Biodiversity & Conservation

CR.SCR.BrAs.NeoPro

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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All three important characterizing species are highly intolerant of substratum loss. The slower growing and longer lived Neocrania anomala will probably be the limiting factor in the recovery of the biotope although both Neocrania anomala and Protanthea simplex have moderate recoverability.
Smothering
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Both Neocrania anomala and Protanthea simplex are highly intolerant of smothering. Ciona intestinalis, being also recorded from areas of modified substratum and high siltation is more tolerant but still intermediately intolerant. The slower growing and longer lived Neocrania anomala will probably be the limiting factor in the recovery of the biotope although both Neocrania anomala and Protanthea simplex have moderate recoverability.
Increase in suspended sediment
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All three of the selected important characterizing species have low intolerance to siltation. Neocrania anomala and Protanthea simplex have very high recoverability from siltation.
Decrease in suspended sediment
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Desiccation
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The deeper water location (greater than 10 m) of this biotope means that desiccation is highly unlikely to be a relevant factor.
Increase in emergence regime
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The deep water location (greater than 10 m) of this biotope means that exposure to an emergence regime is highly unlikely to be a relevant factor.
Decrease in emergence regime
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Increase in water flow rate
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The biotope occurs in the landward basins of fjordic sea lochs where water flow rate is likely to be low. Increases in flow rate may cause high intolerance in Neocrania anomala and intermediate intolerance in Protanthea simplex. The slower growing and longer lived Neocrania anomala will probably be the limiting factor in the recovery of the biotope.
Decrease in water flow rate
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Increase in temperature
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Protanthea simplex has high intolerance to long term chronic temperature increases. The biotope has a restricted distribution along the west coast of Scotland. Long term increases in temperature will cause a decrease in available suitable habitat. Ciona intestinalis may be intermediately intolerant of short term acute decreases in temperature and Neocrania anomala may be intermediately intolerant of short term acute increases in temperature. Intolerance in the lower salinity biotopes where Protanthea simplex is absent may be different. The moderate recoverability of Protanthea simplex from temperature change is likely to be the slowest part of biotope recovery.
Decrease in temperature
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Increase in turbidity
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None of the selected important characterizing species from this biotope are intolerant of changes in turbidity.
Decrease in turbidity
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Increase in wave exposure
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The selected important characterizing species in this biotope may have high or intermediate intolerance to wave exposure. However, the circalittoral and highly sheltered location of the biotope means that changes in wave exposure are extremely unlikely so the factor has been assessed as not relevant.
Decrease in wave exposure
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Noise
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Neocrania anomala has low intolerance to noise vibrations but overall the biotope is unlikely to be sensitive to disturbance by noise.
Visual Presence
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Neocrania anomala has a shadow reflex that causes the valves to clamp shut giving a low intolerance to visual presence but overall, the biotope is unlikely to be sensitive to visual presence.
Abrasion & physical disturbance
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Erect epifaunal species are particularly vulnerable to physical disturbance. Hydroids and bryozoans are likely to be removed or damaged by bottom trawling or dredging (Holt et al., 1995). Veale et al. (2000) reported that the abundance, biomass and production of epifaunal assemblages decreased with increasing fishing effort. Hydroid and bryozoan matrices were reported to be greatly reduced in fished areas (Jennings & Kaiser, 1998 and references therein). Damage to emergent epifauna was the first sign of damage from scallop dredging on horse mussel beds (see Modiolus modiolus) (Service & Magorrian, 1997; Service, 1988; Magorrian & Service, 1998). For example, Protanthea simplex and Ciona intestinalis were both considered to be highly intolerant of physical disturbance and abrasion (see species reviews). The growth form and more durable nature of the valves of Neocrania anomala suggested an intermediate intolerance. Given the likely intolerance of epifaunal communities, an overall intolerance of high has been suggested.

The recolonization of epifauna on vertical rock walls was investigated by Sebens (1985, 1986). He reported that rapid colonizers such as encrusting corallines, encrusting bryozoans, amphipods, and tubeworms recolonized within 1-4 months. Ascidians such as Dendrodoa carnea, Molgula manhattensis and Aplidium spp. achieved significant cover in less than a year, and, together with Halichondria panicea, reached pre-clearance levels of cover after 2 years. A few individuals of Alcyonium digitatum and Metridium senile colonized within 4 years (Sebens, 1986). Large sponges and sea anemones would probably take longer to reach pre-clearance levels. Therefore, a recoverability of moderate has been recorded.

Displacement
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Neocrania anomala individuals are cemented to the substratum and cannot reform an attachment if displaced from the substratum. Ciona intestinalis has some limited ability to reform attachments following displacement. The slower growing and longer lived Neocrania anomala will probably be the limiting factor in the recovery of the biotope.

Chemical Factors

Synthetic compound contamination
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Insufficient information
Heavy metal contamination
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Insufficient information
Hydrocarbon contamination
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Insufficient information
Radionuclide contamination
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Insufficient information
Changes in nutrient levels
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There is some evidence that increased levels of organic nutrients is of benefit to Ciona intestinalis populations (Naranjo et al., 1996). Dissolved organic matter can also form a nutrition component for other species such as sponges. It is unlikely that changes in nutrient levels will have much effect on the biotope.
Increase in salinity
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The biotope SCR.NeoPro contains Protanthea simplex which has intermediate intolerance to decreases in salinity. The sea loch anemone may only survive in fully saline waters as it is not found in the two similar sub-biotopes where salinity is variable, reduced or low. Reductions in salinity in the biotope may cause this species to be lost, changing the biotope. The two sub-biotopes £SCR.NeoPro.Den£ and £SCR.NeoPro.CaTw£ are characterized by low/reduced and variable salinity respectively. In SCR.NeoPro.Den, increases in salinity may cause high intolerance. Recoverability of SCR.NeoPro based on the recoverability of Protanthea simplex from change in salinity is high. However, in the sub-biotopes, where Protanthea simplex is absent recoverability may be different.
Decrease in salinity
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Changes in oxygenation
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Protanthea simplex has intermediate intolerance to decreases in oxygen concentration. In the sub-biotopes where the sea loch anemone does not occur changes in oxygenation may have different effects. Brachiopods can sustain anaerobic metabolism for 3-5 days although at low oxygen concentrations, activity may be reduced. It is likely that characterizing species other than the three selected for the assessment are intolerant of decreases in oxygenation. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. Recoverability of SCR.NeoPro based on the recoverability of Protanthea simplex and Neocrania anomala from change in oxygenation is likely to be high. However, in the sub-biotopes, where Protanthea simplex is absent, recoverability may be different.

Biological Factors

Introduction of microbial pathogens/parasites
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Insufficient information
Introduction of non-native species
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Insufficient information
Extraction
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It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction and we have no evidence for the indirect effects of extraction of other species on this biotope.

This review can be cited as follows:

Jackson, A. 2005. Neocrania anomala and Protanthea simplex on very sheltered circalittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=5&code=1997>