Brenda 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 productionWarm temperatures and sunlight create high rates of production 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 disturbed Subsurface

Temp. Nutrients Light Riparian vegetation Hydrology Geology Geomorphology Climate Macroinvertebrate Communities Macroinvertebrate communities

Macroinvertebrate Communities Common Invertebrates Chironomidae “Midge” Culicidae “ Mayflies” “Mosquitoes” “Water Mites”

Macroinvertebrate Communities Common Invertebrates Simuliidae Elmidae “Riffle Beetles” “Black Flies” Filter feedingFilter feeding many nutrients (nitrogen and/or phosphorus) in watermany nutrients (nitrogen and/or phosphorus) in water “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 Site Substrates Sand 88% Cobble/Gravel 11% Back-waters 1%

Equipment 24*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) macroinvertebrates per m² After Flow Pulse (July) macroinvertebrates per m² Preliminary Results and Conclusions HydracarinaChironomidaeCulicidaeBaetidaeCorixidaeSimuliidaeElmidae Mean Macroinvertebrate Density (ind/m^2) Average June Average July

Density Increased in Cobble Density Decreased in Back-waters Density Increased in Sand 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”