Do microplastic contaminated seafood consumption pose a potential risk to human health?

Microplastics are present in all parts of the ocean and can have deleterious effects on marine resources. The aim of this work was to map the presence of microplastics in commercial marine species such as bivalves (mussels Mytilus galloprovincialis and clams Scrobicularia plana), crabs (Carcinus maenas) as well as fish (Mullus surmuletus) to relate microplastics levels to pollution sources, assess possible impact on marine food chains and on human health. These species were collected from several sites of the Ria Formosa lagoon and along the south coast of Portugal. A quantitative assessment (number, size and color) and typology of microplastics were made in these species. Only one green fragment of polypropylene was detected in the gills of the crabs, while a blue polyethylene fragment was detected in the hepatopancreas of the mullets. Moreover, no microplastics were present in S. plana nor in the crabs whole soft tissues. Among mussels, 86% of microplastics were present from all sites and the number, size and color were site specific. Mussels from the west side of the coast (Sites 1-3) had the highest levels of MPs per mussel and per weight compared to the other sites, probably related to the impact of touristic activity, fishing gears, fresh water and sewage effluents along with the hydrodynamics of the area.

Could molecular effects of Caulerpa racemosa metabolites modulate the impact on fish populations of Diplodus sargus?

The green alga Caulerpa racemosa is a non-native, invasive species in the Mediterranean, and an important stressor for several native organisms. The algal capacity to produce secondary metabolites has been suggested to modulate success of the C. racemosa invasion, although many of potentially involved biological pathways still remain unexplored. In this respect, the aim of the present study was to investigate some molecular and cellular effects in the white seabream Diplodus sargus, an ecologically key species, which included the alien C. racemosa in its diet. Organisms were sampled in 2 seasonal periods from 3 locations of Southern Italy, each characterized by different levels of algal abundance. The level of caulerpin, one of the main secondary algal metabolites, in fish tissues has been used as an indicator of the trophic exposure to the seaweed and related with molecular and cellular responses. Chemical analyses indicated that fish from invaded sites can accumulate caulerpin, with liver concentrations ranging from a few up to hundreds of µg/g. Biomarkers analyses revealed only limited alterations of the main antioxidant defences, such as glutathione reductase and levels of glutathione; on the other hand, increased enzymatic activities of cytochrome P450, glutathione S-transferases and acyl CoA oxidase, as well as enhanced gene transcription for peroxisome proliferator-activated receptor alpha, cytochrome P4501A and vitellogenin 1 were observed in fish more exposed to C. racemosa as indicated by liver concentrations of caulerpin higher than 50 µg/g. Despite a direct molecular relationship with this algal metabolite could not be established, our results suggest that a C. racemosa enriched diet can modulate biotransformation and fatty acids metabolism of D. sargus. Assessing whether similar effects represent short- or long-term effects will be of crucial importance to understand consequences on the general health status and reproductive performance of exposed key fish species in the Mediterranean region.