Aquatic Entomology
• ZOOL 484/584
• Policies
• Course outline - website
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
Where do you find aquatic
insects?
• Water
• Lentic =
• Lotic =
• Highest diversity AI in lotic ecosystems
Stream ecology
Physical Properties
• Hydrologic cycle
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
Cross-sectional area of stream
• Width x Depth
• Total volume at point (discharge, Q) =
– WxDxU
Hydrograph
• Record of discharge
70000
Cubic feet / sec
50000
30000
1st
10000
2nd
0
5/30/04
6/9/04
6/19/04
6/29/04
7/9/04
7/19/04
7/29/04
8/8/04
8/18/04
8/28/04
Material carried by flow
• Particles move along bed = bedload
• Suspended load = silt, clays
• All sediments from erosion:
– Streambed, bank regions
What causes sediment transports?
• Flow events that influence channel form
• Human impacts:
– Ag run-off, urban run-off, channelization, etc.
Discharge relationships
• Profile: steep headwaters, flatten with distance
– Particle size decreases
• Sinuosity
Discharge relationships
• Floodplain:
terrace
floodplain
• Pool-riffle
channel
pool
riffle
pool
riffle
Stream order: always flowing
1
1
3
1 1
2 1
1
2
1
1
2
3
Rivers change over time
Effects of flow on organisms
• Adaptations of aquatic invertebrates
– Attachment devices: hooks, sticky stuff,
suckers
– Body shape: flattened, streamlined
Substrate
• Wentworth scale
–
–
–
–
–
–
Boulder:
Cobble:
Pebble:
Gravel:
Sand:
Silt:
> 256 mm
64-256 mm
16-64 mm
2-16 mm
0.063-2 mm
< 0.063 mm
Most stream organisms live in/on
substrate
•
•
•
•
•
Lithophilous = stony substrate
Psammophilous = sand substrate
Burrowing
Xylophilous = wood-dwelling
Phytophilous = plants
Substrate size and organism
diversity
Species
richness
0.038
3
48
Particle size mm
Water quality and organisms
•
•
•
•
Temperature
Oxygen
pH
Salinity
Read Poff et al. (1997)
• Know:
• What is “natural flow regime”
• How to characterize?
How does streamflow affect:
• Water temperature?
• Channel geomorphology?
• Habitat diversity?
• A “master variable”
River management has been
based on:
• Species of interest
• Commercial interests
• Sportfishing interests
• Not working!
Recent advocates suggest
understanding/restoring natural
flow regime:
•
•
•
•
•
Magnitude
Frequency
Duration
Timing
Rate of change
Lytle & Poff 2005. TREE 19:94
Natural flow regime
• Why do streams differ in flow regimes?
• How have we altered flow regimes?
Ecosystem changes along streams
• River continuum concept (RCC)
• Vannote et al. (1980) Can. J. Fish. Aquat.
Sci. 37:130
• Based on forested headwater streams in
eastern North America
Three basic RCC Principles
• 1. Stream communities are based on
continuous gradient of physical variables
that change from headwaters to mouth
Three basic RCC Principles
• 2. Communities cannot be divorced from
riparian zone or geomorphic catchment.
Three basic RCC Principles
• 3. Downstream assemblage is inextricably
linked to processes occurring upstream.
Major prediction of RCC
• Longitudinal changes in abundances of
functional feeding groups and their food
resources.
RCC
• Predictable
changes in
assemblages with
stream distance:
• Headwaters = leaf
inputs -- shredders,
collectors
RCC
• Midreaches:
sunlight = algae -fewer shredders,
more collectors +
grazers
RCC
• Downstream:
deeper = less light
to bottom, less
allochthonous
inputs -- collectorsfilterers
Problems with RCC
• Not all streams are the same: spring-fed,
arid riparian, blackwater
• Large rivers -- little studied; grazers are
present
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
Alternatives
• Serial discontinuity concept (Stanford +
Ward 1983)
• The effect of a dam is to “reset” the RCC
Alternatives
The riverine ecosystem synthesis. 2006. Thorp,
Thoms, Delong.
Combines previous ideas:
Hydrogeomorphic patches
Functional process zones
Riverine Ecosystem Synthesis
Underground aquatic habitats
• Caves, hyporheic zone
• Organisms live in substrates or in caves
• Caves typically have high endemism
Lentic ecosystems
• Abiotic zones based on light penetration,
distance from shore
– Littoral, epilimnion, hypolimnion, benthic
• Stratification