Effects of suspended coal particles on gill structure and oxygen consumption rates in a coral reef fish

Large quantities of coal are transported through tropical regions; however, little is known about the sub-lethal effects of coal contamination on tropical marine organisms, including fish. Here, we measured aerobic metabolism and gill morphology in a planktivorous coral reef damselfish, Acanthochromis polyacanthus to elucidate the sub-lethal effects of suspended coal particles over a range of coal concentrations and exposure durations. Differences in the standard oxygen consumption rates (MO2) between control fish and fish exposed to coal particles (38 and 73 mg L−1) were minimal and generally not dose dependent; however, the MO2 of fish exposed to 38 mg coal L−1 (21 days) and 73 mg coal L−1 (31 days) were both significantly higher than the MO2 of control fish. Chronic coal exposure (31 days) altered gill structure in the higher coal treatments (73 and 275 mg L−1), with fish exposed to 275 mg L−1 exhibiting significant reductions in gill mucous and thinning of lamellar and filament epithelium. These findings contribute to our limited understanding of the potential impacts of coal on tropical reef species; however, most of the observed effects occurred at high coal concentrations that are unlikely under most coal spill scenarios. Future studies should investigate other contamination scenarios such as the impacts of chronic exposures to lower concentrations of coal. •Differences in standard oxygen consumption rates between control and coal exposed fish were generally not dose dependent•Chronic coal exposure (31 d) altered gill structure in the higher coal treatments•Coal concentrations considered most ecologically relevant did not elicit significant sub-lethal effects