Coccolithophores are a diverse, ecologically-important phytoplankton group ubiquitous in the global ocean and more abundant in colder, oligotrophic waters. Recent studies have suggested that coccolithophores are the least resilient phytoplankton functional type to high (>30^oC) water temperatures, while others show that warm coastal areas are important coccolithophore habitats. To examine how intraspecific diversity and acclimation shape plankton populations, we grew 13 strains of <em>Emiliania huxleyi</em>, isolated from regions of different temperature, for ~45 generations (2 months), each at 6-8 temperatures. We characterized the thermal response curve and flow cytometry-derived cell sizes of each strain. There was a mean difference of 0.63±0.3 day^-1 between maximum and minimum growth rates observed within-strain, while different strains had up to a 0.89 day^-1 difference in maximum growth rate. Even with virtually identical temperature optima and overlapping cell size, strain growth rates varied between 0.45--1 day^-1. While some thermal curves were effectively symmetrical, others had slowly declining growth rates above the “thermal optimum”. We place our experimental results in global context using an ecosystem model simulation of coccolithophores in which several “thermal types” are scaled by cell size, and show how coccolithophore realized niches vary. Taken together, these observed intraspecifically-diverse thermal traits may reveal coccolithophores’ capacity to persist under unusually warm temperatures and exploit seasonal nutrient limitation in a changing ocean.

Primary Presenter: Arianna Krinos, MIT-WHOI (akrinos@mit.edu)

Authors:

Arianna Krinos, MIT-WHOI Joint Program  (akrinos@mit.edu)

Sara Shapiro, Woods Hole Oceanographic Institution  (sara.shapiro@whoi.edu)

Weixuan Li, Massachusetts Institute of Technology  (weixuan@mit.edu)

Stephanie Dutkiewicz, Massachusetts Institute of Technology  (stephdut@mit.edu)

Michael Follows, Massachusetts Institute of Technology  (mick@mit.edu)

Harriet Alexander, Woods Hole Oceanographic Institution  (halexander@whoi.edu)