Natural tracers in dietary studies: data for 210Po and 210Pb in decapod shrimp and other pelagic organisms in the Northeast Atlantic Ocean

Measurements of the concentrations of the naturally-occurring radioactive nuclides ²¹⁰Po and ²¹⁰Pb in a large number of pelagic organisms from the Atlantic Ocean made in the spring/summer of 1984 and 1985 are reported. Marine shrimp are particularly well represented, and in many cases data were obtained for shrimp hepatopancreas, stomach-contents, and posterior intestine plus contents, as well as for whole individuals. The wide ranges found in ²¹⁰Po concentrations group into categories: the shrimp, for example, divide into four categories, two penaeid and two carid. These groupings are explained on the basis of variations in diet between the different categories. A clear difference was also observed between the ²¹⁰Po levels in shrimp of similar species and size from opposite sides of an oceanographic front; this difference too can be explained plausibly in terms of a change in certain penaeid shrimp, and attention is drawn to the need for investigation of cytological and/or genetic effects which could possibly be caused by the very high natural radiation doses to which such organisms are exposed.