2019 Annual Meeting Presentation Awards Name: Meredith E. Seeley University: Virginia Institute of Marine Science, William & Mary Department: Aquatic Health Sciences Type of Degree: PhD Award: 1 st Place Platform ($100) Title: Effect of different microplastics on sediment microbial communities and nitrogen cycling Meredith is a second year Ph.D. student at the Virginia Institute of Marine Science. Her research focuses on understanding the effects of microplastics on marine biota. In particular, Meredith is interested in the complexities of plastic shape and chemistry, and which aspects drive toxicity. Prior to this, Meredith completed her Master’s of Science in Marine Science at the University of Texas Marine Science Institute. Her research focused on the weathering of oil following the Deepwater Horizon oil spill, and advancing techniques used to analyze complex petroleum hydrocarbons. Abstract: Polymer type has been shown to influence the composition of floating marine debris biofilm communities. However, no previous studies have investigated effects of plastics on sediment microbial communities and their biochemical activities, even though microplastics have been found across open ocean, coastal and inland sediments. Here, we present the results of a marsh sediment microcosm experiment established with microplastics (53-300 um) of different petroleum-based polymers (polyethylene [PE], polyvinyl chloride [PVC] and polyurethane foam [PUF]) and one biopolymer, (polylactic acid [PLA]). We characterized the sediment bacterial compositions and functional gene abundances after 7 and 16 days using 16S MiSeq analysis, and measured denitrification rates and nutrient fluxes. We found that bacterial community compositions were different between the biopolymer, petroleum-based polymers and plastic-free sediment, with PVC being the most distinctly different community. Nitrification gene abundances and nutrient fluxes revealed that nitrification was highest in the biopolymer (PLA), followed by PUF and PE, but almost completely inhibited in PVC. Correspondingly, denitrification gene abundances and denitrification rates (calculated via sediment slurry incubation using 15NO3- tracer) revealed an inhibition of denitrification in the PVC, and the highest denitrification activity in PLA treatments. Interestingly, denitrification and nitrification were higher in PE, PUF and PLA treatments than the control (no microplastic), suggesting some plastics may enhance sedimentary nitrogen cycling processes. Overall, this study highlights the distinct effect of different plastics on structure and function of sediment communities, and calls for expanded research in this area.
Name: Ross Cooper University: Virginia Tech Department: Forest Resources and Environmental Conservation Type of Degree: B.S. Award: 2 nd Place Platform ($75) Title: Spatial and Temporal Changes in Water Quality in the Shenandoah River Watershed Ross is an undergraduate student at Virginia Tech graduating in the spring of 2020. Ross majors in Water: Resources, Policy, and Management and minors in Environmental Econo mics. Ross’ research focuses on the effects of land use and wastewater treatment on water quality, and their regulatory implications. Upon graduation from Virginia Tech, Ross intends to attend law school to specialize in environmental law. With Ross’ schol arship, he intends to bridge the gap between science, policy, and law. When Ross is not studying, he enjoys cooking vegan food and gardening. Abstract: The Shenandoah River watershed contains a high density of animal agricultural operations that produce large amounts of nutrient- and bacteria-containing waste. The Commonwealth of Virginia has implemented bacteria and sediment Total Maximum Daily Loads (TMDLs) for many Shenandoah River tributaries. Despite their implementation, there is a lack of data to demonstrate water quality improvement. This study analyzed long-term trends in nutrient concentrations as well as the correlation between these trends and pollution mitigation plans, land use changes, and agricultural best management practices (BMPs). For 27 sites, publicly available citizen-collected data from Friends of the Shenandoah River (FOSR) were analyzed for temporal trends (2002-2017) in nitrate, ammonia, orthophosphate, turbidity and discharge. Slopes from regression analyses were ranked as positive, negative, or no change. These rankings were used in logistic regression to describe the relationship between water quality characteristics, applied BMPs, and TMDL status. Generally, there was no relationship between implemented BMPs in the watershed or TMDL status and analyte trends. Nitrate concentrations increased over time in the majority of tributaries. The probability of increasing nitrate concentrations in winter/spring was related to the amount of agricultural land in tributary watersheds. The probability of increasing nitrate concentrations in summer/fall was related to the BMP practice of linear fence installation. Sites downstream of wastewater treatment plants showed decreasing orthophosphate and stable nitrate trends, suggesting regulations have been more effective in addressing point versus nonpoint source pollution. Results indicate a general disconnect between water quality, TMDL status, and BMP implementation, indicating a need for further assessment of applied practices and possible reevaluation of approaches to nonpoint source pollution mitigation.
Name: Mandar Bokare University: University of Maryland Baltimore College Department: Chemical, Biochemical and Environmental Engineering Type of Degree: Ph.D. Award: 3 rd Place Platform ($50) Title: Ongoing inputs of PCBs to the Anacostia River from its tributaries during storm and base flow conditions Mandar is a 3 rd year PhD student in the Environmental Engineering program at University of Maryland Baltimore County (UMBC). He is currently working in Dr. Upal Ghosh’s research group at UMBC. His research focuses on using passive sampling techniques to understand links between the fate-transport and bioaccumulation of contaminants such as PCBs, PAHs and OCPs in the environment, especially in urban watersheds. Abstract: Polychlorinated biphenyls (PCBs) are major contaminants of concern in the Anacostia River. Elevated PCB levels in fish tissue have led to consumption advisories in the District of Columbia. Uptake of PCBs in aquatic organisms is governed by their dissolved concentration in water. In this study, polyethylene (PE) passive samplers were used to measure dissolved PCB concentration in Anacostia River and its tributaries. Passive sampler measurements, representing base flow conditions, were integrated with PCB concentrations in storm-flow suspended solids, measured by United States Geological Survey, to delineate PCB inputs from tributaries at storm and base flow conditions. For March – July 2017 sampling period, base-flow PCB concentrations ranged from 0.01 – 6.5 ng/L across the tributaries, while average concentration in the river was 1.6 ng/L. Dissolved PCB concentration in Lower Beaverdam Creek (LBC) was 3.4 times the concentration in the Anacostia River. At other tributaries, concentrations were lower than those in the river. Dissolved PCB concentrations in tributaries at storm flow conditions were up to 38 times lower than their respective concentrations at base-flow conditions, indicating that water quality impacts from suspended- sediment bound PCBs are lower than those from dissolved PCBs at base-flow. Total PCB loads, including dissolved- and particulate organic carbon-associated loads, were estimated at 580 g/year. Overall, 50% of dissolved loads are attributed to storm-flow conditions with 95% coming from LBC. LBC also had the most negative impact on water quality with higher chemical activity of dissolved PCBs at both base and storm-flow conditions as compared to PCBs in the Anacostia River. LBC also contributed 83% of the total dissolved load (storm + baseflow). Although storms delivered 98% of total sediment load delivered to the Anacostia River, these sediments were relatively cleaner than the surface sediments in Anacostia River and help in the natural attenuation of PCBs. These results highlight the importance of tracking dissolved pollutants in aquatic systems and the need to complement existing approaches for estimating pollutant loadings with better understanding of chemical activity of pollutants obtained through passive sampling techniques
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