Significance of physicochemical and physiological factors on mercury accumulation in marine fish

Abstract

Since the mercury poisoning in Minamata Bay occurred in 1950s, mercury in fish has raised great public concern. Extensive researches have been done to understand the mercury accumulation in fish and the underlying governing mechanisms. However, there are questions still remaining unclear on Hg accumulation in marine fish. In this study, the relative importance of the influence of Hg speciation and fish physiology on Hg uptake from the waterborne phase in Terapon jurbua, as well as the influences of Hg pre-exposure on Hg accumulation in Acanthopagrus schlegeli were investigated. We found that: (1) In the Hg-Cl complex system, Hg speciation was the dominant factor regulating Hg dissolved uptake, whereas water flux contributed to MeHg uptake at high salinity. In the presence of dissolved organic carbon (DOC), the inhibitory effect was observed in the uptake of Hg(II) but opposite result was observed for MeHg uptake. Therefore, Hg uptake was not solely controlled by its speciation, but was also greatly dependent on the physiological changes. (2) Biokinetic measurements demonstrated that the dietary assimilation efficiency and elimination of Hg(II) decreased significantly in the fish after either Hg(II) or MeHg exposure. The efflux rate of MeHg also decreased when the fish was challenged with MeHg. Such change of Hg biokinetics was strongly related to the metallothionein-like protein (MTLP) concentrations in the fish due to internal handling and storage activities of mercury. Overall, this study demonstrated that physicochemical and physiological factors had significant effect on Hg accumulation in marine fish, and provided detailed information in understanding the variability of Hg accumulation in marine fish under different environmental conditions, as well as the physiological detoxification strategy of fish under Hg stress.

Date of Award	2014
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology