Picophytoplankton Growth Rate and Productivity Estimated via Continuous Flow Cytometry

Picophytoplankton are significant contributors to global marine productivity, especially in oligotrophic zones, and include cyanobacteria (Prochlorococcus, Synechococcus) and eukaryotes less than 2 m in size (picoeukaryotes). Estimates of growth rates and productivity for the picophytoplankton are limited as conducting ship-board incubations are complex and challenging at this resolution and yet, these estimates are essential for validating ecosystem models, particularly for the expansive tropical and subtropical oceans. Here, we estimate Prochlorococcus, Synechococcus, and picoeukaryote growth rates and net productivity by time series decomposition (TSD) of high resolution flow cytometry data. TSD was applied to a total of 2252 cruise days spanning >11,000 km of surface ocean, with most sampling conducted in the North Pacific. Productivity predictions were generated for 1568 cruise days (69.4% success) for the three populations. While total picophytoplankton biomass remained relatively consistent across latitude, inter-population productivity differences ranged from twofold to three orders of magnitude and correlated with transitions into distinct environments. Prochlorococcus was also shown to be the top contributor of productivity in most of the oligotrophic gyres, with picoeukaryotes dominating areas of higher productivity. As these estimations range across many regions and diverse environments, picophytoplankton responses to rapid changes are captured and quantified by examining individual populations at various temporal and spatial scales.

Presentation Preference: Oral

Primary Presenter: Katherine Qi, University of Washington (klqi@uw.edu)

Authors:

Francois Ribalet, University of Washington  (ribalet@uw.edu)

Sangwon Hyun, University of California Santa Cruz  (sangwonh@ucsc.edu)

E. Virginia Armbrust, University of Washington  (armbrust@uw.edu)