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

Morán XA, Alonso-Sáez L, Nogueira E, Ducklow HW, González N, López-Urrutia Á, Díaz-Pérez L, Calvo-Díaz A, Arandia-Gorostidi N, Huete-Stauffer TM - Proc. Biol. Sci. (2015)

Bottom Line: 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.Temperature manipulation experiments in 2012 confirmed a direct effect of warming on bacterial size.The increasing prevalence of these typically oligotrophic taxa may severely impact marine food webs and carbon fluxes by an overall decrease in the efficiency of the biological pump.

View Article: PubMed Central - PubMed

Affiliation: Red Sea Research Center, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia Instituto Español de Oceanografía, Centro Oceanográfico de Xixón, Xixón, Asturies 33212, Spain xelu.moran@kaust.edu.sa.

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 food webs and carbon fluxes by an overall decrease in the efficiency of the biological pump.

No MeSH data available.


Related in: MedlinePlus

(a) Comparison between cell size change versus temperature (ccc-temp) for LNA and HNA bacteria in experimental incubations with surface samples taken in 2012. Darker symbols represent results from April through July. Fitted line: HNAccc-temp = −0.0002 + 1.19 LNAccc-temp, r2 = 0.41, p = 0.024, n = 12. Dashed lines represent no change (0 slope of the linear regression, more details given in the text). (b) Relationship between mean values of bacterial cell size and temperature for the period extending from April through July of the 10 years of available data. Fitted line: April–July cell size + 0.098 − 0.024 April–July temperature, r2 = 0.52, p = 0.017, n = 10.
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RSPB20150371F3: (a) Comparison between cell size change versus temperature (ccc-temp) for LNA and HNA bacteria in experimental incubations with surface samples taken in 2012. Darker symbols represent results from April through July. Fitted line: HNAccc-temp = −0.0002 + 1.19 LNAccc-temp, r2 = 0.41, p = 0.024, n = 12. Dashed lines represent no change (0 slope of the linear regression, more details given in the text). (b) Relationship between mean values of bacterial cell size and temperature for the period extending from April through July of the 10 years of available data. Fitted line: April–July cell size + 0.098 − 0.024 April–July temperature, r2 = 0.52, p = 0.017, n = 10.

Mentions: The 6°C gradient in experimental temperature generally resulted in smaller bacterial cell sizes, both for LNA (eight out of 12 experiments) and HNA cells (nine experiments), as indicated by negative slopes in the cell size versus temperature linear regressions. The respective monthly cell size versus temperature changes were significantly correlated for both groups (figure 3a), with an average 2.2-fold higher decrease in HNA than in LNA cells. Both groups showed highly coherent cell size decreases with temperature from March to September (data not shown), particularly marked for spring–early summer (n = 4), with mean values of −0.00041 and −0.00091 µm3°C−1 in LNA and HNA bacteria, respectively. Figure 3b shows that mean values of bacterial cell size and temperature for the April–July period of the time series were also significantly and negatively correlated.Figure 3.


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

Morán XA, Alonso-Sáez L, Nogueira E, Ducklow HW, González N, López-Urrutia Á, Díaz-Pérez L, Calvo-Díaz A, Arandia-Gorostidi N, Huete-Stauffer TM - Proc. Biol. Sci. (2015)

(a) Comparison between cell size change versus temperature (ccc-temp) for LNA and HNA bacteria in experimental incubations with surface samples taken in 2012. Darker symbols represent results from April through July. Fitted line: HNAccc-temp = −0.0002 + 1.19 LNAccc-temp, r2 = 0.41, p = 0.024, n = 12. Dashed lines represent no change (0 slope of the linear regression, more details given in the text). (b) Relationship between mean values of bacterial cell size and temperature for the period extending from April through July of the 10 years of available data. Fitted line: April–July cell size + 0.098 − 0.024 April–July temperature, r2 = 0.52, p = 0.017, n = 10.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590472&req=5

RSPB20150371F3: (a) Comparison between cell size change versus temperature (ccc-temp) for LNA and HNA bacteria in experimental incubations with surface samples taken in 2012. Darker symbols represent results from April through July. Fitted line: HNAccc-temp = −0.0002 + 1.19 LNAccc-temp, r2 = 0.41, p = 0.024, n = 12. Dashed lines represent no change (0 slope of the linear regression, more details given in the text). (b) Relationship between mean values of bacterial cell size and temperature for the period extending from April through July of the 10 years of available data. Fitted line: April–July cell size + 0.098 − 0.024 April–July temperature, r2 = 0.52, p = 0.017, n = 10.
Mentions: The 6°C gradient in experimental temperature generally resulted in smaller bacterial cell sizes, both for LNA (eight out of 12 experiments) and HNA cells (nine experiments), as indicated by negative slopes in the cell size versus temperature linear regressions. The respective monthly cell size versus temperature changes were significantly correlated for both groups (figure 3a), with an average 2.2-fold higher decrease in HNA than in LNA cells. Both groups showed highly coherent cell size decreases with temperature from March to September (data not shown), particularly marked for spring–early summer (n = 4), with mean values of −0.00041 and −0.00091 µm3°C−1 in LNA and HNA bacteria, respectively. Figure 3b shows that mean values of bacterial cell size and temperature for the April–July period of the time series were also significantly and negatively correlated.Figure 3.

Bottom Line: 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.Temperature manipulation experiments in 2012 confirmed a direct effect of warming on bacterial size.The increasing prevalence of these typically oligotrophic taxa may severely impact marine food webs and carbon fluxes by an overall decrease in the efficiency of the biological pump.

View Article: PubMed Central - PubMed

Affiliation: Red Sea Research Center, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia Instituto Español de Oceanografía, Centro Oceanográfico de Xixón, Xixón, Asturies 33212, Spain xelu.moran@kaust.edu.sa.

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 food webs and carbon fluxes by an overall decrease in the efficiency of the biological pump.

No MeSH data available.


Related in: MedlinePlus