Assessing microplastic pollution in Mediterranean marine caves: a proposal for a methodological approach from sampling to analysis

Mediterranean marine caves are biodiversity hotspots and protected habitats under EU legislation. However, there is still limited knowledge from an ecological and environmental perspective, and anthropogenic pollution remains an unexplored topic. This research aimed to investigate the presence of microplastics (MPs) in sediments and benthic foraminifera from two caves: Ficarella Cave (NW Sicily) and Favignana Cave (Egadi Islands). Different pollution degrees were observed between the two caves (39 ± 41 items/kg and 8 ± 7 items/kg sediment, respectively), with the highest variability of polymer materials in the Ficarella cave. Foraminiferal assemblages of both caves were characterized, identifying typical cave assemblages, and species with different types of tests (Textularia bocki and Sigmoilopsis schlumbergeri from the Ficarella cave, and Lobatula lobatula from Favignana cave) were analyzed through μFTIR. Spectra of all the specimens showed peaks attributable to different exogenous organic materials, among which was polyethylene. Then, benthic foraminifera were confirmed as an early indicator of MP pollution. These results confirmed that the integrated study of MPs in different environmental matrices is a promising approach to recognizing the transfer of these pollutants between different environmental compartments. However, for the development of these new studies and the comparison of results, there is a need to define specific sampling methods and, at the same time, standardized analytical methods. To begin a process of harmonization of the methods to be adopted in these environments, this study, considering also the few earlier studies, also focused on defining specific sampling and analytical methods to detect MPs in different environmental matrices and their incorporation into benthic foraminifera.