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Updated: Aug 6, 2026
09:38
Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
Published on: October 29, 2016
Downwelling persistence modifies nitrogen sources available for benthic food webs
Antonio Bode1, Jaime Otero1, Inés G Viana1
1Instituto Español de Oceanografía (IEO-CSIC), Centro Oceanográfico de A Coruña, Spain.
Marine Environmental Research
|July 16, 2026
Summary
Coastal ecosystems rely on nitrogen from various sources. This study reveals that downwelling periods, not just upwelling, significantly impact nitrogen sources, influencing food webs in Galicia, NW Spain.
Area of Science:
- Marine ecology
- Biogeochemistry
- Oceanography
Background:
- Coastal ecosystems receive new nitrogen from coastal upwelling and other sources, impacting food web dynamics.
- Understanding nitrogen sources is crucial for analyzing changes in food web structure and productivity.
- The Galicia region (NW Spain) is a highly productive coastal ecosystem with complex nutrient dynamics.
Purpose of the Study:
- To determine the relative importance of upwelling and continental waters as nitrogen sources for coastal food webs in Galicia.
- To analyze nitrogen sources on annual time scales using stable isotopes and oceanographic data.
- To investigate the influence of different oceanographic conditions (upwelling vs. downwelling) on nitrogen assimilation.
Main Methods:
- Stable isotope analysis of macroalgae and mussel amino acids to trace nitrogen sources.
- Comparison of isotopic data with time series of nutrient concentrations and oceanographic observations.
- Assessment of nitrogen sources during periods dominated by upwelling versus downwelling.
Main Results:
- During upwelling, oceanic nitrate from Eastern North Atlantic Central Waters (ENACW) was the primary nitrogen source.
- During downwelling (autumn/winter), organisms showed higher isotopic enrichment, indicating additional nitrogen sources.
- Incomplete nitrate uptake and denitrification in sediments were potential sources of enriched nitrate during downwelling.
Conclusions:
- Downwelling periods are crucial for retaining nitrogen in coastal waters, altering food web dynamics.
- Nitrogen sources in coastal food webs are influenced by seasonal oceanographic shifts.
- Further research is needed to fully understand the proposed mechanisms of nutrient retention and enrichment.
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