Selenium in eggs and parental blood of a Dutch marine wader

Abstract

On the basis of earlier reports on high selenium levels in organs of marine waders from the Dutch Wadden Sea, adverse effects in wader reproduction were anticipated. A local breeding population of the wader Haematopus ostralegus, oystercatcher, was examined for embryotoxicity and selenium levels in eggs and parental blood. Egg and/or blood samples from breeding oystercatchers were obtained also from two reference sites, a Dutch meadow nature reserve and a Norwegian Atlantic island. The blood selenium levels were high in the Dutch marine birds (red blood cells contained 21 mg/kg vs 0.1–1.2 mg/kg dry weight in man), but the highest red blood cell levels were recorded in the red cells of birds sampled at the Norwegian reference site (maximal value 42 mg/kg dry weight). Both the concentrations in eggs from the Wadden Sea and in eggs from inland pastures (about 2 mg/kg dry weight), were at background level and embryotoxicity was not observed. Considering the results, it was concluded that selenium is not a potential threat to the reproduction of waders from the Dutch Wadden Sea, despite the high selenium concentrations in the tissues of the waders foraging in this area. Selenium in egg white was about 1.6 times higher than in yolk. The first egg had a 10% higher egg white and a 19% higher yolk concentration compared to the subsequent eggs in the coastal clutches. Red blood cell levels were about 3.5 times higher in marine feeding birds than in inland feeding birds. Selenium concentrations in the plasma and red blood cells were positively correlated.