Sediment-associated tri-n-butyltin chloride and its effects on osmoregulation of freshwater-adapted 0-group European flounder, Platichthys flesus (L.)

The disruption of osmoregulatory processes was examined in European flounde rs exposed to environmental concentrations (150 ng TBTCl g(-1) dry weight s ediment) of sediment-associated tri-n-butyltin chloride (TBTCl), by using r adiotracers to measure changes in hydromineral fluxes and water balance. Th e water permeabilities of TBTCl-exposed fish varied during the course of th e experiment and were significantly lower than those of the corresponding c ontrols that did not change significantly with time. It was found that the maximum decrease in water permeability of TBTCl-exposed fish occurred after 14 days; thereafter there was an increase towards control values. However, there was a differential reduction of the diffusional (P-d) and osmotic (P -os) permeability coefficients, where the former decreased more rapidly tha n the latter, reflecting the reduction of diffusional membrane permeability and the increasing importance of osmotic permeability. In fish exposed to TBTCl sodium efflux and drinking rates were significantl y increased but Na+/K+-ATPase activities and urine production rates were no t affected. The effects of TBTCl exposure are also manifested at the level of the whole organism by a reduction in the increase of the body length of exposed fish, when compared to controls. It was concluded that tributyltin- n-chloride in sediments is capable of significantly disrupting the osmoregu latory functions of a benthic estuarine fish, at concentrations found in th e sediments of Southampton Water and the River Itchen. (C) 2001 Elsevier Sc ience B.V. All rights reserved.