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News and events

News & events

Master's students present at research society meeting

March 21, 2016

Master’s students Dana Devore and Spencer Tassone presented the results of their thesis research at the March 11 Atlantic Estuarine Research Society meeting.  Devore has been working on the Mountains to the Sea project, which is a collaboration among VCU’s Center for Environmental Studies at the Rice Rivers Center, Randolph-Macon College, Washington & Lee, and the United States Geological Survey. Tassone has been analyzing the continuous water quality monitoring data from the Rice Rivers Center pier to better understand the oxygen metabolism of the James. 

Below is the abstract from Devore’s research:

The Effects of Tidal Forcing on Nutrient Fluxes in the Tidal, Freshwater James River Estuary, VA

Dana Devore, Virginia Commonwealth University Center for Environmental Studies
Dr. Paul Bukaveckas, Virginia Commonwealth University Center for Environmental Studies and Department of Biology

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, differences in nutrient concentrations between incoming and outgoing tides, and associated nutrient fluxes. 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.  Our results show that differences in nutrient concentrations between incoming and outgoing tides were small throughout the year.  This finding suggests that nutrient fluxes at the tidal fresh-oligohaline boundary are determined by tidal volume, not gradients in concentrations.   We analyzed changes in water quality during seaward and landward tidal excursions 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 among VCU Center for Environmental Studies at the Rice Rivers Center, Randolph-Macon College, Washington & Lee University, and the United States Geological Survey, participating in the “Mountains to the Sea” project.

Below is the abstract from Tassone’s research:

Estuarine metabolism and zooplankton dynamics in the tidal freshwater segment of the James River

Spencer Tassone, Virginia Commonwealth University, Department of Biology
Paul Bukaveckas, Virginia Commonwealth University, Center for Environmental Studies and Department of Biology

Utilizing daily dissolved oxygen data from a fixed station within the tidal freshwater James River Estuary, VA we examined seasonal and interannual trends in primary production, respiration and net ecosystem metabolism (NEM). Results show that this segment of the James River is net autotrophic on an annual time scale with peak NEM occurring during March-November. Annual mean NEM ranged from 0.8-1.2 g O2 m-2 d-1 with previous studies in Chesapeake Bay reporting ranges from -5.6-0.5 g O2 m-2 d-1. Annual mean production rates were within the same range as previous studies of Chesapeake Bay (5.8-7.5 vs. 5.2-8.9 g O2 m-2 d-1) however respiration rates were lower (2.4-3.2 vs. 4.7-12.3 g O2 m-2 d-1). Dominant zooplankton in this segment were the copepod Eurytemora affinis, the cladoceran Bosmina longirostris, and the rotifer Brachionus calyciflorus. Patterns in zooplankton abundance were then, in some cases, related to NEM along with water temperature and water replacement time. These results provide evidence that the tidal freshwater segment of the James River is among the most productive sites within the Chesapeake Bay Estuary and that high rates of metabolism may in turn influence production at higher trophic levels.

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