Physiological diagnosis of a Southern Ocean diatom’s responses to future complex ocean conditions

Chair: Alistair Hobday

Philip W. Boyd(1), Evelyn Armstrong(2), Peter Dillingham(3), Christina McGraw(3), Chris Cornwall(4), Catriona L. Hurd(1)

1 Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, 7005, Tasmania, Australia
2 Department of Chemistry, University of Otago, Dunedin, New Zealand
3 School of Science and Technology, University of New England, Armidale, 2351, New South Wales, Australia
4 School of Earth and Environment, University of Western Australia, Perth, 6009, Western Australia, Australia

A changing climate is altering many ocean properties that consequently will modify marine productivity. Prior phytoplankton manipulation studies have focussed on individual or subsets of these properties. Here, we investigate the cumulative effects of multi-faceted ocean change on a subantarctic diatom Pseudonitzschia multiseries by concurrently manipulating five stressors (light/nutrients/CO2/temperature/iron) that primarily control its physiology, and explore underlying reasons for altered physiological performance. Climate-change enhances diatom growth mainly due to warming and iron-enrichment, and both properties partially offset the effects of decreased nutrient supply by 2100. Physiological diagnostics and comparative proteomics demonstrate the joint importance of individual and interactive effects of temperature and iron, and reveal biased future predictions from experimental outcomes when only a subset of multi-stressors is considered. Our findings for subantarctic waters illustrate how a composite of regional studies is needed to provide accurate global projections of future shifts in productivity and to distinguish underlying species-specific physiological mechanisms.