Effects of New and Aged Polyethylenterephthalat and Polylactic Acid on Gammarus fossarum (Crustacea: Amphipoda) during Long-Term Exposures

The freshwater amphipod Gammarus fossarum (Koch, 1835) was exposed in four subsequent experiments of each 45 - 48 days to 1 cm2 plastic foil (Polyethylenterephthalat (PET), Polylactic acid (PLA)) with mortality, feeding, and behavior in the Multispecies Freshwater Biomonitor© (MFB) (spontaneous locomotion, gill ventilation) being studied once a week. Mortality was generally high and similar in all experiments, with a slight increase in PLA treatments. PLA exposed animals showed higher ventilation, but spontaneous locomotion was equally high in all treatments during all experiments, showing high reproducibility. Feeding rates reached up to 50% of the provided alder leaf in all treatments and in all experiments. PLA foils started to age by surface cracks, deformation at the edges and loss of transparency esp. in the 4th run with 135 d old foils. Both types of foils were equally colonized with biofilm during 45 days’ exposures, starting with ciliates and flagellates, followed by diatoms and green filamentous algae at last. Some taxa differed in absolute amounts in the 4 subsequent experiments due to seasonal succession. There was only marginal weight loss of the foils during 180 days of exposure. The biopolymer PLA started to degrade slowly after 180 d, whereas PET remained morphologically unchanged. The presence of the plastic foils in the beakers independent of their age had no significant effects on survival, behavior, and feeding of G. fossarum during 45 d of exposure.