Microbial community structure and productivity in the oxygen minimum zone of the eastern tropical North Pacific

作者：Podlaska Agnieszka^*; Wakeham Stuart G; Fanning Kent A; Taylor Gordon T

来源：Deep Sea Research Part I: Oceanographic Research Papers , 2012, 66: 77-89.

DOI：10.1016/j.dsr.2012.04.002

• Chemoautotrophy
• Oxygen minimum zone
• Nitrification
• Anammox
• Diploptene
• Microbial community structure

Microbial abundances and activities (heterotrophic and chemoautotrophic) were profiled in the fall of 2007 along a transect of four stations in the upwelling region between the Tehuantepec Bowl, off the coast of southern Mexico, and the Costa Rica Dome. Heterotrophic potential varied with depth exhibiting relatively low maximum values of 4-8 nM leucine d(-1), but varied among stations by a factor of 2. Generally, heterotrophic potential varied inversely with nitrate implying NO3- draw down by nitrate-reducing chemoorganotrophs. Dark dissolved inorganic carbon assimilation ( approximate to chemoautotrophy) was also highly variable with depth and reached a maximum value of 6.4 mu M C d(-1) at one station, but only attained maxima of 0.02 and 0.2 mu M C d(-1) at other stations. Elevated values of chemoautotrophy corresponded with enrichments in nitrite concentrations suggesting nitrification as well as with depletions in nitrite and ammonium concentrations suggesting anammox processes. Additions of 30 mu M NH4+ at selected depths stimulated chemoautotrophic activity up to 33-fold. Fluorescence in situ hybridization (FISH) analyses revealed elevated abundances of Crenarchaeota and beta-proteobacteria (up to 1.0 x 107 and 10.0 x 10(7) cells L-1, respectively) associated with NH4+ minima and NO3- maxima. Nitrifying beta-proteobacteria were most abundant in the upper oxycline (1.1-1.8 x 10(7) cells L-1) at three stations and exhibited a secondary peak of 0.3 x 10(7) cells L-1 in the lower oxycline at one station. Anammox bacterial (Planctomycetes) abundances were as high as 2.1 x 10(6) cells L-1, but accounted for less than 1% of total DAPI counts. The concentration of diploptene (a hopanoid biomarker found in bacteria) varied from 2 to 15 pg L-1 in the upper oxycline and from 51 to 160 pg L-1 in the lower oxycline. Delta C-13 values of particulate organic carbon (POC) varied from -30 to -21%. in the water column (avg. -25 parts per thousand) Distributions of isotopically light POC coincided with enrichments in diploptene, Planctomycetes cells, nitrite, and chemoautotrophy as well as with nitrate and ammonium depletions, suggesting that anammox and nitrification are important for secondary biological production in this system.

• 出版日期2012-8