Autochthonous%20Energy%20Sources%20in%20Streams

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Autochthonous Energy Sources in Streams
Aulacoseira sp.
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Riverine Ecosystems Energy Sources

• Autochthonous instream
• Allochthonous out of stream

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Autochthonous?

• Definition generated from within
• In this case, in-stream energy sources
• Source of energy sun
• Who captures the energy? - Photoautotrophs - use
  the sun plus inorganic matter
• Includes organisms in the following kingdoms
  Eubacteria, Protista, Plantae

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The sources of energy in streams autochthonous,
allochthonous, DOM
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What is an Autotroph?
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Autotrophs?

• Acquire energy from sunlight
• Acquire materials from non-living sources
• Taxonomy?
• Plantae - "macrophytes" aquatic vascular
  non-vascular (mosses)
• Eubacteria Cyanobacteria
• Protista
• Ochrophyta (mostly diatoms in streams)
• Chlorophyta (greens)
• Rhodophyta (reds, but only a few species)

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Primary Production?

• Definition the capture of energy by
  photosynthesis.
• NPP vs- PP ??
• Who does it? Autotrophs

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How Might You Measure NPP??
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How Do You Measure NPP?

• Biomass accrual over time
• preferred for macrophytes
• Problems getting accurate values for microphytes
• Turnover rates may be too fast
• Measurement of open stream gas exchange
• Entire stream as a unit
• Difficult in low productivity/high turbulence
  streams
• Assumptions about diel productivity flawed . .
  Who respires?
• Light/Dark Bottle method modified for stream beds
• uses 14C uptake
• Difficult requires radioactive materials,
  community often very diverse

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Primary production of periphyton measured by 14C
uptake using substrate placed in recirculating
chambers, New River, VA
Hill and Webster, 1982
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What are the Autotrophs in a Stream?

• Where might they live?

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Benthic autotrophs

• Benthic autotrophs grow on virtually all surfaces
  receiving light in flowing waters and are
  collectively referred to as the periphyton
  community.

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Biofilm

• Slippery film on rocks
• Periphyton
• Aufwuchs

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Periphyton

• Periphyton is a complex matrix of algae and
  heterotrophic microbes attached to submerged
  substrata in almost all aquatic ecosystems.

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Periphyton

• It serves as an important food source for
  invertebrates and some fish, and it can be an
  important sorber of contaminants.

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Habitat Specialization

• Allows for classification of benthic autotrophs
  into groups
• Species that grow on stones (epilithon)
• Species that grow on soft sediments (epipelon)
• Species that grow on other plants (epiphyton)

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Attached and benthic populations

• Many blue-green algae grow attached on the
  surface of rocks and stones (epilithic forms), on
  submerged plants (epiphytic forms) or on the
  bottom sediments (epipelic forms, or the benthos)
  of rivers.

Hoffman Image Gallery
Hoffman Image Gallery
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Attached and benthic populations

• The epiphytic flora of lotic communities is
  usually dominated by diatoms and green algae, and
  blue-greens are of less importance in this
  community.

Hoffman Image Gallery
University of Wisconsin Botanical Images
Collection
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Periphyton taxa mostly diatoms
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What causes microscale patchiness?

• Periphyton variation within a reach is very high.

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What factors potentially influence periphyton?

• Light
• Temperature
• Current
• Substrate
• Scouring effects of floods
• Water chemistry
• Grazing

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Substrate

• Pringle (1990) - used artificial substrates with
  nutrient agar
• Patchiness patterns
• Differences in type of substrate
• Availability of nutrients in water

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Epipelion Periphyton on sandy substrates -
variation by microhabitat

• 1. Bedload sandgrains
• 2. Upper story mat
• 3. Mucilaginous layers
• 4. Understory layer

From Pringle, 1990
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Light

• Green algae associated with high levels
• Diatoms cyanobacteria in lower light
• Motile algae can pick their spot

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Photosynthesis vs. Irradiance Curve light
adapted and shade adapted community responses
Light adapted
Shade adapted
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Seasonality in periphyton
Peaks prior To leaf-out
PAR
Chl a
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Seasonal succession in periphyton communities

• Diatoms dominate during the winter, spring, and
  early summer
• Green algae and cyanobacteria populations
  increase during the summer
• Benthic autotrophs tends to decrease during the
  summer as a result of increased shading,
  increasing again in fall

www.urbanrivers.org/web_images/diatoms.gif
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Shading and other factors

• Not all studies show direct correlation with
  light
• Lack of nutrients can prevent response
• Grazing can keep increased light from increasing
  biomass

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Nutrients

• P, N, and Si most commonly limiting
• Si is rarely in short supply in rivers
• Few studies have looked at influence
• Cyanobacteria, nitrogen fixation

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Nutrient Addition Experiments

• Protocol troughs built beside or in stream, add
  nutrients to streamwater passing through troughs,
  measure periphyton accumulation over time.

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Continuous flow periphyton bioassay system
Nutrient addition
Glass slides
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Changes in dominant diatom species in nutrient
addition experiments.
of diatoms X 1011 m-2
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Nutrient Response

• P seems most important
• N alone has little affect
• But, in specific cases N can be limiting

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Changes in relative abundance of the major
diatoms in response to nutrient
manipulation.Note decline in A. minutissima
in PO4 only.
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Nutrient Response 2

• N/P ratio can matter
• Individual species respond differently

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Diatom abundance on nutrient-releasing substrates
in a nutrient poor stream.
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Light and Nutrients Matter

• What Else?

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Current

• Why?

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Influence of Current

• How well attached
• Current influences substrate type
• Flow renews gases nutrients gt diffusion rates,
  boundary layers
• However, can scour the substrate
• Growth forms within a species responds to
  current Cladophora glomerata is plumose in slow
  water, long rope-like in faster flows (Whitton,
  1975)

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Cladophora glomerata
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Impact of Floods Spates

• What difference should this make?

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Flow vs. periphyton accumulation
Periphyton accumulation has inverse
relationship To flood events.
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Substrate effects?

• Chemical composition of rocks (Parker, et al,
  1973)
• Monostroma quaternarium confined to iron-rich
  rocks
• Hydrurus occurred mainly on lime and sandstone
• Batrachospermum showed no specificity
• Presence of crevices allows some taxa to
  persist in high flow (Keithan Lowe, 1985)

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Stone surface coverage by the moss Hygrohypnum,
as a function of stone size in a mountain stream.
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Macrophytes

• Taxa
• Flowering Plants
• Bryophyta
• Lichens
• Charales
• (complex green algae)

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Macrophyte growth forms

• Emergents banks and shoals
• Floating-leaved stream margins
• Free-floating slow (tropical) rivers
• Submerged midstream (limited by light
  penetration, current speed, and substrate type)

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What adaptations might help in streams?
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Adaptations - Flowing water, current

• Firm attachment by adventitious roots
• Tough, flexible stems and leaves
• Rhizomes
• Vegetative reprodution
• Hydrophillous pollination

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High flow species

• Almost all Bryophytes
• Two families of flowering plant
• Require free CO2
• Most macrophytes do better in backwaters

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Patchy distribution of macrophytes

• Macrophyte distribution and abundance changes
  seasonally (temporally)

www.glifwc.org/
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Coverage varies within a system

• How much of the bottom of streams is covered with
  macrophytic vegetation?
• Variable
• Appalachian rivers 27 - 42
• Bavarian streams 37 of the area had less than
  10 cover

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What might limit growth and distribution?
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Macrophytes Limitation to growth

• What limits?
• Temperature
• temperate dormancy via below sediment rhizomes
  during winter
• Tropical little seasonality
• Nutrients in oligotrophic areas, PO4 most often
  limiting
• Light often more important
• Being rooted can reduce the affect
• Free CO2 availability
• Bryophytes or Gymnosperms?
• Light most often limiting factor, along with
  current

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Macrophyte Energy Flow

• Even in streams with high macrophyte NPP, a small
  fraction of the streams energy comes from
  macrophytes.
• Why?

http//images.fws.gov/
www.epa.gov/25water/exotic/slide15.jpg
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Macrophyte productivity Detrital

• Macrophytes have high fiber content
• Some have high tanin concentrations other
  anti-herbivore compounds (phenolics)
• Fiber tannin indigestible
• animals must adapt to harsh diet
• Most productivity enters a detrital cycle
• OR
• Secretion of dissolved organic matter
• Like Allocthanous input

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So Who Eats the Stuff?

• Mainly vertebrates
• Waterfowl
• Manatee
• Grass carp
• Muskrat
• Moose.
• And some invertebrates
• Rusty Crayfish
• Invasive

http//images.fws.gov/
http//www.fcsc.usgs.gov/posters/Nonindigenous/Non
indigenous_Crustaceans/nonindigenous_crustaceans.h
tml
www.epa.gov/25water/exotic/slide15.jpg
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Phytoplankton

• Lotic phytoplankton include
• Algae
• Protozoans
• Cyanobacteria
• These are small enough to remain suspended in the
  water column and be transported by currents.
• Are there other sources for planktonic input?

Biodidac
Hoffman Image Gallery
Hoffman Image Gallery
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Other Phytoplankton Sources?

• Sloughing
• Import from lentic systems

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What Limits Phytoplankton Productivity?

• Typical for any autotroph
• Light
• Nutrients
• Temperature
• With regard to these factors what might make life
  harder for plankton?

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Light, Turbidity, Turbulence and Depth

• In Hudson River Algae 18-22h below 1 light level
• But, source could be shallower water
• Source-Sink Plankton

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Depth of mixing in Lakes vs. streams
Thermocline
River
Lake
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Nutrients

• Rarely Limiting
• Abundance several times lower than expected based
  upon nutrients
• What Else Limits Phytoplankton Productivity in
  Lotic Systems?

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Lotic Specific Phytoplankton Limiter

• Discharge regime (flooding, current)

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Discharge

• Inverse relationship to plankton
• Population Doubles once or twice per day
• Requires slower flow
• Flood may connect to standing water
• Source of plankton

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Grazing

• Zooplankton not a major factor
• Reproduce too slow
• Mollusks matter!
• Asiatic Clam 40-60 reduction in Potomac
• Zebra Mussels Can filter entire volume of the
  Hudson in 1-4 days!
• 85 drop in phytoplankton biomass
• Changes energy flow
• Increases clarity

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Algal primary productivity
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Water on the Web

• This presentation includes material from Water on
  the Web (WoW)
• WOW. 2004. Water on the Web - Monitoring
  Minnesota Lakes on the Internet and Training
  Water Science Technicians for the Future - A
  National On-line Curriculum using Advanced
  Technologies and Real-Time Data.
• http//WaterOntheWeb.org).
• University of Minnesota-Duluth, Duluth, MN 55812.
• Authors Munson, BH, Axler, R, Hagley C, Host G,
  Merrick G, Richards C.
• I would also like to thank Dr. Jewett-Smith for
  her contributions to this presentation