Patterns in Potamoplankton of the Saginaw River and Shiawassee National Wildlife Refuge, Michigan James K. Stack A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science (Natural Resources and Environment) at the University of Michigan, December 2015 Faculty Advisors: Dr. Michael J. Wiley, Chair Dr. Catherine Riseng Dr. Kurt Kowalski, (USGS-GLSC) Abstract As part of ongoing research evaluating the baseline conditions of the Shiawassee National Wildlife Refuge (SNWR), Michigan, prior to a large scale floodplain wetland restoration, this project focused the variation in phytoplankton and water chemistry; spatially, seasonally, and hydrologically. During the growing season of 2014, phytoplankton and water chemistry parameters were surveyed throughout the SNWR and Saginaw River. These samples were synthesized and data were compared for patterns by season, sample location, and longitudinal position on the Saginaw River. Phytoplankton and water chemistry were also compared to hydrologic data including river slope (which served as an indicator of hydraulic residence time) as well as the occurrence of reverse or stalled flow in the Saginaw River. Results indicated that phytoplankton communities in floodplain wetlands, tributaries, and the main river channel varied significantly by taxonomic composition and abundance, as did key water chemistry parameters (Total Phosphorus, Nitrate, Total Dissolved Solids). Additionally, potamoplankton communities in the Saginaw River varied longitudinally, becoming more abundant, taxonomically rich, and diverse from upstream to downstream. Prolonged residence times due to low slopes also showed more diverse and abundant potamoplankton communities with fewer diatoms than times of high slopes. The occurrence of reverse flow was found to be associated with a homogenizing effect along the course of the Saginaw River both in terms of biology and water chemistry. i Acknowledgements I would like to thank all family, friends, and relatives who have supported me throughout my time as a graduate student. I would also like to especially thank my thesis advisor Mike Wiley, who through his insight and expertise on all things rivers, has been a truly great mentor to me. Additionally I would like to thank Sara Alderstein-Gonzales, Catherine Riseng, Kurt Kowalski, and all other researchers and faculty who have provided me with guidance, advice, and feedback throughout the many phases of this process. A special thank you goes out to all of the staff at the Shiawassee National Wildlife Refuge, with a special thanks to Eric Dunton, Steve Kahl, and David Peters for their involvement, advice, and help on this project. Additionally, I would like to thank the U.S. Fish and Wildlife Service, the USGS Great Lakes Science Center- Ann Arbor, the University of Michigan Rackham School of Graduate Studies, and the School of Natural Resources and Environment for funding that made this project possible. ii Contents Abstract ..................................................................................................................................... i Acknowledgements .................................................................................................................. ii Introduction .............................................................................................................................. 1 Methods ................................................................................................................................... 6 Sampling sites ...................................................................................................................... 6 Sampling Protocols .............................................................................................................. 9 Potamoplankton ................................................................................................................. 11 Statistical Methodology ..................................................................................................... 13 Results.................................................................................................................................... 15 Categorical and Seasonal Variations in Water Quality ..................................................... 15 Categorical and Seasonal Trends in Potamoplankton ....................................................... 16 Longitudinal Trends ........................................................................................................... 18 Flow and Residence Time Related Trends ........................................................................ 18 Discussion .............................................................................................................................. 21 Potamoplankton Community Trends ................................................................................. 21 Longitudinal Variation Within the Saginaw River ............................................................ 23 Influence of Residence Time ............................................................................................. 25 Phytoplankton of SNWR and Saginaw River .................................................................... 32 Conclusions............................................................................................................................ 36 Figures and Tables ................................................................................................................. 39 Figure 1 Maps of Saginaw River Watershed and Sampling Sites ..................................... 39 Figure 2 Shiawassee National Wildlife Refuge Gage and Upstream Discharge ............... 40 Figure 3 Histogram Of Saginaw River Daily Averaged Slopes ........................................ 41 Figure 4 Boxplots of Longitudinal Correlations ................................................................ 42 Figure 5 NMDS Plot of Potamoplankton Communities By Flow Type ............................ 43 Figure 6 Differences in Longitudinal Variations By Flow Type ....................................... 44 Figure 7 Average Potamoplankton Composition by Rivermile and Date ......................... 45 Figure 8 Potamoplankton Composition By Site and Date ................................................. 46 Figure 9 Approximated Residence Times of the Saginaw River ...................................... 47 Figure 10 Boxplots of Biological Parameters .................................................................... 48 Figure 11 Boxplots of Water Chemistry Parameters ......................................................... 49 Figure 12 Method for Calculating Residence Time (Python Code) .................................. 50 Table 1 Sampling Site Characteristics ............................................................................... 51 iii Table 2 Mean Values of Chemical Parameters .................................................................. 52 Table 3 Two-Way ANOVA With Interactions Results ..................................................... 53 Table 4 Mean Values of Biological Parameters ................................................................ 54 Table 5 Pearson’s R Linear Correlation Matrix ................................................................. 55 Table 6 Partial Correlation Matrix ..................................................................................... 56 Table 7 NMDS Scores for Main River Channel Samples ................................................. 57 Table 8 NMDS Scores for Main River Channel Taxa ....................................................... 58 Table 9 Dominant Potamoplankton Genera by Site and Date ........................................... 59 Bibliography: ......................................................................................................................... 60 Appendix 1: Potamoplankton Counts .................................................................................... 65 Appendix 2: Sample Data (Chemistry, Hydrologic, and Potamoplankton Community Metrics) .................................................................................................................................. 68 iv Introduction Floodplain wetlands play a crucial role in the ecology of riverine systems. There are many ways in which they influence important biotic and abiotic processes including flood attenuation, baseflow yields, fish spawning habitat, nutrient processing, and carbon dynamics (Junk et al. 1989, Racchetti et al. 2011, Lizzote et al. 2012, Mackay et al. 2012, Powers et al. 2013). Floodplain systems also affect the quantity and composition of riverine phytoplankton, (potamoplankton) found within the water column of main channel of the river itself (Köhler et al. 2002, Nabout et al. 2006, Walks 2007, Weilhoefer et al. 2008, Houser et al. 2010, Mackay et al. 2012). The Saginaw River in Michigan (Figure 1) constitutes as much as 90% of the tributary nutrient loading to the Saginaw Bay (, Bierman and Dolan 1986, Cha et al. 2013) and plays an important part in shaping the phytoplankton productivity in the inner bay (Stoermer and Theriot 1985). A number of algal taxa common in the Saginaw Bay plankton community are reported to be riverine in origin, including Rhodomonas (Cryptophyte), Gloeotila (Green Algae), Cyclotella, Aulacoseira, Thallasiorsira (Diatoms), Aphanizomenon, and Oscillatora (Cyanobacteria) (Stoermer and Theriot 1985). The Saginaw River therefore provides