CHEMICAL RESIDUES IN EGGS OF BIRDS FROM THE SOUTHERN COAST OF THE NORTH-SEA - TRENDS 1981-1990

In 1981-1990, at four sample sites on the German North Sea coast organochlorine and mercury concentrations were analysed in eggs of Common Terns (Stern hirundo) and Oystercatchers (Haematopus ostralegus) to study temporal trends in contamination. Despite of year to year fluctuations we found increasing levels of alpha-HCH, SIGMA-DDT, Lindane, mercury and SIGMA-PCB and decreases in beta-HCH and HCB. In 1987-1990, the percentage of PCB-congeners containing 6-8 C -atoms was increasing in the PCB mixture. ln 1987 highest levels of several contaminants were found caused by risen contaminants' loads of the rivers owing to high water in spring. In the Common Tern significant trends were more frequent than in the Oystercatcher. The results reveal an increased impact of chemicals on birds in the Wadden Sea, and emphasize the need of reductions of the pollutant loads of the rivers as well as of long-term monitoring of environmental chemicals.