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Nutrient Cycling in Oligohaline Sediments and Marshes: Is Denitrification a Major Sink for Nitrogen?
The biochemical cycling of nitrogen compounds in the Chesapeake Bay plays a critical role in regulating how much nitrogen is available for algal growth and how much becomes unavailable for growth because it is released as nitrogen gas. As a major nutrient source (with phosphorus and silica) for algae, nitrogen overenrichment has contributed to degraded water quality. While there is a very good understanding of nitrogen cycling in the main portions of the Bay, far less is known about the important cycling processes that occur in the many subestuaries that feed the Bay's main stem. Scientists believe that tidal freshwater marshes play a key role in nitrogen cycling.
The fate of nitrogen in these dynamic ecosystems is complex. Nitrogen compounds may be sequestered in the sediments over the long term; they may also be metabolized by microbes and released as nitrogen gas into the atmosphere. This process of denitrification is poorly understood in marsh systems, in part because techniques for measuring the process have been difficult and prone to error. Jeffrey Cornwell and Todd Kana have developed a novel methodology that enables them to take rapid and accurate measurements, which they will employ in a study that compares rates of denitrification in marsh and subtidal sediments. The results will help scientists and managers develop more accurate models of nitrogen flux in the Bay and a better understanding of the ecological role and value of marsh systems.
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Jeffrey C. Cornwell and Todd Kana
University of Maryland
Center for Environmental Science
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