The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library 2002 The Relationship between Green Sea Urchin Spawning, Spring Phytoplankton Blooms, and the Winter-Spring Hydrography at Selected Sites in Maine Lindsay C. N. Seward Follow this and additional works at: http://digitalcommons.library.umaine.edu/etd Part of the Aquaculture and Fisheries Commons, and the Zoology Commons Recommended Citation Seward, Lindsay C. N., "The Relationship between Green Sea Urchin Spawning, Spring Phytoplankton Blooms, and the Winter-Spring Hydrography at Selected Sites in Maine" (2002). Electronic Theses and Dissertations. 354. http://digitalcommons.library.umaine.edu/etd/354 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. THE RELATIONSHIP BETWEEN GREEN SEA URCHIN SPAWNING, SPRING PHYTOPLANKTON BLOOMS, AND THE WINTER-SPRING HYDROGRAPHY AT SELECTED SITES IN MAINE Lindsay C. N. Seward B.S. University of Rhode Island, 1998 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Zoology) The Graduate School The University of Maine May, 2002 Advisory Committee: Robert L. Vadas, Professor of Botany, Oceanography, and Zoology, Advisor Brian F. Beal, Associate Professor of Science, Univ. of Maine at Machias David W. Townsend, Professor of Oceanography THE RELATIONSHIP BETWEEN GREEN SEA URCHIN SPAWNING, SPRING PHYTOPLANKTON BLOOMS, AND THE WINTER-SPRING HYDROGRAPHY AT SELECTED SITES IN MAINE By Lindsay C. N. Seward Thesis Advisor: Dr. Robert L. Vadas An Abstract of the Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Zoology) May, 2002 The relationship between green sea urchin spawning, spring phytoplankton blooms, and hydrography were examined at multiple spatial scales during the winter-spring of 2000 at selected sites along the coast of Maine. To determine factors contributing to the variation observed in the timing of green sea urchin spawning, sea urchins, phytoplankton, and oceanographic variables were sampled biweekly at four sites in central Maine and three sites in eastern Maine. Water column properties and phytoplankton was intensively examined at sites in central Maine, while sites in eastern Maine were less well characterized. Analysis of gonad indices showed that spawning was protracted in central Maine (occurring from late February to May and encompassing a period of 60 + days), while spawning was relatively discrete in eastern Maine (occurring from April to May and encompassing a period of 34 - 50 days). Despite significant variations in gonad indices between sites, changes in gonad indices were synchronous between males and females within each site. Female gonad indices were significantly greater than males during the peak of the spawning period, although this difference diminished over time and varied between sites. Spawning was significantly correlated with both the first, sustained increase in phytoplankton chlorophyll a and with increasing water temperatures at most sites. The strength of this relationship, however, varied between males and females and between sites. Further, sea urchin spawning times were similar between sites despite significant differences in temperature regimes (5-6" C in central Maine versus 4-5" C in eastern Maine) and water column properties. The coastal waters surrounding the sites in central Maine Islands during the winter-spring 2000 were characterized by high concentrations of inorganic nutrients (Si04 > 8 pM; NO3 + NO2 > 5 pM) and low phytoplankton standing biomass (chl a < 2 pg/L) and cell abundance (< 5 x lo3cells L -') within a well- mixed water column. Phytoplankton abundance during 2000 exhibited trends inconsistent with a typical, pronounced spring phytoplankton bloom, which suggests that blooming phytoplankton may not be a reliable proximate spawning cue. Despite the relatively consistent pattern, there is considerable variability in the timing, duration, and environmental correlates, especially water temperature and chlorophyll a, of spawning. The timing of spawning in the green sea urchin may influence the recruitment of this species, which furthermore may have important ecological and economic implications. Futhermore, micro- and meso-scale processes affect both phytoplankton bloom dynamics and sea urchin spawning, and the interaction between these factors may result in locally disparate or atypical patterns. ACKNOWLEDGEMENTS I am indebted to a multitude of people who contributed time or other resources, provided stimulating discussions, or otherwise made my life pleasing while completing this research. I am especially grateful to my advisor, mentor, and friend, Dr. Bob Vadas, for his patience and insights, engaging discussions on science and life, and for being a wonderful person. I would also like to thank my committee members, Drs. Brian Beal and Dave Townsend, for all their support and encouragement. I would particularly like to express my gratitude to Dave Townsend for allowing me access to his fluorometer, salinometer, and inverted microscope, and to Megan DiPirro Schiff, who conducted the nutrient analyses. I appreciate the constructive comments fiom Brian Beal regarding statistical analyses. I gratefully acknowledge the Island Institute, and especially Corrie Roberts, captain of the RNAlice Siegnlund, who made this work logistically possible. Corrie was also instrumental in scheduling and provided many enjoyable conversations. I am grateful for the diving assistance of Tim Dowling, Torrey Scheafe, Mike Wall, and Greg Welch, who agreeably plunged themselves into the frigid waters of coastal Maine during winter. I would also like to thank Tim and Jean Dowling for providing hot, tasty beverages and snacks after long and chilly hours on the water. I appreciate funding fiom the Maine Department of Marine Resources, NOAA- Sea Grant, and the Maine Agricultural and Forestry Experiment Station. I also thank the Department of Biological Sciences for support through research and teaching assistantships. I am extremely thankful to all the wonderful people who have entered my life here and otherwise (you know who you are, and if you're not sure, see me so I may personally express my gratitude), for their support, friendship, humor, and witty banter. I would especially like to thank Kristin Glynn for hours of entertainment and Ellen Klinger for invariably making me smile. I also thank my mother, Helen Seward, for her support and encouragement. Finally, I would like to express my gratitude to my partner, Kevin Chanlpney, for his love, support, kindness, cooking, generosity, fine-tastes, wit, et cetera. I can't thank him enough. TABLE OF CONTENTS .. ACKNOWLEDGEMENTS ............................................................................................. 11 .. LIST OF TABLES ......................................................................................................... vii LIST OF FIGURES .......................................................................................................xi PREFACE: GENERAL INTRODU~TION..................................................................... 1 Chapter 1. PATTERNS OF SPAWNING OF THE GREEN SEA URCHIN. STRONGYLOCENTROTUS DROEBACHIENSIS IN MAINE: A REGIONAL APPROACH ......................................................................................6 Introduction ............................................................................................................... 6 Methods .................................................................................................................... 10 . Site Description ...............................................................................................10 Sample Collection and Processing ..................................................................10 Phytoplankton ................................................................................................. 12 Oceanographic Variables ................................................................................13 Statistical Analyses ........................................................................................13 Results .....................................................................................................................16 Central Maine: Georges Islands Region ......................................................... 16 Sexual differences .......................................................................... 19 Oceanographic variables .................................................................21 Relationship with gonad index ........................................................25 Eastern Maine: Jonesport Region ................................................................... 33 . Sexual differences ...........................................................................33 Oceanographic variables .................................................................37 Relationship with gonad index ........................................................39 Large-scale Spatial Patterns- Between Regions ............................................. 47 Discussion ................................................................................................................. 50 Spawning and Gonad Indices ..........................................................................50