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General Session 3: Biological oceanography & global change |
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Microdiverse populations shape Prochlorococcus niche space and predicted response to future ocean warming
Tuesday 10th @ 1400-1425
Multi-function Hall
Alyse A Larkin* , University of California Irvine
Adam C Martiny, University of California Irvine
Presenter Email: larkinsa@uci.edu
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| Due to its high abundance and primary productivity, the marine cyanobacteria Prochlorococcus sp. contributes a large proportion of energy, carbon, and other bioavailable nutrients to both food webs and elemental cycles in oligotrophic regions of the ocean. Prochlorococcus has previously been shown to exhibit high diversity at a fine genetic scale, but the functional implications of this diversity as well as its effects on the larger community¡¯s response to climate change are poorly understood. We examined high light Prochlorococcus ecotypes (eHL) across large spatial and temporal gradients in the North Pacific to determine the abiotic drivers of ecologically differentiated populations with high genetic similarity at the ¡°sub-ecotype¡± taxonomic level, or ¡°microdiverse¡± populations. Our analysis of Prochlorococcus ITS diversity at high taxonomic resolution reveals that microdiverse populations have unique, cohesive responses to environmental variables and distinct biogeographies. Moreover, we demonstrate that whereas the eHL-I microdiverse clades have distinct niche envelopes, the eHL-II microdiverse clades appear more ecologically similar. Moving to higher levels of organization, we present a theoretical model for how these microdiverse populations shape the fundamental niche of Prochlorococcus as a whole, enabling the genus to have a vast physical distribution in the environment. Finally, by applying our theoretical model in a realized niche model, which uses 35,129 in situ observations of Prochlorococcus to project abundance at the end of the 21st century, we show that Prochlorococcus may experience a ~29% increase in cellular abundance with ocean warming. However, most of the projected increase in both biomass and productivity will occur in the oligotrophic gyre, suggesting that Prochlorococcus¡¯ response to higher ocean temperatures may result in an increase in total productivity in these critical oceanographic ecosystems. Overall, we demonstrate that the examination of microdiverse populations can both inform our understanding of the fundamental and realized niche of microbial taxa and improve predictions of microbial response to climate change. |
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