Data from: Molecular underpinnings and biogeochemical consequences of enhanced diatom growth in a warming Southern Ocean

The Southern Ocean (SO) harbours some of the most intense phytoplankton
blooms on Earth. Changes in temperature and iron availability are expected
to alter the intensity of SO phytoplankton blooms, but little is known
about how environmental change will influence community composition and
downstream biogeochemical processes. We performed experimental
manipulations on surface ocean microbial communities from McMurdo Sound in
the Ross Sea, with and without iron addition, at -0.5 °C, 3 °C, and 6 °C.
We then examined nutrient uptake patterns as well as the growth and
molecular responses of two dominant diatoms, Fragilariopsis and
Pseudo-nitzschia, to these conditions. We found that nitrate uptake and
primary productivity were elevated at increased temperature in the absence
of iron addition, and were even greater at high temperature with added
iron. Pseudo-nitzschia became more abundant under increased temperature
without added iron, while Fragilariopsis required additional iron to
benefit from warming. We attribute the apparent advantage Pseudo-nitzschia
shows under warming to upregulation of iron-conserving photosynthetic
processes, utilization of iron-economic nitrogen assimilation mechanisms,
and increased iron uptake and storage. These data identify important
molecular and physiological differences between dominant diatom groups and
add to the growing evidence for the increasingly important role of
Pseudo-nitzschia in warming SO ecosystems. This study also suggests that
temperature-driven shifts in SO phytoplankton assemblages may increase
utilization of the vast pool of excess nutrients in iron-limited SO
surface waters, and thereby influence global nutrient distributions and
carbon cycle.