Ecosystem Processes and the River Continuum Concept . Unit 1: Module 4, Lecture 5. Objectives. Students will be able to: classify sources of organic matter. diagram the flow of instream organic matter. factors that influence the storage of organic matter in streams.
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Ecosystem Processes and the River Continuum Concept
Unit 1: Module 4, Lecture 5
Students will be able to:
Dissolved organic matter
Soluble organic compounds that leach from leaves, roots, decaying organisms, and other sources
Largest pool of organic matter in streams
Particulate organic matter
Coarse particulate organic matter
Woody material & leaves > 1 mm
Fine particulate organic matter
Leaf fragments, invertebrate feces, and organic precipitates < 1 mm
This figure depicts the routes carbon follows as it is processed within a stream.
Microbes, macro-invertebrates, fish, and other organisms all play roles in the physical and chemical processing of organic matter.
The River Continuum - www.oaa.pdx.edu/CAE/Programs/ sti/pratt/energy.html
A caddisfly of the family Limnephilidae
A blackfly of the family Simulidae
A caddisfly of the family Hydroptilidae
A dipteran of the family Thaumaleidae
A stonefly of the family Perlidae
A “true bug” of the family Notonectidae
Low concentrations in winter and fall
High concentrations in summer
Photos by g. merrick
Organic matter that enters streams may be (percent estimates are approximate and variable):
Stored within the stream bank or channel (25%)
Exported downstream (50%)
Metabolized and respired as carbon dioxide by organisms (25%)
Photo – g. merrick
Bear Brook in New Hampshire is the site of a famous organic matter budget study (Likens, 1973).
In the this small, forested headwater stream it was found that greater than 99% of the carbon input to Bear Brook came from allochthonous sources (POM slightly greater than DOM).
Close to 65% of this input was exported downstream from the 1700 meter long study site.
Input of DOM exceeded exports
Due to leaf fall more POM was exported than entered the site
Low order streams
Shaded headwater streams
Coarse particulate matter (CPOM) provides resource base for consumer community
Energy inputs change as stream broadens
Shading and contribution of CPOM decreases
Sunlight supports significant periphyton production
Upstream processing of CPOM results in input of fine particulate matter (FPOM)