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Stream Ecology. R. Christian Jones June 2008 Tidal Potomac Teacher Training Workshop. Fate of Precipitation in a Watershed. Interception Depression Storage Infiltration Surface Runoff Interflow Groundwater Stormflow Baseflow. Baseflow.

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stream ecology

Stream Ecology

R. Christian Jones

June 2008

Tidal Potomac Teacher Training Workshop

fate of precipitation in a watershed
Fate of Precipitation in a Watershed
  • Interception
  • Depression Storage
  • Infiltration
  • Surface Runoff
  • Interflow
  • Groundwater
  • Stormflow
  • Baseflow
  • Streams continue to flow even when rainfall is not occuring or has not occurred in the past few days
  • The flow not directly associated with at storm is called baseflow
  • It derives from groundwater and part of the throughflow which takes a long time to reach the stream
  • Surface runoff and near surface throughflow result in rapid increases in streamflow following a storm
  • This is called stormflow
storm hydrograph
Storm Hydrograph
  • A storm hydrograph shows the response stream discharge (Q) to a single storm
  • Basin lag is the time between the peak of precipitation and the peak of runoff
  • Stormflow/storm runoff is the surface runoff directly attributable to the storm
watershed size influences the response time and flashiness of the hydrograph
Watershed size influences the response time and flashiness of the hydrograph

Characteristics of Stream & River Flow

Large Watershed

Small Watershed

stream ordering system
Stream Ordering System
  • We can define where we are at in the longitudinal drainage network by determining stream orders
  • The rules for stream ordering are fairly simple:
    • Headwater streams are order 1
    • Stream order increases by 1 when two stream of the same order come together.
stream food webs
Stream Food Webs
  • Sources of Organic Matter
    • Autochthonous: production occuring within stream system (ex. Algae, macrophytes)
    • Allochthonous: production occuring elsewhere and being imported into the stream system (ex. Terrestrial leaves)
stream food webs9
Stream Food Webs
  • Types of Organic Matter by Size
    • CPOM: coarse particulate organic matter
      • (>1mm)
      • [whole leaves, large leaf fragments]
    • FPOM: fine particulate organic matter
      • (<1mm, >0.45 um)
      • [fine leaf fragments]
    • DOM: dissolved organic matter
      • (<0.45 um)
      • [sugars, amino acids, etc.]
longitudinal changes reach scale
Longitudinal Changes – Reach Scale
  • Longitudinal changes are also observed at shorter scales than the entire river length
  • We call this shorter scale the “reach” scale
  • One example of reach scale changes is the pool-riffle pattern found in many streams draining areas with medium gradient like our area
  • Riffle is an area of rapid flow over coarse substrate (rocks) whereas the pool is a slower flowing stretch with finer substrate
stream food webs11
Stream Food Webs
  • Types of Consumers
    • By food type
      • Herbivores: feed on living primary producers
      • Detritivores: feed on dead organic matter and associated microbes
stream food webs12
Stream Food Webs
  • Types of Consumers
    • By feeding mode
      • Scrapers: obtain food by rasping or scraping it from rocks (dominantly herbivores)
      • Shredders: ingest detrital material torn or shredded from large pieces (ex. Leaves)
      • Filter collectors: ingest FPOM collected by filtration, usually from flowing water, often found in riffles
      • Deposit collectors: ingest FPOM collected from deposits, often found in pools
      • Predators: ingest other animals
river continuum concept
River Continuum Concept
  • Stream food web changes in an orderly and predictable way as stream order increases
stream habitats

High current velocity

Larger substrate particles (cobble)

Often shallower

“riffles” ---- “runs”


Low current velocity

Smaller substrate particles (clay, silt)

Often deeper

“pools” ---- “backwaters”

Stream Habitats
consumers taxa
Consumers - Taxa
  • Turbellarians
    • Flatworms
    • Generally carnivores on other small invertebrates
  • Nematodes
    • “round worms”
    • Very small: herbivores and carnivores
consumers taxa17
Consumers - Taxa
  • Annelid worms
    • Oligochaetes
      • Aquatic earthworms
      • Deposit feeders
      • Very common
    • Hirudinea
      • Leeches
      • Carnivores, Detritivores
consumers taxa18
Consumers - Taxa
  • Molluscs
    • Snails
      • Mobile
      • scrapers
    • Bivalves
      • sessile
      • Filter collectors
consumers taxa19
Consumers - Taxa
  • Crustaceans (arthropods)
    • Crayfish
      • Detritivores
      • Large, may be found in urban streams
    • Amphipods
      • Detritivores
      • Medium sized
      • May be important, esp below cow activity & in alkaline waters
consumers taxa20
Consumers - Taxa
  • Insect Life Cycles
    • Complete Metamorphosis
      • Growth and development phases separate
      • Egg  Larvae  Pupa  Adult
    • Incomplete Metamorphosis
      • Growth and development phases combined
      • Egg  Nymph  Adult
consumers taxa21
Consumers - Taxa
  • Insects (arthropods)
    • Plecoptera
      • “stoneflies”
      • Shredders or predators
      • “clean water”
      • Nymph aquatic
    • Ephemeroptera
      • “mayflies”
      • Scrapers or collectors
      • “clean water”
      • Nymph aquatic
consumers taxa22
Consumers - Taxa
  • Insects (arthropods)
    • Trichoptera
      • “caddisflies”
      • Filter collectors and scrapers
      • Many spin nets
      • Mostly clean water
      • Larvae and Pupae aquatic
consumers taxa23
Consumers - Taxa
  • Insects (arthropods)
    • Coleoptera
      • “beetles”
      • Predators or collectors
      • Mostly clean water
    • Megaloptera
      • “hellgrammites”
      • Predators
      • Mostly clean water
consumers taxa24
Consumers - Taxa
  • Insects (arthropods)
    • Diptera
      • “two-winged flies”
      • Includes a wide diversity of feeding types and tolerances
      • Chironomids (“midges”) are a very ubiquitous group
      • Larva and pupa aquatic
adaptation to flowing water
Adaptation to Flowing Water
  • Life Cycles are often adaptive
    • Many aquatic insects are aerial as adults to facilitate dispersal and crossbreeding
    • Some species concentrate their growth phases in periods of favorable conditions (moderate temp, plenty of water and food) and revert to dormant stages (eggs, pupae) during other stages
adaptation to flowing water26
Adaptation to Flowing Water
  • Feeding mechanisms:
    • Scrapers: radula in snails, mayfly nymphs use bristles
    • Filtering mechanisms:
      • Fringes of hairs on mouthparts and legs
      • Caddisfly Nets
      • Blackfly
adaptation to flowing water27
Adaptation to Flowing Water
  • Anchoring
    • Flattening of bodies to stay in boundary layer
    • Suckers, hooks, silky secretions
    • Ballast
comparative energy flow in streams
Comparative Energy Flow in Streams
  • Bear Brook
    • Wooded second order stream in New England
    • Dominated by allochthonous inputs from forest canopy directly and from upstream
comparative energy flow in streams29
Comparative Energy Flow in Streams
  • New Hope Creek, NC
    • Third order stream with more open canopy, but still allochthonous material is more important
large rivers
Large Rivers
  • In large rivers, interactions between main river channel and floodplain become increasingly important
  • Length>2000 km, Order>7
large rivers31
Large Rivers
  • Channel is deep and turbid
  • Substrate is fine and in constant motion
  • Upstream food supplies are of poor quality, best compounds have already been utilized
  • Many backwaters and side channels with slower flow
  • Flood plain inundation is relatively predictable so aquatic communities can adapt to this as a resource
large rivers32
Large Rivers
  • Single large pulse inundates the entire flood plain
  • Land-water interface (littoral) is pushed to the edge of the floodplain
  • As year proceeds, the moving littoral (ATTZ) slowly edges back toward the channel margin
  • ATTZ-aquatic-terrestrial transition zone
large rivers33
Large Rivers
  • Habitats within the floodplain:
    • Backwaters
    • Lakes
    • Wetlands
large rivers exchanges of materials
River brings

Plant nutrients (N&P), organic particulates, inorganic particles from upstream

N&P  fuel high production

Particulates  build up flood plain, carry P

Flood plain contributes

Fresher CPOM, FPOM, DOM than upstream sources

Nursery ground for many invertebrate prey organisms

Many larger predator animals enter flood plain to feed

Large Rivers – Exchanges of Materials