Uptake and release of p-dichlorobenzene in early life stages of Salmo gairdneri

Abstract

Early life stages of Salmo gairdneri from eggs to alevins were exposed to p-dichlorobenzene ( p-DCB) in a series of short-term uptake and release studies and in a long-term continuous test at three different concentrations from 3 to 79 μg/liter. Water concentration was frequently checked and the concentration of p-DCB in eggs and alevins was determined by gas chromatographic analysis of hexane extracts. Total and neutral lipids in the different stages were also determined. Neither macroscopic malformations nor histological changes were observed at hatching. The highest concentration (about 1 10 th of the incipient lethal level for alevins of S. gairdneri) did not show any significant difference in mortality compared to the control. Bioconcentration factors (BCF) experimentally determined on alevins agreed with the theoretical ones, calculated on the basis of water solubility, whereas higher contents of p-DCB up to one order of magnitude were observed in some stages before the hatching. The hypothesis relating accumulation to lipid content was tested; higher concentration factors (CF) of p-DCB were found in stages with higher lipid levels, particularly eggs. Metabolic modifications, occurring during the hatching, on the other hand, increase the rate of release in spite of the still high lipid content at this stage. Kinetic constants of uptake and release were determined for eggs and alevins. It is concluded that more attention has to be paid to compounds with medium theoretical BCF to evaluate the effective accumulation potential of early life stages as in general compounds with very high BCF have a slow rate of uptake.