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Title The Effects of Tidal Forcing on Nutrient Fluxes in the Tidal, Freshwater James River Estuary, VA
Publication Date
Degree MS
Discipline/Department Environmental Studies
Degree Level thesis
University/Publisher Virginia Commonwealth University
Abstract A 12-month study (January to December 2015) focused on the effects of tidal forcing on nutrient fluxes in the tidal, freshwater segment of the James River Estuary (JRE). Discrete sampling of nutrient chemistry and continuous monitoring of tidal discharge were used to determine the volume and timing of the tides, and differences in nutrient concentrations between incoming and outgoing tides. The goal of this study was to improve understanding of tidal influence on nutrient fluxes and their role in nutrient transport to the lower estuary. Results suggested that differences in nutrient concentrations between incoming and outgoing tides were small throughout the year. This finding suggests that nutrient fluxes at the study site, near the tidal fresh-oligohaline boundary of the James, are largely determined by tidal volume owing to weak concentrations gradients. Changes in water quality during seaward and landward tidal excursions into deeper versus shallower segments were analyzed to infer biogeochemical processes. Differences in oxygen production and nitrate utilization suggest greater autotrophy during landward excursions, consistent with more favorable light conditions. This work was conducted as a collaborative effort between Virginia Commonwealth University, the USGS, Randolph-Macon College, and Washington and Lee University participating in the “Mountains to the Sea” project.
Subjects/Keywords Tidal forcing; nutrient fluxes; freshwater estuary; James River; Life Sciences; Terrestrial and Aquatic Ecology
Contributors Paul Bukaveckas
Country of Publication us
Record ID oai:scholarscompass.vcu.edu:etd-5622
Repository vcu
Date Retrieved
Date Indexed 2020-07-20
Created Date 2016-01-01 08:00:00

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…comparison of the daily mean values of each water quality parameter for incoming and outgoing tides was used to assess the effects of tidal forcing on water quality conditions in the tidal fresh segment (Figure 7). Temperature differences were…

…discharge and tidal exchange (Ramesh et al. 2009, Smith 2003, Carstensen et al. 2011). Nutrient concentrations in estuaries are determined by both point and nonpoint source inputs (Figure 1). Point sources inputs are relatively constant…

…rates of nutrient assimilation (Bukaveckas et al. 2011, Fichez et al. 1992). These processes may be particularly important in tidal, freshwater estuaries, which are known to exhibit high rates of biological production and biogeochemical cycling…

…x28;Bukaveckas et al. 2011, Damme et al. 2005). Despite this, tidal freshwaters are comparatively understudied relative to the lower, saline segments of the estuary. Biogeochemical processes that occur in estuaries allow them to mediate a portion…

…mechanisms for nutrients include denitrification and tidal exchange (Boynton et al. 1995). The ability of tides to increase and decrease water level and allow for the exchange of water and materials between the upper and lower segments of the…

…causing the intrusion of water and constituents from the lower estuary. In this way, tidal exchange influences the nutrient concentration, salinity, and suspended particulate matter of an estuary (Montani et al. 1998). Intrusion of downstream…

…developed a monthly mass balance for N and P using data on riverine and point source inputs for the period 2007-2010 (Bukaveckas and Isenberg 2013). This study estimated tidal fluxes using a chloride mass balance approach (Bukaveckas and…

…to calculate the 9 month-to-month change in mass of chloride. As Cl inputs were also known, the effect of tidal exchange (i.e., as a net gain or loss of Cl) could be inferred by difference. Net tidal exchange was…