Ocean Chemistry

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Nitrogen, in the forms of nitrate, nitrite and ammonium, is an important nutrient for all life. In the open ocean the amount of fixed nitrogen controls the amount of primary production and subsequent carbon removal from the atmosphere. Therefore nitrogen also has a role in regulating climate. While fixed nitrogen can be limiting in the open ocean, in coastal areas it is often in excess due to human activities. Humans continue to add fixed nitrogen to the coastal ocean through fertilizer use, wastewater run off and aquaculture feeds. Excess nitrogen causes environmental problems that degrade the environment, making it unsuitable as animal habitat or for human use for tourism and commercial purposes. These issues include overgrowth of algae, oxygen depletion in the water and fish kills. Dr. Buchwald's research program tackles both sides of the global nitrogen cycle. Her research in the Northwest Atlantic on the Scotian Shelf and Labrador Sea aims to predict changes in fixed nitrogen in this climatically important region. It will help model and predict future changes in climate. Currently there is indication that the amount of nitrogen is decreasing in this region. Her work will advance understanding of how this decrease will affect future changes in carbon uptake. The other main objectives in her research program focus on the release of nitrogen in the coastal waters of Nova Scotia. In the first project she will determine the isotopic signature of nitrogen in local wastewater treatment plants. This will improve the ability to track nitrogen from human waste into the environment. Her last main objective is to help facilitate the growth of seaweed aquaculture in Nova Scotia. Nitrogen is one of the major nutrients that limits the growth of seaweed. Understanding nitrogen availability in prospective aquaculture sites will be imperative when choosing suitable locations to farm. Through all these projects Dr. Buchwald will use natural abundance stable isotopes to track the nitrogen. Her laboratory will also continue to specialize in conducting experimental work determining isotope systematics of novel nitrogen cycling processes. The isotope parameters defined in these experiments can be used in the analysis of natural abundance isotopes in the Northwest Atlantic, wastewater treatment plants and on seaweed farms.