Organotropism and biomarker response in oyster Crassostrea gigas exposed to platinum in seawater

Abstract

Platinum (Pt) is a Technology Critical Element (TCE) for which biogeochemical cycles are still 13 poorly understood. This lack of knowledge includes Pt effects on marine organisms, which 14 proved to be able to bioconcentrate this trace element. Oysters Crassostrea gigas were exposed 15 to stable Pt isotope spiked daily in seawater for 35 days. Seawater was renewed daily and spiked 16 (with Pt(IV)) to three nominal Pt concentrations (50, 100, and 10,000 ng.L −1 ) for two replicate 17 series. Organotropism study revealed that gills, and to a lesser extent mantle, are the key organs 18 regarding Pt accumulation, although a time-and concentration-dependent linear increase in Pt 19 levels occurred in all the organs investigated (i.e. digestive gland, gonads, gills, mantle, and 20 muscle). In oysters exposed to Pt concentrations of 10,000 ng.L -1 , significant biomarker 21 impairments occurred, especially at cellular levels. They reflect altered lipofuscin and neutral 22 lipid contents, as well as intralysosomal metal accumulation. These observations were 23 attributed to activation of excretion / detoxification mechanisms, including Pt elimination 24 through faeces and clearly support the importance of the digestive gland in the response to 25 direct Pt exposure. Despite relatively constant condition index, the Integrative Biological 26Response Index (IBR) suggests a generally decreasing health status of oysters. 27