Survey of estrogenic activity in United Kingdom estuarine and coastal waters and its effects on gonadal development of the flounder Platichthys flesus

Estrogenic discharges are known or suspected to be present in many United K ingdom estuaries and are also occurring from offshore oil and gas installat ions. The aim of this study was to establish whether estrogens and their mi mics are present in marine waters at concentrations that can produce biolog ical responses in fish and, if so, to discover whether the effects are like ly to be harmful to populations and communities through changes in reproduc tive and other physiological processes. Laboratory studies and extensive fi eld surveys were carried out with the euryhaline flounder (Plalichthys fles us), using the amount of yolk protein vitellogenin in the blood of free-liv ing male fish as an indicator of exposure to estrogens. Exposure to the syn thetic estrogen ethynylestradiol for 3 weeks confirmed that the vitellogeni n response was made and showed that this species is about one order of magn itude less sensitive than the freshwater species rainbow trout. The fish di d not respond to the estrogen mimic nonylphenol at concentrations of 30 mu g/L. Wild male flounder were sampled from four contaminated United Kingdom estuaries: the Tyne, Crouch, Thames, and Mersey. Fish from one or more site s in each estuary had significantly elevated concentrations of vitellogenin in their blood when compared to concentrations in fish from the clean cont rol estuary (Alde River). Vitellogenin concentrations in the Tyne and Merse y fish were four and six orders of magnitude greater, respectively, than co ntrol concentrations. Elevated vitellogenin concentrations were also seen i n some male flounder caught in coastal areas. Approximately 20% of male fis h from the Mersey estuary contained oocytes in their testes, but this inter sex condition was not seen elsewhere. The implications of these findings fo r fish populations are discussed.