Bowdoin College Bowdoin Digital Commons Honors Projects Student Scholarship and Creative Work 2020 Living Upstream: Kennebec River Influence on Nutrient Regimes and Phytoplankton Communities in Harpswell Sound Siena Brook Ballance Bowdoin College Follow this and additional works at: https://digitalcommons.bowdoin.edu/honorsprojects Part of the Biochemistry Commons, Climate Commons, Environmental Monitoring Commons, Fresh Water Studies Commons, Geology Commons, Geomorphology Commons, Hydrology Commons, Oceanography Commons, and the Terrestrial and Aquatic Ecology Commons Recommended Citation Ballance, Siena Brook, "Living Upstream: Kennebec River Influence on Nutrient Regimes and Phytoplankton Communities in Harpswell Sound" (2020). Honors Projects. 209. https://digitalcommons.bowdoin.edu/honorsprojects/209 This Open Access Thesis is brought to you for free and open access by the Student Scholarship and Creative Work at Bowdoin Digital Commons. It has been accepted for inclusion in Honors Projects by an authorized administrator of Bowdoin Digital Commons. For more information, please contact [email protected]. Living Upstream: Kennebec River Influence on Nutrient Regimes and Phytoplankton Communities in Harpswell Sound An Honors Paper for the Department of Earth and Oceanographic Science By Siena Brook Ballance Bowdoin College, 2020 ©2020 Siena Brook Ballance Acknowledgements This work would not have been possible without the help from my advisor, Collin Roesler and my two Honors committee members, Michelle Fame and Michèle LaVigne. Thank you for all of your help and support this year and throughout my time in the Earth and Oceanographic Science Department at Bowdoin College. ii Table of Contents Acknowledgements ......................................................................................................................... ii Abstract ........................................................................................................................................... 1 Introduction .................................................................................................................................... 1 Harpswell Sound and the Kennebec River ........................................................................................... 2 Questions and Hypotheses ...................................................................................................................... 6 Background .................................................................................................................................... 8 Phytoplankton Classes ............................................................................................................................ 8 Gulf of Maine, Harpswell Sound, and Kennebec River Phytoplankton ............................................................... 8 Controls on Phytoplankton Functional Types ...................................................................................... 9 Nutrients ............................................................................................................................................................... 9 River Flow Regime............................................................................................................................................. 10 River versus Ocean Influence on the Gulf of Maine and Harpswell Sound .................................... 11 Kennebec River Influence .................................................................................................................................. 11 Ocean Influence .................................................................................................................................................. 15 Summary ................................................................................................................................................ 15 Methods ........................................................................................................................................ 16 Sample Collection and Processing ....................................................................................................... 16 Kennebec River .................................................................................................................................................. 16 Harpswell Sound ................................................................................................................................................ 17 Phytoplankton Pigment as a Proxy for Phytoplankton Taxonomy .................................................. 17 Data Analyses ......................................................................................................................................... 18 Lag Correlation Analysis .................................................................................................................................... 19 Hierarchical Cluster Analysis ............................................................................................................................. 20 Empirical Orthogonal Function (EOF) Analysis ................................................................................................ 20 Results........................................................................................................................................... 21 Kennebec Watershed Bedrock and Land Use .................................................................................... 21 Nutrient Concentration and Composition .......................................................................................... 23 Spatial Trends ..................................................................................................................................................... 23 Temporal Trends ................................................................................................................................................ 25 Phytoplankton Pigment Concentration and Composition................................................................. 28 Spatial Trends ..................................................................................................................................................... 28 Temporal Trends ................................................................................................................................................ 30 Kennebec River Phytoplankton Communities ................................................................................... 32 Kennebec River Cluster Analysis ....................................................................................................................... 32 Kennebec River Empirical Orthogonal Function Analysis ................................................................................ 32 EOF Spatial Trends ............................................................................................................................................ 33 EOF Temporal Trends ........................................................................................................................................ 34 Upstream Kennebec River Phytoplankton Communities ................................................................. 37 Upstream Cluster Analysis ................................................................................................................................. 37 iii Upstream Empirical Orthogonal Function Analysis .......................................................................................... 38 EOF Spatial Trends ............................................................................................................................................ 38 EOF Temporal Trends ........................................................................................................................................ 39 Harpswell Sound Nutrient Regime ...................................................................................................... 42 EOF Temporal Trends ........................................................................................................................................ 42 Harpswell Sound Phytoplankton Communities ................................................................................. 44 Harpswell Sound Cluster Analysis ..................................................................................................................... 44 Harpswell Sound Empirical Orthogonal Function Analysis 2011-2013 ............................................................ 44 EOF Temporal Trends ........................................................................................................................................ 45 Harpswell Sound Long Term Trends .................................................................................................. 47 Harpswell Sound Nutrient Empirical Orthogonal Function Analysis 2008-2017.............................................. 47 Harpswell Sound Pigment Empirical Orthogonal Function Analysis 2008-2017.............................................. 49 Discussion..................................................................................................................................... 52 Distinct River and Ocean Nutrient Regimes and Phytoplankton Communities ............................. 52 Upstream, Freshwater Nutrients and Phytoplankton Communities ................................................ 53 Downstream, Tidal Nutrients