INVERTEBRATE ABUNDANCE AND FOOD SOURCES WITHIN RIVERINE- ESTUARINE SYSTEMS ALONG THE WEST COAST OF THE ISLAND OF NEWFOUNDLAND By © Wyn Rolls A thesis submitted to the School of Graduate Studies in partial fulfilment of the requirements for the degree of Master of Science Department of Environmental Science Memorial University of Newfoundland October 2017 St. John’s Newfoundland Abstract Understanding natural patterns and processes underlying the structure and function of biotic communities remains a central aim of ecology. However, there is a paucity of information related to the distribution patterns and community structure of biota that inhabit the transitional zone between rivers and estuaries in boreal estuarine systems. Moreover, the influence of climate change on these patterns is still poorly understood. To better elucidate these patterns this study focused on selected aquatic invertebrates within four boreal riverine-estuarine zones located along a south to north gradient in western Newfoundland, Canada. Samples of Ephemeroptera, Plecoptera and Trichoptera species were collected from each zone and identified to determine whether there was an expected decrease in number of species with both increasing latitude and increasing salinity. A decrease in the number of species with latitude was not observed. Within riverine- estuarine zones a negative correlation was evident between number of species and salinity. Aquatic insects and one amphipod species were collected from Salmon River and categorized into functional feeding groups. These invertebrates, along with biofilm, particulate organic matter, and various terrestrial and aquatic plants were analyzed for carbon, nitrogen, and hydrogen stable isotopes. Hydrogen isotope values were useful as a supplement to carbon in determining sources of energy being utilized by the functional feeding groups. However, the hydrogen isotope values were not distinct between functional groups and therefore, cannot be used in conjunction with nitrogen isotopes to determine trophic levels. i Acknowledgements I wish to extend sincere gratitude to my supervisors, Drs. Wade Bowers and Sue Ziegler for their guidance and support and for always making themselves available for helpful advice. I would also like to thank the other member of my supervisory committee, Dr. David Schneider, for his statistical advice and constructive comments on the thesis. The field work was assisted by Raphael Soucy whose stories and sense of humor made the long days spent in the cold rivers seem to fly by. I also thank Drs. Marilyn Fogel and Roxane Bowden of the Carnegie Institute, Washington for running the stable isotope analyses for me. I am grateful to Dean Strickland and Peter Davis of the Humber River Basin Project for all of their assistance. I would like to express my appreciation to Dr. Ian Warkentin for his helpful advice on the statistical analyses. Thanks also to my colleagues at Grenfell Campus, Memorial University, especially Cheryl Butt, Dara Walsh, Debbie Wheeler, and Mary Secord for reading and helping with editing sections of the thesis. Funding for this research was provided by the Humber River Basin Project, a Carnegie of Canada Research Grant and Memorial University of Newfoundland. Finally, I would like to express my profound gratitude to my friends and family, especially my parents – my father, the late Harry Rolls, for instilling in me a love of nature and the environment, and my mother, Elizabeth Rolls, for providing me with unfailing support and continuous encouragement. ii Table of Contents Abstract……………………………………………………………………………….... i Acknowledgements……………………………………………………………………. ii List of Tables……………………………………………………………………………v List of Figures…………………………………………………………………………. vii 1 Introduction .............................................................................................................. 1-1 1.1 General Introduction ......................................................................................... 1-1 1.2 Estuaries ............................................................................................................ 1-4 1.3 Aquatic Insects .................................................................................................. 1-6 1.4 Stable Isotopes................................................................................................... 1-9 2 Abundance, Diversity and Distribution of Aquatic Insects Within and Among Riverine-Estuarine Systems ............................................................................................. 2-1 2.1 Introduction ....................................................................................................... 2-1 2.1.1 Latitudinal Diversity Gradient ................................................................... 2-2 2.1.2 Conductivity and Salinity .......................................................................... 2-3 2.1.3 Study Objectives ........................................................................................ 2-6 2.2 Methods ............................................................................................................. 2-6 2.2.1 Study Locations, Geological Setting, and Climate Conditions.................. 2-6 2.2.2 Sampling Procedure ................................................................................. 2-19 2.2.3 Analytical Methods .................................................................................. 2-22 2.3 Results ............................................................................................................. 2-27 2.3.1 Richness and Abundance of EPT Taxa .................................................... 2-27 iii 2.3.2 Diversity ................................................................................................... 2-31 2.3.3 Univariate Analysis .................................................................................. 2-37 2.3.4 Ordination – Canonical Correspondence Analysis .................................. 2-44 2.4 Discussion ....................................................................................................... 2-53 2.4.1 Latitudinal Gradient ................................................................................. 2-54 2.4.2 Salinity Gradient ...................................................................................... 2-56 2.4.3 Ordination – Canonical Correspondence Analysis .................................. 2-58 2.5 Conclusions and Recommendations................................................................ 2-59 3 Stable Isotope Analysis of Trophic Levels Within an Aquatic Food Web .............. 3-1 3.1 Introduction ....................................................................................................... 3-1 3.1.1 Stable Isotopes ........................................................................................... 3-5 3.1.2 Study Objectives ...................................................................................... 3-13 3.2 Methods ........................................................................................................... 3-14 3.2.1 Study Location ......................................................................................... 3-14 3.2.2 Sampling Procedure ................................................................................. 3-14 3.3 Results ............................................................................................................. 3-18 3.4 Discussion ....................................................................................................... 3-33 3.5 Conclusion ....................................................................................................... 3-38 4 Summary .................................................................................................................. 4-1 5 References ................................................................................................................ 5-1 iv List of Tables Table 1-1 Classification of functional feeding groups for aquatic insects ................ 1-9 Table 2-1 Name, location, latitude/longitude and climate data for the four sites sampled in this study. .................................................................................................... 2-7 Table 2-2 Wentworth Grain-Size Classification (Wentworth, 1922) ...................... 2-11 Table 2-3 Abiotic data for the five sites at each river for the two sampling dates . 2-21 Table 2-4 Number of species of each Order collected at each river from north to south for two sampling periods, June and August 2010. The number of species that are common between sampling periods are shown in parenthesis. ......................... 2-29 Table 2-5 Common species between June and August for each river system. ....... 2-30 Table 2-6 Shannon-Wiener Index, Relative Species Abundance per River, Number of Species, and Evenness values for four riverine-estuarine systems for June and August 2010. ................................................................................................................. 2-32 Table 2-7 Relative Species Abundance of EPT per Site, Shannon-Wiener Index, Species Richness and Evenness values for sampling sites within rivers for June 2010. ........................................................................................................................................ 2-35 Table 2-8 Relative Species Abundance of EPT per Site, Shannon-Wiener Index, Species Richness and Evenness values for sites