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

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 Deposition Erosion

Discharge relationships Floodplain: Pool-riffle floodplain channel terrace pool riffle pool riffle

Stream order: always flowing

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: mm –Pebble:16-64 mm –Gravel: 2-16 mm –Sand: mm –Silt:< 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 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 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 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