Aquatic Entomology

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Aquatic Entomology

• ZOOL 484/584
• Policies
• Course outline - website

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What is Aquatic Entomology?

• Study of Aquatic Insects,
• habitat consists mainly of a body of water
• have key morphological adaptations to assist them
  in this habitat.
• course is based on ecology and taxonomy of
  aquatic insects

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Where do you find aquatic insects?

• Water
• Lentic
• Lotic
• Highest diversity AI in lotic ecosystems

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Stream ecology Physical Properties

• Hydrologic cycle

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Water in rivers

• Discharge
• Speed of water in channel
• Current velocity U
• Varies across stream
• Highest where friction is lowest (surface, center
  of channel)
• Approaches 0 at substrate surface

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Cross-sectional area of stream

• Width x Depth
• Total volume at point (discharge, Q)
• W x D x U

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Hydrograph

• Record of discharge

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Material carried by flow

• Particles move along bed bedload
• Suspended load silt, clays
• All sediments from erosion
• Streambed, bank regions

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What causes sediment transports?

• Flow events that influence channel form
• Human impacts
• Ag run-off, urban run-off, channelization, etc.

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Discharge relationships

• Profile steep headwaters, flatten with distance
• Particle size decreases
• Sinuosity

Deposition
Erosion
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Discharge relationships

• Floodplain
• Pool-riffle

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Stream order always flowing
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1
1
3
1
2
1
1
2
1
1
2
3
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Rivers change over time
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Effects of flow on organisms

• Adaptations of aquatic invertebrates
• Attachment devices hooks, sticky stuff, suckers
• Body shape flattened, streamlined

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Substrate

• Wentworth scale
• Boulder gt 256 mm
• Cobble 64-256 mm
• Pebble 16-64 mm
• Gravel 2-16 mm
• Sand 0.063-2 mm
• Silt lt 0.063 mm

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Most stream organisms live in/on substrate

• Lithophilous stony substrate
• Psammophilous sand substrate
• Burrowing
• Xylophilous wood-dwelling
• Phytophilous plants

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Substrate size and organism diversity
Species richness
0.038
3
48
Particle size mm
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Water quality and organisms

• Temperature
• Oxygen
• pH
• Salinity

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Read Poff et al. (1997)

• Know
• What is natural flow regime
• How to characterize?

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How does streamflow affect

• Water temperature?
• Channel geomorphology?
• Habitat diversity?
• A master variable

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River management has been based on

• Species of interest
• Commercial interests
• Sportfishing interests
• Not working!

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Recent advocates suggest understanding/restoring
natural flow regime

• Magnitude
• Frequency
• Duration
• Timing
• Rate of change

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Lytle Poff 2005. TREE 1994
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Natural flow regime

• Why do streams differ in flow regimes?
• How have we altered flow regimes?

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Ecosystem changes along streams

• River continuum concept (RCC)
• Vannote et al. (1980) Can. J. Fish. Aquat. Sci.
  37130
• Based on forested headwater streams in eastern
  North America

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Three basic RCC Principles

• 1. Stream communities are based on continuous
  gradient of physical variables that change from
  headwaters to mouth

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Three basic RCC Principles

• 2. Communities cannot be divorced from riparian
  zone or geomorphic catchment.

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Three basic RCC Principles

• 3. Downstream assemblage is inextricably linked
  to processes occurring upstream.

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Major prediction of RCC

• Longitudinal changes in abundances of functional
  feeding groups and their food resources.

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RCC

• Predictable changes in assemblages with stream
  distance
• Headwaters leaf inputs -- shredders, collectors

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RCC

• Midreaches sunlight algae -- fewer shredders,
  more collectors grazers

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RCC

• Downstream deeper less light to bottom, less
  allochthonous inputs -- collectors-filterers

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Problems with RCC

• Not all streams are the same spring-fed, arid
  riparian, blackwater
• Large rivers -- little studied grazers are
  present

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Alternatives

• Flood pulse concept for large rivers
• (Junk et al. 1989)
• Allochthonous material has large impact periodic
  flooding allows riparian materials to wash into
  river

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Alternatives

• Serial discontinuity concept (Stanford Ward
  1983)
• The effect of a dam is to reset the RCC

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Alternatives

• The riverine ecosystem synthesis. 2006. Thorp,
  Thoms, Delong.
• Combines previous ideas
• Hydrogeomorphic patches
• Functional process zones

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Riverine Ecosystem Synthesis
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Underground aquatic habitats

• Caves, hyporheic zone
• Organisms live in substrates or in caves
• Caves typically have high endemism

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Lentic ecosystems

• Abiotic zones based on light penetration,
  distance from shore
• Littoral, epilimnion, hypolimnion, benthic
• Stratification