Bioaccumulation of DEHT in Mytilus galloprovincialis and potential implications in its nutritional value

The accumulation of plastic in marine systems and its degradation into microplastics has become a global issue not only for its environmental ubiquity, but also for the release of intrinsic additives, such as plasticizers, which may negatively affect marine biota [1]. While phthalates are the plasticizers that have been present and accumulated in marine environments for the longest time, alternative non phthalate plasticizers, such as di(2-ethylhexyl) terephthalate (DEHT), have been increasingly employed in the last decades, because of their lower migration frequency and the absence of use restriction. The mussel Mytilus galloprovincialis is an organism of dual value, being considered both as a seafood of great economic importance, and as a sentinel organism in biomonitoring programmes. This species can bioaccumulate a wide variety of contaminants and, consequently, it can provide valuable insights into the pollution scenario of the environment from which it comes [2]. Very few studies have explored the extent to which these plasticizers, including DEHT, accumulate in M. galloprovincialis and the resulting metabolic changes. The aim of this study was therefore to assess the possible effects of exposure of M. galloprovincialis to environmentally relevant doses of the non phthalate plasticiser DEHT. To this purpose, two groups of adult mussels in duplicate were separately exposed to a concentration of DEHT that commonly occurs in the sea [3] (DEHT1:1 mg/L), and to a concentration 100 times higher (DEHT100:100 mg/L). Also, a pool of mussels not exposed to DEHT was considered as the experimental control. Then, the content of such plasticizer was analytically determined in mussel tissues and total lipids, fatty acid (FA) composition, and crud protein were assessed. The pools of mussels significantly bioaccumulated DEHT (123.69 mg/Kg and 595.13 mg/Kg respectively), the control group was considered DEHT-free. Both DEHT1 and DEHT100 groups showed a strong increase in lipid content than control mussels (respectively 5.52%, 8.75% and 8.41%, with p<0.05). Considering the FA composition, a decrease of SFA (i.e., C16:0, C17:0), MUFA, and nutritionally relevant PUFAs, such as C20:5 ω-3 and C22:6 ω-3, and a concomitant increase in C16:1 ω-7, other PUFAs, such as C18.3 ω-4, C20:3 ω-6, was observed in the exposed organisms compared to the control ones. Total protein also shows a decreasing trend in the experimental groups, as DEHT1 and DEHT100 mussels showed respectively a protein content of 14.76 % and 11.46 % with respect to the protein of control group equal to 15.95% (p<0.05). Overall, findings from this preliminary study are consistent with previous studies and highlighted that the differential exposure of M. galloprovincialis to the plasticizer DEHT affected its nutritional parameters, especially in terms of total lipids, total protein, and fatty acid profile.