Ecosystem Processes and the River Continuum Concept Unit 1: Module 4, Lecture 5.

Ecosystem Processes and the River Continuum Concept

Unit 1: Module 4, Lecture 5

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2

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. explain the river continuum concept compare and contrast low order, mid-order,

and high order streams.


geography.uoregon.edu/ .../SCRfig2-33web.jpg

General organic matter pathway


Sources of organic matter

Autochthonous – instream Allochthonous – out of stream

140.211.62.101/streamwatch/ swm10.html

www.landcare.org.nz/SHMAK/ manual/6doing.htm

www.bbg.org/sci/blackrock/ veg/brfredmaple.html


Types of organic matter

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


The River Continuum - www.oaa.pdx.edu/CAE/Programs/ sti/pratt/energy.html

Instream organic matter processing

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.


Shredders Dominant food

Vascular macrophyte tissue Coarse particulate organic material (CPOM) Wood

Feeding mechanisms Herbivores - Chew and mine live macrophytes Detritivores - Chew on CPOM

Representatives Scathophagidae (dung flies) Tipulidae (crane flies)

A caddisfly of the family Limnephilidae

Macroinvertebrate functional roles in organic matter processing


Collectors Dominant food

Decompose fine particulate organic matter (FPOM) Feeding mechanisms

Filterers - Detritivores Gatherers - Detritivores

Representatives Filterers

• Hydropsychidae • Simulidae (black flies)

Gatherers• Elmidae (riffle beetles)• Chironomini• Baetis• Ephemerella• Hexagenia

A blackfly of the family Simulidae

A caddisfly of the family Hydroptilidae

Macroinvertebrate functional roles


Scrapers Dominant food

Periphyton (attached algae) Material associated with periphyton

Feeding mechanisms Graze and scrape mineral and organic surfaces

Representatives Helicopsychidae Psephenidae (water pennies) Thaumaleidae (solitary midges) Glossosoma Heptagenia

A dipteran of the family Thaumaleidae



Predators Dominant food

Living animal tissue Feeding mechanisms

Engulfers - Attack prey and ingest whole animals Piercers - Pierce tissues, suck fluids

Representatives Engulfers

• Anisoptera (dragonflies)• Acroneuria• Corydalus (hellgrammites)

Piercers• Veliidae (water striders)• Corixidae (water boatmen)• Tabanidae (deerflies & horseflies)

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

Seasonal variation in particulate organic carbon


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

Fate of organic matter


Factors that are likely to increase retention time are debris dams, beaver dams, floodplains, and geomorphological features of the stream or river that impede flow.

Storage of organic matter


Net primary production versus litter fall

Stream Autotochthonous Allochthonous

Bear Brook, NH 0.6 g C/m2/year 251 g C/m2/year

Silver Springs, FL 981 g C/m2/year 54 g C/m2/year


Bear Brook, New Hampshire

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


The River Continuum Concept


Stream order and the RCC

Low order streams Shaded headwater

streams Coarse particulate

matter (CPOM) provides resource base for consumer community



Mid-order streams 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)



High order streams As streams widen even more and flows drop,

macrophytes become more abundant In the largest rivers, macrophytes are limited to

the river margins because mid-channel conditions are typically too turbid

Bottom substrate becomes smaller


Carbon fluxes in a stream ecosystem

Figure 12.1

Ecosystem Processes and the River Continuum Concept Unit 1: Module 4, Lecture 5.

Documents

storage of organic matter

organic precipitates

s5 types of organic

family simulidae

river continuum

s8 collectors dominant

high order streams

river continuum concept