This report is a contribution to the Department of Trade and Industry's (now Department of Energy and Climate Change) Strategic Environmental Assessment SEA2. Eight marine mammal species occur regularly over large parts the North Sea: harbour seal, grey seal, harbour porpoise, bottlenose dolphin, white-beaked dolphin, Atlantic white-sided dolphin, killer whale and minke whale. A further 15 cetacean species and five pinniped species are reported less frequently in the region. This report describes the distribution and abundance of these mammals and their ecological importance. The harbour porpoise is the most numerous marine mammal in the North Sea, with a population estimated at 268,000 in summer 1994. The northern and central SEA2 areas are particularly important areas for the harbour porpoise. Marine mammals make use of sound for a variety of purposes: finding prey, detecting predators, communication and probably navigation. The offshore oil and gas industry generates underwater noise at every stage of the process: during exploration seismic surveys, drilling, production and decommissioning. The effects of these different sources of underwater noise on marine mammals are discussed. The use of explosives for underwater cutting and demolition during the decommissioning of platforms and installations may pose a serious threat to some marine mammals. The effects of pollution on seals and cetaceans are discussed, including the effects of oil spills. Large whales can be killed by being struck by ships; increased shipping traffic in an area would increase this threat.

This report is a contribution to the Strategic Environmental Assessment (SEA4) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). It is a synthesis of information describing the seabed habitats, species and communities on the continental shelf of the west of Orkney and Shetland relevant to the SEA 4 area. It provides a summary of the benthic communities and assemblages which inhabit the shallow waters of the SEA4 area, from littoral to offshore areas. A wide range of habitats exist in the area because of the heterogeneity of the seafloor environment, ranging from hard rock sites exposed to the full force of waves and tidal currents to muddy sediments in sheltered inlets. The shelf and offshore areas include varying bedforms of sand and gravel, some of high carbonate content, and considerable amounts of glacigenic material. The epifauna and infauna which inhabit these different environments are summarised. A section of the report discusses the environmental impacts of anthropogenic activities in the area. These include the harvesting of algae from rocky shores, the release of radionuclides on the Caithness coast (Dounreay), dredging for sedimentary material, trawling and mariculture, in addition to the offshore oil and gas industry.

This report is a contribution to the Department of Trade and Industry's (now Department of Energy and Climate Change) Strategic Environment Assessment SEA2 for the North Sea. It draws on a wide range of data sources to provide an overview of the chemicals used in the offshore oil and gas industry, of the chemicals already in the environment and of those released into the environment from other sources. Considering the whole sea area, it should be noted that the water samples with the highest levels of chemical contamination are found at inshore estuary and coastal sites subject to high industrial usage. Approximately 2,000 chemical products are used by the offshore oil and gas industry. In 1999 some 180,000 tonnes of chemicals were discharged into the UK sector of the North Sea. Produced water is now the main source of contaminants, having overtaken drill cuttings since oil-based muds were replaced by less harmful alternatives. 24,286 tonnes of chemicals were reported as discharged to the UKCS in produced water in 1999. As oilfields mature, the amount of produced water increases. The range of chemicals used by the offshore oil and gas industry, the means of regulating them and of monitoring their use, are discussed. Evidence of biological effects caused by the release of contaminants into the sea is reviewed.