Picophytoplankton community response to seasonal and spatial temperature variability across the Northeast US Shelf

Background/Question/Methods

Autonomous flow cytometry at the Martha’s Vineyard Coastal Observatory (MVCO) has allowed for nearly continuous observation of picophytoplankton cells since 2003. These measurements have informed population models to quantify vital rates and relate picoplankton dynamics to seasonal environmental change. To evaluate whether the insights gained from the single (MVCO) location are relevant more broadly, we analyzed flow cytometry measurements made from the underway system of 17 research cruises on the Northeast U.S. Shelf between 2018 and 2021. The cruises sampled a natural temperature gradient which reflects the range of values observed across seasons at MVCO.

Results/Conclusions

We found the relationship between temperature and picoplankton abundance to be consistent throughout the region, regardless of whether the observed variability was spatial or seasonal. The relationships between division rate and environmental parameters from the observatory and cruise data were also similar, though spring division rates were generally lower offshore than would be predicted from temperature alone. These findings improve our understanding of picophytoplankton community response to environmental change as well as the cross-shelf variability in picoplankton ecology.