Abstract
Antifouling biocides such as organotin compounds and their alternatives are potent toxicants in marine ecosystems. In this study, we employed several molecular and biochemical response systems of the Pacific oyster Crassostrea gigas to understand a potential mode of action of antifouling biocides (i.e. tributyltin (TBT), diuron and irgarol) after exposure to different concentrations (0.01, 0.1, and 1 μg L-1) for 96 h. As a result, all the three antifouling biocides strongly induced the antioxidant defense system. TBT reduced both enzymatic activity and mRNA expression of Na+/K+-ATPase and acetylcholinesterase (AChE). Lower levels of both Na+/K+-ATPase activity and AChE mRNA expression were observed in the diuron-exposed oysters compared to the control, while the irgarol treatment reduced only the transcriptional expression of AChE gene. We also analyzed transcript profile of heat shock protein (Hsp) superfamily in same experimental conditions. All antifouling biocides tested in this study significantly modulated mRNA expression of Hsp superfamily with strong induction of Hsp70 family. Taken together, overall results indicate that representative organotin TBT and alternatives have potential hazardous effects on the gill of C. gigas within relatively short time period. Our results also suggest that analyzing a series of molecular and biochemical parameters can be a way of understanding and uncovering the mode of action of emerging antifouling biocides. In particular, it was revealed that Pacific oysters have different sensitivities depend on the antifouling biocides.
Highlights
Biofouling represents the community of organisms that settle and grow on the external surfaces of submerged or semi-submerged objects
We investigated the effects of three antifouling agents (i.e. TBT, diuron, and irgarol) on the lipid peroxidation, antioxidant defense system and heat shock protein (Hsp) expression in the gill tissues
We observed significant increases of MDA contents
Summary
Biofouling represents the community of organisms that settle and grow on the external surfaces of submerged or semi-submerged objects. Extensive applications of TBT-based paints to vessels raise hazardous effects on many marine animals for several decades, in mollusks (e.g. inhibition of spatfall, developmental abnormality, shell malformation, imposex, etc.) [5,6,7]. Even tin-free alternatives can induce damages to marine ecosystems, and their potential persistence may have diverse sublethal effects to marine animals on aspects from a molecular level to individual physiology and reproduction, or even a population level. Despite these concerns, the mode of action of these antifouling agents is virtually unknown in marine animals, and it is still difficult to assess resulting effects of alternatives on marine ecosystems
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