Chapter 23 Primary Producer Consumer Interactions

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Chapter 23 Primary Producer Consumer Interactions

• Christopher Eisler
• Tennessee Tech University

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Ecosystem Processes

• Benthic environments are zones of high
  bioactivity. Processes include
• 1. Primary Production
• 2. Consumption
• 3. Nutrient Cycling
• 4. Decomposition

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Primary Producers

• Primary Producers are the physical-chemical
  interface in streams.
• Producers include bacteria, benthic algae,
  bryophytes, and vascular plants.
• Bio-films found in a variety of habitats.

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Production With Time

• Stable conditions are required for mature algal
  community structure.
• Disturbances such as floods can impair this.
• Algal growth typically follows a pattern which
  grazers can affect.

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Primary Production With Time
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Producers and Consumers

• Producers provide energy for consumers (Grazers).
• Grazing is the consumption of
• living producers or their parts by primary
  consumers.
• Consumption can be either the main
• energy intake or variable depending on the
  species and stream.

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Producers and Consumers

• Consumers can affect primary producers and vise
  versa.
• Grazers can affect algal community biomass.
• Algal biomass and species composition may be
  positively or negatively affected.

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Producers and Consumers

• Primary producers play an important role in many
  stream organisms life cycles.
• Consumers include Fish, Invertebrates, Insects,
  Mollusks, Crustations, and Larval Amphibians.
• Consumers can increase species richness or
  decrease species richness depending on how they
  graze and on mouth structure of the consumer.
• The same applies to biomass.

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Autochthonous Production

• Synthesis of organic matter by primary producers.
  
• Large portion of the food web in most streams.
• Stream orders 3-6 usually rely this since light
  is high, water is shallow clear, temperature
  and nutrients are favorable for growth of benthic
  algae.

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Autochthonous Production

• In higher orders phytoplankton dominate due to
  light reduction, however shallow regions can
  yield high benthic algae production.
• Small shaded streams with low algal biomass can
  yield high grazer numbers due to rapid turnover
  and high nutrient value thus affecting food web
  structure.

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Few Rules Many Exceptions

• Grazers affects on primary producers arent
  applicable to a wide range of streams. Much is
  yet to know.
• The best way is to determine the primary
  production and consumer interactions for your
  stream. This may be done by a variety of methods
• Factors affecting producer consumer interactions
  are tied to season, successional stage, size,
  nutrients, pathogens, habitat disturbances,
  light, depth, types and numbers of species
  present.

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Platform Exclusion

• Tiles are raised and at substrate level to
  determine consumer affects.
• Most invertebrates will be absent in the short
  term.
• Allows comparison between grazed and un-grazed
  tiles.

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Cage Method

• Effects by species.
• Very Controlled

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Electric Shock Exclusion

• Uses electric fence chargers to exclude
  invertebrates.
• Not effective on some types.

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References

• Biggs, B.F., 1996 Patterns in Benthic Algae of
  Streams. Pages 31-56 in R. J. Stevenson, et al.
  (Eds.) Algal Ecology Freshwater Benthic
  Ecosystems. Academic Press, San Diego, C.A.
• Haur, F. R., and G.A. Lamberti, 2006 Methods in
  Stream Ecology 2nd edition. New York, New York
  Academic Press.
• Steinman, A.D., 1996 Patterns in Benthic Algae of
  Streams. Pages 31-56 in R. J. Stevenson, et al.
  (Eds.) Algal Ecology Freshwater Benthic
  Ecosystems. Academic Press, San Diego, C.A.

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Questions
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Chapter Questions

• 1. This question can not be answered without
  field data.
• 3. Grazing decreases algal biomass. You cant
  extend this to all the stream bed or watershed
  since nutrients along with light will very with
  time and space.
• 5. This question cant be fully answered but
  variables exist with light, nutrients or
  consumers present.