Multi-elemental composition and toxicity of bottom sediments from Panama Canal watershed

摘要

The Panama Canal is a milestone in the history of interoceanic communication. Despite its importance, environmental data regarding this important ecosystem is scarce. The aim of this work was to quantify trace-element levels in bottom sediments from 11 sites along the Canal watershed using ICP-MS, and in the case of mercury, employing a direct Hg Analyzer. These data were associated with the biological activity of aqueous sediment extracts tested on wild type and mutant strains of Caenorhabditis elegans, measuring physiological and molecular markers. The levels of trace elements in bottom sediments decreased in the order Sr V Ba Cr Li Sc Ce Ni Y Co Ga Pb Rb Nd La Gd Dy Sm Pr Er Hf Yb U Th Eu Ho Be Tb Tm Ta Hg. The Pollution factor and Pollution Load Index showed that 36% of the sites presented strong sediment pollution by V, Li, Pb, and Sr. Moreover, the Comprehensive Ecological Risk Index based on Cr and Ni levels was exceeded in all stations. Toxicity tests revealed that sediment extracts, despite not being highly lethal against C. elegans, did significantly reduce its mobility and activated toxicity mechanisms associated with the expression of metallothionein and oxidative stress-related genes. These last three endpoints were statistically related to Cr, Ta and Ba concentrations in sediments, respectively. Data suggest elements present in sediments from Panama Canal may be impacting benthonic organisms, and therefore, stronger management regulations should be considered in order to ensure its sustainability.