Category: Research

By Tyjaha Steele

As legacy nuclear sites shift toward long-term stewardship, understanding how contaminants behave in the environment is critical for informed cleanup and monitoring decisions. Radiocesium (¹³⁷Cs), a byproduct of nuclear fission, remains a concern due to its persistence and mobility through food webs. New research from the University of Georgia’s Savannah River Ecology Laboratory (SREL) and the Warnell School of Forestry and Natural Resources enhances our understanding of how freshwater aquatic species absorb and eliminate this contaminant, supporting future risk assessment and remediation strategies.  

Led by former SREL and Warnell graduate student Kathryn Quinlin, the study was conducted at R-Canal, a waterway historically affected by reactor operations at the Savannah River Site (SRS). Researchers focused on four freshwater species: bullfrog tadpoles, red swamp crayfish, eastern mosquitofish, and American white-water lilies.   

“These species were selected for their availability and because they represent distinct ecological roles such as primary producers, benthic omnivores, and pelagic carnivores,” says Quinlin. “Together, they provide a broader picture of how radiocesium moves through freshwater systems.” 

To monitor contaminant uptake, researchers enclosed each species in mesh cages within the contaminated canal. After exposure, they transferred the organisms to a clean reference pond to observe elimination rates. 

Bullfrog tadpoles absorbed radiocesium the fastest, reaching equilibrium in under nine days. Crayfish followed at just over 50 days, and mosquitofish took around 86 days to reach steady levels. Despite the slower uptake, mosquitofish and tadpoles reached similar radiocesium activity concentrations, both higher than those found in crayfish.  

“These findings challenge the idea that sediment-dwellers always accumulate more contamination,” states Xiaoyu Xu, an associate research scientist at SREL and co-author on this study. “Tadpoles likely absorb more radiocesium due to their vascularized skin and higher metabolic rates, while crayfish have hardened exoskeletons and a slower metabolism, which may limit uptake.” 

Once in the clean pond, tadpoles shed half their burden in under eight days, and water lilies cleared ¹³⁷Cs at a similar rate (around 12 days). Crayfish eliminated the contaminant more slowly, with a half-life of 69 days, while mosquitofish took about 43 days.  

Xu notes that, “Slower elimination in crayfish and mosquitofish is likely tied to traits like lower metabolism and less permeable surfaces. Tadpoles, kept in warm indoor tanks, were more active, whereas crayfish were outdoors in cooler weather and unable to molt, a pathway hypothesized to be important for shedding contaminants.” 

Differences in radiocesium storage pools also affect how long species retain radiocesium and influence its persistence in aquatic systems. Tadpoles and water lilies likely store more radiocesium in short-term reservoirs, resulting in rapid cycling, which contrasts with the longer-term reservoirs where crayfish and mosquitofish are thought to be storing this contaminant. 

Radiocesium’s persistence, even at very low concentrations, can quietly influence aquatic communities over time. By capturing these subtle effects, the research contributes to a deeper understanding of radioactive contaminants and their long-term consequences for ecosystem function. 

“This study offers a direct comparison of radiocesium uptake and elimination for a variety of species under natural conditions. By documenting how species absorb and eliminate contaminants over time, the findings inform selection of bioindicator species, improve environmental modeling, and help guide monitoring and remediation at contaminated freshwater sites,” explains Beasley, a professor at SREL and co-author on this study. “This research also adds to the growing body of evidence that radiocesium cycling within aquatic food webs is complex and influenced by a myriad of biotic and abiotic attributes of ecological systems.” 

The full study, Uptake and elimination of ¹³⁷Cs in aquatic biota inhabiting a contaminated effluent canal, was published in the Journal of Environmental Radioactivity. Authors include Kathryn A. Quinlin, Danielle Hill, Xiaoyu Xu, and James C. Beasley. 

By Tyjaha Steele

There’s a reason the phrase “deer caught in headlights” is so well-known. It captures a split-second moment with very real consequences, often at the expense of the driver and the animal themselves. With thousands of injuries and billions of dollars in damages reported each year, researchers are now asking whether changes to vehicle headlights could significantly alter how deer respond, potentially reducing the risk of collisions.

 Carson Pakula, a doctoral graduate research assistant and lead author of the study, conducted 174 trials at the Whitehall Deer Research Facility in Athens, Georgia, through his work with the University of Georgia’s Savannah River Ecology Laboratory and Warnell School of Forestry and Natural Resources. The team worked with 23 captive, wild-type female deer, testing eight lighting combinations using an oncoming electric golf cart outfitted with halogen or LED headlights (set to high or low beam), with or without a rear-facing lightbar. 

“We chose these eight treatments to explore how vehicle lighting might affect deer behavior by testing different headlight types, since halogen and LED give off different colors of light,” explains Pakula. “We also compared low and high beams to see if brightness changes how deer react, and added a rear-facing lightbar to find out if lighting up the front of the vehicle makes it easier for deer to notice.”  

The study focused on short-range encounters, which ranged just 95 meters between the deer and the vehicle, designed to simulate the final seconds before a potential collision. Using infrared cameras, researchers tracked alert behavior, when a deer stopped or reoriented in response to the vehicle, and flight behavior, when it made an apparent attempt to escape. 

Across all trials, deer alerted in 73% of cases and fled in just 52%. Halogen headlights on high beam with the lightbar off produced the most alerts, yet no lighting treatment reliably triggered flight behaviors. 

“Many deer showed no flight behavior and stayed in the vehicle’s path, regardless of lighting treatment. It’s a ‘freezing in the headlights’ response familiar to many drivers,” says DeVault. “Deer reactions seemed driven more by individual personality than lighting. Their dark-adapted vision may not align well with modern headlights.”

This is the first study to test how vehicle lighting affects the behavior of a moving deer during an imminent head-on collision. Previous research has focused on roadside deer or longer-range interactions. These findings establish a baseline for future studies that may explore lighting effects in free-ranging deer or longer-distance approaches, especially as 86% of new vehicles are built with LED systems by default. 

Although LED headlights emit blue wavelengths that correspond to what deer’s eyes are most sensitive to, halogen high beams still prompted the strongest alert responses. It’s unclear whether LED lights overwhelm the deer’s vision, mask movement cues, or simply fail to appear threatening under certain conditions. 

While lighting may influence how deer perceive an oncoming vehicle, it doesn’t appear to change the outcome of a close encounter. Broader mitigation efforts, such as fencing, road design, or population control, remain more consistent and scalable solutions for reducing deer-vehicle collisions. 

The full study, Caught in headlights: Captive white-tailed deer responses to variations in vehicle lighting during imminent collision scenarios, was published in Applied Animal Behaviour Science and was authored by Carson J. Pakula, Gino J. D’Angelo, Adrianna Mowrer, Olin E. Rhodes Jr., and Travis L. DeVault. 

By Tyjaha Steele

Across the United States, there is a battle unfolding between wild pigs and farmers, landowners, and wildlife managers. These fast-breeding animals are an invasive species in North America whose adaptability to different environments has allowed them to thrive in novel areas, while causing extensive ecological and economic damage. Wild pigs in particular harm natural habitats, spread disease, and destroy crops and property as their populations and ranges continue to expand. Scientists are working to evaluate and improve methods for managing wild pig populations to slow their expansion and reduce the costly damage that they cause.  

 Leading this effort is Jim Beasley, a researcher and professor from the University of Georgia’s Savannah River Ecology Laboratory (SREL) and Warnell School of Forestry and Natural Resources. In their most recent study, Jim and members of his lab analyzed data from 867 capture events carried out by 31 professional trappers across four southeastern U.S. states. This research evaluated the effectiveness of the three most common trap designs used today to capture wild pigs, corral, drop, and passive net traps, under varying environmental conditions.  

“The USDA estimates that wild pigs cause $2.5 billion in annual damage and control costs to U.S. agriculture while also significantly impacting native habitats and wildlife across their invasive range,” explains Beasley. “While there are many tools for managing wild pigs, trapping is one of the most widespread methods of wild pig control, especially by agencies and wildlife management professionals.” 

 This research examined how each trap type performed across different landscapes and seasons by reviewing factors like capture efficiency, bait usage, and time to first capture. Previous studies on wild pig trapping have often been limited in scope, location, and scale, so this study was designed to provide a comprehensive evaluation of trapping strategies by incorporating data from multiple ecoregions and a robust multi-year dataset. 

“We believed these to be the most important distinguishing factors when choosing a trap type,” states Chuck Taylor, a former SREL graduate student under Beasley and first author on this study. “By including multiple factors that covered the vast majority of concerns when buying or building a wild pig trap, and monitoring those factors over multiple years, and in multiple states, we were able to thoroughly evaluate each trap type and their strengths and weaknesses.” 

The team found that all of the trap types evaluated in this study were highly effective in capturing entire social groups of wild pigs, achieving at least an 88% success rate in removing all targeted individuals in each capture event. Drop traps had the shortest time to a capture event and performed the best during challenging masting seasons, when natural food resources are abundant, providing wild pigs with natural food sources that make bait less effective.  Corral traps and net traps also performed very well, capturing nearly all targeted wild pigs in 2-3 weeks, on average.  Net traps showed the most consistent results across seasons but required slightly more bait due to their passive nature. However, the few differences found between trap types were deemed to be insignificant, and each trap type was highly effective at capturing wild pigs. 

“One important finding was that all evaluated trap types performed similarly and were highly effective in catching and removing entire social groups of pigs. This is important for developing a successful wild pig management program under various conditions because each of these trap types vary in cost, maneuverability, and effort to monitor and maintain,” says Beasley. “This suggests that managers have numerous options for optimizing trapping programs without sacrificing performance depending on local conditions, resources, and wild pig populations within their management areas.” 

Details of the study can be found in the Wildlife Society Bulletin, under the title “Evaluation of common trap types for capturing wild pigs.” The study was authored by Charles R. Taylor, Lauren Buxton, and James C. Beasley.  

By Tyjaha Steele and Katrina Ford

Researchers at the University of Georgia’s Savannah River Ecology Laboratory studied water movement in wetlands and its role in filtering contaminants in the Tims Branch watershed, a riparian wetland on the Savannah River Site in Aiken, South Carolina.

“We chose this area specifically to understand how water moves. This allows us to predict how wetlands hold onto contaminants,” explains Daniel Kaplan, a senior research scientist at SREL, associate director of the University of Georgia’s Research Institute, and lead investigator of this study.

The research team collected monthly water samples from rainfall, streams, and groundwater at different sites within the watershed. By analyzing stable isotopes of hydrogen (δ²H) and oxygen (δ¹⁸O), they traced how different water sources mixed over time. Additional measurements were collected and helped determine how groundwater chemistry influenced stream water quality.

The study found that groundwater renewed at 2–4% per day, taking about two to four weeks to mix fully. Groundwater contributed up to 4% of stream water in some areas, while stream water comprised nearly 70% of groundwater in others.

These exchanges shifted seasonally, with groundwater flowing into streams more in winter and stream water seeping into the soil in summer, influencing water quality and contaminate movement.

The movement of water within the environment is a key factor in assessing the distribution of various heavy metals and contaminants, including uranium, throughout a riparian wetland. Effective environmental management is crucial to ensuring the health and safety of the Central Savannah River Area.

“For future work, we hope to utilize this hydrological model with other studies to improve contaminant management and reduce risks to both human and environmental health across the CSRA and DOE Complex,” states Kaplan.

The original study titled, “Hydrological controls of a riparian wetland based on stable isotope data and model simulations,” was published in the journal Isotopes in Environmental and Health Studies (IEHS) and was written by Peter H. Santschi, Chen Xu, Peng Lin, Chris M. Yeager, Pieter Hazenberg, and Daniel I. Kaplan. This work was completed in collaboration with researchers from Texas A&M University, Florida International University, and the Argonne National Laboratory, and the University of Georgia’s Savannah River Ecology Laboratory.