Long-term assessment of trace elements in franciscana dolphins from the Rio de la Plata estuary and adjacent Atlantic waters

The estuary of Rio de la Plata, in the eastern coast of South America, isa highly anthropized area that brings a high load of contaminants to the surrounding waters, which may have detrimental effects on the local marine fauna. The franciscana dolphin (Pontoporia blainvillei) is a small cetacean species endemic of the southwestern Atlantic Ocean listed as Vulnerable in the IUCN red list. In this study, we assessed the concentrations of 13 trace elements in bone samples from 100 franciscana dolphins that were found stranded dead or incidentally bycaught in the Rio de la Plata and adjacent coast between 1953 and 2015. Elements were, in decreasing order of mean concentra-tions: Zn > Sr > Fe > Al > Mn > Cu > Pb > Cr > Ni > As > Hg > Cd > Se. The concentrations of Al, Cr and Fe were slightly higher in females than in males. The concentrations of As, Ni, and Pb significantly decreased with body length. Throughout the study period, the concentrations of Al, Cr, Cu, Fe, Mn and Ni significantly increased, while the concentrations of As, Pb and Sr significantly decreased. The increasing trends may be due to increased inputs from river discharges, the leather industry and petroleum refineries, while the decrease in Pb may be due to the ban in the use of this element as an additive in gasoline and as component of car batteries. This investigation supports the validity of analysing trace element in bone, a tissue available in scientific collections and museums, to retrospectively examine variation over long temporal scales and thus assess long-term trends in pollution. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study assessed trace element concentrations in bone samples from franciscana dolphins in the highly anthropized Rio de la Plata area. Results showed higher levels of Al, Cr, and Fe in females, and decreasing concentrations of As, Ni, and Pb with body length. Increasing trends in Al, Cr, Cu, Fe, Mn, and Ni were observed, while concentrations of As, Pb, and Sr decreased over the study period.