Simona Clò

Nowadays, plastic pollution is recognised as a worldwide concern because it causes harm to the environment and generates adverse economic, health and aesthetic impacts. While at the beginning of the study of this subject, the research was focused mainly on the investigation of the macroscopic fraction of the marine litter, in recent years, the attention of scientists has extended also toward the smallest fraction, that is, the micro- (MP, particles < 5 mm) and nano- plastics (NP, < 1µm). In the marine environment, organisms at every trophic level, from primary producers to higher-order consumers such as fish, turtles, sea birds and mammals, have been reported to ingest and/or interact with plastic. In laboratory studies predominantly in crustaceans and molluscs, MPs have been shown to cause a variety of biological effects. However, there are also studies that reported no effect and nowadays a consensus has not yet been reached with regard to their toxicity. In fact, for MPs the evidence surrounding effects is variable and seems to be context dependent. The discrepancy between studies may be due to differences in polymer type, shape, size, and chemicals associated, but also to other factors including species sensitivity and the dose and time of exposure. Another source of variability can be represented by variations of ocean water pH; pH variations can potentially modify the chemical equilibrium of MPs increasing or decreasing the leaching rate of the adsorbed chemicals, and the combined stress (MP + water acidification) can influence the eco-toxicological responses for example by inhibiting, in mussels, the digestive enzymes or altering lipid peroxidation. In addition to pH variations, also the abundance of food was proven to affect the cycle and fate of MPs in marine environment and influence the ingestion/egestion rate of mussels. This project is based on a cycle of experiments focused on the understanding of the eco-toxicological responses of diverse marine organisms following the exposure to PET (polyethylene terephthalate) MP. PET was selected as reference material for different reasons: 7.7 % of total European plastic production is represented by PET, PET litter was found in diverse marine and coastal compartments from seabed to surface water and along the coasts. Moreover, the handful of studies which used PET MPs report contrasting biological effects in freshwater organisms. The selected particles were heterogeneous in shape and size, obtained by double trituration through industrial mills and characterized by irregular edges and surface irregularity, features that well simulate the secondary MPs present in the oceans. The first full paper included in this project investigates the possible interactions between PET MPs and some other factors, namely the water pH (Ac=7.5 and St=8.0) and food variations (presence/absence), by testing the toxicity of leachates and suspensions of different size (5-3,000 µm) of MPs in a multispecies test composed by Vibrio fischeri (Beijerinck, 1889), Phaeodactylum tricornutum Bohlin, 1898, and Paracentrotus lividus (Lamarck, 1816).

The Clean Sea LIFE project aims to raise awareness on marine litter. It is co-funded by the European Commission through the LIFE programme.