Latitudinal patterns in the abundance of major marine bacterioplankton groups

Abstract

The present study describes the abundance of major marine bacterioplanktongroups and 2 bacterial genera (Pseudoalteromonas and Vibrio) in surfaceseawater at 24 stations around the world. Catalyzed reporter deposition-fluorescencein situ hybridization showed that Alphaproteobacteria (average relativeabundance 37%, average absolute abundance 3.7 x 10(5) cells ml(-1))including SAR11 [30% / (3 x 10(5))], Gammaproteobacteria [14% / (1.2x 10(5))] and Bacteroidetes [12% / (1.3 x 10(5))] globally dominatedthe bacterioplankton. The SAR86 clade [4.6% / (4.1 x 10(4))] andActinobacteria [4.5% / (4 x 10(4))] were detected ubiquitously, whereasArchaea were scarce [0.6% / (4.2 x 10(3))]. The Roseobacter clade[averaging 3.8% / (3.5 x 10(4))], Pseudoalteromonas [2.6% / (2.1x 10(4))] and Vibrio [1.5% / (1.3 x 10(4))] showed cosmopolitan occurrence.Principal component analysis revealed a latitudinal pattern in bacterialabundances by clustering samples according to lower and higher latitudes.This was related to significantly different relative abundances ofBacteroidetes (peaking at higher latitudes) and of unclassified Bacteriaand Vibrio (both peaking at lower latitudes) between warmer and colderoceans. Relative abundances of Alphaproteobacteria (peaking at subtropical)and Gammaproteobacteria (polar stations) varied between major oceanicbiomes, as did absolute abundances of Roseobacter (peaking at temperateand polar stations). For almost all groups, absolute abundances werepositively correlated with nutrient concentrations in warmer oceansand negatively correlated with oxygen saturation in colder oceans.On a global scale, Roseobacter and SAR86 were correlated with chlorophylla. Linkages of environmental parameters with relative abundanceswere more complex, with e. g. Bacteroidetes being associated withchlorophyll a. The finding of differing communities in warmer andcolder oceans underlined the presence of biogeographical patternsamong marine bacteria and the influence of environmental parameterson bacterial distribution.