Of extreme interest is then to place side by side the study of the degradation of "standard" plastic with that of the degradation of biodegradable polymers. These polymers, in fact, are built to be decomposed in optimal situations in the compost, then in conditions of temperature and humidity such that the bacteria responsible for biodegradation can act and decompose many of these substances in a relatively short time (3-6 months). In the marine environment, however, these optimal conditions are not reproduced, and therefore the degradation of biopolymers could have very different outcomes, leading to a lengthening of the time of biodegradation and a lower efficiency of this process.

The consequences of this fact are important, as we are currently looking for substitutes for standard plastics in many fields of use, including those related to the marine environment, such as fishing and shellfish farming: materials that can be completely biodegradable, and therefore produce a less harmful environmental impact. It is therefore extremely important to understand what are the degradation processes that operate on such BIO-plastics, and the time-scales with which they act.

In March 2020, in the Bay of Santa Teresa (SP), two cages constructed of stainless steel were anchored to the LAB MARE coastal station (at a depth of about 10 meters). Each cage contains 3 smaller cages closed with a fine mesh steel net. Inside the cages, standard plastic objects of common use were placed, mainly of two types (polyethylene and polypropylene), the most commonly used for the production of plastic objects, and their BIO-plastic equivalents (packaging such as glasses or plates made of polylactic acid - PLA). In addition to macro-plastics, micro-plastics have also been included in the cages, both PP and PE (standard non-biodegradable polymers) and Mater-bi (Novamont S.p.A.'s Biodegradable Material). These have a size of about 4 mm.

In parallel, the same objects were also placed in a sandbox on land, to simulate the beach environment and to be able to make a comparison between degradation in the aerial and underwater marine environment.

Samples of plastics and BIO-plastics are taken approximately every 3 months from both the sandbox and the underwater cages and are subsequently analyzed in the laboratory.

The first paper has been published with the results of the first 6 months of analysis on plastics and bioplastics taken from the cages.Basically, it was seen that plastic pellets (PP and PE) as well as bioplastics (PLA and PBAT) do not undergo significant degradation, unlike what happens, for the latter, in industrial compost (De Monte el al., 2022).

The project is designed and implemented by INGV, CNR-ISMAR and CNR-IPCF and is carried out with the valuable support of the Dipartimento Polizia di Stato - Centro Nautico Sommozzatori Polizia di Stato – LA SPEZIA for the collection of plastic samples and thanks to the collaboration of LabMARE that provides the structure on which the cages are hooked and the environmental monitoring data.