Microplastics are among the major environmental problems to be addressed because it is beginning to affect food chains and is also reaching human populations. The present study investigated the size, color, shape and abundance of microplastics in juvenile silversides (Atheriniformes) belonging to the edible species Odontesthes bonariensis, Odontesthes nigricans and Odontesthes argentinensis from shallow coastal waters. While 100 % of the sampled individuals presented microplastics in stomach contents, fibers were 95 %. There is a correlation between the size of the individuals and the maximum particle size ingested ranging from 0.2 to 1.2 mm. There is no significant difference in the number of particles ingested per individual. The plastic particles had a lower density than seawater, which is why they floated on the surface. These results imply that the protected areas of large ocean currents increase the exposure of local fauna to microplastics increasing the risk of ingestion of PMs.

This study assessed the concentration, bioconcentration, and bioaccumulation of As, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, and Zn in juvenile fishes (Acestrorynchus pantaneiro, Brycon orbygnianus, Cyphocharax voga, Megaleporinus obtusidens, Odontesthes bonariensis, Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis, and Schizodon borelli) in the Lower Paraná River (Argentina), the most extensive floodplain from the Plata Basin. The floodplain is crucial for the reproduction and growth of various species such as P. lineatus, M. obtusidens, and S. brasiliensis, which complete their life cycle in this environment. In total, 90 individuals were sampled for nitrogen stable isotope, and trace element analysis in muscle tissue, water, and sediment was analyzed. The results show that all the studied species bioaccumulate Cr, Mg, Ni, and Zn. In particular, B. orbygnianus and P. maculatus presented the highest bioaccumulation factor for Cr. A biodilution of Co through the food chain was observed. No positive correlation was found between element concentration and trophic level, but we observed significant differences between trophic guilds (herbivorous, omnivorous, and carnivorous). Our findings suggest that feeding habits determine trace element concentrations. To establish differential behavior between different species within the aquatic web further studies are necessary, particularly in the floodplain of the Paraná, which is a crucial nursery area for most commercially important fishes from the Plata Basin. Graphical abstract

Multi-element concentrations (Al, As, Cd, Cr, Hg, Ni, Pb, Se, and Sr) were analyzed in the muscle of six fish species (Hoplias malabaricus, Oligosarcus jenynsii, Rhamdia quelen, Bryconamericus iheringii, Astyanax fasciatus, and Odontesthes bonariensis) with different diets and habits from the Río Tercero Reservoir (RTR) in Córdoba, Argentina, during the wet and dry seasons. Besides, potential human health risks, associated with the consumption of these elements, have been assessed considering the average daily intake (EDI) in children and adults. Additionally, the target hazard quotient (THQ) and carcinogenic risk (CR) were evaluated taking into account the intake by the general population, fishermen, and consumption frequency recommended by the American Heart Association (AHA), the maximum scientific reference in cardiology in the USA and worldwide. All species presented quantifiable values in muscle for all the analyzed elements (Al, As, Cr, Hg, Ni, Se, and Sr), except for Cd and Pb, being Al and Sr the most accumulated elements in all species in both seasons. The consumption of edible muscles of the species studied in this reservoir represents a toxicological risk to humans. Mercury and As were the main elements that presented a health risk through the consumption of fish. Their concentrations in most fish species were above the maximum daily allowable concentrations, and THQ values were several times greater than 1. In addition, according to AHA recommendations, the cancer risk caused by As was greater than the acceptable value of 10⁻⁴ in all species studied, and in both seasons, with the exception of A. fasciatus, in the rainy season. These results indicate that the consumption of fish from the RTR exposes the inhabitants to possible health risks, especially when considering the consumption frequency recommended by the AHA. Therefore, fish intake from this reservoir should be limited to minimize potential risks to the health of consumers. Finally, the results of this study are useful for controlling pollution and developing preventive and palliative policies to protect populations in contact not only with the reservoir but also with other areas of the world with similar conditions.

Río Tercero Reservoir (RTR) is the largest artificial reservoir in the province of Córdoba (Argentina). Water, sediment, plankton, shrimp (Palaemonetes argentinus), and fish (Odontesthes bonariensis) were collected during the wet season (WS) and dry season (DS) from this reservoir. Concentrations of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, P, Pb, Se, U, and Zn were determined to investigate their respective bioaccumulation pattern and trophic transfer in the food chain. Results showed that their concentrations in water were rather low except Pb, which exceed the limits considered as hazardous for aquatic life. The enrichment factor (EF) in sediments showed that most of the element were derived from anthropogenic sources. Furthermore, the bioaccumulation factor (BAF) determined that the elements undergo bioaccumulation, especially in organisms such as plankton. The invertebrates were characterized by the highest BAF for Cu, P, and Zn in both seasons; Ag, As, and Hg during WS; and Se during DS. Fish muscle registered the highest BAF for Hg (DS) and Se (WS). A significant decrease in Al, As, Cd, Cr, Cu (DS) Fe, Mn, Ni, Pb, Se, U, and Zn (DS) concentrations through the trophic chain was observed, indicating biodilution. Some notable exceptions were found as Cu (WS), Hg (DS), and P (both season) that showed biomagnification. Further studies are needed to establish differential behavior with different species and pollutant, particularly when the potential transfer is to edible organisms.