Department Seminar: David Hutchins

Title: Beating the heat:  Phytoplankton survival strategies in a warming ocean

Abstract: Even if some politicians still manage to deny it, the microbes “know” better:  the ocean is rapidly getting hotter.  Phytoplankton and other key microbial functional groups are clearly being challenged by steadily rising mean seawater temperatures, and an even more potentially stressful climate trend is the increasing frequency and intensity of extreme marine heat waves. These manifestations of ocean warming now regularly approach or exceed the upper thermal limits of microbial species as determined by laboratory studies, but relatively little is known about their actual consequences for long-term microbial community diversity and function in natural ocean environments. Mechanisms available to micro-organisms to cope with both chronic and episodic thermal stress begin with molecular-level responses such as altered gene regulation, which are then expressed as physiological changes in central metabolic processes like growth rates and nutrient utilization efficiencies.  Over longer timescales, natural selection and adaptive evolution can fundamentally reshape the basic genetic machinery underlying microbial thermal responses. Extreme heat wave events in particular have the potential to act as evolutionary bottlenecks by exerting strong directional selection on marine microbial populations, biasing the communities that emerge afterwards towards heat-tolerant survivors. Understanding critical ecosystem recovery processes will require learning how resilience to extreme temperatures varies among and within taxa, from major functional groups down to individual species. My talk is intended to offer a window into the future ocean where differential resilience to warming will reshuffle marine microbial communities in novel ways, with implications for changing food webs and biogeochemical cycles in marine regimes around the world.