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Extramural Research

Grantee Research Project Results

Grantee Research Project Results

Can Microbial Communities in Stream Sediments be Used To Evaluate the Availability and Composition of Dissolved Organic Carbon in Stream Ecosystems?

EPA Grant Number: U914799
Title: Can Microbial Communities in Stream Sediments be Used To Evaluate the Availability and Composition of Dissolved Organic Carbon in Stream Ecosystems?
Investigators: Sobczak, William V.
Institution: Cornell University
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1995 through January 1, 1996
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1995)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology



The objective of this research project is to understand how changes in both dissolved organic carbon (DOC) quantity and quality alter the hyporheic zone's bacterial community, and ultimately, its role in hyporheic food webs and ecosystem processes.


An appreciation of hyporheic microbial processes in streams linking agricultural sections of the watershed with the Hudson River's main channel is fundamental to understanding the sources, disposition, and transformation of organic matter in the Hudson River ecosystem. We will address the following: (1) how does variation in the quality and quantity of DOC affect bacterial biomass and productivity in the hyporheic zones of tributaries entering the Hudson River? (2) how does DOC originating from contrasting sources within the Hudson River watershed affect bacterial biomass and productivity in the hyporheic zone? and (3) do hyporheic zones function as significant carbon sinks?

We have selected several stream systems for detailed study based on an extensive regional (Hudson River Valley, NY) survey of surface water DOC concentrations. We surveyed a wide array of tributaries (n = 43) to facilitate the selection of tributaries that represent a natural range of DOC concentration (1.1-7.7 mg/L). On each of the five rivers/streams that we are currently studying, we located gravel bars in riffles in which exchange of surface water and hyporheic water was likely and established transects (two per stream) of shallow (0.5 m deep) wells made of PVC pipe (diameter = 1.91 cm). These wells permitted porewater DOC and dissolved oxygen (DO) to be sampled along predicted hyporheic flow paths. In a subset of these transects, we incubated artificial substrates within larger well points (diameter = 3.81 cm) to compare differences in bacterial productivity and biomass between rivers and within transects in which DOC gradients were documented. Wells were leveled so that flow path slopes could be determined. Hydrologic parameters (hydraulic conductivity, porosity, velocity) were estimated for the stream sediments.

Supplemental Keywords:

fellowship, dissolved oxygen, DO, dissolved organic carbon, DOC, hyporheic, Hudson River watershed, ecosystem., RFA, Scientific Discipline, Water, Water & Watershed, Environmental Chemistry, Biochemistry, Ecology and Ecosystems, Watersheds, dissolved organic matter, bacteria, agricultural watershed, stream ecosystems, dissolved organic carbon, stream water chemistry, Hudson River, microbial food web

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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