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River Continuum
- headwater vegetation is the source of energy for the stream
- insects are divided into four functional feeding groups called shredders, grazers, collectors, predators
- fallen leaves CPOM are consumed and smaller particles FPOM are released down the river
- FPOM is consumed by collectors, grazers eat periphyton, predators eat other insects
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allocthonous
- refers to external sources of organic material in rivers and streams transported in a dead or decaying state
- primary productin is outside the system
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autochtonous
- refers to the internal souces of organic material in rivers and streams through the photosynthesis of algae, macrophytes, and periphyton
- primary production is inside the system
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headwaters
- oligotrophic, cold, clear, low stream order (narrow width), steep gradient, V-shaped valley, shaded by riparian vegetation
- PR<1 due to low levels of photosynthesis
- zone of erosion of sediment
- heterotrophic community
- allochtonous energy souce
- mostly riffles
- 100-250 invertebrate species with shredders and collectors abundant
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shredders
feed on CPOM produced from riparian vegetation
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collectors
- feed on FPOM produced by shredders
- filter-feeders, gatherers, and suspension-feeders
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midreach
- zone of storage and transport of sediment
- carry water from several tributarie
- higher stream order so wider than headwaters
- no overhanging vegetation leads to higher primary production
- PR>1 so autotropic and autochtonous
- channel becomes braided (small channels separated by small and often temporary islands)
- moderate gradient
- most species rich sectin of the river with 200-500 species with mostly collectors and grazers, but no shredders because no CPOM
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collectors
feed on FPOM at the headwaters and at the midreaches where FPOM descended from headwaters
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large river
- murky from a lot of FPOM and dissolved organic matter so not a lot of light can penetrate the water, leading to reduced primary production
- heterotrophic community and homogenous habitat
- mostly collectors, no grazers or shredders, and phytoplankton is the primary producer
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predators
- founds in equal proportions throughout all sections
- are carnivores who attack prey and pierce tissues ans suck suck fluids
- at headwaters, mostly invertebrates
- at midreaches, trout and bottom-grazing fish
- at large river setting, aquatic beetles and bottom-feeding fish
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ultimate base level
- where all stream erode towards
- also called sea level
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acquatic insects
- evolved in land, moved into headwater streams, and spread down to lower warmer settings
- sorted into niches based on temperature
- aquatic insects that metamorphose into flying forms represent a net loss of aquatic productivity
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grazers
- eat periphyton
- are either herbivores (graze surfaces for algae) or eat living cell and tissue fluid of filamentous algal cell fluids
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species richness in oligotrophic vs eutrophic lakes
- oligotrophic lakes have little riparian vegetation and little or no periphyton; about 25-100 species
- eutrophic lakes have limited insects and plants in the limnetic zone; about 10-50 species
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nutrient spiraling
- refers to the use and re-use of energy as it descends a watershed
- shredders eat CPOM then die, disintegrating to FPOM or DOM (dissolved OM); likewise predators can eat them
- predators die and produce FPOM that in turn is taken up by collecters
- same recycling occurs in all functional feeding groups
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