WINTER CONDITIONS ARE HYPOTHESIZED TO SET THE STAGE FOR AQUATIC COMMUNITIES THROUGHOUT THE REST OF THE YEAR INCLUDING THE SEVERITY OF HARMFUL ALGAL BLOOMS (HABS). HOWEVER LITTLE IS KNOWN ABOUT THE MECHANISMS OF HOW WINTER PHYSIOCHEMICAL CONDITIONS INFLUENCE PHYTOPLANKTON DYNAMICS. DECREASED LAKE ICE AND WINTER SNOWFALL MAY HAVE DISPROPORTIONATE EFFECTS ON PHYTOPLANKTON DUE TO CHANGES IN LIGHT TRANSMISSION THERMAL STRUCTURE AND NUTRIENT CYCLING DURING WINTER AND THUS INFLUENCE STARTING TRAJECTORIES OF PHYTOPLANKTON COMMUNITY SUCCESSION DURING THE OPEN-WATER SEASON. I WILL TEST LINKS BETWEEN WINTER METEOROLOGICAL CONDITIONS AND SUMMER ALGAL PRODUCTION USING STANDARDIZED MEASUREMENTS FROM DATA GLEANED FROM SATELLITE IMAGERY AND FROM A GLOBAL NETWORK OF LONG-TERM LAKE MONITORING DATA. ADDITIONALLY I WILL PERFORM UNDER-ICE AND EARLY SPRING RESEARCH TO BETTER UNDERSTAND HOW A CHANGING WINTER CLIMATE MAY IMPACT PHYTOPLANKTON COMMUNITIES DURING WINTER AND INTO THE OPEN WATER SEASON. SPECIFICALLY I WILL EVALUATE THE FOLLOWING HYPOTHESES: (1) EARLIER SPRING RUNOFF AFTER RELATIVELY WARMER WINTERS LEADS TO REDUCED TOTAL PHYTOPLANKTON BIOVOLUME DURING THE SUMMER (2) LIGHT LIMITATION HAS A STRONGER EFFECT ON PHYTOPLANKTON THAN ZOOPLANKTON GRAZING UNDER ICE AND (3) DIFFERENCES IN PHYSICAL CONDITIONS BETWEEN RELATIVELY WARM AND COLD WINTERS ALTER THE TIMING AND STRUCTURE OF SEASONAL SUCCESSION OF PHYTOPLANKTON. THIS RESEARCH ALIGNS WITH THE "EARTH SCIENCE APPLICATIONS: WATER RESOURCES" SECTION OF NASA'S RESEARCH OPPORTUNITIES IN SPACE AND EARTH SCIENCES (ROSES 2016) BY ADVANCING KNOWLEDGE OF ECOLOGICAL CONDITIONS THAT MAY BE LINKED TO HABS THAT IMPACT DRINKING WATER SECURITY.