Transcript Mod4-E Stream Ecology

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.
 explain the river continuum concept
 compare and contrast low order, mid-order, and
high order streams.
Developed by: Merrick, Richards
Updated: August 2003
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General organic matter pathway
geography.uoregon.edu/ .../SCRfig2-33web.jpg
Developed by: Merrick, Richards
Updated: August 2003
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Sources of organic matter
 Autochthonous – instream
 Allochthonous – out of stream
www.landcare.org.nz/SHMAK/ manual/6doing.htm
140.211.62.101/streamwatch/ swm10.html
Developed by: Merrick, Richards
www.bbg.org/sci/blackrock/ veg/brfredmaple.html
Updated: August 2003
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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
Developed by: Merrick, Richards
 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
Updated: August 2003
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Instream organic matter processing
 This figure depicts the
routes carbon follows as
it is processed within a
stream.
 Microbes, macroinvertebrates, fish, and
other organisms all play
roles in the physical and
chemical processing of
organic matter.
Developed by: Merrick, Richards
Updated: August 2003
The River Continuum - www.oaa.pdx.edu/CAE/Programs/ sti/pratt/energy.html
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Macroinvertebrate functional roles in
organic matter processing
 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)
Developed by: Merrick, Richards
A caddisfly of the
family Limnephilidae
Updated: August 2003
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Macroinvertebrate functional roles
 Collectors
 Dominant food
 Decompose fine particulate organic matter (FPOM)
 Feeding mechanisms
 Filterers - Detritivores
 Gatherers - Detritivores
 Representatives
 Filterers
A blackfly of the
family Simulidae
• Hydropsychidae
• Simulidae (black flies)
 Gatherers
•
•
•
•
•
Elmidae (riffle beetles)
Chironomini
Baetis
Ephemerella
Hexagenia
Developed by: Merrick, Richards
A caddisfly of the
family Hydroptilidae
Updated: August 2003
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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
Developed by: Merrick, Richards
A dipteran of the
family Thaumaleidae
Updated: August 2003
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Macroinvertebrate functional roles
 Predators
 Dominant food
 Living animal tissue

Feeding mechanisms
 Engulfers - Attack prey and ingest whole animals
 Piercers - Pierce tissues, suck fluids

A stonefly of the
family Perlidae
Representatives
 Engulfers
• Anisoptera (dragonflies)
• Acroneuria
• Corydalus (hellgrammites)
 Piercers
• Veliidae (water striders)
• Corixidae (water boatmen)
• Tabanidae (deerflies & horseflies)
Developed by: Merrick, Richards
A “true bug” of the
family Notonectidae
Updated: August 2003
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Seasonal variation in particulate organic carbon
 Low concentrations in
winter and fall
Developed by: Merrick, Richards
 High concentrations in
summer
Updated:
August
2003
Photos by
g. merrick
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Fate of organic matter
 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
Developed by: Merrick, Richards
Updated: August 2003
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Storage 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.
Developed by: Merrick, Richards
Updated: August 2003
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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
Developed by: Merrick, Richards
54 g C/m2/year
Updated: August 2003
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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.
Developed by: Merrick, Richards
 Input of DOM exceeded
exports
 Due to leaf fall more
POM was exported than
entered the site
Updated: August 2003
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The River Continuum Concept
Developed by: Merrick, Richards
Updated: August 2003
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Stream order and the RCC
 Low order streams
 Shaded headwater
streams
 Coarse particulate
matter (CPOM)
provides resource
base for consumer
community
Developed by: Merrick, Richards
Updated: August 2003
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Stream order and the RCC
 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)
Developed by: Merrick, Richards
Updated: August 2003
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Stream order and the RCC
 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
Developed by: Merrick, Richards
Updated: August 2003
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Carbon fluxes in a stream ecosystem
Figure 12.1
Developed by: Merrick, Richards
Updated: August 2003
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