Combined exposure of poly(lactic-co-glycolic acid) microplastics and global warming affects the population dynamics of a coastal copepod

Microplastics induce ecotoxicological effects on coastal and estuarine organisms, but their combined effects with other environmental stressors such as climate change are poorly understood. The goal of the present work was to assess the combined effects of microplastics and water warming on the benthic copepod Nitokra spinipes at individual-level and to estimate population effects. Nitokra spinipes were exposed to Poly(lactic-co-glycolic-acid) microbeads (5 μm) at 0, 0.1, and 1% of food content, at 22 and 25 °C (+3 °C, based on IPCC-SSP5-8.5). The obtained filtration rates, a proxy for energy assimilation (assuming constant assimilation efficiency), were used in an individual-based model implementation of the dynamic energy budget theory (DEB-IBM) to extrapolate population-level effects under a warming scenario. Our results indicate a reduction in filtration rates by PLA microplastics at +3 °C, with 96-h EC = 0.029% microplastics to food content, and the DEB-IBM model indicated a population-level EC = 0.0098% microplastics to food content. Our results suggest that the combined exposure to elevated water temperatures and microplastics induces a decrease in energy assimilation on benthic copepods, with negative effects at population level.