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Dissolved organic matter quality and bioavailability changes across an urbanization gradient in headwater streams
Jacob D Hosen1, Owen T McDonough, Catherine M Febria
1Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science , Solomons, Maryland 20688, United States.
Environmental Science & Technology
|June 12, 2014
Summary
Urbanization alters stream dissolved organic matter (DOM) quality and increases its microbial breakdown. This shift impacts carbon cycling in headwater streams, affecting ecosystem metabolism and organic carbon fate.
Area of Science:
- Environmental Science
- Ecology
- Biogeochemistry
Background:
- Landscape urbanization significantly impacts watershed and stream ecosystems.
- The effects of urban nonpoint source pollution on dissolved organic matter (DOM) quantity, quality, and fate remain unclear.
Purpose of the Study:
- To assess DOM quality and microbial bioavailability in headwater streams along an urbanization gradient.
- To understand how watershed impervious cover influences stream DOM composition and microbial processing.
Main Methods:
- Analyzed DOM quality using fluorescence excitation-emission matrices (EEMs) and parallel factor analysis (PARAFAC).
- Assessed microbial bioavailability through biodegradable dissolved organic carbon (BDOC) incubations.
- Studied eight first-order Coastal Plain headwater streams without point source discharges.
Main Results:
- Increased watershed impervious cover correlated with reduced humic-like DOM and increased anthropogenic fulvic acid-like and protein-like DOM.
- DOM bioavailability was higher in urbanized streams during warmer months, linked to shifts in DOM composition.
- Enhanced bioavailability corresponded with increased extracellular enzyme activity.
Conclusions:
- Watershed urbanization significantly alters stream DOM quality, favoring more bioavailable forms.
- Changes in DOM quality can influence stream ecosystem metabolism and the fate of organic carbon.
- Urban nonpoint source pollution plays a critical role in shaping aquatic carbon cycles.
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