Distribution and age-related changes of trace elements in kittiwake Rissa tridactyla nestlings from an isolated colony in the German Bight, North Sea

Tissue distribution of five trace elements (Se, Hg, Cd, Zn, Cu) was investigated in soft tissues and feathers of Kittiwake nestlings from the Island of Helgoland, North Sea. The tissue distribution of metals was similar in all age classes. Feathers and down contained highest mercury and zinc concentrations, whereas elevated levels of selenium and cadmium were found in the kidney. The concentrations of cadmium, copper and zinc in liver and kidney were low in hatchlings and increased with age of the nestlings, indicating the importance of the ingestion of contaminated food during chick growth. In the case of mercury, concentrations were high shortly after hatching and decreased when the chicks grew older. This indicates, that egg contamination was more important in chicks than contaminated food items. The total liver burden of all trace elements increased throughout chick development. Significant positive correlations between essential and non-essential elements were found in liver and/or kidney of all age classes. However, only the correlations between zinc and copper levels maintained throughout chick growth. The number of interactions between elements were increasing with progressing chick age. Correlations between cadmium and the essential elements copper and zinc appeared to depend on contaminant levels of cadmium, whereas mercury was correlated to essential elements in low and highly contaminated chicks. It was demonstrated that particularly older chicks (≥ 6 days old) were reliable bioindicators of mercury and cadmium contaminations around Helgoland Island.