10 Years of Environmental Monitoring at Danish North Sea Platforms

摘要

In 1989 M?rsk Olie og Gas AS (Maersk Oil) initiated a monitoringrnprogramme at selected North Sea platforms, focusing onrnsediment chemistry and benthic fauna composition and abundance.rnIn 1998 the results of the first 10 years' monitoring werernreviewed and analysed.rnThe main conclusions of the study are:rn- drilling discharges are the cause of local impact at the localitiesrninvestigated, but the major changes in the bottom fauna duringrnthe 10-year period are linked to natural factors varying in spacernand time.rn- variations in bottom fauna composition are correlated to bariumrnand hydrocarbon concentrations in the sediment, leading to arncharacteristic zonation pattern with major impacts mainly at thern100 m and some 250m stations, and minor impacts observable atrnsome 750m and 1500m stations.rn- spreading and mixing of the bottom sediment reduce chemicalrncontamination after cessation of discharge. Hydrocarbon levelsrndecline more rapidly than barium levels, possibly due to naturalrndegradation of hydrocarbons.rn- the reduced contamination after cessation of discharges leads tornreductions in the biological impact, but the recovery of somernspecies such as the brittle star Amphiura filiformis is slow. Thisrnspecies appears to be the most sensitive to contamination.