recovery should also be rapid. Although not a species indicative of sensitivity, Littorina littorea is an active grazer and its activity may be important in keeping the rapidly growing Ulva sp. in check. Removal of the littorinid may increase the density of green algae in the biotope although the infralittoral position of the biotope means that large scale collection is unlikely. Some extraction of various members of the community may occur and intolerance has been suggested to be intermediate. Recovery is likely to be high since the majority of the population will remain.

Additional information icon Additional information

Recoverability
Recovery of the biotope is expected to be fairly rapid as the dominant species are highly fecund, iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. Fucus serratus and Fucus vesiculosus recruit readily to cleared areas, especially in the absence of grazers (Hawkins & Hartnoll, 1985). In addition fucoid species are found on all British and Irish coasts so there are few mechanisms isolating populations aiding rapid recovery. Chorda filum is an annual species reappearing every year so appearance of the species on cleared areas in suitable conditions will be possible within a year. Although there is no information available on recovery of green algae, species such as Ulva sp. and Ectocarpaceae are opportunistic ephemeral species that can recruit rapidly when conditions are suitable. Infaunal organisms, such as Arenicola marina, are able to migrate in from unaffected areas. Recolonization is also possible. For example, the post larvae of Arenicola marina are capable of active migration by crawling, swimming in the water column and passive transport by currents. Günther (1992) suggested that post-larvae of Arenicola marina were transported distances in the range of 1 km. The three-spined stickleback, Gasterosteus aculeatus, can migrate back into affected areas. Therefore, the time for the biotope community to recover is likely to be only a few years although development of a stable community structure may take a little longer due to competitive interactions. Recoverability is therefore, set to high.

This review can be cited as follows:

Hill, J.M. 2001. Mixed fucoids, Chorda filum and green seaweeds on reduced salinity infralittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21/04/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=356&code=1997>