An integrated environmental risk assessment for marine protected areas in Hong Kong with special reference to the ecological impacts of endocrine disrupting chemicals

Abstract

Marine protected areas (MPAs) have been established with the primary aim of protecting and conserving invaluable ecosystems and marine biodiversity. MPAs in Hong Kong are, however, situated close to urbanized areas and inevitably influenced by human activities, and hence marine organisms living there may be at risk. This thesis aims to identify the major threats to MPAs, and assess their environmental risks through an integrated environmental risk assessment and management (IERAM) framework. As an example, the environmental risk at the Cape D’ Aguilar Marine Reserve (CAMR) was comprehensively evaluated using the IERAM. The results pinpointed that chemical pollution could be the major threat to the marine reserve.

Since an effective water quality monitoring in the CAMR was missing, a real-time telemetric system was established for monitoring the dynamics of important environmental variables once every 15 minutes. With high-frequency water quality data, a support vector regression model was developed for forecasting the occurrence of harmful algal blooms in the marine reserve.

As identified by the IERAM, partially treated sewage discharges contained various harmful chemical pollutants which may pose adverse effects to the marine organisms inhabiting the CAMR. By examining chemical constituents in sewage effluents from three sewage treatment plants nearby the CAMR, 12 endocrine disrupting chemicals (EDCs) were identified, and among them, nonylphenols (NPs) and bisphenol A (BPA) were the most abundant. Diluted effluents caused abnormal development and growth impairment in embryos and larvae of the marine medaka fish species. Since these chemicals can trigger harmful effects on reproduction, growth and development in marine organisms like fishes at low concentrations, their continuous release from sewage effluents is clearly a matter of grave concern.

The environmental fate of NPs and BPA in seawaters, suspended particles and sediments taken from three suspected pollution sources to CAMR was further investigated. Organic carbon-normalized apparent partition coefficients (log K’OC) for NP (5.82) and BPA (4.65) indicated a strong affinity of both EDCs to sedimentary organic matter, suggesting sediment as their sink. Elevated levels of NPs and BPA were detected in all environmental and biota samples. Natural seawaters from the CAMR elicited expression of estrogen-related genes in the marine medaka. According to a probabilistic ERA, the resident marine species are having 35% and 21% of chance to be at risk due to exposure to NPs and BPA, respectively.

The integrative ERA approach was extended to four MPAs in Hong Kong where eight EDCs were detected in environmental samples, transplanted mussels and semi-permeable membrane devices. Both yeast estrogen screen assay and catechol-o-methyltransferase assay in MCF-7 cells revealed an elevated estrogenicity in the environmental samples, and indicated an ecological risk to marine organisms living in the MPAs, except Hoi Ha Wan Marine Park.

The contamination of EDCs in Hong Kong’s MPAs is widespread. The ecological risk of NPs to marine organisms living in the MPAs, especially the CAMR is high. The current results call for proper risk reduction measures such as upgrading preliminary sewage treatment to secondary treatment, and tightening up regulations on the use and release of EDCs.