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 |
| Substratum change |
Development: docks, ports & marinas |
High |
Natural shorelines are replaced with artificial substrata for
a variety of reasons. On sheltered shores waterfront developments including harbours,
marinas and even residential complexes are common place. Colonisation of virgin artificial
substrata and subsequent succession is similar to that observed on natural substrata
(Hawkins, Southward & Barrett 1983; Cannon 1997). The time for a ‘mature’
community to develop is therefore expected to depend on the scale of the development. |
| Synthetic compound contamination |
Uses: boats/shipping (anti-fouling) |
Intermediate |
The toxic affects of tributyltin (TBT) on molluscs,
especially the dog whelk Nucella lapillus, are well-documented (Bryan et al.
1986, 1987). TBT was extensively used in antifouling paint specifically to kill marine
fouling organisms. Unsurprisingly, it therefore had a major ecological impact. Many
shallow coastal waters escape the pollution associated with busy harbours and
industrialisation. However, the expansion of recreational boating exposed previously clean
areas to the effects of TBT. The use of TBT paints on small boats was banned in the late
1980s. TBT is still used on ships and its impact is greatest in areas with heavy boat
traffic and close to ports and marinas where boat mooring and maintenance activities are
concentrated. Very low concentrations of TBT can lead to the condition known as imposex
(the development of male sexual characteristics) in dogwhelks. Dogwhelks are an important
predator on rocky shores and their decline might be expected to have a profound effect on
the rest of the community. TBT also affects mussels, an important space-occupying species
on rocky shores and may therefore have important effects on community structure. |
| |
Uses: boats/shipping (oil spills) |
Low |
Modern dispersants have a lower toxicity and are unlikely to
do any more harm than the oil. |
| Hydrocarbon contamination |
Uses: boats/shipping (oil spills) |
High |
The sensitivity of a rocky shoreline to oiling is dependent
on its topography and composition as well as its position. A gradually sloping boulder
shore in a calm backwater of a sheltered inlet can trap enormous amounts of oil which may
penetrate deep down through the any available substratum. Some shores are well known to
act as natural collection sites for litter and detached algae and oil is carried there is
the same way. As on all types of shoreline, most of the oil is concentrated along the high
tide mark while the lower parts are often untouched. It is not long before the waves and
tides that carried the oil onto the shore gradually remove it again, but the rate of such
weathering is dependent on weather conditions and shore characteristics. On a sheltered
shore it may take years for the limited water movement to remove oil trapped under
boulders or in gullies and crevices. Gradual leaching of this oil could result in constant
low level pollution of, for example; a rockpool. |
| Abrasion |
Recreation: popular beach/resort |
Intermediate |
The recreational use of the shore can have adverse effects on
the biological community. The effect of people simply walking on the shore can be
damaging. This is particularly apparent when the topography of the shore causes people to
follow a limited number of routes, leading to the appearance of paths characterised by
reduced cover of fauna and flora (Fletcher 1997). Community structure can be affected by
even light trampling. Fletcher & Frid (1996) found light trampling sufficient to
reduce the abundance of fucoids which in turn reduced the microhabitat available for
epiphytic species. Light trampling pressure has also been shown to damage and remove
barnacles (Brosnan & Crumrine 1994). |
| Changes in nutrient levels |
Waste: sewage discharge |
Intermediate |
The most severe effects of sewage effluent discharge occur in
semi-enclosed areas such as estuaries and sheltered bays. The ecological effects of large
sewage outfalls may stretch to a few hundred metres while the effects of smaller
discharges are usually confined to within about 10 m of the pipe (Raffaelli & Hawkins,
1996). Effluent discharges can encourage the growth of ephemeral green algae in the
affected area. Sewage outfalls may introduce plastics and other solids to the marine
environment which may be deposited on to the foreshore of sheltered stretches of
coastline. |
| Removal of target species |
Collecting: kelp/wrack harvesting
|
High |
Several rocky shore species are exploited by man in the UK.
The main commercial species are the seaweeds knotted wrack Ascophyllum nodosum and Laminaria
spp. Seaweeds are responsible for much of the primary production on rocky shores and are
important providers of microhabitat for other species. The recovery of any species will
depend on the degree of exploitation. Clumps of Ascophyllum on the other hand, can
regrow after careful hand cutting. Such careful harvesting is necessary since Ascophyllum
is slow to recruit after it is completely lost. |
| |
Collecting: shellfish (winkles, mussels) |
Intermediate |
Other species, which are commercially harvested, include
winkles Littorina littorea, mussels Mytilus edulis and peeler crabs Carcinus
maenas. The removal of these species can have unforeseen effects on other members of
the community (Wells & Alcala 1987). |
| |
Collecting: bait digging |
Intermediate |
Disturbance is also associated with harvesting and bait
collection. Rocks turned over during the collection of peeler crabs might not be replaced
and the removal of mussels can destabilise neighbouring animals. The impact of any
harvesting or collecting activity will vary depending on the species exploited, how it is
done and to what extent. |
