Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
Browse
3 results
Search Results
Item FACTORS AFFECTING MERCURY CONCENTRATIONS IN 3 SPECIES OF STREAM SALAMANDER IN GARRETT COUNTY, MARYLAND(2018) Kaumeyer, Morgan John; Castro, Mark; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)I sampled 9 streams in Western Maryland during the spring, summer and fall of 2010. 5 species of stream salamander were collected at these streams and analyzed for total mercury; northern dusky salamanders (Desmognathus fuscus), northern two-lined salamanders (Eurycea bislineata), Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus), seal salamanders (Desmognathus monticola), and eastern red spotted newts (Notopthalmus viridescens). The streams were also analyzed for various water chemistry factors; pH, Acid Neutralizing Capacity (ANC), Total Mercury (THg), Methyl Mercury (MeHg), Chloride (Cl-), Nitrate (NO3-), Sulfate (SO42-), Total Suspended Solids (TSS), and Dissolved Organic Carbon (DOC). In all but two streams adult northern two-lined salamanders had significantly higher concentrations of total mercury in their tissues than larval northern two-lined salamanders. Adult northern two lined salamanders also had the highest concentrations of the three species that were statistically analyzed; northern two-lined salamanders, northern dusky salamanders, and Allegheny Mountain dusky salamanders. Stream methyl mercury concentrations and stream DOC were also found to significantly influence salamander tissue total mercury concentrations.Item TEMPORAL AND SPATIAL VARIABILITY OF METHYLMERCURY ACCUMULATION IN SMALL STREAM ECOSYSTEMS(2018) Oster, Jacob Matthew; Heyes, Andrew; Lapham, Laura L; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Maryland has state-wide fish consumption advisories for mercury, and there is a need to explain these trends. I explore two tools for characterizing MeHg conditions in Maryland. The first explores benthic macroinvertebrates as vectors of MeHg from sediments to fish. I examined macroinvertebrate communities over two years from two first-order streams differing in land-use and historical stream water MeHg concentrations. I assessed temporal and spatial variability in invertebrate populations in conjunction with an assessment of the distribution of MeHg in water and sediment. I tested a second tool, an autonomous continuous water sampler that would allow MeHg to be measured without laborious expeditions. I observed differences in concentrations of MeHg across trophic levels between watersheds and identified a candidate organism as a bioindicator of MeHg exposure risk and watershed MeHg condition, as well as a potential sampling mechanism for MeHg in aquatic ecosystems.Item THE IMPORTANCE OF PHYSICAL MIXING AND SEDIMENT CHEMISTRY IN MERCURY AND METHYLMERCURY BIOGEOCHEMICAL CYCLING AND BIOACCUMULATION WITHIN SHALLOW ESTUARIES(2004-11-24) Kim, Eun-Hee; Mason, Robert P; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The objective of this study was to examine, using mesocosm experiments, the long-term effects of sediment resuspension on the fate, transport, and bioaccumulation of Hg and MeHg in shallow ecosystems. A bioenergetic-based model including sediment resuspension was developed to assess MeHg bioaccumulation into benthic and pelagic organisms under the experimental conditions. In addition, this study examined the spatial distribution of Hg and MeHg in the sediments from the Chesapeake Bay and used the model developed to examine the important factors in Hg and MeHg distribution and bioaccumulation in the Bay. Using STORM (high bottom Shear realistic water column Turbulence Resuspension Mesocosm) mesocosms, two 4-week experiments were conducted in July and October of 2001 (experiments 1 and 2) with Baltimore Harbor sediments. Tidal resuspension (4 h-on and 2 h-off cycles) was simulated with three replicates of the resuspension (R) and no-resuspension (NR) tanks. In experiment 1, there was no benthic macrofauna. In experiment 2, hard clams, Mercenaria mercenaria, were added to the sediment in the mesocosm tanks. Water, sediment, and biota (zooplankton and clams) samples were collected and analyzed for Hg and MeHg. Using Hg stable isotopes, Hg methylation and MeHg demethylation rates were determined. The STORM experiments showed that during sediment resuspension there was a significantly higher suspended particulate total Hg (THg) (on a mass basis), while particulate MeHg was significantly lower, as sediment particles with relatively poor MeHg were dominant in the water column. The results suggested that equilibrium partitioning between the dissolved and particulate phases for THg and MeHg was not occurring. It appeared that resuspension enhanced Hg methylation in the top sediment layer, especially in summer. Concentrations of THg and MeHg in biota showed that resuspension had a complex effect of system productivity and bioaccumulation. It appeared that organic matter content played an important role in the distribution of THg and MeHg in sediments and bioaccumulation into benthic and pelagic organisms. The modeling studies demonstrated that sediment resuspension played a role in transporting the enhanced MeHg to the water column and ultimately in increasing the MeHg burden into biota.