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This is a 19-year time series of the abundance of eukaryote picophytoplankton and Synechococcus at 4 meters depth at the Martha's Vineyard Coastal Observatory, about 3 km south of Katama Beach, Edgartown, Massachusetts, USA. Picophytoplankton were sensed in situ by a submersible flow cytometer (FlowCytobot, or FCB). Sampling frequency was continuous at approximately 20-minute intervals binned to hourly resolution with some exceptions (e.g., winter in some years). This time series is ongoing for Northeast U.S. Shelf Long-Term Ecological Research (NES-LTER). 

Climate affects the timing and magnitude of phytoplankton blooms that fuel marine food webs and influence global biogeochemical cycles. Changes in bloom timing have been detected in some cases, but the underlying mechanisms remain elusive, contributing to uncertainty in long-term predictions of climate change impacts. Here we describe a 13-year hourly time series from the New England shelf of data on the coastal phytoplankter Synechococcus, during which the timing of its spring bloom varied by 4 weeks. We show that multiyear trends are due to temperature-induced changes in cell division rate, with earlier blooms driven by warmer spring water temperatures. Synechococcus loss rates shift in tandem with division rates, suggesting a balance between growth and loss that has persisted despite phenological shifts and environmental change. 

Abstract Synechococcusis a widespread and important marine primary producer. Time series provide critical information for identifying and understanding the factors that determine abundance patterns. Here, we present the results of analysis of a 16‐yr hourly time series ofSynechococcusat the Martha's Vineyard Coastal Observatory, obtained with an automated, in situ flow cytometer. We focus on understanding seasonal abundance patterns by examining relationships between cell division rate, loss rate, cellular properties (e.g., cell volume, phycoerythrin fluorescence), and environmental variables (e.g., temperature, light). We find that the drivers of cell division vary with season; cells are temperature‐limited in winter and spring, but light‐limited in the fall. Losses to the population also vary with season. Our results lead to testable hypotheses aboutSynechococcusecophysiology and a working framework for understanding the seasonal controls ofSynechococcuscell abundance in a temperate coastal system. 

Imaging FlowCytobot (IFCB) deployments have been conducted since June 2006 at the Martha’s Vineyard Coastal Observatory (MVCO; 41° 19.5’ N, 70° 34.0’ W). IFCB, an automated submersible imaging-in-flow cytometer, is specially designed to operate in the ocean and image plankton and other particulate material approximately 5 to 200 micrometers in length. In conjunction with image acquisition, IFCB also uses a diode laser to measure the chlorophyll fluorescence and light scattering associated each imaged target. IFCB typically produces thousands of photomicrographs and associated laser signals each hour. The web-based IFCB dashboard provides browse capability and access to the entire image data set.