Understanding the role of (bio)minerals and metals on marine plastic biogeochemistry and degradation processes

Plastics are an omnipresent contaminant, with the marine environment serving as their largest sink. Their unique properties, including low density, surface charges, and remarkable resilience introduce novel conditions to aquatic ecosystems. The biofilm forming on plastic surfaces - the so-called Plastisphere, is an emerging ecological niche and has been found to harbor a variety of microorganisms, minerals, metals and organic matter. The biotic and abiotic properties of this complex eco-corona facilitate biogeochemical interactions and have wide implications for ecosystem and human health.Plastisphere composition can drive or hinder biological uptake and gene transfer, alter plastic transport, influence element cycling and promote polymere degradation or prolong plastic stability in the environment. Abiotic minerals such as salts, carbonates, and silicates, along with biominerals and metal deposits, form or attach to plastic surfaces, functioning as attachment and nucleation sites and catalysts for further reactions. Metals such as iron, manganese, and copper further enhance surface reactivity and microbial metabolic activity. The Plastisphere can therefore foster environments conducive to horizontal gene transfer, potentially amplifying the spread of antibiotic resistance genes and enhancing the ability of pathogens to thrive. These interactions modulate marine geochemistry, impacting processes such as silica and carbon cycling, metal fluxes, and microbial metabolism.Here, we characterize mineral-plastic interactions across scales, employing bioimaging, geochemical and polymer analysis, outlining their significance for biogeochemical cycling of plastics, plastic degradation and environmental and human health. Furthermore we discuss the potential impacts of micro- and nanoplastics on biomineralization processes and the implications within the marine silica and carbon cycles.