Ecotoxicological assessment of persistent organic and heavy metal contamination in Hong Kong coastal sediment

The aim of the present project is to determine the feasibility of measuring hepatic cytochrome P4501A1 (CYP1A1) and metallothionein (MT) mRNA in fish as an integrative measurement of persistent organic pollutants (POPs) and h eavy metal contamination in sediment arising in Hong Kong. Sediment samples were collected from different sites, including Victoria Harbour (VS6), Yim Tin Tsai (YTT) at Tolo Harbour, Mai Po marshes (MPM) at Deep Bay, and Sout hern Waters (SS6) of coastal waters. The samples were analyzed for total an d extractable concentrations of Cd, Cu, Ni, Zn, and Pb, as well as PCBs and PAHs. In addition, biomarker responses were studied in tilapia exposed exp erimentally to coastal sediment for 7 days. Using RT-PCR technique, hepatic CYP1A1 and MT mRNA were measured. Three control groups were used, includin g one negative control group maintained in sea water only; the second and t hird positive control groups were in sea water but were intraperitoneally i njected with either beta-naphthoflavone (40 mu g/g body weight) or cadmium chloride (10 mu g/g body weight), respectively. The chemical data showed th at VS6, YTT, and MPM were classified as Class C sediment according to the s ediment quality criteria defined by the Hong Kong Environmental Protection Department, indicating the sites were heavily polluted. The exposure of til apia to the sediment induced hepatic CYP1A1 (VS6 > YTT > MPM > SS6) and MT (VS6 > MPM > YTT > SS6) levels. The induction pat terns were comparable to the levels of POPs and metal contamination in the sediment, indicating that the biomarker responses could be used to differentiate low to high levels of contamination among sediment.