Multi-Level Responses of Benthic Macroinvertebrates to Experimental Microplastic Pollution in a Boreal Lake
Correa Braga Camara A Neves, Natasha
Microplastic , Plastic pollution , Benthic macroinvertebrates , Benthos , Hyalella azteca , Ecotoxicology , Aquatic ecology , Freshwater , Boreal lake , Mesocosm
The effects of plastic pollution on freshwater benthic macroinvertebrates are not well understood. In the present study, we investigated the effects of microplastics on benthic macroinvertebrates under an environmentally relevant gradient of pollution. Twelve open-bottom limnocorrals were deployed in the littoral zone of a boreal lake at the International Institute for Sustainable Development – Experimental Lakes Area in Ontario, Canada. In June 2022, a mixture of polymers (polystyrene, polyethylene terephthalate, and polyethylene) was added to the limnocorrals to achieve target sediment concentrations of 251 to 2,511,886 microplastic particles per kg of dry weight sediment. Naturally pre-colonized leaf litterbags (5x3 mm mesh size) were added to the limnocorrals and sampled after eight weeks of microplastic exposure to characterize the benthic macroinvertebrate community. We quantified the relationship between sediment microplastic concentrations and benthic macroinvertebrate responses at the organismal (head size of Hyalella azteca), population (sex ratio of Hyalella azteca and relative abundance of nine taxa), and community (total abundance, diversity, structure) levels. We found evidence of moderate effects of microplastic on the sex ratio of Hyalella azteca (F1,10 =5.88, p = 0.036), and weak effects on total richness (lm, F1,10 = 3.827, p = 0.079) and community structure (PERMANOVA pseudo-F1,34 = 1.99, p = 0.083) of benthic macroinvertebrates. Moreover, we found no evidence of effects of microplastics on size of Hyalella azteca nor on total abundance or diversity of benthic macroinvertebrates. The results of this study suggest that under ecologically relevant conditions, exposure to microplastics may only have minor effects on benthic macroinvertebrates, at least on the short term.