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 |
Rank |
Comments |
| Siltation |
Waste: spoil dumping |
Intermediate |
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 |
Low |
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) |
Low |
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 |
High |
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. |
| Displacement/ Abrasion |
Fishing: benthic trawling |
High |
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: potting/creeling |
Low |
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 |
| |
|
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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. |
