Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution and Abundance in a

78 Pages·2015·2.03 MB·English

Georgia State University
ScholarWorks @ Georgia State University
Geosciences Theses Department of Geosciences
5-7-2011
Particle Size, Critical Shear Stress, and Benthic
Invertebrate Distribution and Abundance in a
Gravel-bed River of the Southern Appalachians
Helen Mayoral
Georgia State University
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Mayoral, Helen, "Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution and Abundance in a Gravel-bed River of the
Southern Appalachians." Thesis, Georgia State University, 2011.
http://scholarworks.gsu.edu/geosciences_theses/31
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PARTICLE SIZE, CRITICAL SHEAR STRESS, AND BENTHIC INVERTEBRATE
DISTRIBUTION AND ABUNDANCE IN A GRAVEL-BED RIVER OF THE SOUTHERN
APPALACHIANS

by

HELEN M. MAYORAL

Under the Direction of Jordan A. Clayton

ABSTRACT
To determine the relationship between the abundance and density of benthic invertebrates,
and the critical shear stress of individual grain sizes, a reach along Smith Creek, was divided into
ten 2m x 2m quadrants. Within each quadrant, five randomly selected clasts for each grain size
ranging from 2.26 to 25.6 cm were cleaned for benthic invertebrates. Wolman pebble counts for
each quadrant were also conducted and used to determine the critical Shields stress per grain size
fraction from the model given by Wiberg and Smith (1987) that explicitly accounts for particle
hiding/sheltering effects in mixed-bed rivers. Particle entrainment values were then compared
with estimated bankfull Shields stress values to determine sediment transport potential during
bankfull flow. Invertebrate abundance was strongly positively correlated with critical Shields
stress up to the 18.0 cm grain size, indicating a preference for certain grain sizes; while density
was positively correlated with all grain sizes present.
INDEX WORDS: Benthic invertebrates, Shear stress, Critical Shields stress, Invertebrate abundance,
Embeddedness, Invertebrate diversity, Organism-substrate relationships, HEC-RAS.
Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution and Abundance
in a Gravel-bed River of the Southern Appalachians

by

HELEN M. MAYORAL

A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Arts
in the College of Arts and Sciences
Georgia State University
2011
Copyright by
Helen Mary Mayoral
2011
Particle Size, Critical Shear Stress, and Benthic Invertebrate Distribution, Abundance and
Density in a Gravel-bed River of the Southern Appalachians

by

HELEN M. MAYORAL

Committee Chair: Dr. Jordan A. Clayton
Committee: Dr. Daniel Deocampo
Dr. Seth Rose

Electronic Version Approved:

Office of Graduate Studies
College of Arts and Sciences
Georgia State University
May 2011
iv

DEDICATION
First, I‟d like to start by thanking my parents. You‟ve given so much support, over the past
several years especially. I appreciate all that you have done for me. The more people I come to
know, the more I realize what all you have given and sacrificed for your children. It does not go
unnoticed or unappreciated, and I can only hope to one day, be able to repay the kindness and
support that you have shown me. I can never make you two sufficiently proud, and it is
something I strive for constantly. I love you both with all of my heart. Now to only get you to
retire…
For my sister, you have been supportive through it all - thank you for being so patient and
understanding of my lack of time. I love you. I look forward to spending more time together.
Rudy, what can I say. You have allowed yourself to become second priority in my life for
the sake of my studies. I am excited about starting a new chapter of our lives, together. You are
my rock. I love you. And I‟m holding you to those cooking classes you promised…
All of you will be walking across the stage with me on May 7th. And though I shake the hand
of important officials and significant professors, the true honor is having you all in my life - my
family, forever. There are no words to sufficiently express my gratitude.
v

ACKNOWLEDGEMENTS
I would like to thank my thesis advisor, Dr. Jordan Clayton, for the infinite patience he has
shown me over the time that I have been under his direction. You have been a steady, reliable
instructor and advisor. I feel honored to have been extended your acceptance as your graduate
student and hope that despite the mayhem, I have made you a proud adviser.
To Dr. Dan Deocampo, I leave sorry that I did not come to know you sooner. You are the
reason students stay in school beyond their undergraduate degrees. Thank you for the use of
your lab and equipment. Your charisma and positive outlook helped motivate me.
Dr. Seth Rose, you remind me a lot of my father. He has a quiet strength, with just a touch of
intimidation to keep you on track. Thank you for your direction.
Dr. Jeremy Diem, you were a constant reminder to never take myself too seriously and to
have fun. Thank you for all your direction with the statistics!!
To Mr. Michael stone, thank you for your assistance with identification. To Dr. Marsh
Youngbluth, Dr. Masterson, and Dr. Cook at Harbor Branch Oceanographic Institute - I attribute
most of my ability to write and think scientifically to your instruction and the institution. My
professors and I thank you! To Mr. Stephen Zelenty, for believing in me before I even knew
how to. You all instilled in me an attention to detail and a strong work ethic that I am proud of.
To Zoia Comarova and Serghei Mangul, I could not have done it without you. Undoubtedly.
My fellow TAs who helped with my labs: Brian Vann, Cheryl Nye and Tracy Dahl, among
others; and the Hydrology students that helped with field work - Thank you SO much!!
Last, but certainly not least, I would also like to thank GA Department of Natural Resources,
Georgia State Parks, the staff at Unicoi State Park, Park Manager Scott Hudgins, and Park
Resource Manager Ellen Graham for the permit to conduct the research and their assistance.
vi

TABLE OF CONTENTS
ACKNOWLEDGEMENTS v
LIST OF TABLES viii
LIST OF FIGURES ix
1 INTRODUCTION 1
1.1 Purpose of the Study 3
1.2 Expected Results 3
2 BACKGROUND 3
2.1 Summary 14
3 STUDY INFORMATION 15
3.1 Site Setting 15
3.2 Methodology 16
3.2.1 Site Characteristics 16
3.2.2 Bankfull Shields stress 18
3.2.3 Critical shear stress 20
3.2.4 Benthic invertebrates 20
3.2.5 Statistical tests 25
3.2.6 Surface area analysis 26
3.2.7 Embeddedness 26
4 RESULTS 27
4.1 Site Characteristics 27
4.2 Shear stress, Shields stress and critical Shields stress 29
4.3 Embeddedness 30
4.4 Benthic Invertebrates 31
4.4.1 Benthic invertebrate abundance 31
4.4.2 Benthic invertebrate density 32
vii

4.4.3 Benthic invertebrate abundance and density by Order, per grain size 33
4.4.4 Correlative relationships with critical Shields stress 34
5 DISCUSSION 36
5.1 Sediment transport potential 36
5.2 Benthic invertebrate abundance and density by grain size 37
5.3 Benthic invertebrate abundance and density by Order 40
5.4 Benthic invertebrate abundance and critical Shields stress 40
5.5 Benthic invertebrate density and critical Shields stress 42
6 CONCLUSIONS 43
REFERENCES 46
APPENDIX A 53
APPENDIX B 56
APPENDIX C 57
APPENDIX D 63
viii

LIST OF TABLES
Table 4.1. Critical Shields stress values per grain size fraction. 29
Table 4.2. Percent of potential exposure used to reduce surface area of larger grains to
account for embeddedness. 30
Table 4.3. Benthic invertebrate abundance by grain size and order. 32
Table 4.4. Invertebrate density accounting for embeddedness. 33