Top predator feeding ecology and microplastic (MP) contamination on the far eastern South American coast: Evidence of MP trophic biotransfer

This study describes the feeding ecology, spatial distribution of each ontogenetic phase and the corresponding plastic debris contamination, in the Caribbean sharpnose shark, Rhizoprionodon porosus as a function of spatial-temporal parameters in the Western South American coastal region. The density and biomass of all individuals, captured in a surface drift gillnet fishery, were 1.3 ± 0.3 ind.day −1 and 877 ± 232 g.day −1, respectively. Neonates, and juveniles were captured during all seasons. Adults were largely caught during the late rainy and early dry seasons, probably moving offshore to adjacent open waters during the late dry season. The diet of R. porosus consisted mainly of fish (FO = 71.8%). All ontogenetic phases were contaminated by plastic debris (FO = 100%). Among the plastic debris detected in R. porosus, 91.6% were microplastics (MP) (<5 mm), of which blue fibers contributed 53.7%. The MP samples were identified as polyethylene by Optical microscopy (OM), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and by Energy dispersion X-ray spectroscopy (EDS). R. porosus has a high gut concentration of MP compared to fishes of lower trophic levels. In addition, many fishes within the stomach contents of R. porosus were themselves contaminated with MP (e.g., Eugerres brasilianus, Harengula clupeola, Rhinosardinia bahiensis, Anchovia clupeoides, Monacanthus ciliatus, Polydactylus virginicus, Trachinocephalus myops, Eucinostomus melanopterus, and Lutjanus analis). The piscivorous diet of R. porosus likely leads to accumulation of MP contamination in this top predator through trophic transfer.

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