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) =– W x D x U

Hydrograph

• Record of discharge

0

10000

30000

50000

70000

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

Cub

ic f

eet

/ sec

1st 2nd

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

Depos

ition

Erosio

n

Discharge relationships• Floodplain:

• Pool-riffle

floodplain

channel

terrace

pool

riffle

pool riffle

Stream order: always flowing

1

123 1

11

2 1

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: > 256 mm– Cobble: 64-256 mm– Pebble: 16-64 mm– Gravel: 2-16 mm– Sand: 0.063-2 mm– Silt: < 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

0.038 3 48

Particle size mm

Species richness

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 -- collectors-filterers

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