DIC and CO2 analysis as a means of quantifying community metabolism in the Delaware Bay Estuary
Date
2011
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Publisher
University of Delaware
Abstract
Carbonate system parameters can be used to measure community metabolism in aquatic systems. Delaware Bay provides an area to study biological processes in a system subjected to tide and flow driven changes in salinity and nutrient concentrations. Through a combination of light incubations and discrete measurements, community metabolism in the Delaware Estuary was examined. Dissolved inorganic carbon (DIC) analysis of both discrete and incubated samples allowed for a detailed analysis of carbon system dynamics. By performing bay transects throughout the year, this study developed an understanding of DIC dynamics in the Delaware Estuary over a spatial and temporal scale. Applying DIC flux measurements to depth-integrated areal estimates allowed for quantification of uptake and production of carbon. With DIC analysis we were able to simultaneously measure both primary production and respiration within a sample, allowing net-primary production to be determined As had been expected, the processes of primary production and respiration dominate metabolic processes in the study site. The production patterns observed in this study were compared to historical patterns of primary production from Sharp lab studies using the radioactive tracer 14C during the 30 years predating this study. This has shown that in general, the DIC method gives an accurate representation of primary production on both a spatial and temporal scale. While this study has shown the utility of the DIC method, future areas of research remain. The DIC method gives production values higher than those measured using isotopic methods. This study aimed to account for this by measuring dissolved organic carbon (DOC) excretion, nitrification and CO2 loss from samples. None of these processes alone proved satisfactory in explaining the production discrepancy between the DIC and 14C method. However, inevitable CO2 loss from samples and DOC excretion leading to bacterial growth on the walls of the sample bottles may explain much of it. Although I wasn’t able to directly measure it, inorganic carbonate precipitation due to pH increase could also lead to this discrepancy. Future research must be done before DIC can be employed as a routine method of measuring primary production and respiration in aquatic systems.