Cadmium accumulation in zebrafish (Danio rerio) eggs is modulated by dissolved organic matter (DOM)

Experiments were conducted to investigate factors influencing the accumulation of cadmium (Cd2+) into zebrafish (Danio rerio) eggs. The accumulation of 109Cd was affected by: (1) concentration, (2) time, (3) presence of dissolved organic material (DOM), (4) different origin of DOM and (5) different parts of fish eggs. Over a 5-h exposure, zebrafish eggs showed a steady increase in Cd-accumulation. DOM-concentrations over 15 ppm carbon (C) decreased Cd-uptake significantly. Both samples of DOM, brown water marsh (LM) and a eutrophic pond (SP), at 16.9 ppm C, reduced the Cd-accumulation in the chorion, perivitelline liquid and the embryo. Cd was mainly accumulated in the egg's outer shell chorion (61%) and only small amounts passed through the chorion into the perivitelline liquid (38%) and embryo (1%). In the presence of LM-DOM, the accumulation of Cd into the egg components was decreased by 43% (chorion), 52% (perivitelline liquid) and 52% (embryo), respectively, compared with the control group. Similarly, the presence of SP-DOM reduced the Cd-accumulation by 29% (chorion), 61% (perivitelline liquid) and 60% (embryo), respectively, compared with the controls. DOM-concentration should be taken into consideration when determining ecotoxicological effects of Cd on fish populations.