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

Cladophora rupestris forms a permanent attachment to substrata, so would be intolerant of substratum loss. Intolerance has been assessed to be high. Recoverability has been assessed to be very 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

Cladophora rupestris is a stout shrub-like seaweed, whose fronds may grow up to 20 cm in height. A covering of sediment to a depth of 5 cm is likely to partially cover the seaweed, and at low tide the whole plant may be covered whilst lying limply on the rock. Unless the sediment is removed by the incoming tide, photosynthesis would be inhibited and fronds begin to decay over the duration of one month. Spores, germlings and juveniles are likely to be highly intolerant of smothering by sediment (Vadas et al. 1992). An intolerance assessment of intermediate has been made to reflect the probable impact of smothering on germlings, thereby preventing recruitment for that period, and the inhibitory effects upon more mature specimens. On return to prior conditions, the species is likely to recover, either new growth will arise from the resistant multicellular branching rhizoids (van den Hoek, 1982) that may remain in situ, or the species is likely to recruit to cleared substrata via its 'swarmers' (reproductive propagules). Recoverability has been assessed to be very high. For instance, after the Torrey Canyon tanker oil spill in mid March 1967, recolonization by sporelings of Ulva and Cladophora had occurred by the end of April.

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

The filamentous branching morphology of Cladophora rupestris would probably enable it to effectively accumulate sediment from suspension. For instance, Boney & Venn (1982) observed Cladophora rupestris to accumulate deposits of ferric oxide from suspension, derived from iron ore spillage and wind-winnowed dust from stockyards on the British Steel Hunsteston Peninsula, Firth of Clyde, Scotland. However, the specimens were apparently healthy with green chloroplasts and starch filled pyrenoids, despite incrustations of ferric oxide. The probable indirect effects of increased suspended sediment are addressed elsewhere, and include smothering (above) as a result of siltation, and increased turbidity and therefore light attenuation (see below). Available evidence suggests that Cladophora rupestris is tolerant of elevated levels of suspended sediment and an assessment of tolerant has been made, but at low confidence.

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

Cladophora rupestris is unlikely to be adversely affected by a decrease in suspended sediment concentrations, and an assessment of tolerant has been made.

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

Cladophora rupestris is a bushy filamentous algae, Norton et al. (1982) supposed that the numerous filaments retained large quantities of water when the plant became exposed on the shore, which might be a vital function in the prevention of desiccation. However, as soon as the seaweed is removed from water its photosynthetic rate drops sharply, owing to the restriction of inorganic carbon (Lobban & Harrison, 1997). Those individuals living at the highest level on the shore are living at the top of their physiological tolerance limits and so would not be likely to tolerate a further increase in emersion levels. This would probably result in the upper extent of the species being depressed. An intolerance assessment of intermediate has been made. On return to prior conditions, the species is likely to recover, and recoverability has been assessed to be very high (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

An increase in the period of emersion involves exposure to desiccation, chilling or heating, removal of most nutrients required for growth, and, frequently, changes in the salinity of the water in the surface film on the seaweed and in the free space between cells (Lobban & Harrison, 1997). Although Cladophora rupestris is tolerant of a range of salinity, it is likely to be intolerant of desiccation stress resulting from an increase in the emergence regime, and an intolerance assessment of intermediate has been made. Should the abundance of the species be affected, e.g. decline in the upper distribution, on return to prior conditions, recovery is likely to be rapid (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

Cladophora rupestris is found in the shallow sublittoral and therefore could potentially benefit from a decrease in the emergence regime. Cladophora rupestris is considered to be relatively palatable to invertebrates (Dodds & Gudder, 1992), all of which will probably be more active grazing during periods of immersion, so that the additional grazing pressure may affect the abundance of the species. An intolerance assessment of low has been made. A recoverability of very high has been recorded (see additional information, below).

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

Lewis (1964) named Cladophora rupestris to be amongst the understorey algae of tidal rapids at Lough Ine. Part of the success of species of the genus Cladophora is probably related to its ability to withstand the shear stress experienced in rocky intertidal habitats. The thallus of the seaweed is tough, but flexible, and allows water to flow through and around it (Dodds, 1991). At low current velocities the thallus spreads out, but becomes more streamlined as the current velocity increases. As tufts of Cladophora become more compact with higher current, transport of materials to and from the plant may be inhibited or self shading may increase, leading to an overall decrease in photosynthesis (Pfeifer & McDiffett, 1975). An intolerance assessment of low has been made to reflect the possible effects of increased water flow on photosynthesis by the seaweed. Following a reduction in water flow, recovery is likely to be immediate, as the fronds splay out and photosynthesis increases.

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

Water flow is important to macroalgae as the processes of photosynthesis, respiration and growth is dependent on a flux of substrates (CO₂, O₂ & nutrients) and to remove waste products. Therefore a reduction in the water flow below a certain level may have an adverse effect on the species. An intolerance assessment of low has been made as the viability of the species may be affected. On return to prior conditions, recovery is likely to be immediate.

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

Cladophora rupestris occurs to the south of the British Isles, so is likely to be tolerant of a chronic increase in temperature of 2 °C. Fortes & Lüning (1980) and Lüning (1984) reported that Cladophora rupetrsis from Helgoland were able to survive at temperatures between 0 - 28°C (for a period of a week), so the species is likely to tolerate the benchmark acute increase in temperature, the species is also characteristic of upper shore rock pools, where water and air temperatures are greatly elevated on hot days. An assessment of tolerant has been made.

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

Growth measurements of Cladophora rupestris from Roscoff, France, led Cambridge et al. (1984) to conclude that the species was tolerant of temperatures of below -5°C and at the benchmark level the species has been assessed to be tolerant of a decrease in temperature.

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

Although Cladophora rupestris is common on shaded overhangs (Lewis, 1964) the light attenuating effects of increased turbidity are likely to impact on the photosynthetic efficiency of the species, with consequential effects on growth. An intolerance assessment of low has been made to reflect the effect of increased turbidity on the viability of the species. On return to prior conditions recovery is likely to be rapid and growth resume, a recoverability of very high has been recorded.

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

As a photoautotroph, Cladophora rupestris is likely to benefit from reduced turbidity, as the light attenuating effects of turbid water reduce photosynthesis. An assessment of tolerant* has been made.

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

Cladophora biomass in rock pools is affected by wave action. Loosely attached mats slough off with wave action as they become thick (Dethier, 1982) and cause a localized decline in abundance. Morphology of Cladophora has also been linked to hydrodynamic factors. Branching of marine species of Cladophora may become more pronounced with increased wave energy (Van den Hoek, 1964; 1982). Increased wave action may therefore cause distortion of morphology. Furthermore, wave action is likely to be effective in the dislodgement/breaking off of fronds of Cladophora rupestris. Either new growth will arise from the resistant multicellular branching rhizoids (van den Hoek, 1982) that may remain in situ, or the species is likely to recruit to cleared substrata via its 'swarmers' (reproductive propagules). Recoverability has been assessed to be very high. For instance, after the Torrey Canyon tanker oil spill in mid March 1967, recolonization by sporelings of Ulva and Cladophora had occurred by the end of April. Intolerance has been assessed to be low. Recovery has been assessed to be very high.

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

Cladophora rupestris is unlikely to be adversely affected by reduced wave action, as it also thrives in wave sheltered locations. An assessment of tolerant has been made.

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

Seaweeds have no known mechanism for noise perception.

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

Seaweeds have no known mechanism for visual perception.

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

As Cladophora rupestris may grow in the form of a thick turf over the rock, and amongst other algae it may be more resistant to abrasion in the form of trampling and dragging of chain for example, owing to the cushion effect of the fronds overlying the holdfast. Individual fronds may incur damage, but the factor is unlikely to cause a substantial decline in the species abundance. At the benchmark level an assessment of tolerant has been made, but with low confidence. A more severe abrasive impact such as the grounding of a vessel would be likely to cause damage and intolerance expected to be higher.

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

Cladophora rupestris forms a permanent attachment to solid substrata. It is likely to be intolerant of displacement as, once removed, mature plants are unable to reattach. Intolerance has been assessed to be high. The species has a considerable ability for recovery. For instance, after the Torrey Canyon tanker oil spill in mid March 1967, recolonization by sporelings of Ulva and Cladophora had occurred by the end of April. Recoverability has been assessed to be very high.

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

Following the Torrey Canyon tanker oil spill in 1967, copious amounts of non-ionic detergents were employed to disperse the oil. The detergents used contained a surfactant, an organic solvent and a stabilizer; the solvents all contained a proportion of aromatic compounds which made the detergent more effective but more toxic. Porthleven Reef, Cornwall, was badly polluted, an estimated total of 35 000 gallons of detergent was used in an eight day period. The algae most seriously damaged occurred at the higher levels of the shore. Smith (1968) reported Cladophora rupestris to be amongst the algae of very unhealthy appearance, with bleached fronds and dead specimens, although apparently healthy specimens were still found lower on the shore. In follow-up toxicity experiments, Cladophora rupestris was found to be the most intolerant of the intertidal species tested. Severe damage was noted at the apical cells of the filaments, which are the growing points, after six hours immersed in 6% solutions of all detergents (except BP1002, which was apparently harmless at that concentration). Less severe, but irreversible damage was noted down to about 1% concentration. Intolerance has been assessed to be intermediate. The species has a high capacity for recovery. On return to prior conditions, the species is likely to recover, either new growth will arise from the resistant multicellular branching rhizoids (van den Hoek, 1982) that may remain in situ, or the species is likely to recruit to cleared substrata via its swarmers. Recoverability has been assessed to be very high. For instance, after the Torrey Canyon tanker oil spill in mid March 1967, recolonization by sporelings of Ulva and Cladophora had occurred by the end of April.

Heavy metal contamination

Evidence

The order of metal toxicity to algae varies, with the algal species and environmental conditions, (Rice et al., 1973; Rai et al., 1981) but Bryan (1984) suggested that the general order for heavy metal toxicity in seaweeds is: Organic Hg > inorganic Hg > Cu > Ag > Zn > Cd > Pb. No information was found concerning the specific effects of heavy metals on Cladophora rupestris.

Hydrocarbon contamination

Evidence

The toxic effects of oil on algae may be categorized as those associated with the coating of the fronds, e.g. coating by oil is likely to reduce CO₂ diffusion and light penetration to the plant, and those attributable to the uptake of hydrocarbons and subsequent disruption of cellular metabolism (Lobban & Harrison, 1997).
Cullinane et al. (1975) summarized the damage caused to Cladophora rupestris following the crude oil spill in 1974 in Bantry Bay, Ireland. No damage was immediately apparent to Cladophora rupestris, but microscopic examination of material from rock pools at League Point showed complete bleaching of the terminal cells (only). Burrows (1991) indicated that following damage to the apical cells of fronds, that regeneration was possible.
Bokn et al. (1993) examined the long term effects of the water-accommodated fraction (WAF) of diesel oil on rocky shore populations. Two doses (average hydrocarbon concentration in diesel oil equivalents; High: = 129.4 µmg l-1, and Low = 30.1µmg l-1) of WAF of diesel oil were delivered via sea water to established rocky shore mesocosms over a two year period, however there were no demonstrable effects in the abundance patterns of Cladophora rupestris, Ulva spp. or Ulva lactuca in the oil contaminated compared with the control mesocosms at the end of that period. Intolerance has been assessed to be intermediate. On return to prior conditions, the species is likely to recover, either new growth will arise from the resistant multicellular branching rhizoids (van den Hoek, 1982) that may remain in situ, or the species is likely to recruit to cleared substrata via its swarmers. Recoverability has been assessed to be very high. For instance, after the Torrey Canyon tanker oil spill in mid March 1967, recolonization by sporelings of Ulva and Cladophora had occurred by the end of April.

Radionuclide contamination

Evidence

Insufficient
information.

Changes in nutrient levels

Evidence

Nutrient enrichment of the water column, e.g. resulting from sewage discharge, can stimulate blooms of opportunistic benthic macroalgae, especially Cladophora and Ulva (Knox, 1986). An assessment of tolerant* has been made, as the species may increase in abundance as a result of nutrient enrichment.

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

Cladophora rupestris found in intertidal rock pools can withstand 5-30 psu (Jansson, 1974) and as the species is successful in the high intertidal zone it is likely that the species has a broad salinity tolerance (Dodds & Gudder, 1992). At the benchmark level an assessment of not sensitive has been made.

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

Cladophora rupestris can tolerate salinities as low as 5 psu (Burrows, 1991) and as the species is successful in the high intertidal zone it is likely that the species has a broad salinity tolerance (Dodds & Gudder, 1992). At the benchmark level an assessment of not sensitive has been made. However, Thomas et al. (1988) found that, at extreme temperatures, Cladophora rupestris had a reduced salinity tolerance range, e.g. the most marked inhibition of photosynthesis occurred in conditions of low salinity (0 psu) and high temperatures (25 - 30°C).

Changes in oxygenation

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

Evidence

There insufficient information available to make an assessment about the effects of reduced oxygen in the water column upon Cladophora rupestris.

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 was found concerning the effects of microbial pathogens on Cladophora rupestris.

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 non-native species are known to adversely impact upon Cladophora rupestris.

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

The benchmark for extraction is the removal of 50% of the Cladophora rupestris population from the area under consideration. Intolerance has therefore been assessed to be intermediate and recovery very high as a local population of the species will remain from which recruitment can 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 other species are identified to be host or prey items for Cladophora rupestris. During experiments to investigate intertidal and subtidal canopy interactions, Hawkins & Harkin (1985) removed the overlying canopy of both Fucus serratus and Laminaria digitata on shores of differing wave exposure, and results led them to conclude that in the region that spans the boundary between the intertidal and subtidal on N.W. European shores, canopy effects are the dominant biological factors structuring the community. It was noted that, following removal of Fucus serratus, the more permanent understorey algae (Cladophora rupestris and Corallina officinalis) became covered to some extent by Ulva intestinalis, Palmaria palmata and Fucus serratus, and decreased in cover but still survived. Ulva intestinalis grew on and amongst the understorey, whereas Palmaria palmata and Fucus serratus shaded the plants by growth from gaps in the understorey turf. An intolerance assessment of low has been made to reflect the fact that the understorey alga Cladophora rupestris may decline in abundance following removal of key structuring macroalgae, owing to overgrowth, but still survive.