BIOACCUMULATION OF LEGACY POLLUTANTS IN FRESHWATER SYSTEMS USING LONTRA CANADENSIS (NORTH AMERICAN RIVER OTTER) AS BIOINDICATORS

While environmental quality has improved significantly over the last 40 years, assessing water quality alone cannot predict the ecological impacts of metal pollution. In order to quantify these impacts, bioaccumulation and biomagnification in organisms must be studied. Because of their long environmental residence times, metals can remain in an environment for decades where they may be or may become bioavailable. Once introduced into a food web, these metals may bioaccumulate and biomagnify and can reach toxic levels very quickly. For example, fish tested in this study had average Pb = 3 to 6.5 ug/dL depending on trophic level. Fish maintain equilibrium with the water they inhabit, and they are pH, temperature, and most importantly, pollution tolerant. This allows fish to carry metal burdens throughout their lifespan.

Keystone species are often used to assess bioavailability of pollutants. The North American river otter, a piscivorous keystone species in fresh water systems, is an ideal choice as a surrogate for fish and a proxy from human fish consumption. As a pollution sensitive, apex predator, river otters hold the potential for both bioaccumulation and biomagnification. The purpose of this research is to evaluate the metal content of whole livers collected from otters that were surrendered to IN DNR during the 2017-2018 trapping season. Analysis of the livers revealed Pb levels 4Xs the levels found in fish, with average Pb = 22 ug/dL, suggesting bioaccumulation of Pb is occurring in freshwater systems in Indiana. In addition, elevated liver Pb concentrations were found in all counties where otters were trapped and surrendered.

Ongoing research includes further analysis of otter livers for metal concentrations, identifying the presence of and quantification of Zn protoporphyrin (ZPP) in the otter livers, and an analysis of liver tissue for hydropic degeneration. ZPP increases as Fe and Cu levels decrease resulting from the inhibition of heme and hemoglobin production. ZPP levels are often used in children to determine the toxicity of lead. Otters tested, to date, have low levels of Fe and Cu and high levels of Pb and Zn. Hydropic degeneration of liver cells is an indication of chronic lead exposure. The results of this research will provide an alternative assessment of potential metal exposure to humans through fish consumption.