Warming-induced microplastic accumulation and physiological toxicity in fiddler crabs

Under natural conditions, organisms are exposed to multiple stressors simultaneously, such as microplastic (MP) contamination and rising global temperatures. To assess the combined effects of acute MP exposure and increasing temperatures on the fiddler crab Minuca rapax, we exposed the crabs to polyethylene microspheres (0 and 2 mg L⁻¹, size 53–63 μm) at three different temperatures (24, 27, and 30 °C). Physiological responses were assessed by measuring oxygen consumption and evaluating the biochemical activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) alongside lipid peroxidation (LPO) in the gills and hepatopancreas. MP bioaccumulation was quantified in the gills, digestive tract, and muscles. Our findings revealed that MP bioaccumulation was highest in the gills, followed by the digestive tract and muscles. Notably, elevated temperatures (30 °C) suppressed MP accumulation. At 30 °C, MP-exposed crabs showed increased oxygen consumption, while at 27 °C, SOD and GPx activities were elevated. In contrast, in MP-exposed crabs, catalase activity and LPO levels decreased at 30 °C. Overall, the combined effects of MP exposure and temperature-induced stress exacerbated physiological toxicity in Minuca rapax, underscoring the importance of considering multiple environmental stressors when evaluating the impacts of MP contamination.