Ecotoxicology

Anthropogenic contaminants are widespread throughout many ecosystems and represent one of the greatest threats to biodiversity world-wide. Recognition of this threat has prompted extensive investigation into the accumulation and effects of contaminants in a variety of taxa. Given their reliance on aquatic ecosystems and unique life history, much of this focus has been centered on understanding effects in amphibians. However, some contaminants may biomagnify within food webs and thus investigation into the fate and effects of contaminants among various levels of trophic organization is of critical importance. In particular, investigation into accumulation of contaminants within consumable tissues of game species is of acute importance to human health, yet few data are available for many commonly harvested species. Such research is particularly important for migratory species or those capable of long-distance movements (e.g., waterfowl) where potential exposure risks to hunters may be unknown. Our lab conducts research on both the accumulation of contaminants in a diversity of wildlife as well as the effects of contaminant exposure in ecosystems across the globe.

Contaminants in game species and potential risks to human consumers

Over the last several years we have been sampling common game species in the southeastern U.S. to quantify concentrations of radiocesium, mercury, and a suite of other metals/metalloids in consumable animal tissues. In addition, for some species we are collecting endoparasites and other biological samples to assess the sub-lethal effects of contaminant exposure to wildlife. These studies are being conducted in habitats on the Savannah River Site where the distribution and extent of environmental contaminants has been extensively mapped, as well as other locations in the southeast with no known contaminant inputs. Our focus currently is on resident species such as wild pigs, raccoons, beavers, gray squirrels, wild turkeys, otters, as well as various migratory waterfowl species. To assess contaminant accumulation rates, we also are conducting studies on waterfowl inhabiting contaminated waterbodies to develop contaminant accumulation models as well as inform risk assessments for human consumption of waterfowl. From this research we will be able to determine the extent to which these species accumulate contaminants of concern within their body tissues and be able to assess whether consumption of animals inhabiting contaminated habitats poses any potential risks to human health.

Effects of methylmercury exposure on waterfowl exposed during embryonic development

Methylmercury (MeHg) is a pervasive heavy metal toxicant that is known for its detrimental effects on wildlife in diverse ecosystems across the globe. In aquatic, terrestrial, and marine ecosystems, MeHg can bioaccumulate in wildlife via dietary exposure, and undergoes biomagnification with each increasing trophic position in food webs. For birds, some species of waterfowl, waterbirds, and raptors are at the upmost risk of MeHg accumulation given their intermediate to high trophic position and associated diet within wetland environments, as well as their species-specific sensitivity to MeHg. Birds exposed to MeHg have been shown to experience adverse health and reproductive effects, and even death. MeHg is also maternally transferred to eggs laid by contaminated females, exposing embryos during sensitive stages of development. Although studies have previously examined the teratogenic and embryotoxic effects of waterfowl exposed to MeHg in ovo, few have examined its effects on offspring post-hatch. Therefore, the objective of this study is to further investigate MeHg accumulation in waterfowl embryos exposed during embryonic development, and to assess its effects on newly hatched duckling health, behavior, condition, and survival. Not only will this research further examine the negative effects associated with anthropogenic pollution in wildlife, but it will also further demonstrate how sub-optimal conditions during embryonic development can have potential life-long effects.

Environmental contaminants and blood parasite loads in Black and Turkey Vultures

Recent links between catastrophic vulture declines and anthropogenic hazards have drawn international attention to the vulnerability of scavengers to environmental contamination. Vultures rely on carrion resources, have relatively long lifespans, and are thus particularly susceptible to bioaccumulation of metals and other anthropogenic contaminants. Further, many vulture species may be exposed to anthropogenic contaminants on a regular basis due to frequent foraging at hunter-killed carcasses (which may contain lead fragments), landfills, and other contaminated sites. Despite their potential exposure to contaminants, comparisons of metal and metalloid contamination in sympatric black and turkey vultures are lacking, particularly in the southeastern United States. Thus, understanding levels and sources of contamination to which vultures are exposed is an important area of research to guide future management and conservation efforts. To address this knowledge gap, we are collecting samples from black and turkey vultures in the southeastern U.S. to quantify metal/metalloid burdens and elucidate the relationship between contamination levels and blood parasite loads in vulture populations. Results from this study will provide information on the extent to which avian scavengers are exposed to contaminants and the potential effects of contaminants on the health of scavenging communities in the southeastern United States.

Effects of coal combustion residual exposure on community structure of terrestrial vertebrates

Coal combustion residuals (CCR) are anthropogenic pollutants associated with coal-fired energy production throughout the world and contain potentially toxic trace elements such as arsenic, selenium, and mercury. Historically underregulated methods of CCR disposal have facilitated environmental exposure. Negative effects of CCR exposure on survival, growth, reproduction, and recruitment have been well-studied across a variety of taxa, but community-level effects require additional attention. Our research aims to describe the current community structure of small terrestrial vertebrates within a site on the Department of Energy’s Savannah River Site (SRS), that received CCR effluents during the mid-1900s but has since undergone natural attenuation. Our objectives are to 1) characterize herpetofauna and small mammal communities through mark-recapture and camera trap surveys, 2) compare community composition across a gradient of CCR exposure, and 3) quantify body burden of CCR contaminant within our surveyed species. We will be comparing measures of species richness, diversity, contaminant exposure, and similarity of herpetofauna and small mammals occurring within the core of a CCR contamination area, an intermediate site (the interface of uncontaminated and contaminated area), and reference sites. Results of this study will help guide remediation decisions on SRS and in similar sites with CCR contamination.

Uptake and depuration of 137Cs in aquatic species inhabiting a contaminated canal on the Savannah River Site

Radionuclide contamination can be found across the globe as a result of nuclear weapons testing, nuclear power plants, and nuclear accidents. Of the radionuclides released by anthropogenic sources 137Cs is among the most prevalent and concerning due to its slow decay time and high bioavailability. In aquatic systems, 137Cs sorbs readily to the sediment leaving low concentrations of its labile species suspended in the water column. Thus, benthic organisms and rooted macrophytes may be at an increased risk to accumulate this radionuclide and transfer it into the food web. Numerous studies have reported concentrations of 137Cs in exposed biota, but few have assessed detailed toxicokinetics such as the accumulation and elimination over time, and even fewer have allowed exposed organisms to reach maximum concentrations during uptake. The objective of our study is to quantify the uptake and depuration of 137Cs in taxa from multiple aquatic trophic levels and assess the impact of contaminated sediment removal on 137Cs bioavailability. Using plant, invertebrate and multiple vertebrate species as model organisms, in this study we are quantifying accumulation of 137Cs from initial exposure until equilibrium is reached. Similarly, we are quantifying depuration rates over a similar timeframe. These studies are being conducted in parallel with other experiments to monitor accumulation of contaminants in these same biota both before and after remedial actions of a contaminated canal. These findings will further our knowledge of the transport and fate of radionuclide contaminants in aquatic ecosystems and provide insight into the efficacy of remedial actions on sediment-bound contaminants.

Effects of anthropogenic contaminants on invertebrate communities

Trophic food webs directly influence ecosystem functions, such as energy flow and nutrient cycling, and decomposers play a major role in these processes because they feed at every level of the food web. Decomposing vertebrates represent a resource pulse that creates mass heterotrophic activity in a localized area. Some invertebrates are specialized in decomposition and their role in this process is important to food-web architecture: perhaps increasingly important due to trophic downgrading and the disappearance of top predators. Despite the importance of invertebrate scavengers to food webs, little is known about how specific disturbances —e.g., contamination by radioactive pollution and metals—affect their assemblages. Further, due to their trophic position as apex consumers within food webs, invertebrate decomposers may be useful bioindicators of contaminants within ecosystems. We are conducting studies to monitor insect assemblages linked to nutrient cycling and the decomposition of carrion at both contaminated and uncontaminated sites on the Savannah River Site, as well as to quantify contaminant burdens in select species. Since environmental disturbances can alter community dynamics, we also are investigating whether soils contaminated with metals and radionuclides lead to shifts in scavenging insect community composition and structure, with a focus on coleopteran species. Results of these studies will be used to further our understanding of the effects of anthropogenic contaminants on invertebrate communities.

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