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.
|Synthetic compound contamination
||Uses: boats/shipping (anti-fouling)
||A number of studies have demonstrated toxic effects of TBT,
including mortalities, at concentrations in water of 0.4 ug/l-1 or less (Widdows &
|Heavy metal contamination
||Waste: industrial effluent discharge
||Mussels were missing from a wider area of a Cumbrian shore
than were other organisms around a large, phosphate-rich outfall, the effluent from which
was contaminated by a number of heavy metals (Pope et al. 1997).
On the other hand,
distribution of shore organisms around other industrial or mixed outfalls has shown
mussels to be among the least sensitive shore organisms (McKenzie & Perkins 1979).
The bioaccumualtion of environmental contaminants and their effects on the physiology
of mussels was reviewed by Widdows & Donkin (1992). Bokn, Moy & Murray (1993)
found Mytilus to be the most sensitive to diesel fuel when compared with other intertidal
|Changes in nutrient levels
||Waste: sewage discharge
||It is known that phytoplankton blooms can sometimes cause
problems, including mortalities in Mytilus. Long-term nutrient enrichment and
increasing phytoplankton production have been reported in the southern North Sea (De Jonge
1997; Smayda 1990). An associated problem is that of enrichment which often appears to be
associated with changes in the species composition of phytoplankton, often favouring
smaller groups at the expense of diatoms (Smayda 1990) and this could have consequences
for all filter feeding organisms including Mytilus.
|Removal of target species
||Collecting: shellfish (winkles, mussels)
|In virtually every cSAC location around Britain where mussel
beds form mud-mound reefs, the mussels have been fished or are now fished. When fished by
||moderate levels by persons with traditional skills, the
biogenic reefs will probably retain most of their intrinsic biodiversity. Mussels are also
taken on quite a large scale by hand for use as angling and long-line bait, although the
latter is now less in demand. Anglers tend to have most impact where the beds are adjacent
to roads leading to favoured shore fishing locations. A small mussel bed adjacent to a
road causeway in Anglesey has virtually been eliminated over the years.