The Marine Life Information Network

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Lithophyllum incrustans is permanently attached to the substratum. Therefore, loss of substratum will entail loss of this species. Spores will settle and new colonies will arise rapidly on bare substratum but growth rate is slow (2-7 mm per annum - see Irvine & Chamberlain 1994). Colonies may be up to 30 years old (Edyvean in Irvine & Chamberlain 1994).

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

Encrusting coralline algae are frequently subject to cover by sediment and appear to survive well.

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Silt settling onto encrusting coralline algae may be removed by production of mucus. Reduction in light penetration may reduce or prevent photosynthesis but, in the situation where the increased siltation is for a short period, colonies are likely to survive. If death occurred, recoverability would be low (see additional information).

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Encrusting coralline algae are likely to benefit from a decrease in siltation.

Desiccation

1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

Occurrence of encrusting coralline algae seems to be critically determined by exposure to air and sunlight. Colonies survive in damp conditions under algal canopies or in pools but not on open rock where desiccation effects are important. Harkins & Hartnoll (1985) noted that the presence of fucoid canopies allowed encrusting corallines to extend their upper limit higher on the shore. Canopy removal experiments in the Isle of Man, noted that encrusting corallines died within a week of removal of the protection canopy of Fucus serratus (Hawkins & Harkin, 1985). Removal of the Laminaria digitata canopy lower on the shore resulted in bleaching of encrusting corallines (Hawkins & Harkin, 1985) probably due to increased light intensity (see turbidity). Hawkins & Hartnoll (1985) reported extensive damage to encrusting and articulate corallines during the hot summer of 1983 at several sites in Britain. Therefore, desiccation is an important factor limiting the distribution of encrusting coralline algae on the shore, and an intolerance of high has been recorded. Recovery is likely to be slow (see additional information, below).

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Occurrence of encrusting calcareous algae seems to be critically determined by exposure to air and sunlight. Colonies survive in damp conditions under algae or in pools but not on open rock where desiccation effects are important. Increased emergence will increase the risk of desiccation (see above). If killed recovery will be slow (see additional information below).

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

There may be less light reaching the seabed for photosynthesis but it is not expected that established colonies of Lithophyllum incrustans will be adversely affected.

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Colonies of Lithophyllum incrustans appear to thrive especially in conditions exposed to strong water movement, including very strong wave action. Increase in the strength of tidal flow over colonies in therefore unlikely to have an adverse impact and may remove silt so that there will be a favourable effect.

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Lithophyllum incrustans tolerates a wide range of water flow conditions. However, where wave action is not the primary source of water movement, a marked decrease in water flow may have an adverse effect especially if it allows siltation to occur. In the situation where increased siltation is for a short period, colonies are likely to survive. However, if water flow is reduced over a long period or permanently, there may be mortality and loss.

Increase in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

Lithophyllum incrustans occurs in a wide geographical range in temperatures that are much warmer (air and water) than in Britain and Ireland. It is therefore, probalby tolerant of an increase in temperature. However, increased temperature may result in an increased risk of desiccation (see above).

Decrease in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

Lithophyllum incrustans occurs in a wide geographical range in temperatures that are much colder (air and water) than in Britain and Ireland. It is therefore likely to tolerate a decrease in temperature, at the benchmark level.

Increase in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Reduction in light penetration may reduce or prevent photosynthesis but, colonies are likely to survive. However, at the lower limit of its range, colonies will most likely be adversely affected by long-term (< one year) change. Removal of the protective canopy of Laminaria digitata in the Isle of Man (Hawkins & Harkin, 1985) resulted in bleaching of encrusting corallines, suggesting that Lithophyllum incrustans may be intolerant of high light intensities. As a shade tolerant species, increased light due to decreased turbidity in the absence of shading algae may have adverse affects.

Decrease in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

The major effect is likely to be increased light penetration which will have a favourable effect on colonies of Lithophyllum incrustans.

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Colonies of Lithophyllum incrustans appear to thrive in conditions exposed to strong water movement. Irvine & Chamberlain (1994) observe that the species is best developed on wave exposed shores. In some situations where water movement has been low, increased exposure to wave action may be beneficial but in many situations, an assessment of 'tolerant' is appropriate.

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

A marked decrease in wave exposure may have an adverse effect on growth especially if it allows siltation to occur. However, mortality would only be expected if the decrease in wave exposure was for a long period. Therefore intolerance is assessed as low.

Noise

1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

Lithophyllum incrustans has no known sound receptors.

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

Lithophyllum incrustans has no known visual receptors.

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

Littler & Kauker (1984) suggested that crustose algal forms were resistant to predation, sand scour and wave shear. Colonies on rock may be completely removed over part of the area affected but recolonize from parts protected in crevices or unaffected parts. Remaining parts of the crust will expand once the source of abrasion is removed.
Schiel & Taylor (1999) reported the death of encrusting corallines one month after trampling due to removal of their protective canopy of fucoids by trampling (10 -200 tramples where one trample equals one transect walked by one person). A higher proportion of corallines died back in spring treatments presumably due to the higher levels of desiccation stress expected at this time of year (see desiccation). However, encrusting corallines increased within the following year and cover returned to control levels within 21 months (Schiel & Taylor, 1999).

Spores will settle and new colonies will arise rapidly on bare substratum but growth rate is slow (2-7 mm per annum - see Irvine & Chamberlain 1994). Colonies are up to 30 years old (Edyvean in Irvine & Chamberlain 1994)

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

Removal from the substratum for such an encrusting species is unlikely and it is more likely that the substratum (e.g. cobbles or boulders) with the organism attached will be moved. Providing that the move is to a similar habitat, the effect is likely to be minimal.

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

• evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
• evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
• evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

Little information has been found. Hoare & Hiscock (1974) recorded that 'lithothamnia' was absent from the rocky shore up to 150 m distant from an acidified halogenated effluent. Once the impact is removed, spores will settle and new colonies will arise rapidly on bare substratum but growth rate is slow (see additional information below).

Heavy metal contamination

Evidence

Insufficient
information

Hydrocarbon contamination

Evidence

Where exposed to direct contact with fresh hydrocarbons, encrusting coralline algae appear to have a high intolerance. Crump et al. (1999) describe "dramatic and extensive bleaching" of 'Lithothamnia' following the Sea Empress oil spill. Observations following the Don Marika oil spill (K. Hiscock, own observations) were of rockpools with completely bleached coralline algae. However, Chamberlain (1996) observed that although Lithophyllum incrustans was quickly affected by oil during the Sea Empress spill, recovery occurred within about a year. The oil was found to have destroyed about one third of the thallus thickness but regeneration occurred from thallus filaments below the damaged area. A recoverability of high is therefore suggested. If colonies were completely destroyed new growth would be slow and, because of low growth rates, recoverability would be low (see additional information below).

Radionuclide contamination

Evidence

Insufficient
information

Changes in nutrient levels

Evidence

Sewage pollution (as a source of nutrients) appears to have little or no effect. In the case of erect coralline algae, numbers might increase (reviewed in Fletcher 1996). Increased nutrients may result in overgrowth by other algae. Where mortality occurs, spores will settle and new colonies will arise rapidly on bare substratum but growth rate is slow (see additional information below).

Increase in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Lithophyllum incrustans lives in full salinity seawater. Increase in salinity may occur if evaporation in intertidal pools occurred. However, no information has been found on tolerance to hypersaline conditions.

Decrease in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Little direct information on the effect of salinity change on encrusting coralline algae was found but red seaweeds are generally more intolerant of reduced salinity conditions than brown or green algae (Kain & Norton 1990). However, in the case of short-term change, encrusting coralline algae must be able to withstand the effects of heavy rain in diluting seawater in pools and in run-off as entirely freshwater over exposed corallines. Recovery is likely to be fairly rapid if, as in the impact of oil spills (see above), only the cell layers near the surface are adversely affected. If colonies were completely destroyed new growth would be slow and, because of low growth rates, recoverability would be low (see additional information below).

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

No information concerning the effects of oxygen levels on encrusting corallines were found.

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

Insufficient
information

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

Currently, there appear to be no non-native species in Britain that adversely affect encrusting coralline algae. However, aggressive invasive species could out-compete Lithophyllum incrustans and over-grow it.

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

It is not believed that this species would be extracted.

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Extraction of species such as kelps, where encrusting coralline algae grow on holdfasts, may have a small localised adverse effect but growth from surrounding crusts would fill any gaps in cover and re-growth of encrusting corallines occurs on re-growth of kelps.