Ecotoxicological Assessment of Metal Pollution using Aquatic Organisms in Surface Sediments from a Tropical Urbanized Lagoon System

Abstract This study documents an ecotoxicological evaluation of bottom sediments ( n = 21) from a tropical lagoon complex performed in the Itaipu-Piratininga system (Rio de Janeiro State), an impacted urban tropical estuary. To achieve this purpose, three lines of evidence were adopted: sediment characterization, metal contamination and toxicity to tropical species (bioassays with mussels Perna perna , tanaids Kalliapseudes schubartii , amphipods Tiburonella viscana , and microalgae Cylindrotheca closterium) . The sediments from Piratininga lagoon were muddier and more organically enriched than those from Itaipu lagoon, once only the last one is influenced by an active connection with the ocean. Sediment texture and organic matter played a crucial role in metal distribution, but contaminated river mouths and the canal connecting the lagoons presented elevated Zn, Cu, Cd, Cr, Ni and P concentrations, which seem to be linked to domestic sewage discharges and other anthropic wastes. In addition, Pb and Mo hot spots were associated with an embayment area in Piratininga lagoon. Mussel embryo-larval development was 100% abnormal for all the samples. Although almost all the samples were toxic to tanaids and amphipods, tanaid mortality (mean ± SD = 76.4 ± 23.6%) was significantly higher than amphipod one (56.3 ± 20.4%). Inhibition of algae reproduction was the endpoint of lower concern (31.1 ± 26.5%). The toxicity was especially higher in river mouths and in the canal that connects the lagoons, being significantly correlated with sewage-related pollutants (Zn, Cu and P). Finally, although spatial variability of the toxicity has been explained by metal pollution along the lagoons, other toxicants should also be considered as stressors.