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08:05
Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
Published on: October 7, 2020
Nitrogen uptake, dissolved organic nitrogen release, and new production
Science (New York, N.Y.)
|September 23, 1994
Summary
Phytoplankton release significant dissolved organic nitrogen (DON) during nitrogen uptake. Traditional methods underestimate nitrogen uptake and production by failing to measure DON release, impacting ecological assessments.
Area of Science:
- Marine biology
- Biogeochemistry
- Oceanography
Background:
- Phytoplankton are crucial primary producers in marine ecosystems.
- Nitrogen is a key limiting nutrient for phytoplankton growth.
- Dissolved inorganic nitrogen (DIN) uptake by phytoplankton can lead to the release of dissolved organic nitrogen (DON).
Purpose of the Study:
- To quantify the release rates of DON by phytoplankton in oceanic, coastal, and estuarine environments.
- To assess the impact of DON release on the accuracy of nitrogen uptake measurements using traditional methods.
- To determine DON turnover times in different marine environments.
Main Methods:
- Nitrogen-15 (N-15) uptake experiments were conducted.
- Measurements included the release of dissolved inorganic nitrogen (NH(4)(+) and NO(3)(-)) and dissolved organic nitrogen (DON).
- DON release rates and turnover times were calculated for oceanic, coastal, and estuarine sites.
Main Results:
- Phytoplankton released 25–41% of absorbed inorganic nitrogen as DON.
- DON release rates in oceanic systems varied from 4 to 26 ng-N L⁻¹ h⁻¹.
- Traditional N-15 techniques underestimated new and regenerated production by up to 74% and 50%, respectively, due to unmeasured DON release.
Conclusions:
- DON production is a significant process in marine nitrogen cycling.
- Accurate assessment of phytoplankton production requires accounting for DON release.
- Established nitrogen uptake methodologies may require revision to incorporate DON measurements for precise ecological modeling.
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