Mercury and Other Metals in British Seals

Abstract

INCREASING concern about environmental pollution has led to many investigations of heavy metals and their distribution in the sea, air and biological materials. There have, however, been few investigations of seals and here we give some preliminary results of analyses of British seals. Soft-tissue samples were taken from ninety-six seals (Table 1), both common seals (Phoca vitulina) and grey seals (Halichoerus grypus), from six sites around Britain between February 1968 and January 1972; these were collected during the course of long-term population studies. Results from some areas lack data on samples from the middle age-group as mature seals cannot be aged by external features but by examination of canine teeth^1,2. Data from East Anglia for both species were pooled because of small sample sizes. Brain and liver samples were obtained from most seals and kidney and teeth from about a third; all tissues were placed individually in uncontaminated polythene bags and stored at −20° C. The wet samples were digested in nitric acid and total mercury was estimated using a Perkin–Elmer 305 atomic absorption spectrophotometer (AAS). Cadmium in soft tissues was estimated by AAS using a flame technique; teeth, collected from 1968 onwards, were dissolved in nitric acid and analysed on a Perkin-Elmer 303 AAS for lead, cadmium, copper, chromium and zinc.