Savannah River Ecology Laboratory REU in Radioecology - Student sampling by canoe on a former reactor cooling reservoir

Themes

1. Radiocesium in biota associated with reactor effluent cooling canals, impoundments and SRS streams. Cooling water from five production reactors on the SRS was released into a system of canals, impoundments and/or streams to allow the water to cool before reaching the Savannah River. Accidental releases of radioactive contaminants, primarily radiocesium (137Cs), from the reactors and waste storage basins entered these aquatic systems in the 1950s – 1960s and were subject to early research and monitoring efforts documenting bioaccumulation of 137Cs in biota. Now, 50+ years post-release, 137Cs is still bioavailable and may accumulate to levels of risk to biota and/or humans, the latter through consumption of game species. Students participating in this program would conduct independent research projects examining 137Cs uptake in aquatic and/or terrestrial biota (fauna and/or flora) associated with one of these aquatic systems and potentially compare their findings to historical studies. Depending on organisms studied, the student may specifically examine the influence of size/age of biota and environmental conditions/habitat type on overall 137Cs concentrations of individuals, assess potential trophic effects on cesium uptake, and/or how the differences in concentrations may influence assessment of risk. Recent REUs have examined 137Cs uptake in frogs, tadpoles, crayfish and fish in cooling water canals and impoundments. The student(s) will work to finalize project design and learn sampling equipment assembly. Working within UGA and SRS safety protocols established for these contaminated systems, students will be involved in sample collection (in the field) and sample preparation and analysis for radiocesium (laboratory). Mentor: Larry Bryan, Research Professional.

processing samples in the lab2. Radioecology of game species entering the human food chain. Game species are important components of ecosystems and represent a highly valued hunting resource with an associated economic impact totaling many tens of millions of dollars in the U.S. each year. Since its closure to the public in the 1950s, the SRS has provided refuge to large numbers of game species, including breeding and wintering waterfowl, wild turkeys, and white-tailed deer. In particular, waterfowl are present in virtually every suitable SRS aquatic habitat, including those that have been contaminated by DOE related activities (e.g., former reactor cooling reservoirs, stream systems, and seepage/settling basins). Many of these species are highly mobile and use off-site areas where they may be subjected to hunting by humans. Thus, game species on the SRS are potential vectors of contaminants to the public and warrant particular scrutiny. SREL has contributed >40 years of research on game species in an effort to gain a greater understanding of the interaction between these species and environmental contaminants, and to promote sound stewardship of this significant resource. Participating students will not only assess the possibility/extent of 137Cs currently entering the human food chain, but they will also have access to historical data to investigate decades-long attenuation patterns of 137Cs in biota, all within the context of regulatory limits. Students will participate in all aspects of active research on waterfowl, wild turkey, and other game species, in particular the measurement of 137Cs levels in whole-body and various tissues, and the integration of current data into models of long-term contaminant and human-risk decline. It is expected that data collected by the REU participants will be used in part or in whole as the basis for development of a publication in the primary literature on which they will participate as an author. The student involved in this research also will have the opportunity to work on numerous ongoing related studies within the PI’s lab and more broadly within SREL. Mentor: Dr. James Beasley, Assistant Professor.

3. Effects of contaminants on mosquito immunity and vector competence. Mosquitos transmit many diseases to humans and animals globally. Even today over a million people die from mosquito-borne diseases annually. The factors affecting the ability of mosquitoes to transmit diseases to humans and animals remains one of the most important challenges in controlling mosquito-borne disease. One specific area of interest in our lab is to understand how acute and chronic exposure to radionuclides and/or heavy metals associated with nuclear operations during the aquatic larval stage of the mosquito lifecycle affects mosquito development, the ability of adult mosquitoes to fight parasite infection (immunity), survive the negative effects of being infected with parasites (tolerance) and transmit parasites to the next vertebrate host (vector competence). Students working on this project will be involved in field sampling of mosquitoes, as well as lab-based experiments on mosquito immunity, tolerance and vector competence. Our lab utilizes an interdisciplinary approach to addressing research questions. Thus, undergraduates will be encouraged to design their own specific experiments utilizing a broad range of tools – ecological, entomological, molecular and computational – under the guidance of the mentor and his postdocs and/or graduate students. It is expected that data collected by the REU participants will be used in part or in whole as the basis for development of a publication in the primary literature for which they will participate as an author. Mentor: Dr. Guha Dharmarajan, Assistant Research Scientist.

student with seine net4. Physical and biological factors influencing contaminant accumulation in aquatic organisms. SRS industrial areas involved in processing nuclear materials have contaminated some stream and wetland systems with radionuclides, metals and metalloids. Macroinvertebrates accumulate a variety of contaminants and represent trophic links between primary production and higher trophic level vertebrates. Analyzing contaminant accumulation in macroinvertebrates and fish is enhancing our knowledge of contaminant mobility in SRS wetland systems by examining bioavailability and trophic transfer. In addition to direct predation on aquatic biota by a variety of semi-terrestrial or terrestrial predators, because adults of many stream aquatic insects are flying terrestrial organisms, emerging insects also represent potential vectors of contaminant transport from aquatic to terrestrial food webs. Comparison of different functional feeding groups allows discernment of potential vectors of contaminant uptake and trophic transfers. Habitat specificity, even within closely related taxa such as dragonfly nymphs provide an exceptional opportunity to compare contaminant accumulation in syntopic macroinvertebrates that are all predators within the same order (Odonata) and suborder (Anisoptera), but differ vastly in their habitat use and body form. Similarly, diverse fish species residing in these systems often differ in habitat use, feeding strategies and trophic levels. Accounting for these factors provides critical information on where contaminants enter aquatic communities. The student will design a project to assess contaminant dynamics in aquatic organisms of contaminated systems and then actively participate in all aspects including field collection of samples, identification of specimens, laboratory preparation of samples for chemical analyses, and data analysis. The student will learn to use a direct mercury analyzer and a gamma-counter. Overall, the project will provide opportunity for the student to learn an array of field and laboratory techniques and participate in data analyses aimed at publication, while establishing levels of contaminants entering aquatic communities. Mentor: Dean Fletcher, Research Professional.

student at field site with floating tadpole enclosures5. Amphibian ecotoxicology and disease susceptibility. Environmental contaminants and emerging diseases have been implicated as contributing factors to the global decline of amphibian populations. Amphibians are susceptible to exposure from a wide variety of contaminants including organics such as pesticides and phenols, and inorganics such as metals/metalloids. Numerous studies have examined the lethal or sub-lethal effects of organic contaminants on amphibians; these effects can include increased mortality, decreased growth rates, malformations, endocrine disruption, and immunosuppression. However, substantially less is known concerning the effects of radionuclides and heavy metals associated with nuclear operations on amphibian populations. In addition, almost nothing is known concerning the interaction of contaminant and disease stressors. Several species on the SRS (including eastern narrowmouth toads, southern toads, and spadefoot toads) can breed in late May/early June and have rapid development (30-60 days) making them ideal subjects for REU projects. Our typical studies involve a factorial design with multiple source populations, clutches, treatments and replicates and therefore can get very large—with over 400 tadpoles per experiment. Students can run highly controlled experiments in SREL’s Animal Care Facility and less controlled experiments in situ in a variety of contaminated wetlands/streams on the SRS. Thus, the REU student(s) would be directly involved in studies designed to examine the impacts of radionuclides, metals, and mixed contaminants on amphibians. They would get hands on experience in all aspects of running a large experiment with live organisms in the lab and/or in the field including experimental design, field collection, species ID, animal husbandry and handling, image analyses for growth rates, viral exposures, DNA extraction, quantitative PCR, and metal and radionuclide analyses. Mentor: Dr. Stacey Lance, Associate Research Scientist.

6. Influence of environmental radiation exposure on fundamental aging processes. Projects in the Parrott Lab focus on environmental health and REU students will be encouraged to work on projects examining the impacts of radiation exposure on development, aging, and epigenetic programming. The underlying etiology of many complex disease phenotypes is intimately associated with age-associated processes. Epigenetic mechanisms integrate environmental signals into biological responses, and the epigenome undergoes stereotypical age-associated changes over the course of the vertebrate lifespan. Accelerated epigenetic aging (epigenetic age vs. chronological age) is linked to disease risk and mortality in humans. Recently, we observed that mercury exposure is correlated to accelerated epigenetic aging in the American alligator, suggesting that epigenetic aging might have environmental determinants. Potential projects will examine the interaction between radiation exposures and epigenetic aging, at the DNA methylation level, in fish exposed using the Low Dose Irradiation Facility and also those fish exposed in natural environments. Students will be expected to contribute towards all aspects of the project from experimental design, performing experiments, molecular analyses, and interpretation of findings. Students will gain exposure to basic concepts in environmental radiation, public health, and the molecular pathways that link environments to biological responses. Students will bolster practical skillsets related to field and laboratory methodology, as well as enhance their data interpretation and communication abilities. Mentor: Dr. Ben Parrott, Assistant Professor.

student with largemouth bass7. Contaminant uptake in aquatic species. Contaminant uptake subsequent to disturbance is an important area of ecotoxicology, especially as it pertains to resurgence of contaminant flow through food webs in diverse aquatic ecosystems. In particular, heavy metals and radionuclide transport into game species (e.g., largemouth bass) that may be consumed by humans is an important area of research. REU students in this project will be involved in capture, marking, and sampling of largemouth bass in the Par Pond reservoir on the SRS. Par Pond has been the focus of much past research on contaminant concentrations in soil, water, and biota and has a legacy of contamination with both heavy metals and radionuclides. The focus of this research is to evaluate metal and radionuclide contamination in bass subsequent to a major perturbation of this reservoir, which occurred in the 1990s. Data on population size, movement behavior and contaminant loads of bass will be used to parameterize risk assessment models for contaminant uptake of this species. Specifically, students will conduct experiments focused on estimation of population size, movement, and contaminant concentrations in largemouth bass as members of the broader team of faculty, graduate students, and postdocs working on contaminant transfer in aquatic systems. Mentor: Dr. Gene Rhodes, Director and Professor.

student testing microbial colonies8. In situ immobilization of radionuclides and metals. The disposition of radioactive waste is a major environmental concern facing both the federal government and the nuclear industry. While the disposition of high level waste remains an issue, especially for the nuclear industry, the development of methods for remediating large areas that are marginally contaminated with radionuclides and other contaminants remains a major challenge at sites within the U.S. and abroad. Less expensive in situ contaminant immobilization strategies typically rely on the introduction of chemical additives chosen to alter target contaminant speciation in a manner that enhances solid-phase partitioning in order to reduce migration, bioavailability and ultimately the associated exposure hazard. However, the use of in situ remediation techniques requires a fundamental understanding of the underlying geochemical processes, as the contaminant remains in place with the potential to become a hazard at a later date. REU students will conduct replicated mesocosm studies in the lab to improve our understanding of the chemical speciation, and fate and transport of radionuclides (e.g., U, 137Cs, 99Tc, etc.) in the environment, and the development and testing of both short- and long-term radioactive waste containment strategies. REU students will be involved in all phases of the project, including experimental design and data collection, analysis and interpretation. Mentor: Dr. John Seaman, Senior Research Scientist.

student loading autogamma counter9. Long-lived reptiles as ecological receptors. Due to their relatively long life spans, physiology, high trophic status, and use of both aquatic and terrestrial habitats, many reptile species are ideal ecological receptors for assessing risks associated with long-term contaminant exposure. We will use a variety of field and laboratory approaches to study the biological effects of exposure to radionuclide and metal contaminants in reptiles at the individual, population and community levels. Specifically, undergraduate students working on the project will develop and conduct independent research projects conceptually centered on (1) factors affecting the assimilation and transfer of contaminants among biota, (2) the physiological consequences and sublethal effects associated with exposure to or bioaccumulation of contaminants, or (3) integration of archived samples and historical mark-recapture data into studies of contaminant dispersion among biota and contaminant persistence through time. Participation in other ongoing projects will increase student interactions with other lab members and broaden the scope of research techniques they learn, including a suite of laboratory procedures, such as respirometry, bacteria killing assays, corticosterone assays, the preparation of samples for isotope and heavy metal analysis, and wildlife health diagnostic profiles. Students will be encouraged to use their data for the development of an undergraduate senior thesis project. It is expected that their research would also result in or contribute to peer-reviewed publications and that students would fully participate in the publication process. Mentor: Dr. Tracey Tuberville, Associate Research Scientist.