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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
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50
100
150
200
250
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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”