Metal incorporation by benthic fauna: Relationships to sediment inventory

A radionuclide addition experiment was conducted in a large-scale experimental mesocosm to study the behaviour and fate of trace metals in a coastal marine environment. Twelve radionuclides (⁷Be, ¹⁰⁹Cd, ¹³⁴Cs, ⁵⁸Co, ⁶⁰Co, ⁵¹Cr, ⁵⁹Fe, ⁵⁴Mn, ²⁰³Hg, ²³³Pa, ¹¹³Sn, and ⁶⁵Zn) were added and their concentrations in benthic organisms and sediments were measured during the following nine months. The ability of benthic organisms to concentrate radionuclides was related to the vertical distribution and feeding behaviour of the organisms. Surface living fauna incorporated more radionuclides than deeper fauna. Calculations of total annual radionuclide incorporation by benthic fauna indicated that meiofauna incorporated a similar amount of the labelled metals as the macrofauna, even though the latter have a larger standing stock biomass. These calculations suggest that benthic metazoan fauna can annually cycle from 1% (Sn) to nearly 50% (Cd) of the amount of added radionuclides measured in sediments.