Occurrence and risk assessment of algal toxins in marine water of Hong Kong

Harmful algal blooms (HABs) is in frequent outbreak throughout the world in recent decades which resulted from rapid multiplication of algae cells when nitrogen and phosphorus pollution concentrated in near-coast waters, and brought great influence to marine water and human health. Over the past several decades, climate change and increasing environmental degradation provided good growth environment for certain phytoplankton species. Under favorable environmental conditions, proliferation and occasional dominance of these phytoplankton species can result in high densities of algae and the formation of algal blooms. Harmful algae can produce biotoxins to the aquatic system, which poison the aquatic organisms such as shellfish, crab and fish and destroy aquatic ecological balance, even endangers the human health through the biological enrichment. Toxins causing the PSP syndrome are of the saxitoxin (STX) group. Alexandrium spp. And Gymnodinium spp. are the main organisms which caused paralytic shellfish poisons (PSP). Hong Kong is located on the southern coast of China at the Pearl River Estuary and the South China Sea which is surrounded by the South China Sea on the east, south, and west. Hong Kong has suffered the damage of PSP for long history and two phytoplankton species, Alexandrium spp. And Gymnodinium catenatum. Therefore, studying the characteristics and the level of the algal toxins and assessing their risks in Hong Kong are of particular importance. In present study, 30 marine sites at the high incidence of HABs in the past of Hong Kong were sampled. Alexandrium spp. And Gymnodinium catenatum were quantified by Q-PCR, while PSTs were detected by HPLC-MS of 20 coastal water samples along Hong Kong. Risk assessment caused by marine toxins was measured. The present study can be useful to the local aquaculture development and provide effective suggestions and theoretical basis for present HAB monitoring and management.