Aquatic environments require nutrients such as phosphorus and nitrogen to function properly and form the base of complex food webs. However, excess inputs of these nutrients through anthropogenic pollution commonly results in algal blooms, hypoxia, and dead zones. In this study, surface water samples were taken from five sites located around the city of Fredericksburg (City Dock, Old Mill, Ficklen Island, Motts Run Reservoir, and Little Falls). Samples were collected weekly between February 17th – March 24h in 1000mL bottles and analyzed for the presence and concentrations of total phosphorus, nitrate, nitrite, copper, and chlorine using colorimetric assays. During the six weeks of sampling no concentrations of nitrite, copper, or chlorine were detected at any location. Nitrate levels fluctuated at each site with levels ranging from 1.0mg/L to 5.0mg/L. Phosphate was observed to be a cause for concern as concentrations were consistently found at 0.4mg/L to 1.0mg/L in all streams. While the sources of these excess nutrients are unclear, possibilities include excess wastewater treatment facility effluent discharge during heavy precipitation events, construction over waterways that loosens sediment and increases runoff events, and proximity to more heavily populated areas. These results suggest the need for a long-term study to assess what influence seasonal temperatures and precipitation have on nutrient pollution and how these excess nutrient levels impact aquatic organisms in these locations.
The Chesapeake Bay, one of the largest estuary systems on the east coast of the United States, has numerous coal-burning power stations located along its waterways. Coal ash, or fly ash, is a form of industrial waste that is mainly produced by coal-burning power stations and is known to be enriched with trace metals that are at high risk for leaching into waterways, resulting in the presence of these contaminants within aquatic environments. Few studies have examined the distribution of trace metals in the James River watershed, a tributary of the Chesapeake Bay, and the implication of a coal-burning power station located in its upper reaches. Thus, the goal of this study was to evaluate the spatial and temporal distribution of trace metals in both water and sediments within the James River in the vicinity of the Chesterfield power station (Richmond, VA). Water and sediment samples (grab and core) were collected upstream, midstream, and downstream from the Chesterfield power station. The samples were analyzed using ICP-OES (a spectrometer used for analyzing environmental samples for trace metals) for the concentration of twelve trace metals including Al, As, Cd, Ca, Cr, Cu, Fe, Pb, Mg, Mn, Se, and Zn. The preliminary results of water and grab samples show high concentrations of trace metals downstream as well as behind the power station near Dutch Gap Conservation Area. Cadmium concentrations in the water (0.005-0.017 ppm) exceeded the EPA’s MCL’s for drinking water. Complete water and sediment cores samples analyses will provide a clearer picture of trace metals spatial as well as temporal variability and loading at the study site. This study will provide vital information regarding the potential impacts of coal-burning repositories on the presence and mobilization of trace contaminants within aquatic ecosystems and their future impacts on terrestrial and aquatic organisms.
Excess sediment runoff, as a result of anthropogenic activity, is one of the major contributors to the pollution of the Chesapeake Bay, Rappahannock River, and Hazel Run. To reduce the sediment entering different watersheds, different best management practices (BMPs) have been implemented. Agencies like the Chesapeake Bay Program and United States Geological Survey use models to predict how effective different BMPs are. Traditional models used by the USGS like ESTIMATOR use streamflow-based regression. However, regression relations fail to account for the variableness of sediment transfer during storm events (Jastram et al., 2009). Leigh et al. (2019) concluded that turbidity-based models which include temporal autocorrelation and heteroscedasticity were the most accurate and precise in predicting sediment and nutrient concentrations from high-frequency water-quality data, which we will be following. The Rappahannock River’s possession of only one monitoring station and how both it and Hazel Run have degraded water quality make it appropriate to conduct a pilot study. We will be utilizing in-situ sensors, which collect and store data, compared to manual samples. Using in-situ measurements allows data to be frequently collected, even during high-transport events like storms and floods, giving better records of the water quality. The goal of this capstone is to detail a pilot study project and complete a grant proposal to apply for the Jeffress Trust Awards Program in Interdisciplinary Research grant. The project in question will be a pilot study utilizing a proxy-model methodology using the deployment of many in-situ sensors to monitor and predict sediment and nutrient load in Hazel Run, a tributary of the Rappahannock River.
Models used in climate predictions today are dependent on paleoclimate proxies, or recorders of past climate conditions. Eastern oyster shells contain oxygen isotopes that have the potential to be valuable paleoclimate proxies of seasonal changes in the Chesapeake Bay. Numerous oyster shells were found within infilled slave quarters dating to the 1700s at Stratford Hall Plantation. The fact that these slave quarters were backfilled when slavery was still prevalent in nearby regions is surprising. It is hypothesized that localized climate perturbations may have played a role in the abandonment of these slave quarters, as the 1700s took place during the Little Ice Age (LIA), a time when Europe and North America endured cold winters and only mild summers. Oxygen isotopes within the Stratford Hall fossil oyster shells were compared with oyster shells collected in 2019 to test their suitability as paleoclimate proxies and better understand the decline in slave quarters at Stratford Hall. Although the oxygen isotopes were lighter in the fossil oysters, further analysis must be conducted to better understand how differences in salinity between the collection sites of the fossil and modern oysters are affecting the results.
In the US, nearly 24.5 million tons of road salt was distributed across public roadways in 2014. Of the various substances used in these formulations, NaCl accounted for 90% of these treatments. After application, up to 55% of these salts have been shown to enter local waterways via runoff and have been shown to cause many negative effects on the environment including inhibition of algal growth, reductions in activated sludge respiration rates, and mortality in all life stages of some amphibians. However, the effects of NaCl on aquatic invertebrates has been poorly explored. Thus, the goals of this study were to determine 1) the effects of NaCl on Physa acuta egg cluster viability, 2) methods to assess the baseline locomotion behavior of Physa acuta (average mobile speed, average speed, total distance traveled, acceleration, number of frozen events and time spent frozen), and 3) assess the effect of NaCl on these endpoints. Sixteen newly laid egg clusters were collected and exposed to 0, 100, 500, or 1000 mg/L NaCl and viability determined after 15 days of exposure. The locomotor behavior of seven unexposed adult snails were recorded and analyzed using ToxTrac (v. 2.83) to determine the basal movement patterns of this species. To assess the impacts of NaCl exposure on adult mobility, adult Physa acuta (n=3) were exposed to the above treatments for 7 days and locomotor behaviors quantified on days 3 and 7. While this study is still ongoing, it is expected that increased NaCl concentrations will cause a decrease in egg cluster viability and dose dependent impacts on mobility. These findings will help to elucidate the impacts of a commonly used deicing substance on a common invertebrate species.