Thermal trait variation may buffer Southern Ocean phytoplankton from anthropogenic warming

Ian W. Bishop, Stephanie I. Anderson, Sinead Collins, Tatiana Rynearson

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Despite the potential of standing genetic variation to rescue communities and shape future adaptation to climate change, high levels of uncertainty are associated with intraspecific trait variation in marine phytoplankton. Recent model intercomparisons have pointed to an urgent need to reduce uncertainty in the projected responses of marine ecosystems to climate change, including Southern Ocean (SO) surface waters, which are among the most rapidly warming habitats on Earth. Because SO phytoplankton growth responses to warming sea surface temperature (SST) are poorly constrained, we developed a high-throughput growth assay to simultaneously examine inter- and intra-specific thermal trait variation in a group of 43 taxonomically diverse and biogeochemically important SO phytoplankton called diatoms. We found significant differential growth performance among species across thermal traits, including optimum and maximum tolerated growth temperatures. Within species, coefficients of variation ranged from 3% to 48% among strains for those same key thermal traits. Using SO SST projections for 2100, we predicted biogeographic ranges that differed by up to 97% between the least and most tolerant strains for each species, illustrating the role that strain-specific differences in temperature response can play in shaping predictions of future phytoplankton biogeography. Our findings revealed the presence and scale of thermal trait variation in SO phytoplankton and suggest these communities may already harbour the thermal trait diversity required to withstand projected 21st-century SST change in the SO even under severe climate forcing scenarios.

Original languageEnglish
Pages (from-to)5755-5767
Number of pages13
JournalGlobal Change Biology
Issue number19
Early online date3 Jul 2022
Publication statusPublished - 1 Oct 2022

Keywords / Materials (for Non-textual outputs)

  • Southern Ocean
  • adaptive potential
  • diatoms
  • intraspecific diversity
  • phytoplankton
  • thermal performance traits


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