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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
Published on: October 29, 2016
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Warming alters coupled carbon and nutrient cycles in experimental streams
Tanner J Williamson1, Wyatt F Cross1, Jonathan P Benstead2
1Department of Ecology, Montana State University, Bozeman, MT, 59717, USA.
Global Change Biology
|January 1, 2016
Summary
Warming significantly boosts biofilm growth and productivity in freshwater, altering carbon and nitrogen cycles. Increased nitrogen fixation, not dissolved nitrogen uptake, fuels this growth at higher temperatures.
Area of Science:
- Freshwater Ecology
- Biogeochemistry
- Environmental Science
Background:
- Benthic biofilms are crucial biogeochemical hotspots in freshwater ecosystems.
- Understanding how warming affects biofilms is key to predicting elemental cycle responses.
- Limited knowledge exists on warming's impact on nitrogen and phosphorus cycling linked to carbon.
Purpose of the Study:
- To investigate the effects of temperature on freshwater benthic biofilm structure and function.
- To link changes in carbon flow to nitrogen and phosphorus dynamics under warming.
- To determine how temperature influences nutrient cycling and biofilm stoichiometry.
Main Methods:
- Experimental streamside channels were used to simulate a temperature gradient (7.5–23.6°C).
- Biofilm communities were analyzed for structural (biomass, stoichiometry, assemblage) and functional (metabolism, N2-fixation, nutrient uptake) attributes.
- Natural diel and seasonal temperature variations were maintained with a common water and propagule source.
Main Results:
- Biofilm biomass and net ecosystem productivity increased significantly with temperature (2.8- to 317-fold).
- Carbon:nitrogen ratios remained stable, while carbon:phosphorus ratios slightly decreased with warming.
- Nitrogen (N2)-fixation rates increased up to 120-fold, supplying most nitrogen at higher temperatures, despite increased ammonium uptake.
Conclusions:
- Temperature strongly influences carbon cycling and its coupling with nitrogen and phosphorus in freshwater biofilms.
- Warming decouples carbon fixation from dissolved inorganic nitrogen supply, driving significant changes in biofilm development and elemental cycling.
- These findings suggest potential alterations in downstream nutrient and organic matter export due to warming-induced shifts in biofilm processes.
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