Organochlorine pesticides in eggs of two waterbird species ( Fulica atra, Podiceps cristatus) from the same habitat: Reference site Lake Belau, Germany

Organochlorine (OC) residues were analyzed in eggs of Coot ( Fulica atra) and Great Crested Grebe ( Podiceps cristatus) from Lake Belau, North Germany. Concentrations were compared to concentrations in eggs of other species, and Lake Belau was suggested to be a relatively low contaminated reference area. Great variability could be measured between clutches of the same species but all eggs of Great Crested Grebe were significantly higher contaminated than eggs of Coot. Food contamination seems to be the major reason for the residues. The variability between clutches was greater than within the same clutch and no decreasing or increasing concentration in the sequentally laid eggs was obvious. Great Crested Grebes are better indicators for the contamination status of a lake.