Are baleen whales exposed to microplastics threat? The case study of the Mediterranean Fin whale

Impacts of microplastics on marine organisms are largely unknown. Micro-debris floating on theMediterranean Sea have reached amaximum of 892,000 per km2particles.Untilnownodataarereportedontheeffects of microplastics on baleen whales which with the filtrating activities potentially undergo to the ingestion of micr-litter. Here we present the case study of the Mediterranean fin whale (Balaenoptera physalus), exploring for the first time the potential impact of microplastics in the baleenwhale, suggesting the use of phthalates as a tracer ofmicroplastics assumption through micro-debris and plankton ingestion. The finwhale, the only resident mysticete in the Mediterranean, feeds largely on euphasiacean species, with each mouthful can trap about 70,000 liters of water, could potentially undergo to the risk of the ingestion and degradation of microplastics. The work is implemented through four main steps: 1) collection and count of microplastics in superficial plankton samples in Pelagos Sanctuary (PS) (MPA); 2) ecotoxicological investigation of phthalate content in superficial plankton samples of PS; 3) detection of phthalate content in stranded fin whale specimens collected on the Italian coasts; 4) ecotoxicological comparison, by skin biopsy, between the Mediterranean and Sea of Cortez (MX) fin whales. Among the 23 superficial plankton samples, 13 have shown the presence of plastic particles. The highest “microplastic density” (9.63 debris/m3)was found in the sample collected close to the Portofino MPA (Ligurian Sea). High concentration of phthalate MEHP and DEHP have been detected in superficial plankton samples collected in the PS areas, with values approximately four time higher in the samples of the Ligurian Sea than the samples of Sardinian Sea. Regarding chemical harm to Mediterranean whales, related to the assumption of plastic derivates, this preliminary data underline for the first time the presence in the blubber of stranded fin whales relevant concentration ofMEHP. This data suggest the use of phthalates as a potential tracer of microplastics assumption by fin whale by micro-litter and plankton ingestion and represent the first warning of the baleen whale to this emerging threat.