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

Removal of the substratum would also remove the Rhodothamniella floridula growing on it. Intolerance has therefore been assessed as high. Recoverability is likely to be high (see additional information below).

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

The plant would be completely buried under 5 cm of sediment and would be unlikely to survive. Intolerance has been assessed as high. Recoverability is likely to be high (see additional information below).

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

Rhodothamniella floridula binds sand, mud or peat to it's filaments to form a sponge-like turf. A slight increase in suspended sediment may mean that there is more sand to bind with the plant and will probably have little adverse effect on it. However, it is not known how much of an increase in suspended sediment concentration could be withstood. An increase in suspended sediment concentration above this threshold will increase light attenuation (considered in 'turbidity') and siltation. Furthermore, Connor et al. (1997b) noted that, although the species is sand-tolerant, where sand scour is more severe, Rhodothamniella floridula may be rare or absent and ephemeral algae such as Ulva spp. and Porphyra spp. dominate the substratum. Therefore intolerance has been assessed as intermediate. Recoverability is likely to be very high.

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

Rhodothamniella floridula is unlikely to be affected by a small decrease in suspended sediment. However, the species needs sediment to bind to and will therefore need enough available to do so. Intolerance has therefore been assessed as low. Recoverability is likely to be very high.

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

Rhodothamniella floridula is subject to some desiccation on the lower shore where Dickinson (1963) observed that plants may dry out and develop a purplish tinge. It seems likely that at the benchmark level that the upper parts of plants may be adversely affected. However, the habit of the alga living in sponge-like masses suggests that lower parts may be kept moist and regrowth would be expected. Therefore, intolerance has been assessed as intermediate and recoverability is likely to be very high.

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

The benchmark increase in emergence would result in the individuals furthest up the shore experiencing greater risk of desiccation and greater fluctuations in temperature and salinity. Some mortality is likely and therefore intolerance has been assessed as intermediate. Recoverability has been recorded as high (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

Rhodothamniella floridula occurs predominantly in the littoral and sublittoral to about 5m depth (Dickinson, 1963; Dixon & Irvine, 1997) (as Rhodochorton floridulum and Audouinella floridula respectively) and is often found in rockpools. It is therefore the species would probably tolerate a decrease in emergence.

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

Moderate water movement is beneficial to seaweeds as it carries a supply of nutrients and gases to the plants and removes waste products. However, if flow becomes too strong , plants may become displaced. Additionally, an increase to stronger flows may inhibit settlement of spores and remove adults or germlings. Rhodothamniella floridula has a compact solid 'mat' or 'cushion'. Whilst the biotope with which it is associated occurs in 'moderately strong' or 'weak' tidal flows, the compact nature of the mat probably makes it resistant to displacement by an increase in water flow. The species has been assessed as tolerant of an increase in water flow.

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

The biotope with which Rhodothamniella floridula is associated occurs in areas where the water flow rate is either 'moderately strong' or 'weak' (Connor et al., 1997b). If a decrease in water flow rate to 'weak' or 'very weak (negligible)' may mean that the supply of nutrients to the seaweed would be depleted. However, adverse effects would probably only be seen in plants inhabiting the 'very weak' water flow areas. Intolerance has therefore been assessed as low. Recoverability is likely to be very high.

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

Maximum sea surface temperatures around the British Isles rarely exceed 20 °C (Hiscock, 1998) and, as Rhodothamniella floridula occurs throughout north west Europe it will therefore be subject to a wider range of temperatures than experienced in the British Isles. It is therefore expected that an increase in temperature will not result in mortality of the species.

However, high temperatures may cause photosynthesis and growth to be impaired. For instance, Dixon & Irvine (1977) observed that the growth of Rhodothamniella floridula (as Audouinella floridula) is much faster in winter, whilst in the summer the spongy cushion can become bleached or disrupted. Stegenga (1978) found that tetraspores of cultured Rhodothamniella floridula (as Rhodochorton floridulum) were formed under all combinations of temperatures from 4 °C to 16 °C at any length of daylight, although they were most abundant at high temperatures and long days.

Rockpool temperatures could also rise significantly and some mortality may occur in exceptional conditions. Intolerance has been assessed as low. Physiological processes should quickly return to normal when temperatures return to their original levels so recoverability has been assessed as very high.

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

Minimum surface sea water temperatures rarely fall below 5 °C around the British Isles (Hiscock, 1998) and, as Rhodothamniella floridula occurs throughout north west Europe it will therefore be subject to a wider range of temperatures than experienced in the British Isles. It is therefore expected that a decrease in temperature will not result in mortality of the species.

Dixon & Irvine (1977) observed that the growth of Rhodothamniella floridula (as Audouinella floridula) is much faster in winter, whilst in the summer the spongy cushion can become bleached or disrupted. It is therefore likely that a reduction in temperature will increase the growth rate of the species.

However, low temperatures may delay or slow reproduction. Stegenga (1978) found that tetraspores of cultured Rhodothamniella floridula (as Rhodochorton floridulum) were formed under all combinations of temperatures from 4 °C to 16 °C at any length of daylight, although they were most abundant at high temperatures and long days. intolerance has therefore been assessed as low. The reproductive rate should quickly return to normal when temperatures return to their original levels so recoverability has been recorded as very high.

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

In general, subtidal red algae are able to exist at relatively low light levels (Gantt, 1990). Rhodothamniella floridula (as Audouinella floridula) inhabits areas in shelter, partly under larger seaweeds (Hayward et al., 1996) and is probably adapted to growth in low light conditions. Stegenga (1978) found that tetraspores of cultured Rhodothamniella floridula (as Rhodochorton floridulum) were formed at any length of daylight, although they were most abundant at high temperatures and long days. This suggests that a decrease in the amount of light reaching the plant will result in a decrease in the reproductive potential of the species. No information is available concerning mortality associated with an increase in turbidity, but is likely that at high levels of turbidity some mortality will occur. Therefore, intolerance has been assessed as intermediate. Recoverability is likely to be high (see additional information below).

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

Stegenga (1978) found that tetraspores of cultured Rhodothamniella floridula (as Rhodochorton floridulum) were formed at any length of daylight, although they were most abundant at high temperatures and long days. This suggests that an increase in the amount of light reaching the plant will result in an increase in the reproductive potential of the species, if there is no overriding temperature effect. Therefore, Rhodothamniella floridula is recorded as being 'tolerant' to a decrease in turbidity, with the potential to benefit from the factor.

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

The biotope with which Rhodothamniella floridula is mostly associated occurs in 'Moderately exposed', 'Sheltered' and 'Very sheltered' conditions (Connor et al., 1997b). Stronger wave action is likely to cause damage to filaments, resulting in reduced photosynthesis and compromised growth, but more likely dislodgement by the force of wave action and by scouring from sand and gravel mobilised by increased wave action (Hiscock, 1983). The deepest living individuals are likely to avoid the worst impact of wave exposure, but some mortality in the total population is likely. Therefore, intolerance has been assessed as intermediate. Recoverability is likely to be high (see additional information below).

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

As the biotope with which Rhodothamniella floridula is mostly associated occurs in 'Moderately exposed', 'Sheltered' and 'Very sheltered' conditions (Connor et al., 1997b) the species is unlikely to be affected by a decrease in wave exposure. It is therefore recorded as 'tolerant'.

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

Algae have no mechanisms for detection of sound and, therefore would be not sensitive to disturbance by noise.

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

Algae have no visual acuity and, therefore would not be affected by visual disturbance.

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

No information was found concerning the effects of abrasion on Rhodothamniella floridula. However, this species is characteristic of sand scoured habitats and is probably tolerant. But an anchor, or similar impact, is likely to rip through the mat and remove a proportion of population. Intolerance has been assessed to be intermediate. Recoverability is likely to be high (see additional information below).

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

It is unlikely that the holdfast would survive removal from the substratum and be able to attach to a new substratum. Intolerance has therefore been assessed as high. Recoverability is likely to be high (see additional information below).

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

No information was found relating to the effects of synthetic chemicals on Rhodothamniella floridula. However, inferences may be drawn from the sensitivities of red algal species generally. O'Brien & Dixon (1976) suggested that red algae were the most sensitive group of algae to oil or dispersant contamination, possibly due to the susceptibility of phycoerythrins to destruction. They also reported that red algae are effective indicators of detergent damage since they undergo colour changes when exposed to a relatively low concentration of detergent. 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). Cole et al. (1999) suggested that herbicides, such as simazine and atrazine were very toxic to macrophytes. The evidence suggests that in general red algae are very intolerant of synthetic chemicals. Intolerance has therefore been recorded as high. Recoverability has been assessed as high (see additional information below).

Heavy metal contamination

Evidence

Bryan (1984) suggested that the general order for heavy metal toxicity in seaweeds is: Organic Hg > inorganic Hg > Cu > Ag > Zn > Cd > Pb. Cole et al. (1999) reported that Hg was very toxic to macrophytes. The sub-lethal effects of Hg (organic and inorganic) on the sporelings of an intertidal red algae, Plumaria elegans, were reported by Boney (1971). 100% growth inhibition was caused by 1 ppm Hg. No information was found concerning the effects of heavy metals on Rhodothamniella floridula specifically, and therefore an intolerance assessment has not been attempted.

Hydrocarbon contamination

Evidence

No evidence was found specifically relating to the intolerance of Rhodothamniella floridula to hydrocarbon contamination. However, inferences may be drawn from the sensitivities of red algal species generally. O'Brien & Dixon (1976) suggested that red algae were the most sensitive group of algae to oil or dispersant contamination, possibly due to the susceptibility of phycoerythrins to destruction. 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 life stages (Grandy, 1984, cited in Holt et al., 1995). Intolerance has been assessed as high. Recoverability has been recorded as high (see additional information below).

Radionuclide contamination

Evidence

No evidence was found concerning the intolerance of Rhodothamniella floridula to radionuclide contamination.

Changes in nutrient levels

Evidence

A moderate increase in nutrient levels may enhance the growth of Rhodothamniella floridula. However, excessive eutrophication would probably result in the species being out-competed by ephemeral species with rapid growth rates, such as filamentous green and brown algae. Therefore intolerance has been assessed as intermediate. Recoverability has been recorded as high (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

Rhodothamniella floridula occurs in full salinity conditions. Although no information has been found on survival in hypersaline conditions, the species occurs in rockpools where evaporation may occasionally lead to higher than normal salinities. However, occurrence of the species in full salinity leads to an intolerance assessment of 'not relevant'.

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

No information was found on the effects of reduced salinity on Rhodothamniella floridula. However, as this species occurs only in full salinity conditions it is probable that a proportion of the population would die in lower salinities. Therefore, intolerance has been assessed as high. Recoverability is likely to be high (see additional information below).

Changes in oxygenation

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

Evidence

The effects of reduced oxygenation on algae are not well studied. Plants require oxygen for respiration, but this may be provided by production of oxygen during periods of photosynthesis. Lack of oxygen may impair both respiration and photosynthesis (see review by Vidaver, 1972). A study of the effects of anoxia on another red alga, Delesseria sanguinea, revealed that specimens died after 24 hours at 15°C but that some survived at 5°C (Hammer, 1972). Insufficient
information is available to make an intolerance assessment for Rhodothamniella floridula.

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

No information has been found.

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

No information on the effects of alien species on Rhodothamniella floridula were found.

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

There is no extraction of Rhodothamniella floridula known to occur.

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

No information was found concerning effects of harvesting other species on Rhodothamniella floridula.