| Endocrine disrupting chemicals (EDCs) are capable of disturbing endocrine system of wildlife and human beings, causing abnormality in reproduction, development and activity, which consequently pose threats to human health and even cause collapse of organism population. As receptors of domestic, agricultural and industrial wastewater, wastewater treatment plants (WwTPs) contain a large amount of EDCs. All these EDCs can’t be removed in wastewater treatment process, and therefore WwTPs effluent is considered as the major resource of EDCs in aquatic environment and have attracted a great deal of scientific attention worldwide. As a popular biomarker for estrogens and estrogen mimics, vitellogenin (Vtg) has been widely used in screening the estrogenic effects of EDCs.High-back crucian carp(Carassius auratus), which is peculiar to Dianchi Lake, was selected as the experimental animal in this study. With Vtg as the biomarker, as well as condition factor (CF), gonadosomatic index (GSI) and hepatosomatic index (HSI) as endpoints, a chronic exposure to WwTP effluent was undertook, Compared with fish controls caged in Dianchi Lake, the biological effects of WwTP effluent were assessed in high-back crucian carp during different life stages, covering early-life-stage (ELS), prespawning period and postspawning period. Meantime, a depuration study was carried out to check whether the estrogenic effects caused by effluent exposure can be got rid off after moving fish into EDCs-free water.(1) High-back crucian carp were caged in Demonstration Base of Biological Purification for Filter-feeding Fish, an area mildly contaminated by EDCs in Dianchi Lake, as controls. CF, HSI, GSI and plasma Vtg levels of high-back crucian carp caged in Dianchi Lake were generally in accordance with seasonal change. All of them increased with time in ELS and arrived maximum right before spawning, and after spawning, HSI kept in this level while the others fell to initial levels. Values of all endpoints of high-back crucian carp caged in Dianchi Lake were situated in normal variation ranges and mildly affected by EDCs in Dianchi Lake.(2) From August2010to May2011, high-back crucian carp were exposed in effluent of the Fifth WwTP of Kunming, and the effects of EDCs in the effluent were assessed in high-back crucian carp during different life stages. The results showed that WwTP effluent was not acutely toxic and the fish exposed in it had good condition in body growth. Effluent exposure inhibited gonadal growth, diminishing GSI in ELS while elevating it around spawning, aggravated liver burdens, elevating HSI, and induced abnormal Vtg expression in juvenile high-back crucian carp, boosting Vtg concentrations in plasma. Around spawning period, Vtg in high-back crucian carp were mainly induced by endogenous estrogens, and EDCs in effluent had less contribution on them. These results mirrored that ELS is especially sensitive to EDCs effects.(3) From day21, high-back crucian carp exposed in WwTP effluent were held in laboratory for depuration study, and the role of depuration played in eliminating EDCs effects were assessed. Staying in EDCs-free water for30days made high-back crucian carp recover from effects of previous effluent exposure, relieving inhibition of gonadal development and hypertrophy of liver as well as reducing Vtg induced by EDCs in effluent. In addition, compared with natural food in effluent and Dianchi Lake, artificial diet provided in depuration study supplied less nutrition, making high-back curican carp kept in laboratory smaller than that in WwTP effluent and Dianchi Lake. |
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