Plastics are widely used due to their versatility and durability; however, these same properties also contribute to their accumulation in marine environments, where they pose significant ecological risks. In 2020, global plastic production reached 367 million tonnes, with the COVID-19 pandemic adding an estimated 8.4 million tonnes of plastic waste. Marine organisms are harmed through ingestion, entanglement, and disrupted nutrition, while plastics themselves may act as sources of toxic substances. Although initially regarded as passive absorbers of pollutants, plastics are now recognised for releasing hazardous additives –such as plasticisers, flame retardants, and UV stabilisers– during environmental degradation. These additives, numbering in the thousands, are often poorly assessed and have been shown to be toxic in model organisms and marine cyanobacteria.

Despite rising awareness, the role of environmental factors and microbial activity in altering toxicity remains poorly understood. This research aims to investigate: (1) the potential of plastisphere communities to degrade a range of plastic additives, (2) their role in facilitating additive leaching, and (3) whether microbial biotransformation mitigates or exacerbates toxicity. To address this, we will use microbial enrichments, metabolomics, proteomics, and ecotoxicity monitoring of native marine cyanobacteria. This study will shed light on a complex and underexplored dimension of plastic pollution, helping to inform better environmental policies.