Project Title: The Use of Biomarkers for Ecotoxicological Assessments of Persistent Organic Pollutants (POPs) and Heavy Metals on Birds at Mai Po Nature Reserve and Other Wetlands

Applicant : The Hong Kong Baptist University

Project Proponent : Professor MH WONG

Total Approved Grant : $ 588,000.00

Duration : 1/4/2005 to 31/3/2007

Project Status/Remarks : Completed

Scope :
The major aim of the present proposal is to investigate the potential use of feather and eggshells, instead of eggs, to setup and evaluate biomarkers in birds for risk assessment of POPs and heavy metals at Mai Po Marshes. If significant correlations can be established between the two (eggshells and feather, with eggs), future biomarkers can be performed on eggshells and/or feather, instead of eggs, which will be more convenient and less invasive. Three sites have been identified, including Mai Po Marshes Nature Reserve of Hong Kong, Taihu Lake (at Jiangsu Province, a polluted site due to industrial, agricultural and domestic discharges,) and Dafeng Milu Nature Reserve (also at Jiangsu Province, a clean site serves as the control) of China. Two common resident fish-eating aquatic feeding bird species including Little Egret (Egretta garzetta) and Black-crown Night Heron (Nycticorax nycticorax), sharing similar habitats as Black-faced Spoonbill and Nordmann’s Greenshank will be studied.

Summary of the Findings/Outcomes :
Distribution of metals and POPs in the sediments at Inner Deep Bay Ramsar Site shows that the source of contamination was the nearby rivers (Kam Tin River and Shenzhen River) and the Pearl River. High biota-sediment accumulation factors (BSAFs) were observed for bottom-dwelling and sediment-feeding species, including both tilapia and mud carp, indicating that POPs such as PAHs and OCPs could be readily bioaccumulated in the bodies of these fish species. The OCPs and PAHs data for ardeids in Jiangsu Province revealed bioaccumulation of the pollutants via exposure to both contaminated sediment and fish. A significant linear regression was obtained between OCPs concentrations in ardeids eggs and prey fish, and the equation was useful for estimating OCPs concentrations in ardeids of at Inner Deep Bay Ramsar Site. Significant (p < 0.05) linear regressions were also found between heavy metal contents in different tissues of birds and fish, including: eggshell-egg (for Cr and Pb), feather-fish (for Cd and Cu) and eggshell-fish (for Ni), which are useful for extrapolating heavy metal contents in different waterbirds, including endangered species. Biomagnification of methyl-Hg from sediments to fish and finally to bird eggs/feathers was identified in samples from Jiangsu Province and the Inner Deep Bay Ramsar Site. Although the Inner Deep Bay Ramsar site contained the highest levels of total PCDD/Fs in the sediments and fish compared with the sampling sites in Jiangsu Province, bioaccumulation of dioxins in the feathers of the birds at the Inner Deep Bay Ramsar Site was not as high as that at Jiangsu Province.

A battery of toxicity tests using different trophic organisms, including bacteria, algae, microcrustacean and plant, was used to evaluate toxicity of sediments of Mai Po. Sediments (and corresponding elutriates) of mudflat and gei wai 24g, respectively, were shown to be the most and least toxic in all tests (except the algal growth inhibition test). The highest toxicity of the mudflat appeared to be related to the higher concentrations of heavy metals, PAHs and OCPs in the sediments. The MicrotoxR solid phase test, Daphnia mortality test and ryegrass seed germination / root elongation test are suggested to be useful tools to evaluate sediment toxicity of Mai Po and potential biological impacts of the contaminated sediments to organisms. Intake of heavy metals from artificial fish feeds led to significant increase in hepatic MTs in tilapia.