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LARGE RIVER FOOD WEBS: INFLUENCE OF NUTRIENTS, TURBIDITY, AND FLOW, AND IMPLICATIONS FOR MANAGEMENT A Dissertation by KATHERINE ANNE ROACH Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2012 Major Subject: Wildlife and Fisheries Sciences LARGE RIVER FOOD WEBS: INFLUENCE OF NUTRIENTS, TURBIDITY, AND FLOW, AND IMPLICATIONS FOR MANAGEMENT A Dissertation by KATHERINE ANNE ROACH Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Kirk O. Winemiller Committee Members, Stephen E. Davis, III Micky D. Eubanks Lee A. Fitzgerald Amanda L. Stronza Head of Department, John B. Carey August 2012 Major Subject: Wildlife and Fisheries Sciences iii ABSTRACT Large River Food Webs: Influence of Nutrients, Turbidity, and Flow, and Implications for Management. (August 2012) Katherine Anne Roach, B.Sc., Buena Vista University; M.A., University of Kansas Chair of Advisory Committee: Dr. Kirk O. Winemiller Humans impact rivers in many ways that modify ecological processes yielding ecosystem services. In order to mitigate anthropogenic impacts, scientists are challenged to understand interactions among physicochemical factors affecting large river food webs. An understanding of socioeconomic factors also is critical for ecosystem management. In this dissertation, I explore spatiotemporal patterns in floodplain river food webs and political barriers to management of environmental flows, an important factor influencing river ecology. In Chapter II, I reviewed the scientific literature to test conceptual models of river food webs and predictions of environmental factors that might produce variation in basal production sources supporting consumer biomass. My review indicates that algae are the predominant production source for large rivers worldwide, but consumers assimilate C3 plants in rivers 1) with high sediment loads and low transparency during high flow pulses, 2) with high dissolved organic matter concentrations, and 3) following periods of high discharge or leaf litter fall that increase the amount of terrestrial material in the particulate organic matter pool. iv In Chapter III, I descrobe field research conducted to examine relationships among hydrology, nutrient concentrations, turbidity, and algal primary production and biomass in the littoral zone of five rivers in Texas, Peru, and Venezuela differing in physicochemical conditions. I used stable isotope signatures to estimate contributions of algal- versus terrestrial-based production sources to consumers during different hydrologic periods. My research indicates that during flow pulses in floodplain rivers, a decrease in algal biomass and productivity, combined with increased inputs of terrestrial organic matter, can result in increased terrestrial support of metazoan consumers in the aquatic food web. In 2007, Texas Senate Bill 3 directed that environmental flow recommendations be developed for river basins. Despite emphasis on use of the “best available science” to develop environmental flow regimes and “stakeholder involvement” to address needs of all water users, for the first two basins to complete the SB3 process, final environmental flow rules did not mimic a natural flow regime. In Chapter IV, I reviewed this process, concluding that incentives for river authorities to increase compromise with diverse stakeholders should result in more sustainable management of freshwater. v To Mama and Daddy, who limited TV watching to one hour a day vi ACKNOWLEDGEMENTS I am extremely grateful to the many mentors and colleagues who have assisted me during my pursuit of a PhD. My advisor, Kirk Winemiller, is the reason I chose to move to College Station, Texas. I couldn’t have made a better decision – Kirk taught me more about food web ecology, fisheries biology, and the scientific process than I ever could have imagined. He also is an excellent editor, and I appreciate his rapid feedback on manuscripts. In addition to his support as a mentor, Kirk provided me with a great deal of funding for my own research. I am also grateful to other mentors who influenced my intellectual development. Steve Davis has consistently provided me with detailed, insightful feedback on manuscripts and research proposals. Furthermore, he allowed me to not only use his five internally logging Hydrolab minisondes, but also to travel with them to Benin, Peru, and Venezuela. The Peruvian field school led by Lee Fitzgerald, Amanda Stronza, and Don Brightsmith was instrumental in teaching me how to get around Peru before conducting my own field research. Micky Eubanks also provided support and instruction during my time at Texas A&M University. I also thank all of the graduate and post-doctoral students in Kirk Winemiller’s lab: Liz Carrera, Bibiana Correa, Dan Fitzgerald, Andrew Jackson, Nathan Lujan, Chevaun McCray, Carmen Montaña, JV Montoya, Chouly Ou, Allison Pease, Becca Pizano, Michi Tobler, and Crystal Watkins. The opportunity to routinely interact with students from all over the world, including Brazil, Cambodia, Colombia, Peru, and vii Venezuela, in addition to the US, has been extremely fulfilling. I was fortunate to have been able to take classes, conduct research, and travel with such an enjoyable, intelligent group of people. Also, thank you to the many colleagues who assisted me in the field, particularly those who helped me with field work in the Tambopata River in Peru. It would not have been possible without the help of Crissel Vargas Laura, who cheerfully assisted me with purchasing equipment in Peru months before the field season began so that I could begin conducting research as soon as I arrived. Thank you to Gaby and Don Brightsmith, who let me use their boat, the Pionus menstruus. I am grateful to the Ese Eja community of Infierno for granting me access to their land, and to local field assistants David Flores and Roberto Amosins for their invaluable assistance in catching fish. Kurt Holle, manager of the ecotourism company Rainforest Expeditions, allowed Andrew Jackson, Carmen Montaña and me to stay at the ecotourism lodge Posada Amazonas. Hernan Ortega Torres, curator of fishes from the Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, helped me to obtain a permit so that I could take samples from Peru into the United States. I am also grateful to the Applied Biodiversity Science field school participants who took chlorophyll a and nutrient samples. At the Cinaruco River in Venezuela, Wilson and Yarisma Garcia collected stable isotope samples, Carmen Montaña and JV Montoya assisted with handing off of sampling supplies, and JV Montoya allowed me to use his nutrient, primary production, and chlorophyll a data. A large group of undergraduate students, graduate students, and visiting researchers assisted with sampling in the Brazos, Guadalupe, and Neches Rivers: viii Anthony Braden, Andrew Jackson, Adam Landon, Nathan Lujan, Zach Peterson, Nicole Smolensky, Ursulla and Fabio Souza, Crystal Watkins, Chevaun McCray, and many others. Finally, I am grateful to those who took the time to explain their perspective of the Texas Environmental Flow program to me: Kathy Alexander, Kip Averitt, Dave Buzan, Ken Kramer, Kevin Mayes, David Roemer, Mark Wentzel, and Kirk Winemiller. I was fortunate to receive the Merit Fellowship from Texas A&M University which funded my first year of PhD study. The Applied Biodiversity Science IGERT at Texas A&M University program provided me with funding for two years, in addition to encouraging me to collaborate with graduate students outside of my discipline. I was fortunate to spend many hours attending Applied Biodiversity Science – sponsored events, including journal club, seminars, and the Peruvian field school. I value the time I spent with fellow ABS students and coordinators, Elizabeth Shapiro and Leslie Ruyle. I also wish to extend my gratitude for receiving the Tom Slick Graduate Research Fellowship, which funded me while I wrote this dissertation. I owe thanks to my parents, Mike and Sara Roach, who have provided endless encouragement throughout my long-term graduate student status. They were not only cheerleaders, but also assisted me financially by paying for clothing, plane tickets home for Christmas, and student fees. Finally, I thank my husband Andrew Jackson. He not only endured bowel problems, extreme humidity, and sand fly bites during four months of field work in Peru and several months of field work in Texas, but also has provided me with emotional support while finishing his own thesis. ix TABLE OF CONTENTS Page ABSTRACT .............................................................................................................. iii DEDICATION .......................................................................................................... v ACKNOWLEDGEMENTS ...................................................................................... vi TABLE OF CONTENTS .......................................................................................... ix LIST OF FIGURES ................................................................................................... xi LIST OF TABLES .................................................................................................... xiii CHAPTER I GENERAL INTRODUCTION ........................................................... 1 Chapter