More, smaller bacteria in response to ocean's warming?

Xose Anxelu G. Moran, Laura Alonso-Sáez, Enrique Nogueira, Hugh W. Ducklow, Natalia González, Ángel López-Urrutia, Laura Díaz-Pérez, Alejandra Calvo-Díaz, Nestor Arandia-Gorostidi, Tamara M. Huete-Stauffer

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Heterotrophic bacteria play a major role in organic matter cycling in the ocean. Although the high abundances and relatively fast growth rates of coastal surface bacterioplankton make them suitable sentinels of global change, past analyses have largely overlooked this functional group. Here, time series analysis of a decade of monthly observations in temperate Atlantic coastal waters revealed strong seasonal patterns in the abundance, size and biomass of the ubiquitous flow-cytometric groups of low (LNA) and high nucleic acid (HNA) content bacteria. Over this relatively short period, we also found that bacterioplankton cells were significantly smaller, a trend that is consistent with the hypothesized temperature-driven decrease in body size. Although decadal cell shrinking was observed for both groups, it was only LNA cells that were strongly coherent, with ecological theories linking temperature, abundance and individual size on both the seasonal and interannual scale. We explain this finding because, relative to their HNA counterparts, marine LNA bacteria are less diverse, dominated by members of the SAR11 clade. Temperature manipulation experiments in 2012 confirmed a direct effect of warming on bacterial size. Concurrent with rising temperatures in spring, significant decadal trends of increasing standing stocks (3% per year) accompanied by decreasing mean cell size (-1% per year) suggest a major shift in community structure, with a larger contribution of LNA bacteria to total biomass. The increasing prevalence of these typically oligotrophic taxa may severely impact marine foodwebs and carbon fluxes by an overall decrease in the efficiency of the biological pump. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
Original languageEnglish (US)
Pages (from-to)20150371
JournalProceedings of the Royal Society B: Biological Sciences
Volume282
Issue number1810
DOIs
StatePublished - Jun 10 2015

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