The Influence of Polyethylene Nanoplastics on The Toxicity of Methoxychlor on D. magna

by Thanh-Binh Duong

Faculty Mentor: Dr. Tyler Frankel

Nanoplastics (NPs), defined as plastic particles < 0.1 mm, have become an emerging concern in aquatic environments due to their multiple pathways of entry into rivers and streams. NPs may originate from the manufactured beads for personal care products as well as the from the fragmentation of larger plastic items. Due to their small size they are easily ingested by aquatic organisms, resulting in detrimental health effects such as digestive tract obstructions, feeding debilitation, and energy depletion. Due to their physiochemical attributes, NPs have also been shown to sorb and mobilize organic pollutants such as pesticides, suggesting that interactions between these two types of pollutants may result in an altered biological response compared to the effects of each individual contaminant. This study assessed the potential synergistic or antagonistic effects of polyethylene nanoparticles and the organochlorine pesticide methoxychlor on the viability and mobility of Daphnia magna. Adult D. magna were exposed to either 1) virgin 10-20µm polyethylene pellets, 2) methoxychlor, or 3) various combinations of the same pellet and methoxychlor concentrations for 48 hours or 7 days using a static exposure method. Mortality and paralysis were assessed per 24 hours of exposure. Mobility was assessed after 24 hours of exposure. To assess mobility, individuals were recorded in a light-controlled behavioral chamber for 3 minutes. Footage was analyzed using ToxTrac to quantify mobile speed, acceleration, and distance traveled. While this project is currently ongoing, we expect to find a significant difference in mobility parameters and mortality rates when exposed to the combination of polyethylene pellets and methoxychlor compared to the effects from each contaminant alone. Thus far, few studies have examined the ability of NPs to influence the toxicity of organochlorine pesticides in aquatic invertebrates. This study will help explicate the impacts of plastic pollution on aquatic biota in freshwater systems.

The impacts of pH on trace contaminant leaching and toxicity of coal ash in Planorbella duryi

by Catherine Crowell

Faculty mentor: Dr. Tyler Frankel

Coal fly ash is a major industrial waste that is primarily produced by coal-burning power plants. Ash contains multiple trace contaminants that have the potential to leach into waterways after rain events, causing undesirable effects on aquatic species in these ecosystems. Few laboratory studies have examined the relationship between acidified rainfall and the release of trace metals from coal ash and the impacts of such rainfall on the toxicity of coal ash leachates on aquatic invertebrates. Thus, the goals of this study were to 1) evaluate the effect of varying pH’s on the leaching of trace contaminants from coal ash and 2) examine the impacts of these leachates on the viability, development, and hatch rate of embryonic Planorbella duryi, a freshwater snail species found in intermittent streams throughout North America. Briefly, 100g of coal fly ash obtained from a local coal ash repository was added to individual glass vessels containing 1L of synthetic water adjusted to pH’s of 4.5 to 7.5. After 48 hours, all leachates were vacuum filtered and an aliquot analyzed for aluminum, arsenic, calcium, cadmium, chromium, cobalt, iron, mercury, magnesium, manganese, lead, selenium, and zinc using ICP-OES. Embryonic P. duryi clusters (<2hrs old) were then exposed to each leachate for 10 days using a 48hr static-replacement assay, and the number of viable individuals and hatchlings in each cluster assessed daily. To examine the impacts on growth, photographs of each embryo were obtained every 24 hours. While this project is currently ongoing, we expect to find increases in aqueous trace contaminant concentrations as a result of decreased pH in leachates as well as decreased viability, growth, and hatching success. This study will provide important information regarding the potential impacts of acidified rainfall on the mobilization of trace contaminants and toxicity of coal ash leachates on aquatic invertebrates.

The Presence, Distribution, and Concentration of Microplastics In the Lower Basin of the Chesapeake Bay, USA Near Wastewater Treatment Plants

by Thanh-Binh Duong

Faculty Mentor: Dr. Ben Kisila

The Chesapeake Bay is a large estuary located along the east coast of the United States, with numerous wastewater treatment plants (WWTP) located throughout its basin. This area supports a vast diversity of aquatic biota and provides for numerous communities throughout the eastern United States. While effluent from WWTPs has been identified as a major contributor to microplastic pollution, little research has been conducted to examine microplastic contamination in the Chesapeake Bay watershed areas surrounding these effluent streams. Microplastics are unique in that their size (<5mm) enables ease of ingestion by aquatic organisms, causing adverse health effects such as energy depletion and digestive tract obstructions. MPs may also biomagnify throughout trophic levels, ultimately posing a threat to human health due to unintended consumption. In this study, the presence of microplastics in major rivers in the lower basin of the Chesapeake Bay, USA was examined. Water samples and sediment samples were collected in the Potomac and Rappahannock river upstream, midstream, and downstream of WWTP outfall sites via dip sampling and grab sampling, respectively. Sediment samples were treated with a wet peroxide oxidation using Fenton’s reagent to digest natural organic matter and sodium chloride to separate MPs from the sample. Surface water samples were filtered by vacuum filtration to separate suspended particles from water. Presence, type, and quantity of MPs were assessed using light microscopy. While this project is currently ongoing, we expect to find that MPs are more abundant in samples collected at WWTP outfall locations rather than locations upstream or downstream from those sites. The results of this study will provide novel information regarding the presence, distribution, and concentrations of MPs in water and sediment samples from several areas of the Chesapeake Bay watershed due to inputs from WWTP effluent.

Evaluation of Metal Contamination and Soil Properties at Former Mine Sites in Poland

by Kaitlyn McClung and Emily Brooks

Faculty mentor: Dr. Melanie Szulczewski

Surface mining dramatically affects the environment, both where the resource extraction takes place and in the areas where mining wastes and overburden are deposited. Poland is Europe’s top coal producing country and is also home to many mines for pyrite, sand, and other mineral resources. We studied soil samples from three former mining areas in Poland: the Bełchatów and Smolnica coal mines, and the Piaseczno sulfur mine. Various substrates, amendments, and trees had been used for remediation, with activities taking place up to 36 years previously. The success of reforestation and soil development varied greatly, especially in pH, organic matter, and metal concentrations.

Sublethal Effects of Sulfoxaflor Pesticide on Physiology and Behavior of Daphnia magna

by Mary Hoffman

Faculty mentor: Dr. Tyler Frankel

Insect pests are a major concern for large-scale agriculture as a result of increasing insect resistance to pesticides, driving a need for the development of new pesticides. Sulfoxaflor, a sulfoximine pesticide recently approved for use by the USEPA, was developed in order to replace neonicotinoid use and has shown to have high efficacy in the field. It is used in rotation with other pesticides, with environmental introduction caused primarily by wet spray application or agricultural runoff. In insects, sulfoxaflor binds to nicotinic acetylcholine receptors, triggering over-activation that leads to paralysis and death. Preliminary exposure studies have shown neonatal effects and development of liver tumors in rats and mice, and moderate oral toxicity in bobwhite quails and fathead minnows. Little research into the effects of the chemical on aquatic non-target invertebrates has been conducted; as such, this research aims to identify potential physiological and behavioral impacts of sulfoxaflor on adult Daphnia magna at concentrations of 0, 0.1, 1, 10, 100, and 1000 µg/L. Impacts on mobility were determined using top-down recordings and behavioral analysis software ToxTrac (v2.84). Heart rate was analyzed through analysis of minute-long heart recordings to quantify beats per minute. While this research is currently ongoing, it is expected that these treatment levels are sub-lethal at 24 hours, and that exposure to sulfoxaflor at higher concentrations will inhibit heart rate and mobility in adult Daphnia magna. The research aims to help elucidate the potential sub-lethal impacts of sulfoxaflor on non-target aquatic invertebrates.

Exposure effects of thiamethoxam on the viability, growth, and behavior of Physa acuta

by Spencer Saunders

Faculty mentor: Dr. Tyler Frankel

Thiamethoxam is a neonicotinoid insecticide that targets the nicotinic acetylcholine receptors of target organisms. It is used on a wide variety of crops and can be applied in multiple methods including seed coatings, broadcast sprays, or foliar sprays. As thiamethoxam is highly soluble, it easily enters aquatic environments and surface water through run-off events from agricultural fields. Detected environmental concentrations have ranged from the low ng/L range up to 225 ug/L. While the effects of thiamethoxam exposure has been well studied in aquatic vertebrates, few studies have examined their impacts on freshwater invertebrates. As such, this study assessed the impacts of thiamethoxam exposure on the viability, behavior, and shell growth of juvenile freshwater bladder snails (Physa acuta). Adult P. acuta specimens were collected from local waterways in Fredericksburg, VA and bred under laboratory conditions for several generations. Laboratory hatched one-week old juveniles were then exposed to various concentrations of thiamethoxam (0 (EtOH control), 1.56, 3.13, 6.25, 12.5, or 25 ug/L) for two weeks using a static replacement exposure method (100% change every four days). Mortality was assessed every 24 hours, while shell growth and behavior were assessed on day 7 and day 14. Photos of each snail were obtained after one and two weeks and growth was measured using ImageJ (v1.8.0). Behavior was assessed using ToxTrac (v2.83) including average speed, average velocity, total distance traveled, and time spent stationary. While this experiment is still ongoing, we expect to see higher mortality rates and decreased growth concurrent with higher concentrations of thiamethoxam. We also expect to see increases in average speed, average velocity, and total distance traveled with increased exposure concentrations. Our findings will help expand our knowledge on how thiamethoxam impacts multiple physiological endpoints of a novel freshwater invertebrate species.

Oxygen isotope variability in Crassostrea Virginica shell from the Chesapeake Bay: applications to regional paleoclimate

by Cheyenne Palmo

Faculty mentor: Dr. Pamel Grothe

Future climate predictions in the Chesapeake Bay region suggest unprecedented warming (Cronin et al., 2003) and more intense periods of rainfall (Najjar et al., 2010). In order to quantify present and future changes in climate variability, we need a long baseline of natural climate variability that extends far beyond the instrumental record. Paleoclimate records can be used to help quantify anthropogenic climate change from natural climate variability. However, reconstructing regional climate in an estuary system is challenging, resulting in a lack of pre-instrumental era climate records for the Chesapeake Bay. The Common Eastern Oyster, Crassostrea Virginica, is a promising natural archive to reconstruct natural, or pre-industrial, climate in the Chesapeake Bay region. Stable oxygen isotopes (δ18Oshell) recorded in their calcium carbonate shell are indicators of both changes in temperature and the δ18O of the water (δ18Osw), which is typically a function of salinity. In this study, the δ18Osw and δ18Oshell values were analyzed to understand how the variability in the δ18O of Crassostrea Virginica calcium carbonate shell reflects changes in sea surface temperature and salinity in the Chesapeake Bay in order to validate it as a paleoclimate archive. The oysters were sampled along their banded growth structure, providing yearly resolution for isotopic analysis. We predict that the δ18O of the oyster shell will reflect the same δ18O trends as the water, meaning the shells will precipitate at isotopic equilibrium. Additionally, we predict that salinity, dependent on temperature and precipitation, is the primary driver for changes in δ18O of the shell, whereas increased δ18Oshell values reflect higher salinity values. This work will provide the foundation for understanding the controls between estuarine water and shell geochemistry, with the potential to apply this relationship to regional paleohydrology and paleoclimate reconstruction using fossil Crassostrea Virginica shells.