Sources and Ages of Carbon and Organic Matter Supporting Macroinvertebrate Production in Temperate Streams DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Amber Renee Bellamy Graduate Program in Evolution, Ecology and Organismal Biology The Ohio State University 2017 Dissertation Committee: Dr. James E. Bauer, Advisor Dr. Yu-Ping Chin Dr. Jonathan J. Cole Dr. Peter S. Curtis Dr. Andrea G. Grottoli Dr. S. Mažeika P. Sullivan Copyrighted by Amber Renee Bellamy 2017 Abstract Streams and rivers are tightly integrated into the terrestrial landscape and as a result are responsible for transporting and transforming globally significant amounts of terrestrially-derived materials. Much of this terrestrially-derived organic matter (OM) that is transported by streams and rivers is hundreds to thousands of years in age. Over the past couple decades, research has increasingly demonstrated the importance of terrestrial OM (i.e., allochthonous) to consumer nutrition in many aquatic ecosystems. However, there has been far less research to date on assessing the ages of carbon (C) and OM from different allochthonous and autochthonous (i.e., derived from within aquatic systems, e.g., algal and macrophytic) sources that are utilized by aquatic consumers and incorporated into aquatic food webs. There is also a need to better understand how human-mediated processes such as land use and climate change may lead to shifts in the inputs and nutritional roles of allochthonous and aged materials in streams and rivers. Stable isotopes (δ13C, δ15N, and δ2H) have been employed frequently in aquatic food web and ecosystem studies to quantitatively assess contributions of different nutritional resources to the biomass and secondary production of aquatic consumers. Natural abundance radiocarbon (14C) has been employed far less frequently in food web and ecosystem studies, however, because of its far greater dynamic range than most stable isotopes, the use of natural 14C as a tracer of C and OM inputs and utilization in ii inland waters allows for potentially greater differentiation between potential nutritional resources than stable isotopes alone. Natural 14C also uniquely allows for determination of the ages of the nutritional resources that contribute to aquatic consumer biomass and secondary production. In the present study, natural stable and radiocarbon isotopes were measured to assess contributions of allochthonous and autochthonous C and OM of varying age to the biomass of aquatic macroinvertebrates belonging to different functional feeding groups (FFGs) in a number of temperate streams in sub-watersheds of the Mohawk-Hudson River, New York (USA); Susquehanna River, Pennsylvania (USA); and the Ohio River, Ohio (USA). The overarching goals of the study were to i) estimate allochthonous and authochthonous nutritional contributions to aquatic macroinvertebrate consumers in these systems, ii) determine relative contributions of C and OM resources of varying ages to macroinvertebrate nutrition, and iii) assess how nutritional resource utilization varied as a function of stream physical characteristics, watershed land use and lithology, and temporal variability. Aquatic macroinvertebrates collected from the majority of streams studied were found to be primarily reliant on autochthonous OM, with greater contributions to the biomass of some FFGs (scrapers and filtering collectors; up to 99%) compared to others. However, allochthonous OM in the forms of terrestrial vegetation and soil/sediment OM also made significant contributions to the biomass of multiple FFGs (up to 85% and 46%, respectively), primarily shredders, chironomids, and collector-gatherers, across all systems studied. Macroinvertebrates collected from streams having a large proportion of iii agricultural land use in their watersheds were more reliant on soil/sediment-derived OM compared to macroinvertebrates collected from streams with low watershed agriculture. In addition, greater agricultural activity also led to elevated δ15N of algal biomass and macroinvertebrate consumer biomass but had minimal impacts on macroinvertebrate δ13C and δ2H values. The ∆14C values and ages of macroinvertebrates varied widely across sites and sampling times (-499‰ to 23‰; 5,550 years B.P. equivalent age to modern-aged, respectively). The apparent 14C “ages” observed for many of the macroinvertebrates measured were attributable to some combination of their consumption and utilization of i) truly aged soil/sediment OM and ii) apparently “aged” algae that fixed aged dissolved inorganic carbon (DIC). Finally, a comprehensive review and synthesis of studies that have used natural abundance 14C as a tracer in inland aquatic food webs was undertaken. With the exception of very large lakes (e.g., Lake Superior), in essentially every system studied one or more forms of aged C and/or OM contributed to the biomass of aquatic consumers, suggesting that geologically aged forms of C and OM are present in, and support to varying extents, modern-day aquatic ecosystems. In future studies, improved knowledge of the ages of C, OM, and consumers in inland water and other aquatic food webs could have fundamental implications for our understanding of terrestrial-aquatic linkages and the role(s) that the ages of nutritional resources may play in aquatic food web and ecosystem structure and function. iv Acknowledgments I would like to thank my major advisor, Dr. James Bauer, for providing guidance throughout the development of my project, supporting my project financially, encouraging me to interact with other scientists, and providing substantial feedback on this document. Thanks go to Dr. Jonathan Cole for his help and advice throughout this process, and his timely responses to my questions as they came up during various phases of my project. I am especially grateful to Dr. Andrea Grottoli who helped me extensively with finding and using the best approaches for analyzing my data. Additional thanks go to my other committee members Dr. Mazeika Sullivan, Dr. Peter Curtis, and Dr. Yu-Ping Chin who each encouraged me to think about my project from a variety of different perspectives. Without the assistance of Amy Barrett in the field and laboratory this project would not have been possible, and I am extremely grateful for her help and friendship throughout this process. I also thank my former lab mates Thomas Evans, Steven Gougherty, Scott Kelsey, and Dr. Katie Hossler for field assistance and their experienced advice and support throughout this process. Thanks also to Yohei Matsui in the OSU Stable Isotope Biogeochemistry lab, who always took great care in analyzing my samples. Finally, I would also like to thank the Hudson River Foundation for awarding me a year-long Mark B. Bain Graduate Fellowship that provided me with the resources to conduct the study of the Mohawk-Hudson watershed. v Vita 2005................................................................Dobyns-Bennett High School 2009................................................................B.S. Environmental Science, Gardner-Webb University 2010-2011 ......................................................AmeriCorps VISTA 2011-2012 ......................................................Graduate Research Assistant, Department of EEOB, Ohio State University 2012-2016 ......................................................Graduate Teaching Associate, Department of EEOB, Ohio State University Fields of Study Major Field: Evolution, Ecology and Organismal Biology vi Table of Contents Abstract ............................................................................................................................... ii Acknowledgments............................................................................................................... v Vita ..................................................................................................................................... vi Fields of Study ................................................................................................................... vi Table of Contents .............................................................................................................. vii List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................. xvii Introduction ......................................................................................................................... 1 Chapter 1: Influence of Land Use and Lithology in Sources and Ages of Nutritional Resources for Stream Macroinvertebrates: A Multi-Isotopic Approach ............................ 7 Abstract ........................................................................................................................... 8 Introduction ..................................................................................................................... 9 Methods ......................................................................................................................... 12 Results ........................................................................................................................... 18 Discussion ....................................................................................................................