Sharp accumulation of heavy metals after weaning in the South American fur seal Arctocephalus australis

Abstract

4 Direccion Nacional de Recursos Acuaticos del Uruguay, Av. Constituyente 1497, 5to Piso, 11200, Montevideo, Uruguay ABSTRACT: In marine mammals, the transition period between lactation and independent feeding pro- vides an opportunity to evaluate the influence of the first solid food on heavy metal concentrations in their tissues at early stages of their life cycle. The aim of the present study was to compare mercury, cad- mium, zinc and copper levels in lactating and recently weaned South American fur seal Arctocephalus australis pups from Uruguay and northern Argentina, in order to evaluate the heavy metal intake through solid food shortly after weaning. Heavy metal concentrations in liver, muscle and kidney were determined by atomic absorption spectroscopy. Mercury levels in suckling pups reached up to 0.60 and 0.40 µg g -1 wet weight in liver and kidney tissues, respectively. This group presented lower levels of cadmium, with maximum concentrations of 0.11 µg g -1 and 0.17 µg g -1 in liver and kidney tissues, re- spectively. Weaned pups showed significantly higher levels of both cadmium (liver = 6.93 ± 4.73 µg g -1 ; kidney = 20.89 ± 5.00 µg g -1 ) and mercury (liver = 3.91 ± 1.16 µg g -1 , kidney = 0.57 ± 0.15 µg g -1 ). These significantly higher levels, and a clear distributional pattern between organs, strongly suggest a rapid intake of heavy metals during the first months after weaning. The presence of mercury and cadmium in weaned pups also indicates relevant early predation on fish and squid, representing a considerable con- tribution of both metals, but mainly cadmium, for South American fur seal pups. This sharp accumula- tion could be used as an indicator of the weaning process. Furthermore, heavy metal levels of pups would constitute a relevant baseline level in the early life of the South American fur seal.