The effects of imidacloprid and polyester microfibers on the larval development of the endangered sunflower star

Sea star wasting syndrome has affected numerous species of sea star, with populations of Pycnopodia helianthoides (Brandt, 1835) left most at risk. As their populations are struggling to recover, it is important to gain a better understanding of the impacts that the multiple stressors in their habitats can have on their populations. Contaminant stressors in particular are of increasing importance, because aquatic organisms can be exposed to a dynamic range of contaminants from nearby anthropogenic activity that may affect their future recovery efforts. This study is the first to quantify the effects of contaminant stressors on the larvae of P. helianthoides. We exposed P. helianthoides larvae to the neonicotinoid insecticide imidacloprid and polyester microfibers, both individually and in combination, at environmentally relevant concentrations (10 ng/L and 25 fibers/L, respectively) to measure the effects of these contaminants on their early life stages. Imidacloprid exposure resulted in stomach malformation in 10% of larvae and increased mortality during early development (p < 0.001), and all treatments resulted in increased larval lengths relative to controls (p < 0.001). During settlement, imidacloprid resulted in more rapid settlement responses than in the controls (p < 0.01). These findings highlight the need for further research investigating the effects of contaminant stressors to endangered organisms during reintroduction as well as a more comprehensive understanding of the effects of pesticides to nontarget organisms.