Das Projekt "Refraktaere organische Substanzen und Wasserschadstoffe" wird vom Umweltbundesamt gefördert und von Forschungsverbund Berlin, Leibniz-Institut für Gewässerökologie und Binnenfischerei durchgeführt. Experiments were done to investigate factors influencing the accumulation of cadmium (Cd) into zebrafish (Danio rerio) embryo and larva. The accumulation of 109 Cd was affected by 1) concentration, 2) time, 3) presence of dissolved organic material (DOM) and 4) the development stage of the fish. Zebrafish eggs showed a steady increase in Cd-accumulation over an 8 h exposure. This rise was slightly decreased by DOM at concentration up to 10 mg C/L. DOM concentrations over 15 mg C/L decreased Cd uptake significantly. Cadmium is mainly accumulated in the fish egg's outer shell or chorion and only small amounts pass the eggshell barrier and are found in the perivitelline liquid and embryo. The accumulation of the Cd was significantly lowered when DOMs were present in concentrations of 10 mg C/L. The DOM was isolated from a brown water marsh (LM) and a eutrophic pond (SP). Both samples of DOM at 10 mg/L reduced the Cd-accumulation in the perivitelline liquid, the embryo, and the chorion. Newly hatched larvae showed an accumulation related to their developmental stage. In the 4 h exposed larvae the accumulation of Cd is reduced by both DOMs, but to a greater degree by LM. In larvae exposed for 24 h, CD accumulation was still reduced by the presence of LM, but not by SP. The increased uptake of Cd in older larvae may be a consequence of increased active Ca uptake, and therefore Cd uptake, in the growing embryo.