Master of Science

Tidal freshwater reaches of estuaries may play an important role in mitigating nutrient fluxes from watersheds to the coastal zone due to their location at the interface between riverine and estuarine systems. We developed annual N and P budgets for the tidal, freshwater James River over 4 calendar years (2007-2010) taking into account riverine inputs at the Fall Line, local points sources (including CSO events), ungagued inputs, riverine outputs, and tidal exchange. The tidal freshwater James River experiences high areal loading rates of TN (383 mg/m2/d) and TP (70 mg/m2/d) due to the combined effects of large watershed area and local point source discharges. On an annual basis, riverine sources dominated TN and TP inputs (59% and 84%, respectively), whereas during low discharge summer months (May-Oct) point sources were more important. Proportional retention of TP inputs (59±7%) was greater than TN retention (27±4%) with annual absolute retention being 1,800±350 kg TP/d, and 5,900±2,700 kg TN/d. Proportional retention of TN and dissolved inorganic fractions of N and P was highest during the low discharge summer months due to reduced loading rates and increased residence times and biotic activity. TP retention was greatest during high discharge winter months (Nov-Apr) when loading rates were highest. High retention during this period of low biotic activity suggests that trapping of riverine derived particulate-bound P via sedimentation was an important mechanism of P retention. Understanding this seasonal variation in nutrient inputs and retention can help to inform management decisions regarding reducing nutrient inputs to the Chesapeake Bay and improving local water quality.

Substrate composition plays a critical role in determining the spawning success of Atlantic sturgeon. A benthic analysis of the tidal freshwater portion of the James River, Virginia, was performed to locate and protect remaining sturgeon spawning habitat within the James River system. I modeled structural habitat, substrate distribution, and river bathymetry from Richmond, Virginia to the Appomattox River confluence. A classification model was developed to describe the dominant substrate type (mud/silt, sand, gravel, bedrock) using side scan sonar data collected from August 2011-Febuary 2012. River depth, bottom imagery, substrate density (hardness), and ground truth substrate samples were interpolated into a GIS model to spatially describe and quantify essential sturgeon spawning habitat. Finally, I attempted a change analysis of historical substrate composition throughout the study area. Gravel, cobble, and bedrock, swept clean of silt or mud, was deemed a hard bottom substrate suitable for spawning success. Mud and silt dominated the vast majority of river substrate, representing approximately 67 % of river bottom surveyed. Sand comprised 17 % of river bottom, gravel represented 11 % and bedrock represented 5 %. Sixteen percent of the reach was hard bottom habitat consisting of a bed substrate dominated by gravel, cobble, or bedrock. Regions of hard bottom habitat found at depths ≥ 10 m were selected to model essential sturgeon spawning habitat. The river bottom within the reach contained approximately 8 % essential spawning habitat. The majority of hard bottom habitat was located in major bends of the river where scouring occurs. The historical comparison of available hard bottom habitat identified a 28 % loss of hard bottom since 1853. The greatest losses in hard bottom occurred in the upper portions of the study area (55 % loss in hard bottom habitat). Hard bottom habitat lost in the lower portion of the study area was partially offset by the creation of new hard bottom habitat within the narrow channel cuts bypassing Jones Neck and Turkey Island. Historical comparison of the Hatcher Island, Turkey Island, and Jones Neck oxbows identified heavy siltation and reduced depths likely due to anthropogenic alterations in the meander bends linked to shipping channel creation. The altered flow regime has resulted in increased sedimentation and has drastically reduced available hard bottom substrate within the natural channel of Jones Neck and Turkey Island. The increased availability of hard bottom habitat within the confines of the shipping channel has indicated that the alteration of the river bottom, through flow modification and dredging practices, may have replaced a portion of lost historical spawning habitat. Fisheries managers could use the data from the substrate analysis to better understand and protect essential areas necessary for Atlantic sturgeon spawning success.

Tidal freshwater wetlands (TFW) are at significant risk of loss or alteration due to global climate change, and saltwater intrusion from sea level rise is of particular concern for these habitats due to their proximity to coastal areas. A space-for-time model was used to investigate the effects of saltwater intrusion on soil methanogen communities along naturally occurring salinity gradients on the Waccamaw, James, and Hudson Rivers. Amplification of the methyl coenzyme-M reductase (mcrA) functional gene was used in qPCR, reverse transcription qPCR, and T-RFLP to measure the abundance, activity, and community composition of soil methanogens. Both the abundance and activity of methanogens decreased with increasing salinity, and the both total and active methanogen community composition shifted in response to changes in salinity. This research demonstrates that saltwater intrusion will alter carbon cycling in TFWs, potentially altering their ability to sequester carbon and keep pace with rising sea level.

Thesis (M.S.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 81-83). Also available online.

This thesis details the literary and visual influences in my work, the definition of American Gothic, and its connection it to my work. Literary sources such as Edgar Allan Poe and Fanny Kemble help spark a vision of the landscape. Visual influences include Japanese woodblock prints, scenic wallpapers, vintage postcards and Victorian mourning pictures. My regional explorations span the James River, Tidewater swamps and architecture within the city of Richmond.My work depicts local history and ecology inspired by Richmond and the surrounding region. Subtle Gothic elements add anxiety to the otherwise pastoral scenes. Gothic foreboding in the work questions our ecological future and the permanence of our human presence in the landscape.