Trophic transfer of Cs-134 in the Manila clam Ruditapes philippinarum

Abstract

Bioaccumulation of radiocaesium in many marine organisms occurs through complex trophic transfer mechanisms. The present study addresses the trophic transfer of Cs-134 in the widely distributed marine bivalve, the Manila clam Ruditapes philippinarum, by experimentally determining the assimilation efficiency (AE) and the specific role of food quality or diet on the AE in this marine invertebrate. Pulse-chase feeding experiments were carried out on this clam using the phytoplankton species Tetraselmis chuii, Phaeodactylum tricornutum and Isochrysis galbana. Deputation kinetics of Cs-134 over 21 days were analysed using a two-component exponential model. Observed assimilation efficiencies were consistently less than 10% but slightly varied among individuals fed on the three different phytoplankton species diets (T chuii: AE = 8.4 +/- 0.6%; P. tricornutum: AE = 9.8 +/- 0.5%; 1. galbana: AE = 53 +/- 0.6%), although no statistical differences were observed. Comparing results from these experiments with existing data from the literature on the same species exposed to caesium through seawater, it appears that trophic transfer processes are the main accumulation pathway, contributing up to 96% of the global Cs-134 bioaccumulation in this bivalve species. (C) 2017 Elsevier Ltd. All rights reserved.