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

The Southern Ocean (SO) harbors 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 these changes will influence community composition and downstream biogeoc...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2021-07, Vol.118 (30)
Main Authors: Jabre, Loay J, Allen, Andrew E, McCain, J Scott P, McCrow, John P, Tenenbaum, Nancy, Spackeen, Jenna L, Sipler, Rachel E, Green, Beverley R, Bronk, Deborah A, Hutchins, David A, Bertrand, Erin M
Format: Article
Language:English
Subjects:
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Biogeochemistry
Biological Sciences
Carbon cycle
Climate Change
Community composition
Diatoms - physiology
Ecosystem
Eutrophication
Fragilariopsis
Gene Expression Regulation
Harbors
Iron
Light-Harvesting Protein Complexes - metabolism
Marine microorganisms
Microbial activity
Microorganisms
Nitrogen - metabolism
Nutrient cycles
Nutrient uptake
Nutrients
Oceans and Seas
Photosynthesis
Photosynthesis - physiology
Physical Sciences
Phytoplankton
Plankton
Plastocyanin
Pseudo-nitzschia
Surface water
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Summary:The Southern Ocean (SO) harbors 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 these changes will influence community composition and downstream biogeochemical processes. We performed light-saturated experimental manipulations on surface ocean microbial communities from McMurdo Sound in the Ross Sea to examine the effects of increased iron availability (+2 nM) and warming (+3 and +6 °C) on nutrient uptake, as well as the growth and transcriptional responses of two dominant diatoms, and We found that community nutrient uptake and primary productivity were elevated under both warming conditions without iron addition (relative to ambient -0.5 °C). This effect was greater than additive under concurrent iron addition and warming. became more abundant under warming without added iron (especially at 6 °C), while only became more abundant under warming in the iron-added treatments. We attribute the apparent advantage shows under warming to up-regulation 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 body of evidence for 's increasingly important role 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 distribution and carbon cycling.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2107238118