Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years.
It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate "baseline" variability on glacial-interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.
GNS Science, Lower Hutt 5040, New Zealand; School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington 6140, New Zealand; j.crampton@gns.cri.nz.
James S
JS
Crampton
GNS Science, Lower Hutt 5040, New Zealand; Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand;
Rosie D
RD
Cody
GNS Science, Lower Hutt 5040, New Zealand;
Richard
R
Levy
Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588.
David
D
Harwood
Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand;
Robert
R
McKay
Antarctic Research Centre, Victoria University of Wellington, Wellington 6140, New Zealand;
Tim R
TR
Naish
D000864:Antarctic Regions; D057231:Climate Change; D009792:Oceans and Seas; D010839:Phytoplankton
Antarctica; Miocene; Pliocene; diatoms; phytoplankton