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

Antifouling paints have been used to combat biofouling on submerged surfaces. 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 (C ₉ H ₁₁ Cl ₂ FN ₂ O ₂ S ₂ ), is a biocide present in antifouling paints which toxicity to tropical marine organisms is poorly understood. This study aimed to evaluate the effects of dichlofluanid at a cellular and biochemical level on bivalves exposed to seawater and sediment contaminated with this biocide, also considering sediments with two different concentrations of organic matter. Aqueous-phase tests were carried out with the mussel Perna perna , while tests with sediments used 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 P. perna , 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 for the sediments. At higher concentrations, the NRRT assay showed effects in mussel hemocytes, denoting loss of lysosomal stability. Mussels also showed changes in biochemical biomarkers in the digestive glands and gills. In the 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 showed that dichlofluanid can affect marine bivalves at environmental concentrations and that organic matter may contribute to dichlofluanid exposure in clams.