The accumulation of137Cs by brackish water invertebrates and its relation to the regulation of potassium and sodium

Abstract

The relationship between the ability of brackish water invertebrates to regulate Na and K and the extent to which the radioactive fission product137Cs can be accumulated has been studied.The brackish water isopodSphaeroma hookeriand the gastropodPotamopyrgus jenkinsihave been acclimatised to a wide range of sea-water dilutions. UnfedSphaeromacan survive in sea-water concentrations of 100–2·5%, whilePotamopyrguscan live fairly indefinitely in concentrations of 50–0·1%. Measurements of Na and K in the whole animals of both species and in the blood ofSphaeromahave been made. Salt movements are quite rapid and acclimatization to new media is achieved by both species in less than 10 h. Concentration factors for inactive K in particular increase to high values in the more dilute media.Uptake of the isotopes42K and137Cs from solution has been examined in both species over a range of sea-water concentrations. All of the body K is exchangeable with 42K and in Sphaeroma exchange of42K between the blood and tissues is so rapid that the body surface appears to be the limiting factor in the uptake of the isotope. Both species exchange42K more rapidly in the higher concentrations of sea water and one reason for this may be the existence of an exchange diffusion component of exchange which increases as the salinity of the medium is raised. Indirect evidence suggests that the excretion of42K in urine is probably not an important factor in exchange.