Brenda C. NietoBrenda C. Nieto

Flow Pulse Effects on the Macroinvertebrate Community

Structure in the Rio Salado, an Arid Stream Ecosystem

Aim

Introduction

Arid land stream ecosystems

Flow pulses versus floods

Macroinvertebrate communities

Hypothesis and specific goals

Material and methods

Preliminary results and conclusions

Outline

Professional

Understand the interdisciplinary field of Environmental Sciences and Ecology

Personal

Have skills and knowledge for future scientific research and collaborate with other research and colleagues for experience.

Scientific

Study the effects of flow pulses on the macroinvertebrate community

Aim

•Exist in setting defined by water limitationExist in setting defined by water limitation

•Periods of declining or absent flowPeriods of declining or absent flow

•Extremes in magnitude and variance of dischargeExtremes in magnitude and variance of discharge

•Warm temperatures and sunlight create high rates of Warm temperatures and sunlight create high rates of productionproduction

Arid Land Stream Ecosystems

Flood

Flow Pulse

Flow Pulse- high flow that does not exceed the threshold of sediment motion.

Flood- high flow that involves sediment motion and therefore becomes a disturbance.

Flow Pulses vs. floods

Disturbance threshold

Abrasion by bedload

Initiation of sediment motion

Flow

Surface

Disturbance

Flow Pulses vs. floods

Depth

Non disturbedSubsurface

Temp.Nutrients LightRiparian

vegetationHydrology

Geology Geomorphology Climate

Macroinvertebrate Communities

Macroinvertebrate communities

Macroinvertebrate CommunitiesCommon Invertebrates

www.bgsd.k12.wa.us

HydracarinaHydracarina

www.epa.govChironomidaeChironomidae

““Midge”Midge”

CulicidaeCulicidae

www.ru.ac.zawww.ru.ac.za

www.waterbugkey.vcsu.edu

BaetidaeBaetidae

“ “ Mayflies”Mayflies”

““Mosquitoes”Mosquitoes”““Water Mites”Water Mites”

Macroinvertebrate CommunitiesCommon Invertebrates

www.bgsd.k12.wa.us

CorixidaeCorixidae

www.epa.gov

SimuliidaeSimuliidae

www.ghsonline.net

ElmidaeElmidae

““Riffle Beetles”Riffle Beetles”““Black Flies”Black Flies”

• Filter feedingFilter feeding

• many nutrients (nitrogen many nutrients (nitrogen and/or phosphorus) in water and/or phosphorus) in water

““Water Boatman”Water Boatman”

Macroinvertebrates and Hydrology

Rio Salado is a temporal and spatial intermittent stream.

Desert streams are characterized by flash floods and droughts.

Effects of floods and droughts as a disturbance are well studied but less is known about flow pulses.

Hypothesis and Specific goals

The effects of flow pulses after a long drought period will increase the density of macroinvertebrates and change the composition of substrates.

To see the differential effect of flow pulses in different habitats.

Study Site

Rio Salado

Study SiteSubstrates

Sand 88%

Cobble/Gravel 11%

Back-waters 1%

Equipment24*20cm sample surface border

Net

Large Pan

No. 35 graded sieve

26 plastic cups

Ethanol

Methods and Materials

In June and repeated in July…5 samples were taken from Sand

5 samples from Gravel

3 samples from Back-waters

Placed into cups with 70% Ethanol

Sorted with Leica Stereozoom 4 microscope

Isolated macroinvertebrates in cups

Identified to family

Methods and Materials

During Drought (June)

194.9 macroinvertebrates per m²

After Flow Pulse (July)

418.9 macroinvertebrates per m²

Preliminary Results and Conclusions

400

0

50

100

150

200

250

300

350

Hydracarina Chironomidae Culicidae Baetidae Corixidae Simuliidae Elmidae

Mea

n M

acro

inve

rteb

rate

Den

sity

(in

d/m

^2)

Average June

Average July

Density Increased in Cobble

Density Decreased in Back-waters

Density Increased in Sand

Preliminary Results and Conclusions

Preliminary Results and Conclusions

Macroinvertebrates By Substrate

• Hyrdracarina appeared in sand and cobble

•Chironomidae largest increase in back-waters

•Culicidae decreased in sand

•Corixidae decreased in back-water

•Simuliidae increase in cobble

July Results Compared to June

• Hydracarina present

•Increase in Chirononmidae in all 3 substrates

•Culicidae increased in cobbles

•Baetidae remained similar

•Corixidae increased in cobble; decreased back-waters

•Simuliidae increased in cobble and back-water

•Elmidae decreased

Preliminary Results and Conclusions

General Patterns

•Macroinvertebrates density increased after flow pulse.

•Massive emergence Chironomidae, may relate with an increase of habitat extent and increase in sediment moisture

•Eggs in sediment

•Flow pulse involved a change in the community composition

Difference in Substrate•Some families found in one habitat, are specialized

•Reduction in habitat conditions of back-waters caused Corixidae decrease

•Sand and cobbles were more stable in terms of composition

Preliminary Results and Conclusions

Acknowledgements

U.S. Fish and Wildlife

Vicenç Acuña Salazar

Jennifer Johnson

Mike Friggens

John Craig

Alex Benhumea

Tara Blackman

Tierney Adamson

Caitlin Smith

Ashwana Fricker

“Fred”