Synechococcus is 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 of Synechococcus at 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 about Synechococcus ecophysiology and a working framework for understanding the seasonal controls of Synechococcus cell abundance in a temperate coastal system.

Data was collected and processed as described in Hunter-Cevera et al. 2019, Seasons of Syn, Limnology and Oceanography. Scripts used for data processing are available at http://github.com/hsosik/NES-LTER/tree/master/.

Data is organized into 3 tab-delimited text files:

Synechococcus data and more: lno2019_syn_temp_light.txt

File includes daily values or averages of hourly data for:

• Synechococcus cell concentration (cells per mL)
• estimates of division rate for Synechococcus population (per day)
• calculated loss rate from subtraction of net growth rate from division rate (per day)
• net growth rate calculated from day-to-day change in Synechoocccus cell concentration (per day)
• Minimum mode of cell volume (micrometer³)
• PE fluorescence at dawn
• PE fluorescence at dawn normalized by cell volume at dawn (1/micrometer³)
• Temperature (degree Celsius)
• Daily incident radiation (MJ/m²)

Missing data is denoted as NaNs.

Nutrient data: lno2019_nutrient_data.txt

For available days, file includes:

• Concentration of nitrate+nitrite (microMolar)
• Concentration of ammonium (microMolar)
• Concentration of phosphate (microMolar)
• Concentration of silicate (microMolar)

PAR attenuation coefficeint data: lno2019_attenuation_coefficients.txt

For available days, file inlucdes:

• Station Latitude
• Station Longitude
• Attenuation coefficient (K) for PAR (meters^-1)

Please see corresponding paper for more details about data processing or corresponding scripts.