First evidence of in vitro cytotoxic effects of marine microlitter on Merluccius merluccius and Mullus barbatus, two Mediterranean commercial fish species

Abstract

Marine litter, which is composed mainly of plastics, is recognized as one of the most serious threats to marine ecosystems and a global environmental concern. Microplastics (MPs) densities were estimated in all environmental compartments: marine organisms are highly exposed to and ingest them, resulting in disruption of biological functions. Ecotoxicological approaches have also started elucidating the potential severity of MPs in controlled laboratory studies, but the commercially-available and pristine materials employed hardly reflect the actual composition of the environmental litter, which can be contaminated by chemical pollutants or biological agents. Building on the lack of research employing marine environmental MPs or microlitter as a whole, we characterized the quantity and quality of litter in the coastal epipelagic and in the digestive tract of two commercially-relevant fish species, and exposed primary cell cultures of mucosal and lymphoid organs to marine microlitter. A concentration of 0.30 ± 0.02 microlitter items m-3 was found in the water column of the Northern Tyrrhenian sea. μFT-IR analysis revealed that particles of plastic origin, namely polypropylene, HDPE and polyamide, were present in 100% and 83.3% of M. merluccius and M. barbatus stomachs, respectively, which overall ingested 14.67 ± 4.10 and 5.50 ± 1.97 items. Microlitter was confirmed as a vector of bacteria, fungi and flagellates. Lastly, and for the first time, the apical end-point of viability was significantly reduced in splenic cells exposed in vitro to two microlitter conditions. Considering the role of the spleen in the mounting of adaptive immune responses, our results warrant more in-depth investigations for clarifying the actual susceptibility of the biota to anthropogenic microliter.Highlights0.30 ± 0.02 microlitter items m-3 was found in the coastal epipelagic Northern Tyrrhenian sea14.67 ± 4.10 and 5.50 ± 1.97 items were retrieved from hake and mullet stomach contentsA subsample of the ingested microlitter was of plastic originMicrolitter was validated as a carrier of bacteria, fungi and flagellatesSplenic cells exposed to both microlitter conditions for 72 hours suffered cytotoxicity