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, be it shell, rock, or cobble will result in removal of the attached colonies of Conopeum reticulum. Therefore, an intolerance of high has been recorded. Recoverability is likely 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

Smothering by 5 cm of sediment is likely to prevent feeding, and hence growth and reproduction, as well as respiration. In addition, associated sediment abrasion may remove the bryozoan colonies. A layer of sediment will probably also interfere with larval settlement. Therefore, an intolerance of high has been recorded. Recoverability has been assessed as very 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

The abundance of most bryozoan species declines with increasing suspended sediment loads. Bryozoans are suspension feeding organisms that may be adversely affected by increases in suspended sediment, due to clogging of their feeding apparatus. The abundance of bryozoans is positively correlated with supply of hard substrata and hence with current strength as strong currents decrease the potential for siltation (Eggleston, 1972b; Ryland, 1976). However, Conopeum reticulum has been recorded on stones and boulders, around which fine sediments tend to collect. In addition, Conopeum reticulum occurs in estuarine waters, such as the higher reaches of the River Tamar, Plymouth which, while below the turbidity maxima, are probably of higher turbidity and suspended sediment loads than coastal waters. However, in areas of siltation it may be restricted to vertical or steep surfaces. Therefore, Conopeum reticulum may be more tolerant of siltation and suspended sediment than most encrusting bryozoans, and an intolerance of low has been suggested at the benchmark level.

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

A decrease in suspended sediment may reduce the availability of organic particulates. However, a decrease in particulates is likely to encourage the settlement and growth of bryozoans including Conopeum reticulum. Therefore, tolerant* has been recorded. A decrease in sediment load is also likely to allow competitors such as other bryozoans and ascidians to colonize the habitat.

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

Lower shore populations of Conopeum reticulum may be adversely affected by desiccation. Conopeum reticulum is restricted to damp habitats or rockpools on the shore. Therefore, an increase in desiccation at the benchmark level, or resulting from overturning of boulders or stones to which colonies are attached, would probably kill the affected colonies. Therefore, an intolerance of intermediate has been recorded to represent loss of the populations extent in the intertidal. The subtidal is unlikely to be exposed to desiccation. Recoverability is likely 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 emergence will result in a larger proportion of the population being exposed to intertidal conditions, increased extremes of temperature, reduced ability to feed and an increased risk of desiccation (see above). Therefore, an intolerance of intermediate has been recorded. Recoverability is likely to be very 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

A decrease in emergence, at the benchmark level, is likely to provide additional habitat for colonization by Conopeum reticulum as well as other bryozoans and epifauna, and reduce the risk of desiccation to existing colonies. Therefore, tolerant* has been recorded.

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

Conopeum reticulum has been reported in strong to weak tidal streams (JNCC, 1999). Therefore, it is probably tolerant of a wide range of water flow. However, an increase in water flow from e.g. moderately strong to very strong may interfere with larval settlement and remove shells and small stones, to which colonies were attached. Therefore, a proportion of the population may be lost and an intolerance of intermediate has been recorded. Recoverability is likely to be very high (see additional information below).

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

Conopeum reticulum has been recorded from sites subject to strong to weak tidal streams (JNCC, 1999). The abundance of bryozoans is positively correlated with supply of hard substrata and hence with current strength as strong currents (Eggleston, 1972b; Ryland, 1976). Bryozoans are active suspension feeders, however, their feeding currents are probably fairly localized and they are dependent on water flow to bring adequate food supplies within reach (McKinney, 1986). A decrease in water flow to very weak, in the absence of compensatory wave action, is likely to reduce food availability and increase the risk of siltation. Therefore, a proportion of the population may be lost and an intolerance of intermediate has been recorded. Recoverability is likely to be very high (see additional information below).

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

Menon (1972, 1974) reported Conopeum reticulum acclimated to temperatures between 6 to 22 °C and that increasing temperature increased growth and feeding rate but reduced zooid size. Acclimation to increased temperatures increased the median lethal temperature. Menon (1972) reported an upper lethal temperature of 30 °C in colonies acclimated to 22 °C and 32 °C in colonies grown at 22 °C. Therefore, it is likely that colonies will tolerate higher temperatures in the summer months than in the winter months. However, Menon (1972) noted that colonies kept at 6 or 22 °C in culture did not reach sexual maturity. Overall, Conopeum reticulum exhibited the highest temperature tolerance of the bryozoans studied by Menon (1972). Conopeum reticulum is probably widely distributed around the British Isles and into the Mediterranean, and occurs in the Cochin backwaters of the southwest coast of India (Menon, 1973). Therefore, it is probably tolerant of long term change in temperatures in British waters. It would probably also tolerate acute temperature change at the benchmark level. Therefore, an intolerance of low has been recorded, to represent the effects of temperature on growth and reproduction.

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

Menon (1972) reported that colonies acclimated to 6 and 12 °C survived below zero, polypides only dying at ca -1.8 °C when ice crystals appear in seawater. Polypides of colonies acclimated to higher temperatures died above zero, e.g. at 2.5 °C in colonies acclimated to 22 °C. Therefore, colonies are probably more tolerant of low temperatures in winter than summer. However, Menon (1972) noted that colonies kept at 6 or 22 °C in culture did not reach sexual maturity. Eggleston (1972a) noted that the unusually cold winter of 1962/63 delayed the onset of reproduction in some species of bryozoan by up to 2 months. However, Ryland (1970) suggested that temperature was but one factor controlling summer growth and reproduction in temperate bryozoans.
Conopeum reticulum is probably widely distributed in the British Isles and has been suggested to occur in boreal waters (Hincks, 1880; Menon, 1972). It is unlikely to be adversely affected by long term chronic or short term acute changes in temperature at the benchmark level in British waters. Intertidal specimens may nevertheless succumb to sharp frosts when emersed. Overall, an intolerance of low has been recorded to represent the effects of temperature on growth and reproduction.

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

An increase in turbidity will decrease light penetration, and hence primary productivity, potentially decreasing the food available to Conopeum reticulum. However, Conopeum reticulum would probably be able to feed on organic particulates. It may be more intolerant in the summer months, when lack of food would reduce growth and reproduction. In addition, larval growth may be delayed, and hence larval mortality increased. Therefore, an intolerance of low 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

A decrease in turbidity is likely to result in an increase in primary productivity and phytoplankton availability. Therefore, tolerant has been recorded.

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

Conopeum reticulum has been recorded from wave exposed to extremely wave sheltered habitats (JNCC, 1999). Its encrusting habit may allow this species to survive in areas of greater wave exposure. However, its intolerance will probably depend on its substratum. Colonies on stable hard substrata such as bedrock will probably survive, whereas colonies of boulders, rocks or cobbles are likely to be destroyed by rolling or overturning. In addition, colonies on stones on sediment may be destroyed by additional sediment abrasion. Therefore, an increase in wave exposure from sheltered to exposed will probably not adversely affect the population, whereas an increase from moderately exposed to very exposed may result in loss of a proportion of the population, depending on substratum, and an intolerance of intermediate has been recorded. Recoverability is likely to be very 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

Conopeum reticulum is recorded from wave exposed to extremely wave sheltered habitats. A further decrease in wave exposure may increase the risk of deoxygenation (stagnant conditions) or siltation (see above) unless the tidal streams were sufficient to ensure adequate water exchange. Suspension feeding organisms are reduced in abundance or absent from areas with little water movement (either due to currents or wave action or both). Therefore, in areas of sufficient water flow due to currents a further reduction in wave exposure may have negligible effects. Therefore, an intolerance of low has been recorded. Populations in areas subject to only weak or negligible current are likely to be more intolerant.

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

The species is unlikely to be sensitive to changes in noise vibrations.

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

The species is unlikely to be sensitive to changes in 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

Conopeum reticulum has been recorded on boulders, rocks and stones on sediment (JNCC, 1999). Therefore, it is probably tolerant of some sediment scour. However, it is likely that Conopeum reticulum colonies on stones and rocks, and to some extent boulders, are probably ephemeral, being removed by scour by increased wave action due to winter storms. Abrasion by a passing anchor is likely to roll or overturn stones, to which colonies are attached, and damage but not remove colonies on bedrock. A passing scallop dredge is likely to damage but not remove colonies, unless they are removed with rocks to which they are attached (see substratum loss). Overall, an intolerance of intermediate has been recorded, although recoverability is probably very 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

Conopeum reticulum may be displaced together with the rocks or cobbles to which they are attached. If they are displaced to suitable habitats they will probably survive as long as they were not crushed in the process. However, removal of a colony from its substratum would probably be fatal, and encrusting bryozoa are not known to be able to reattach. Therefore, an intolerance of high has been recorded. Recoverability is likely to be very 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

Bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper-containing anti-fouling paints (Soule & Soule, 1977; Holt et al., 1995). Bryan & Gibbs (1991) reported that there was little evidence regarding TBT toxicity in bryozoa with the exception of the encrusting Schizoporella errata, which suffered 50% mortality when exposed for 63 days to 100ng/l TBT. Rees et al. (2001) reported that the abundance of epifauna (including bryozoans) had increased in the Crouch estuary in the five years since TBT was banned from use on small vessels. This last report suggests that bryozoans may be at least inhibited by the presence of TBT. Hoare & Hiscock (1974) suggested that Polyzoa (Bryozoa) were amongst the most sensitive species to acidified halogenated effluents in Amlwch Bay, Anglesey but did not record Conopeum spp. in their survey. Overall, an intolerance of intermediate has been recorded to represent the likely intolerance of bryozoans to synthetic contaminants. Recoverability is likely to be very high (see additional information below).

Heavy metal contamination

Evidence

Bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper-containing anti-fouling paints (Soule & Soule, 1977; Holt et al., 1995). Bryozoans were shown to bioaccumulate heavy metals to a certain extent (Holt et al., 1995). For example Bowerbankia gracilis and Nolella pusilla accumulated Cd, exhibiting sublethal effects (reduced sexual reproduction and inhibited resting spore formation) between 10-100 µg Cd /l and fatality above 500 µg Cd/l (Kayser, 1990). However, given the tolerance of bryozoans to copper based anti-fouling treatments, and assuming similar physiology between species, an intolerance of low has been recorded albeit with very low confidence.

Hydrocarbon contamination

Evidence

Little information on the effects of hydrocarbons on bryozoans was found. Houghton et al. (1996) reported a reduction in the abundance of intertidal encrusting Bryozoa (no species given) at oiled sites after the Exxon Valdez oil spill. Soule & Soule (1979) reported that the encrusting bryozoan Membranipora villosa was not found in the impacted area for 7 months after the December 1976 Bunker C oil spill in Los Angeles Harbour. Of the eight species of bryozoan recorded on the nearby breakwater two weeks after the incident, only three were present in April and by June all had been replaced by dense growths of the erect bryozoan Scrupocellaria diegensis. Mohammad (1974) reported that Bugula spp. and Membranipora spp. were excluded from settlement panels near a Kuwait Oil terminal subject to minor but frequent oil spills. Encrusting bryozoans are also probably intolerant of the smothering effects of oil pollution, resulting in suffocation of colonies. Therefore, given the above evidence of intolerance in other Membraniporidae, a intolerance of high has been recorded, albeit at low confidence. Recoverability is probably very high (see additional information below).

Radionuclide contamination

Evidence

Insufficient
information

Changes in nutrient levels

Evidence

A moderate increase in nutrient levels may increase the food available to Conopeum reticulum, either in the form of phytoplankton or detritus. Jakola & Gulliksen (1987) reported that encrusting bryozoans were excluded from the vicinity of a sewage outfall from Tromsö, Norway. However, they suggested that the effect was primarily due to sedimentation. Little other information on the effects of nutrients enrichment on bryozoans were found.

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

Conopeum reticulum may be found intertidally in damp locations, under boulders and in rockpools. It may, therefore be exposed to increased salinity due to evaporation and is probably more tolerant than subtidal bryozoans. However, no information sufficient to make an assessment was found.

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

Conopeum reticulum is found in marine and estuarine waters and is considered to be euryhaline, although Ryland (1970) noted that its estuarine distribution may be inaccurate due to common confusion with Conopeum seurati and Electra crustulenta. However, Conopeum reticulum was abundant in the higher reaches of the Crouch and Tamar estuaries at salinities of 21- 32psu (Cook, 1964; Hayward & Ryland, 1998). Menon (1973) reported that Conopeum reticulum occurred in the outer reaches of the Cochin backwaters in southern India, which were affected by significant freshwater runoff during the monsoon season. In the Cochin backwaters Conopeum reticulum was more abundant in the shallow subtidal (1-2m) and absent from the intertidal.
Conopeum reticulum would probably survive a reduction in salinity from full to reduced in the short or long term but be excluded form sites if the salinity became low (<18psu). Therefore, an intolerance of low has been recorded at the benchmark level.

Changes in oxygenation

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

Evidence

Little information concerning the effects of hypoxia on bryozoans was found. Sagasti et al. (2000) reported that epifauna communities, including dominant species such as Conopeum tenuissimum and Membranipora tenuis, were unaffected by periods of moderate hypoxia (ca 0.35 -1.4 ml/l) and short periods of hypoxia (<0.35 ml/l) in the York River, Chesapeake Bay. Therefore, assuming similar physiology between species of Conopeum, an intolerance of low has been recorded.

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 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 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

Conopeum reticulum is unlikely to be subject to specific extraction.

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

Conopeum reticulum is not known to be associated with species or habitats subject to extraction.