Master of Science (MS)
Semester of Degree Completion
Karen F. Gaines
The Department of Energy's (DOE) Savannah River Site (SRS) faces a legacy of radionuclide and metal contamination from industrial processes that occurred within the site. The risks posed to ecosystems on the site from contaminants are quantified using the ecological risk assessment process, which often uses the health of a particular species as an ecological endpoint. Northern river otters (Lontra canadensis) are appropriate receptors for studying the effects of long-term, low-level contamination because they are long-lived, higher trophic level organisms likely to accumulate high levels of pollutants. However, little information about river otters on the SRS is known; in particular, knowledge of their distribution within the site is lacking. The purpose of this study was to use latrine surveys to examine patterns of wetland, latrine, and microhabitat usage; explicitly model northern river otter resource selection on the landscape level; and utilize the model results within the accepted ecological risk assessment framework to assess the effects of metals and radiocesium on the population of river otters on the SRS. Wetland shores were sampled for latrine sites over a thirteen month period. Scats were also collected and counted for radiocesium activity to validate model results. Wetland usage, seasonal latrine usage, and microhabitat usage patterns were examined using Pearson's Chi-square goodness of fit tests and two sample t-tests. The spatially explicit resource model was developed using logistic regression to relate heavy otter use of a particular reach to a variety of landscape level environmental variables. The ecological risk assessment used deterministic and probabilistic allometric exposure models to examine the effects of nine heavy metals and cesium137 on the SRS population of river otters. River otters on the site preferentially used streams over other wetland habitat types. Seasonal latrine patterns occurred in the predicted pattern, but peaks occurred late in the year than expected. Microhabitat variables that differed between revisited and single-use latrine sites included presence of flood debris, canopy cover, height, distance to water, and slope. The final spatially explicit resource selection functions contained several parameters with negative estimates including low bank, floodplain width, and the landscape metric patch size coefficient of variation; and several parameters with positive estimates including, proportion bottomland hardwoods, proportion dense-canopy pines proportion floodplain hardwoods, proportion evergreen hardwoods, and open-canopy pines. The ecological risk assessments revealed that the only contaminant that occurred at high enough levels to cause population effects was mercury and that the observed levels were probably not high enough to cause significant damage. However, river otter scats collected for validation suggested that river otters were extensively utilizing the contaminated man made A01 wetland and exposures from non-stream sources were not considered for our estimates.
McCallen, Emily B., "The North American River Otter (Lontra canadensis) on the Department of Energy's Savannah River Site" (2017). Masters Theses. 2751.