Effect of bio-based microplastics on earthworms Eisenia andrei

The contribution of bio-based plastics in the global market is gradually growing and diversifying. Therefore, it is necessary to assess their environmental impact including the biotic parts of ecosystems. Earthworms are regarded as functionally essential and useful bioindicators of ecological disturbances in the terrestrial ecosystems. The purpose of this study was to evaluate the impact of three innovative bio-based plastics on earthworms Eisenia andrei in the long-term experiments. It comprised the mortality, body mass and reproduction ability of earthworms as well as the oxidative stress response. Regarding the latter the activities of catalase (CAT) and superoxide dismutase (SOD) involved in the antioxidant system of earthworms were determined. Two out of three bio-based materials tested were polylactic acid-based (PLA-based) plastics, while one was poly(hydroxybutyrate-co-valerate)-based (PHBV-based) plastic. Neither mortality nor weight of adult earthworms was affected even at high concentration of the bio-based plastics up to 12.5 % w/w in the soil. Reproduction ability occurred to be more sensitive endpoint than mortality or body mass. At the concentration of 12.5 % w/w each of the studied bio-based plastics contributed to the decrease of the earthworm reproduction at statistically significant level. PLA-based plastics exerted stronger effect on earthworm reproduction ability than PHBV-based plastic did. CAT activity turned out to be a good indicator of the cellular response against oxidative stress induced by bio-based plastics in earthworms. The activity of this enzyme increased in the response to the exposure to the bio-based plastics compared to the level achieved in the control tests. It was from 16 % to about 84 % dependent on the material tested and its concentration in the soil. Finally, the reproduction ability and catalase activity are recommended to be used in the evaluation of the potential impacts of bio-based plastics on earthworms.