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 Rank Comments
Synthetic compound contamination Uses: boats/shipping (anti-fouling) Intermediate 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 & Donkin 1992).
Heavy metal contamination Waste: industrial effluent discharge Intermediate 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 organisms.

Changes in nutrient levels Waste: sewage discharge Intermediate 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 hand at
      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.

Next Section                     References