Sensitivity to human activities

Activities listed are those which influence, or are likely to influence this habitat and which are assessed in the UK marine SAC project review. The sensitivity rank may require amendment in the light of new information becoming available.

Sensitivity to: Human activity


Siltation Waste: spoil dumping


Small and temporary increases in silt deposition will be dealt with by the ability of species to self-clean. However, deposition of thick silt through dumping is likely to both smother the species present to an extent where they are unable to self-clean or dig-out and may produce a substratum which is unsuitable for re-colonisation.
Changes in turbidity Coastal defence: dredging

Extraction: navigational/ maintenance dredging


Dredging results in the suspension of the fine silt and clay fractions of the sediment, which is deposited by inshore currents. Effects are uncertain but may clog feeding structures.
Hydrocarbon contamination Uses: boats/shipping (oil spills)


Oil would have to be dispersed deep into the water column to affect these biotopes and, because they occur in sheltered locations, it is unlikely that storms would do this. Effluents disposed into enclosed areas such as sealochs and fjords could be retained and have an effect. Callianassa subterranea appears to be highly sensitive to sediment contamination by oil-based drilling muds
Changes in oxygenation Aquaculture: fin-fish

Waste: sewage discharge


The burrowing species in particular require well-oxygenated water. Whilst able to tolerate quite high levels of organic material (which may result in hypoxia), seapen faunal communities are absent from areas which are de-oxygenated and characterised by a distinctive Nutrient enrichment would have an impact most likely through resultant hypoxia.bacterial community.


Fishing: benthic trawling


The seapens Funiculina quadrangularis and Pennatula phosphora are most likely to be affected, as they do not retract into the sediment. The score applies to removal. Displaced individuals, which are not damaged, will re-burrow. Burrowing species probably occur too deep to be displaced and can most likely dig-out after a trawling event.
Removal of non-target species Fishing:



Qualitative observations of pots and creels being dropped and hauled in Devon and Scotland showed that potting did not appear to have any immediate effect on sea pens (Eno et al. 1996). It was found that seapens began to bend away from pots dropping on top of them
      even before the pot had made contact with the animal. This was a passive response of the animals to the pressure wave travelling ahead of the dropping pot, which effectively removed their tips from direct impact. The sea pens consistently righted themselves following the removal of the pots. However, the long term effects of such impacts are not known and it would require further study to determine whether the apparent immediate recovery was consistent in the long term or whether there is a gradual but cumulative deterioration of condition in impacted animals.

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