Dynamics of cadmium accumulation and effects in common carp (Cyprinus carpio) during simultaneous exposure to water and food (Tubifex tubifex).

In this study, the influence of exposure time and concentration on the accumulation of cadmium and the occurrence of adverse effects was investigated when carp were simultaneously exposed through contaminated water and food. As exposure concentrations increased (9, 105, and 480 microg/L through water and 9.5, 122, and 141 microg/g dry weight through food) the accumulation pattern of cadmium changed, with progressively more cadmium being accumulated in the liver and especially the kidney and less in the gills and the intestine. A strong concentration- and time-dependent effect of cadmium exposure on plasma calcium concentrations was observed, leading to a decrease, with approximately 16% in the mid group and up to 50% in the group exposed to the highest cadmium concentration. Also at the highest exposure concentrations, sodium and chloride levels as well as plasma osmolality were significantly reduced, indicating a disturbed ion homeostasis. Furthermore, an increase in plasma alanine transaminase activity indicated liver damage caused by the cadmium accumulation in this organ. At the end of the experiment, general stress responses such as decreased hematocrit, growth, and mortality (17%) also were observed. All together, these results suggest that plasma hypocalcemia as an ion-disruptive phenomenon is the most sensitive effect during cadmium exposure, although the occurrence and magnitude both depend on exposure time and concentration.