A Thesis entitled Habitat Use and Community Structure of Unionid Mussels in Three Lake Erie Tributaries by Jeffrey D. Grabarkiewicz Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science in Biology, Ecology-track ___________________________________ Dr. Johan Gottgens, Committee Chair ___________________________________ Dr. Elliot Tramer, Committee Member ___________________________________ Dr. Daelyn Woolnough, Committee Member ___________________________________ Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo August 2012 An Abstract of Habitat Use and Community Structure of Unionid Mussels in Three Lake Erie Tributaries by Jeffrey D. Grabarkiewicz Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science in Biology, Ecology-track. The University of Toledo August 2012 Nearly 300 species of freshwater mussels (Bivalvia: Superfamily Unionoidea) have been documented in the United States. Unfortunately, this diversity is in peril, with 76 species currently listed as threatened or endangered under the Endangered Species Act. This research established unionid population estimates and habitat use within six reaches of three Western Lake Erie tributaries: the Blanchard River, Swan Creek, and Beaver Creek. Particular emphasis was placed on the federally endangered Rayed Bean (Villosa fabalis ). Quantitative sampling documented 22 live unionid species and 1,197 live individuals across all reaches and streams. Evidence of recent recruitment was documented for 10 species and size class diversity was found for 15 species. Unionid density and species richness were highest in the Upper Blanchard with a mean reach density of 4.48 unionids per m 2 and 15 live species. Rayed Bean (V. fabalis ) were estimated at 0.29 per m 2 in the Upper Blanchard and 0.13 per m 2 in Middle Swan Creek. Size class diversity for V. fabalis was found in both reaches, with many young individuals (< 18 mm) present in the Upper Blanchard. Qualitative Habitat Evaluation Index (QHEI) predicted species richness (R2 = 0.63) and density (R2 = 0.52) at the reach iii scale. Diversity peaked at an intermediate QHEI. Principal Components Analysis (PCA) suggested patterns in habitat use where Kidneyshell ( Ptychobranchus fasciolaris) and V. fabalis were more common in gravel while White Heelsplitter ( Lasmigona complanata complanata ), Giant Floater ( Pyganodon grandis ), and Fatmucket ( Lampsilis siliquoidea ) were substrate generalists. Components 1 and 2 explained 62.6 % of the data variation. Different burrowing patterns were observed among species, with V. fabalis, Spike (Elliptio dilatata ), Wabash Pigtoe ( Fusconaia flava ), Kidneyshell ( P. fasciolaris ), and Rainbow ( Villosa iris ) present in subsurface samples across most size classes. Shell lengths were significantly shorter for E. dilatata (p < 0.0001) and F. flava (p < 0.0001) found in subsurface samples across all reaches and streams using Mann-Whitney. These patterns appeared to link more with life history than substrate texture. Subsurface sampling highlighted the need to excavate sediments to accurately quantify population size, most notably for V. fabalis which were collected almost exclusively from subsurface samples (93%). This is the first large-scale quantitative unionid assessment of Western Lake Erie tributaries and the first extensive sampling of subsurface habitat. Future projects may use these data and results as a baseline when assessing changes in population sizes, determining the need to sample subsurface sediments, and identifying areas where populations of V. fabalis may occur. iv Acknowledgements I first would like to thank my advisor Dr. Johan Gottgens, whose guiding hand and patience with a part-time graduate student facilitated my academic development and this research project. I also wish to thank my committee members, Dr. Elliot Tramer and Dr. Daelyn Woolnough, for their valuable suggestions that helped formulate and refine my thesis. A special thanks is warranted to my undergraduate assistant, Craig Krajeski, who endured an intense sampling season during the summer and fall of 2010. I would like to recognize the Lake Erie Protection Fund (grant SG-383-10) for their valuable financial support. I would also like to thank the Department of Environmental Sciences for their support over the course of my graduate education. I remain in debt to the staff and Board of Supervisors at the Lucas Soil and Water Conservation District who gave me the flexibility to complete my degree. Finally, to my wife Melanie, daughter Nora, and family, for taking care of things I couldn't over the past few years. v Table of Contents Abstract iii Acknowledgements v List of Tables viii List of Figures xi 1 Introduction 1 2 Methods 7 2.1 Description of Streams, Reaches, and Sampling Sites 7 2.2 Qualitative Habitat Evaluation Index 9 2.3 Site Sampling Design 12 2.3.1 Site Preparation and Quadrat Sampling 12 2.4 Unionid Processing 15 2.5 Unionid Data Analysis 15 2.6 Habitat Data Analysis 17 3 Results and Discussion 19 3.1 Unionid Data 19 3.1.1 Blanchard River Unionids 20 3.1.2 Swan Creek Unionids 28 3.1.3 Beaver Creek Unionids 34 vi 3.2 Qualitative Habitat Evaluation Index 40 3.3 Microhabitat Use 44 3.4 Subsurface Sampling 50 4 Summary and Conclusions 58 References 63 vii List of Tables 2.1 Modified Wentworth scale used to classify surface and subsurface 15 substrate samples (Wentworth 1922). 3.1 Sorenson Similarity Index scores for all six reaches and three streams sampled during 2010. 20 3.2 Population and density estimates of freshwater mussels found in the Middle Blanchard River. 23 3.3 Population and density estimates of freshwater mussels found in the Upper Blanchard River. 24 3.4 Recruitment data for the Middle and Upper Blanchard River reaches. All shell measurements are in millimeters (mm). 25 3.5 Population and density estimates of freshwater mussels found in Middle Swan Creek. 30 3.6 Population and density estimates of freshwater mussels found in Upper Swan Creek. 30 3.7 Recruitment data for the Middle and Upper Swan Creek reaches. All shell measurements are in millimeters (mm). 31 viii 3.8 Population and density estimates of freshwater mussels found in Middle Beaver Creek. 36 3.9 Population and density estimates of freshwater mussels found in Upper Beaver Creek. 37 3.10 Recruitment data for the Middle and Upper Beaver Creek reaches. All shell measurements are in millimeters (mm). 38 3.11 Summary of mean surface substrate quadrat measurements for the eight most 49 common species across all reaches and streams. 3.12 Percentage of individuals found in subsurface samples (Qb) as a percentage 52 of total live individuals found (Q + Qb). 3.13 Mean shell lengths for E. dilatata across reaches and streams for individuals 53 found in surface samples (Q) and subsurface (Qb) samples. 3.14 Mean number of individuals less than 50 mm found in surface (Q) and 53 subsurface samples (Qb) across all reaches and streams. 3.15 Table of mean substrate and penetration data for individuals found in 57 subsurface (Qb) and surface samples (Q) with variance in parentheses. ix List of Figures 2-1 The location of field sampling streams, reaches, and sites. 10 2-2 Location maps of sampling reaches and sites: Middle Blanchard River (A), Upper Blanchard River (B), Middle Swan Creek (C), Upper Swan Creek (D), Middle Beaver Creek (E), and Upper Beaver Creek (F). 11 2-3 Sampling grid design used throughout this study, based on Smith et al. (2001) and Strayer and Smith (2003). 13 3-1 Shell length frequency distributions of selected unionid species found in the Blanchard River. 27 3-2 Shell length frequency distributions of selected unionid species found in the Upper Blanchard River. 28 3-3 Shell length frequency distributions of selected unionid species found in Middle Swan Crek (MSWAN). 32 3-4 Shell length frequency distributions of selected unionid species found in Upper Beaver Creek (UBEAV) and Middle Beaver Creek (MBEAV). 39 3-5 QHEI exploration, linear regression, and 2 nd order polynomial regression for all sampling reaches. 41 x 3-6 Principal Components Analysis (PCA) of all stream reaches based on mean surface substrate composition. 43 3-7 PCA of surface substrate use by Giant Floater ( P. grandis ) (A), White Heelsplitter ( L. c. complanata ) (B), Spike ( E. dilatata ) (C), and Rayed Bean (V. fabalis ) (D). 45 3-8 PCA of surface substrate use by Fatmucket ( L. siliquoidea ) (A), Fragile Papershell ( L. fragilis ) (B), Kidneyshell ( P. fasciolaris ) (C), and Wabash Pigtoe ( F. flava ) (D). 46 3-9 PCA of surface substrate use by Giant Floater ( P. grandis ) (A), White Heelsplitter ( L. c. complanata ) (B), Spike ( E. dilatata (C) ), and Rayed Bean (V. fabalis ) (D). 47 3-10 PCA of surface substrate use by Fatmucket ( L. siliquoidea ) (A), Fragile Papershell (L. fragilis ) (B), Kidneyshell ( P. fasciolaris ) (C), and Wabash Pigtoe ( F. flava ) (D). 48 3-11 Two-way burrowing histograms. The zero line represents the substrate surface. White bars indicate the number of mussels captured on the surface and gray bars represent the number of mussels found in subsurface samples. The two upper histograms represent Spike ( E. diltatata ) in UBLAN (A) and MBLAN (B). 51 3-12 Two-way burrowing histograms. The number zero represents the substrate surface. White bars indicate mussels captured on the surface and gray bars represent mussels found in subsurface samples. 54 xi Chapter 1 Introduction Freshwater mussels (Bivalvia: Superfamily Unionoidea) are distributed nearly worldwide, inhabiting every continent except Antarctica. Approximately 780 species belonging to 140 genera have been identified to date, with species diversity maximized in the creeks, rivers, and lakes of North America (Graf and Cummings 2007). Nearly 300 species are known from the United States, the vast majority of which belong to the family Unionidae. While this diversity is also of conservation concern, with 76 species now listed as threatened or endangered under the U.S.