Potential Relation Between Mercury Concentrations and Necropsy Findings in Cetaceans from sGerman Waters of the North and Baltic Seas

Abstract

Concentrations of total mercury and methylmercury were analysed in muscle, kidney and liver samples from 57 harbour porpoises and three white-beaked dolphins, stranded or by-caught from the German waters of the North and Baltic Seas. Levels of total mercury ranged between 0.6 and 450 μg/g dry weight (dw) and of methylmercury between 0.2 and 26 μg/gdw. No differences in concentrations of either total mercury or methylmercury were observed between stranded and by-caught animals nor between males and females. However, a difference in mercury content of cetaceans from the North and Baltic Seas was found. A significant correlation between animal age and total mercury as well as methylmercury in all examined organs could be demonstrated. Pathological, microbiological and parasitological studies were performed on the animals. The majority of pathological lesions were caused by helminths. Lesions characteristic of acute or chronic intoxication with mercury could not be found. However, there were significant associations between mercury levels and severity of lesions with respective to nutritional state of the cetaceans examined, demonstrated by means of polychotomous logistic regression for ordinal variables and adjusted for the effects of age and location.