Effects of dichlofluanid in tropical marine bivalves exposed to water and spiked sediments: an assessment of biomarker responses.

Antifouling paints have been used to control biofouling on submerged surfaces for decades. They contain biocidal compounds that may be released into the environment and harm aquatic ecosystems; however, their effects on tropical organisms are little known. Dichlofluanid, or N-dichlorofluoromethythio-N',N'-dimethyl-N-phenylsulfamide (C₉H₁₁Cl₂FN₂O₂S₂), is a biocide present in antifouling paints and its toxicity to tropical marine organisms is poorly understood. This study aimed to evaluate the effects of dichlofluanid at the cellular and biochemical levels in bivalves exposed to seawater and sediment contaminated with this biocide, considering sediments with two different concentrations of organic matter. Aqueous-phase tests were performed using the mussel Perna perna, and tests with sediments were performed using the clam Anomalocardia flexuosa. Then, cellular and biochemical biomarkers were analyzed. The neutral red retention time assay (NRRT), a cellular biomarker, was assessed only in mussels, while biochemical biomarkers (DNA damage, LPO, GSH, and activities of GST, GPx, EROD, and AChE) were analyzed in both organisms. Particle size, calcium carbonate content, and organic matter analyses were also conducted on the sediments. At higher concentrations, the NRRT assay showed effects on mussel hemocytes, indicating a loss of lysosomal stability. Mussels also showed changes in the biochemical biomarkers of the digestive glands and gills. In clams exposed to sediment, adverse effects occurred in both organs and were more evident in animals exposed to sediments with higher levels of organic matter. Our study demonstrated that dichlofluanid can affect marine bivalves at realistic environmental concentrations and that organic matter may contribute to dichlofluanid exposure to clams.