Savannah River Ecology Laboratory

Currently Funded Projects

Environmental Organic Chemistry Studies (Gary Mills)
Organic contaminants such as PCBs, PAH, petroleum hydrocarbons, and chlorinated solvents have been released to environments on the SRS by various cold-war era processing facilities. Natural physical, chemical, and biological processes act to reduce the concentration, mobility, and toxicity of such contaminants in the environment. Monitored natural attenuation is a remediation strategy that makes of these processes within an overall management plan to clean up contaminated soils and ground water to achieve acceptable levels of risk to human health and the environment. These processes include microbial degradation, sorption to soil or aquifer particles, volatilization to the atmosphere, and chemical reactions with natural materials. Students may participate in studies examining abiotic and biological transformations involving organic contaminants in aquatic and terrestrial ecosystems. While conducting these experiments, students will also gain knowledge and hands-on experience using instruments for the analysis of organic contaminants such as high resolution gas chromatography (HRGC) and gas chromatography-mass spectrometry. Recent student projects have studied biogeochemical processes affecting PCE and TCE degradation in hyporheic sediments in streams and the trophic transfer of PCB contaminants in an aquatic food web.

Constructed Wetlands for the treatment of SRS facility discharge waters (Gary Mills, Ken McLeod, J Vaun McArthur)
Constructed wetlands offer many advantages over more highly engineered water treatment systems, but they also have limitations. DOE has constructed two treatment wetlands to remove metals (Cu, Zn) from facility discharge waters prior to entering receiving stream waters regulated by state and federal agencies. Seasonal patterns of temperature, rainfall, evaporation, and hydrologic conditions impact wetland efficiency. As the constructed wetlands develop over time, metal extraction increases in efficiency, approaching that of a mature wetland system. Critical development stages where active measures can encourage or inhibit the rapid development need to be identified and evaluated. The efficient removal of Cu and other metals from solution will be dependant upon active microbial populations, especially sulfate reducing bacteria (SRB) which metabolize anaerobically on sulfate. Sulfide is expected to sequester divalent metal species forming insoluble precipitates. Thus a key research focus will be to analyze changes in the microbial community (as it adapts from aerobic to anaerobic conditions) using the 16s rRNA gene in DNA extracted from sediment samples, as a molecular marker. We will also observe how changes in the microbial populations are reflected in the sedimentary metal geochemistry. Changes in bacterial community profile will be assessed using terminal restriction fragment length polymorphism as well as by membrane derived phospholipid fatty acids (PLFA). Predictions as to the prevailing metabolic activity of the population can be made using such an approach, but we will also use specific gene targeting to more accurately quantify desirable metabolic sulfate reduction. Specifically, we will employ quantitative polymerase chain reaction studies aimed at establishing the relative frequency of dissimilatory sulfite reductase (dsrAB) genes in the microbial population. These genes are highly conserved across a wide range of SRB and thus provide a good indicator of relative density of such bacteria in a target environment. The presence of such genes provides evidence of a strongly reducing environment within wetland sediments. As these approaches are linked to geochemical observations, it will be possible to identify patterns of spatial and temporal correlation for a variety of ecological variables Such studies will provide both temporal and spatially relevant evidence for the presence of microbial processes likely to contribute to Cu remediation, as well as providing an estimate for the length of time required for such processes to become established in newly built constructed wetlands.

Effect of heavy metals on the incidence of antibiotic resistance in aquatic bacteria (J Vaun McArthur)
One of the legacies left by mankind during their rapid colonization of the earth has been heavy metal pollution. Heavy metals, like lead, mercury, arsenic, and cadmium, have been used in a wide variety of industrial, energy and technological processes. The direct effects of heavy metals on organisms are severe and can often be lethal. Another legacy created by man is the increase in antibiotic resistance of bacteria and in particular disease causing or pathogenic bacteria during the last 50+ years. This phenomenon is thought to be the direct result of the misuse and over prescription of antibiotic containing drugs. The problem is getting more and more acute with fewer antibiotic drugs being effective and more and more bacteria showing resistance to multiple drugs. Bacteria can become resistant to the effects of both heavy metals and to antibiotics. We have demonstrated that bacteria exposed to heavy metals have increased incidences of antibiotic resistance to a variety of clinically relevant drugs. There are several unanswered questions regarding the mechanisms of acquisition of antibiotic resistance traits. REU students may work on projects to determine whether lateral transfer of resistance genes is occurring among stressed bacteria using GFP-labeled bacteria that fluoresce either when receiving a plasmid or which have plasmids that fluoresce after being transferred. In addition, students may work on projects to contrast the incidence and acquisition antibiotic resistance between lentic and lotic habitats.

Persistence of amphibians in patchy habitats (Tracey Tuberville, Whit Gibbons, Kurt Buhlmann)
The ability of animals to move between habitat patches or fragments and their differential success in these habitats critically affects numerous ecological processes, including the persistence of species populations. With increasing land-use intensity, the loss and degradation of suitable habitat reduces overall habitat availability, fragments remaining patches into smaller, more isolated units and generates increasing amounts of edge habitat. Thus, understanding why and how individuals move among patches of habitat and determining the fate of individuals is essential to understanding important ecological processes, especially population persistence, and is critical to balancing land use with the conservation of biodiversity. The major objective of our research is to understand the behavior and success of juvenile amphibians during the critical terrestrial stage of their life cycle. We seek to understand: 1) the tradeoff between juvenile settling and dispersal, 2) what biotic and abiotic factors contribute to settling or dispersal, 3) how species behavior and vital rates differ, 4) how land use can modify choices or costs, and 5) the consequences of differential dispersal success for long-term population persistence. Students will have the opportunity to design and conduct field-based research projects that support or complement ongoing small-scale field experiments.

Effects of cleared sites on amphibian and reptile populations (Whit Gibbons)
Alteration of terrestrial habitat is an inevitable, albeit often overlooked, consequence of infrastructure development for energy production. Clearing for utility rights-of-way (ROWs) and land clearing for facilities creates open habitats that may constitute poor-quality habitat for amphibians and reptiles, or present significant barriers to dispersal. They may also create positive microhabitats for some species, such as nesting areas for turtles, foraging habitats for rodent-eating snakes, and more suitable burrowing habitats for some amphibians. We have completed five years of an NSF-funded study of land-use effects on amphibian populations (LEAP), which addressed large scale, experimental investigation of the responses of terrestrial life stages of amphibians to fragmentation from clearing of forest adjacent to wetlands. The experimental treatments of the mixed hardwood and pine habitats included clearcuts, partial cuts, and controls (no harvest). We will augment the earlier findings with a student project that can be accomplished within the designated time period that asks questions related to dispersal of metamorphosing frogs, toads, and salamanders and gravid turtles from wetlands. The basic question will be, Do ROWs inhibit, enhance, or have no effect on distances traveled from nearby wetlands by selected species? Proven techniques that will be used will be drift fences with pitfall traps and coverboards for capture of target species. Species routes will be determined by fluorescent pigments (amphibians) and thread trailers (turtles). In assessing the impact of permanent clearcuts (i.e., ROWs) on amphibian and reptile species, information will be gathered on survivorship of metamorphs in clearcuts compared to control woodlands, and the success of egg-laying by turtles in the two habitat types. Student projects will be conducted in coordination with on-going studies in which successful approaches have been established.

Contaminant fate and transport in the soil environment (John Seaman)
The SREL program in contaminant fate and transport addresses several active environmental research areas: solute and contaminant transport modeling, including a more recent focus on the vadose (unsaturated) zone; the physicochemical factors controlling heavy metal, chlorinated solvent and radionuclide adsorption/migration in soil and aquifer system; the land application and disposal on animal wastes and coal combustion by products, and their effects on soil physical properties; and in situ contaminant (U, Ni, 137Cs, Cr(VI), etc.) immobilization. Research projects include both laboratory and field components with a focus on improving our fundamental understanding of various soil physicochemical processes (i.e., mineralogy and physical chemistry), and the necessity to evaluate such processes at different experimental scales in order to develop an effective remediation strategy. Summer REU students will develop a research project looking at the migration of a contaminant the soil system under specific geochemical conditions inherent to the degraded environment, and evaluate the efficacy of several common remediation approaches in meeting regulatory standards.

Maternal effects of incubation variation on fitness in birds (Robert Kennamer)
Incubation of eggs is an important maternal effect and is a critical part of reproduction in birds. Optimal growth and development of embryos takes place within a narrow range of incubation temperatures, and parents must balance the competing demands of maintaining good body condition while caring for developing eggs. The importance of incubation has often been overlooked in studies of avian reproductive costs, but recent experimental evidence shows that incubation costs can limit both current and future reproductive success. Our primary objectives are to: (1) investigate how variation in neonate phenotype caused by differences in the incubation environment affects components of fitness, such as growth and development, survival, recruitment to the breeding population and subsequent reproductive success of neonates, (2) examine effects of incubation temperature on energy expenditures of developing embryos, (3) examine effects of incubation temperature on thermoregulation in ducklings, and (4) examine how variation in incubation period of adult females affects incubation behavior, body mass dynamics, and subsequent survival. Overall goals are to examine the importance of incubation temperature during early development, and to provide a better understanding of how reproductive tradeoffs made by females influence their fitness.

Mitigating the attractive features of wetlands near airports to birds (Robert Kennamer)
Airports servicing metropolitan areas are frequently constructed away from urban centers, and the decisions of where to build airports are usually based on socio-economic and political arguments rather than on biological factors. Consequently, airports are placed in undeveloped areas that often have high potential as wildlife habitat and may also serve as sites for municipal waste treatment and disposal. In 1997, the City of Augusta, GA, was placed under a court order to improve the quality of its wastewater discharges to the Savannah River. Augusta officials opted to develop a "Constructed Wetlands" project to provide the finishing treatment of effluents before their release into the river, and by 2002, 360 acres of primarily monoculture giant cut grass wetlands were brought into service adjacent to Augusta's wastewater treatment facility, which was also within one mile of Augusta Regional Airport. The area quickly became attractive to a variety of wetland-associated birds, including waterfowl, wading birds and, in particular, nighttime roosting blackbirds which now number into the millions each fall/winter. Our research initially sought to document and describe seasonal variation in levels of wetland use by birds and their flight patterns in the vicinity of the wetlands and the airport. Currently, our studies seek to find cost-effective and otherwise suitable methods to lessen the attractiveness of the wetland vegetation to birds and to implement and evaluate tactics to disrupt the birds. Some of the techniques being evaluated include manipulation of wetland vegetation with fire, water level control, and mechanical alteration with airboats. In addition, scare tactics directed at the birds that are being considered include the use of pyrotechnics and propane cannons. The results from this research have worldwide implication as increasing air traffic brings together more aircraft and birds in a greater conflict for flight space.

Phytoremediation of soil contaminants (Ken McLeod)
One promising means of cleaning up soils contaminated with organic or inorganic pollutants from energy production or other industrial activities is phytoremediation, the process of using plants to clean up environmental contaminants. Remediation through plant mediated processes is feasible when the combination of plant uptake rates, contaminant tolerance, and plant productivity are optimized. There are many species with their own unique characteristics that could be used to remediate soil contaminated with heavy metals, radionuclides, or organic compounds. Remediation with plants is also accomplished differently depending on the contaminant. For example, elemental or radioactive contaminants must be concentrated and contained in the plant tissue, whereas organic compounds may be broken down into less toxic or benign byproducts. Natural plant communities have apparently adapted over time to tolerate high levels of various contaminants, as evidenced by the plant cover existing on former mine spoils and ash basins, as well as in areas of high natural radioactivity. These plant species must be identified and surveyed to determine their ability to serve in the phytoremediation of soil contaminants. The potential of various wild species for use in phytoremediation can be readily identified through controlled uptake experiments in field, mesocosm, or greenhouse studies, which are very amenable to the schedule and degree of scientific ability of undergraduate students. Some recent undergraduate research projects included examination of native wildflowers for their ability to take up lead, the accumulation of tritium in plant tissues, the comparison of growth rates of hybrid and native poplars in the south eastern US, and the comparison of soil treatments to aid in the establishment of a vegetative cover. Potential future projects include examining wetland vegetation to determine interaction between the plants and heavy metals, use of plants to dewater and detoxify dredged sediments, and use of plants to aid in the degradation of recalcitrant pesticides in soil. This type of research produces results for practical application (cleanup of contaminated soils at particular sites), as well as exposing students to basic principles in ecology, botany and soil science.

Ecological stewardship and conservation of rare plant species (Rebecca Sharitz)
Long-term stewardship of federal lands requires management that is sustainable and maintains ecological services such as productivity, biodiversity, and rates of biogeochemical cycling. An important aspect of maintaining biological diversity is conservation of appropriate habitat for rare species. Federal lands along the Fall-Line region of the southeastern United States include military installations and the Department of Energy's Savannah River Site (SRS). These federal lands are managed for a variety of purposes, including military training, remediation of contaminated sites, and forest productivity. Furthermore, forests on these federal lands are also managed to promote open pine woodlands as habitat for the federally endangered red-cockaded woodpecker (RCW) which occurs throughout this region. Such RCW habitat management includes frequent burns to remove hardwood understory species. There are also extensive areas of sandhills along the Fall-Line; these sandy, nutrient-poor habitats support a unique flora and fauna, including a suite of threatened, endangered and sensitive (TES) plant and animal species. Thus, ecological stewardship of these federal lands requires balancing various land-use activities with the conservation of appropriate habitat for TES species. Unfortunately, there is limited information on the population biology and habitat requirements of most of the rare sandhills plants. Specifically, the reproductive biology, seed viability, and germination requirements of most sandhills TES plants are not known. Undergraduates will have the opportunity to work on field projects evaluating the population status and reproduction of selected TES plants growing under differing forest management treatments, as well as on laboratory and greenhouse experiments assessing seed viability, germination requirements, and seedling survival and growth.

Development and use of molecular markers for applied conservation and management (Tracey Tuberville)
Molecular markers provide a powerful tool for developing, implementing and monitoring conservation strategies for rare species. Hypervariable markers, such as microsatellites, allow detection of genetic variation at multiple levels of biological organization, from the identification of individuals, distinction among populations, to resolution among taxa. Microsatellite markers are also valuable in elucidating individual behavioral (e.g., mating behavior, dispersal) and how that behavior can influence population-level processes that are not always easily revealed through field work alone. Undergraduates will have the opportunity to learn basic molecular techniques in the lab, including polymerase chain reaction (PCR), fragment analysis, and genotyping. In addition, each student will develop an independent research project using microsatellite markers in one of the following main areas of research: 1) translocation or reintroduction of rare species to their native habitat, with potential projects focusing on the selection of candidate release animals or on post-release genetic monitoring; 2) genetic monitoring and management of captive species; or 3) effects of landscape context on population processes and metapopulation dynamics.