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
Substratum change Development: land claim


Extensive areas of intertidal sandflats have been removed through land claim coupled in some areas with rising sea levels (Davidson et al. 1991; Burd 1992). Some estuaries have lost up to 80% of the area, most of which has been the land claim of intertidal mud and sandflats. The greatest impact of land claim is due to depletion of the main prey rather than simply the area loss and each prey and predator species will differ in their response (McLusky, Bryant & Elliott 1992).
Changes in temperature Climate change/global warming


Many intertidal species have wide tolerances for temperature and can also alter metabolic activity, or simply burrow deeper in the sediment or move seaward to combat temperature change (Brown 1983). Severe changes in temperature in intertidal areas will result in a seasonal reduction in benthic species richness and abundance, although the species are well adapted to such changes.
Hydrocarbon contamination Uses: boats/shipping (oil spills)


Oil-spills can cause large-scale deterioration of communities in intertidal and shallow sub-tidal sediment systems (Majeed 1987). Tidal-pulsing will push oil into intertidal sands. Oil pushed into coarse sands will destabilise the sediment and produce an oxygen demand where oxygen is available but little degradation at depth where aeration does not occur.
Synthetic compound contamination/

Heavy metal contamination/

Hydrocarbon contamination

Waste: industrial effluent discharge





Industrialised and urbanised estuaries and coastlines may receive effluent discharges which contain conservative contaminants i.e. those with a long half-life, are likely to bioaccumulate (remain within the food chain) and thus have a toxic effect (Clark 1997). Such contaminants include heavy metals, radionucleides and synthetic organic compounds. The lethal and sub-lethal effects of these pollutants vary according to the state and availability of the compound and its characteristics and the organism it affects. Some effects may be lethal, by removing individuals and species and thus leaving pollution-tolerant and opportunistic species. Other effects may be sub-lethal, in affecting the functioning of organisms such as their reproduction, physiology, genetics and health, which will ultimately reduce their fitness for survival (Nedwell 1997). In contrast to low energy areas (e.g. mudflats), the higher energy sediment biotopes are less likely to receive and/or retain these contaminants. The coarser sediments of exposed intertidal sandflats and the hydrodynamic characteristics, including high dispersion, dictates that there are few cases of severe pollution in such habitats. However, chemical pollution of intertidal sands can occur and will remove elements of the fauna.
Changes in nutrient levels Waste: sewage discharge


Aquaculture: fin-fish


High organic inputs coupled with poor oxygenation lead to conditions of slow degradation and produces anaerobic conditions in the sediments. In turn this increases microbial activity and reduces the redox potential of the sediments (Fenchel & Reidl 1970). Ultimately this increases the production of toxic substances such as hydrogen sulphide and methane. Moderate enrichment provides food to increase the species abundance and a mixing of organisms with different responses increases diversity (Elliott 1994). With greater enrichment, the diversity declines and the community becomes increasingly dominated by a few pollution-tolerant, opportunistic species such as the polychaete Capitella capitata. In grossly polluted environments, the anoxic sediment is defaunated and may be covered by sulphur-reducing bacteria. Such a change will affect the palatability of any remaining prey and thus impair functioning of marine areas.
Removal of non-target species Collecting: bait digging


The effect of bait digging is to reduce community diversity and species richness, especially by commercial digging for worms and other macrofauna on intertidal sandflats (Brown & Wilson 1997). This removal of target species leading to community and population changes at the ecological and genetic levels will effect predators e.g. the removal of bait organisms such as Arenicola from intertidal sandflats will effect shorebird predation.

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