Microplastics Affect Rates of Locomotion and Reproduction via Dietary Uptake in Globally Invasive Snail Physa acuta

Abstract

Given the omnipresence and potential of entering the food web, the recently emerged pollutant microplastics (MPs) has become a global threat. The impacts of MPs in marine ecosystems are well documented, but the freshwater environment is relatively understudied. Improper disposal of industrial and commercial waste introduces MPs in the freshwater environment where it is either transported to the ocean or eventually settles down to the bottom. To elicit the impacts on components of fitness, the effect of inert particles on the reproductive and behavioral performance on organisms can only be translated after long-term experiments, but most of the available information on freshwater benthos relies only on short-term experiments. This study investigated the rates of microplastic ingestion, locomotion and reproduction in the globally invasive snail Physa acuta (Gastropoda, Pulmonata) at six environmental concentrations (0, 2.5, 5, 10, 20 and 40 mg/200 mL) of polystyrene (PS) MPs particle (size = 32–63µm) for 93 days after maturity. The PS particle ingestion was confirmed by analysis of P. acuta excreta and tissue digestion. P. acuta displayed Type II functional response to MPs. We measured locomotion speed and reproductive rate for 93 days after maturation at 20, 30 and 40 mg/200 mL concentrations of PS MPs equivalent to 500 × 104, 750 × 104 and 1000 × 104 particles/200 mL, respectively. Average locomotion speed and egg capsule production were significantly lower in the MP applied environment than in the control. The percent reduction in ovisac production and egg hatching success were a direct function of MP concentrations in the medium., although, in a natural setup, plastic debris was observed as a frequent oviposition substrate for P. acuta favoring the species in dispersal. The present results point to a higher tolerance of P. acuta to MPs and their role as a vehicle of MP transfer from sediment to fish.