RAPID: Collaborative Research: Autumn transition in plankton ecology during an ocean heatwave on the Northeast U.S. Shelf

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The continental shelf waters off the Northeast U.S. are some of the most productive on the globe. They are also warming at a faster rate than average. While a variety of climate change impacts on ocean biology have been documented, mechanistic understanding lags behind. The goal of the Northeast U.S. Shelf Long-Term Ecological Research (NES-LTER) project is to understand and predict how the composition and structure of planktonic food webs change through space and time in response to the environment and how changes in the community impact ecosystem productivity, particularly at higher trophic levels. This decade has brought an increased prevalence of heat waves in the waters of the Northeast Shelf, and 2020 was no exception. This project incorporates the effect of an unusual warm temperature summer into the NES-LTER conceptual framework, recognizing that marine heat waves are superimposed on long-term warming trends. The Northeast Shelf provides an array of ecosystem services including food, energy extraction, shipping, recreation, and conservation; its integrity is critical to the function of the Northeast U.S. economy. In the face of climate change and other patterns of disturbance, sustaining these ecosystem services will require effective and efficient management. One broader impact of the study is the contribution of key knowledge for the effective management of the region through improved understanding of ecosystem dynamics and functioning. Educational opportunities for six early career scientists include research training in the field and the laboratory. These early career scientists are involved in critical data collection in a year when opportunities for new observations have been extremely limited due to disruptions caused by the COVID-19 pandemic. A special process cruise is dedicated to characterizing food webs and production regimes across the Northeast Shelf during the autumn transition following the summer 2020 ocean heat wave. Field observations are documenting the nature of the transition and testing the hypothesis that autumn conditions fall along a linear continuum between summer and winter community structure, productivity, and export. The suite of NES-LTER measurements applied to past summer and winter transects are being carried out, including underway continuous sampling for pico- to micro-plankton and gas tracer-based productivity, discrete water sampling to initiate incubation experiments for plankton growth and grazing rates at stations along a cross-shelf transect, and net tows to sample larger plankton for genetic diversity and isotopic analysis for food web characterization. Ultimately, quantifying and understanding variability on seasonal, interannual, and decadal time scales is enabling prediction of future productivity and ecosystem state.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.