Ecology and recolonization of benthic macroinvertebrates in a

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Ecology and recolonization of benthic macroinvertebrates in a

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ECOLOGY AND RECOLONIZATION OF BENTHIC MACROINVERTEBRATES IN A GROUNDWATER-DEPENDENT STREAM IN NORTH CENTRAL TEXAS DURING A SUPRA-SEASONAL DROUGHT Rosemary A. Burk, B.S.
Dissertation Prepared for the Degree of DOCTOR OF PHILOSOPHY
UNIVERSITY OF NORTH TEXAS May 2012
APPROVED: James H. Kennedy, Major Professor Paul F. Hudak, Committee Member Thomas W. La Point, Committee Member Barney Venables, Committee Member Earl Zimmerman, Committee Member Art Goven, Chair of the Department of
Biological Sciences James D. Meernik, Acting Dean of the
Toulouse Graduate School

Burk, Rosemary A. Ecology and recolonization of benthic macroinvertebrates in a groundwater-dependent stream in North Central Texas during a supra-seasonal drought. Doctor of Philosophy (Biology), May 2012, 124 pp., 19 tables, 13 figures, 162 reference titles.
Extreme climatic events such as droughts are known to eliminate aquatic biota and alter community structure and function. Perennial headwater springs provide important drought refugia to benthic macroinvertebrates and an important source of colonists via drift or aerial adults to intermittent streams post-drought. During a supra-seasonal drought in North-central Texas summer and fall 2006, benthic macroinvertebrates from persistent groundwater-dependent macrohabitats of varying hydrological connectivity and riparian shading were studied: perennial riffles, connected pools, shaded disconnected pools, and full sun disconnected pools. Riffles were a distinct habitat with significantly higher taxa richness, proportion of lotic taxa, diversity and evenness than other macrohabitats. Macrohabitats were found to be important refugia for 106 benthic macroinvertebrates and 4 microcrustacean taxa. Throughout the extreme drought, perennially flowing habitats were refugia to 19 taxa (17.9% total taxa) not collected in disconnected pools. Shaded disconnected pools contained lotic taxa not previously known to be able to complete their lifecycles in lentic habitats, emphasizing the importance of groundwater effluent and shading. With the resumption of flow at a downstream intermittent site of Ash Creek in mid-October 2006, an annual recolonization study was conducted comparing the perennial headwaters’ benthic macroinvertebrate taxa richness, densities and community ecology with the downstream intermittent site. The headwaters supported higher mean taxa richness than the intermittent site over the duration of the study (ANOVA P < 0.001). However, the unexpected result of overall decreasing taxa richness at the perennial headwater site from August 2006 to April 2008 appears to reflect lag effects of the supra-seasonal drought combined with effects of

multiple spates of 2007, which are factors confounding the point of recovery for taxa richness. Recovery of taxa richness at the intermittent site took 9 months compared to 1 to 2 months reported in other arid and semi-arid streams in the United States recovering from seasonal drying and floods. Sustainable use of groundwater resources and conservation of riparian corridors is vital to protecting groundwater-dependent ecosystems that play a vital role in maintaining regional biodiversity by serving as biotic refugia during catastrophic disturbance.

Copyright 2012 by
Rosemary A. Burk
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ACKNOWLEDGEMENTS I gratefully acknowledge the following people:
My major professor, Dr. James H. Kennedy for his mentorship and patience. Committee member, Dr. Paul Hudak for his course in Groundwater Hydrology and for taking the time to visit the study area, which provided me insight into groundwater and geology of the area. Committee members Dr. Thomas La Point, Dr. Barney Venables and Dr. Earl Zimmerman for their mentorship. Dr. Leonard Ferrington, Jr. for taxonomic verification of Chironomidae pupal exuviae. Aquatic Ecology students Tamara Contador, Claire Curry, Benjamin Lundeen, Jaime Slye, and Allison Stamatis for their assistance in the field. Sanju Eswaran, Stephanie Middleton, and Rebecca Wilson for their assistance sorting benthic samples and slidemounting Chironomidae. I am grateful to the private property owners of Ash Creek who granted me access to study sites. This research would not have been possible without their support.
I am grateful to my husband, Jan Kallberg, and family for their unwavering support and encouragement throughout this process.
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TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS........................................................................................................... iii
LIST OF TABLES ........................................................................................................................ vii
LIST OF FIGURES ....................................................................................................................... ix
CHAPTER 1 SPRINGS AS REFUGIA: DIFFERENCES IN INVERTEBRATE COMMUNITIES FROM GROUNDWATER-DEPENDENT HABITATS WITH VARYING HYDROLOGY AND RIPARIAN COVER DURING A SUPRA-SEASONAL DROUGHT ...... 1
Introduction......................................................................................................................... 1 Disturbance and Drought ........................................................................................ 1 Importance of Groundwater-Dependent Ecosystems ............................................. 3 Springs as Refugia .................................................................................................. 4 Study Objectives ..................................................................................................... 6
Materials and Methods........................................................................................................ 7 Study Area .............................................................................................................. 7 Study Area Climate............................................................................................... 10 Field and Laboratory Methods.............................................................................. 12 Data Analyses ....................................................................................................... 15
Results............................................................................................................................... 16 Macrohabitat Community Composition ............................................................... 18 Community Structure and Function...................................................................... 21
Discussion ......................................................................................................................... 25 Community Structure Differences Among Macrohabitats ................................... 27 Future Research Needs ......................................................................................... 31 Groundwater Conservation Management ............................................................. 32
CHAPTER 2 RECOLONIZATION AND COMMUNITY STRUCTURE DYNAMICS OF BENTHIC MACROINVERTEBRATES FOLLOWING A SUPRA-SEASONAL DROUGHT IN A FREQUENTLY DISTURBED GROUNDWATER-DEPENDENT STREAM IN SOUTHCENTRAL UNITED STATES..................................................................................................... 34
Introduction....................................................................................................................... 34 Disturbance ........................................................................................................... 34 Extreme Climatic Events ...................................................................................... 35
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Prior Drought Research......................................................................................... 36 Invertebrate Adaptations to Drought .................................................................... 36 Study Objectives ................................................................................................... 39 Materials and Methods...................................................................................................... 40 Study Site Description .......................................................................................... 40 Supra-Seasonal Drought 2005-2006 and Spring Spates of 2007.......................... 42 Field and Laboratory Methods.............................................................................. 43 Data Analyses ....................................................................................................... 44 Results............................................................................................................................... 46 Environmental Parameters .................................................................................... 46 Seasonal Changes in Trophic Structure ................................................................ 52 Post-Spate Communities ....................................................................................... 58 Dry Year 2006 versus Wet Year 2007 .................................................................. 59 Discussion ......................................................................................................................... 60 Initial Colonization at the Intermittent Study Site ................................................ 60 Post-winter Succession of Taxa at Intermittent Study Site................................... 62 Dry Year and Wet Year Comparison.................................................................... 63 Taxa Restricted to Perennial Habitats................................................................... 64 Flow Permanence Maintenance Temporal and Spatial Spring Refugia ............... 66
CHAPTER 3 CHIRONOMIDAE COMMUNITY COMPOSITION AND EMERGENCE PHENOLOGIES FROM PERENNIAL AND INTERMITTENT SITES IN A GROUNDWATER-DEPENDENT STREAM FOLLOWING A SUPRA-SEASONAL DROUGHT ................................................................................................................................... 71
Introduction....................................................................................................................... 71 Study Objectives ................................................................................................... 73
Materials and Methods...................................................................................................... 74 Study Site Description .......................................................................................... 74 Hydrological Periodicity and Sampling Dates...................................................... 75 Chironomidae Pupal Exuviae Collection Methods and Taxonomic Determinations ............................................................................................................................... 76
Results............................................................................................................................... 78 Overall Chironomidae Community Composition and Taxa Richness.................. 78 Annual Chironomidae Community Composition ................................................. 80
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Seasonal Differences in Chironomidae Community Composition....................... 83 Emergence Phenologies of Taxa Dominant at Both Study Sites .......................... 86 Resumption of Flow and Emergence Phenology Differences Between Intermittent Sites....................................................................................................................... 93 Seasonal and Overall Community Similarity of Chironomidae ........................... 94 Discussion ......................................................................................................................... 95 CHAPTER 4 SUMMARY AND CONCLUSIONS ................................................................... 104 Research Implications and Challenges to Groundwater Conservation........................... 109 Cultural Path Dependency .............................................................................................. 111 LITERATURE CITED ............................................................................................................... 113
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LIST OF TABLES
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TABLE 1.1. Mean, minimum and maximum ranges for environmental variables in persistent perennial (riffle and connected pool) and intermittent (shaded and full sun disconnected pool) macrohabitats in north-central Texas during the 2006 supra-seasonal drought ........................... 17
TABLE 1.2. Mean (±1 SD) taxonomic diversity, evenness, and richness of macroinvertebrates in riffles and pools of a perennial and intermittent stream in north-central Texas during August 2006-November 2006 ................................................................................................................... 19
TABLE 1.3. Lotic benthic macroinvertebrate taxa from macrohabitats of Ash and Silver Creeks August to November 2006 during a supra-seasonal drought........................................................ 20
TABLE 1.4. Mean standardized densities (D) (no./m2) and relative abundances (RA) of the 43 most abundant invertebrate taxa among macrohabitats of varying permanence and canopy-cover from summer to late fall 2006 during the supra-seasonal drought in north-central Texas ........... 22
TABLE 1.5. Relative abundance (%) values of macroinvertebrate functional feeding groups by macrohabitat type. FC filtering-collectors, GC gathering-collectors, PR predators, SHR shredders, SCR scrapers................................................................................................................ 23
TABLE 2.1. Environmental instream variables based on periodic point measurements in Ash Creek at Study Sites 1 and 2 (perennial) and Study Site 3 (intermittent) from August 2006 to July 2008. (“-” = no data available)...................................................................................................... 47
TABLE 2.2. Mean (±1 SE) taxonomic richness, density [log10 (x+1)], diversity, and evenness of macroinvertebrates in riffles of Ash Creek in north-central Texas from fall 2006 to summer 2007 and spring 2008............................................................................................................................. 50
TABLE 2.3. Relative abundance (%) values of macroinvertebrate functional feeding groups (FFG) at Study Site 1 (perennial headwaters) during the study.................................................... 53
TABLE 2.4. Relative abundance (%) values of macroinvertebrate functional feeding groups (FFG) at Study Site 3 during the study ......................................................................................... 53
TABLE 2.5. Mean standardized densities (D; no./m2) and relative abundances (RA) of invertebrate taxa with seasonal abundances >0.3% at Study Sites 1 and 3 during the 2005-2007 supra-seasonal drought in north-central Texas ............................................................................. 54
Table 2.6. Mean standardized densities (D; no./m2) and relative abundances (RA) of invertebrate taxa with seasonal abundances >0.3% at Study Sites 1 and 3 spring 2007 and spring 2008 following the 2005-2007 supra-seasonal drought in north-central Texas .................................... 55
TABLE 2.7. Mean standardized densities (D; no./m2) and relative abundances (RA) of invertebrate taxa with seasonal abundances >0.3% at Study Sites 1 and 3 spring 2007 and spring 2008 following the 2005-2007 supra-seasonal drought in north-central Texas ........................... 56
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TABLE 2.8. Mean standardized densities (D; no./m2) and relative abundances (RA) of invertebrate taxa with seasonal abundances >0.3% at Study Sites 1 and 3 summer2007 and summer 2008 following the 2005-2007 supra-seasonal drought in north-central Texas.............. 57 TABLE 3.1. Total samples collected, observed species richness, and community complementarity of Chironomidae in Ash Creek at the perennial headwaters (Study Site 1), perennial mid-stream site (Study Site 2), and intermittent site (Study Site 3) ................................................................ 79 TABLE 3.2. Annual and seasonal Chironomidae community composition (relative and actual abundances) for Study Sites 1 and 3 from Ash Creek in samples collected in summer 2006 to summer 2007 and fall 2008........................................................................................................... 81 TABLE 3.3. Dominant taxa that account for 90% of total emergence at Study Sites 1 (n = 518) and 3 (n = 382) during summer 2006-summer 2007 .................................................................... 85 TABLE 3.4. Observed emergence patterns of Chironomidae by subfamily at all study sites as determined by collections of pupal exuviae.................................................................................. 87 TABLE 3.5. Relative abundance emergence patterns of Chironomidae at Study Sites 1 and 3 on Ash Creek as determined by collections of pupal exuviae. .......................................................... 90 TABLE 3.6. Summary of comparable Chironomidae studies and reported community compositions by subfamily/tribe and species richness. ................................................................ 97
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Ash CreekPoolsDensitiesAbundancesTaxa Richness