Ecosystem uptake and transfer of Sellafield-derived radiocarbon (C). Part 1. The Irish Sea.

Ecosystem uptake and transfer processes of Sellafield-derived radiocarbon (C) within the Irish Sea were examined. Highly variable activities in sediment, seawater and biota indicate complex C dispersal and uptake dynamics. All east basin biota exhibited C enrichments above ambient background while most west basin biota had C activities close to background, although four organisms including two slow-moving species were significantly enriched. The western Irish Sea gyre is a suggested pathway for transfer of C to the west basin and retention therein. Despite ongoing Sellafield C discharges, organic sediments near Sellafield were significantly less enriched than associated benthic organisms. Rapid scavenging of labile, C-enriched organic material by organisms and mixing to depth of C-enriched detritus arriving at the sediment/water interface are proposed mechanisms to explain this. All commercially important fish, crustaceans and molluscs showed C enrichments above background; however, the radiation dose from their consumption is extremely low and radiologically insignificant.