Biogeochemical cycling of nitrates in Irish Estuaries

Biogeochemical cycling of nitrates in Irish Estuaries

Estuaries are the major conduit between land and sea, through which nutrient run-off from human activity flows into coastal systems. As a result increased concentrations of nitrates are entering nitrogen limited estuarine and marine systems stimulating primary productivity. However, estuaries are not passive channels and microbially driven processes within sediments mediate the nitrogen levels passing though them. These include nitrate reduction, whereby nitrate is reduced to nitrite, which subsequently can be reduced by denitrification (DN) (the stepwise reduction of nitrite to dinitrogen gas) or via dissimilatory nitrate reduction to ammonium (DNRA). Depending on the pathway (DN or DNRA) nitrate is either removed or conserved within the system, directly affecting the nutrient status of the estuary and coastal ecosystems. The specific aims of the research project are to determine potential rates of nitrate reduction, DN and DNRA in three Irish estuaries of contrasting nutrient status over various time and spatial scales. This will be achieved, using a combination of estuarine sediment microcosm experiments to determine potential rates and molecular techniques to target and quantify the microorganisms within the sediments responsible for the processes. Finally, using actual rate process data generated, a biogeochemical model of nitrogen in Irish estuaries will be constructed.

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Environmental Protection Agency 2012-W-PhD-6
Cindy Smith

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