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Supplementary Information
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Study sites. Investigations were conducted on five major cruises to the Pacific Ocean (R/V Ocean
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No.1, March –July 2007; May-August, 2008)，Indian Oceans (R/V Ocean No.1, January-February
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2006) and the China seas (R/V Dongfanghong No.2, February and November 2007) (Fig. 1). A
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total of 211 BChla sampling stations including 110 depth profiles were investigated. Salinity,
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temperature, depth and the photosynthetic available radiation were measured at each station using
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a SeaBird CTD (SBE 9/11 plus, SeaBird Inc., USA).
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Determination of bacteriochlorophyll a (BChla) and chlorophyll a (Chla).
Measurements of
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BChla and Chla concentrations by high-performance liquid chromatography (HPLC) (Goericke,
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2002) and by high sensitive infrared kinetic double modulation fluorometer (FL5000, Photon
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Systems Instruments, Czechia) ( Koblížek et al., 2007) were conducted in a pilot study in the East
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China Sea, both methods yielded consistent results (BChla
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N=72; Chla HPLC = 0.844ChlaFlu + 0.21, R2 = 0.69, N=72). The fluorometry method was employed
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for BChla and Chla quantification for its applicability in the field in this study. Photochemical
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efficiency (Fv/Fm) and relative functional cross section (σRC) of reaction center were determined
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by FIRe system (Satlantic Inc., Canada) (Gorbunov and Falkowski, 2004). Samples for
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determination of BChla based phototrophic parameters were concentrated to at least 10 fold the
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ambient concentration using a tangential cross-filtration system (Millipore) so as to obtain reliable
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data.
HPLC=0.83
BChla Flu + 0.77, R2=0.83,
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Determination
of
AAPB
abundance
by
time-series
observation
based
infrared
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epifluorescence microscopy (TIREM). The TIREM protocol is as described by Jiao et al. (Jiao
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et al., 2006). Infrared fluorescence from bacterial chlorophyll a was the diagnostic signal of AAPB.
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Cells were viewed with an infrared-sensitive charge-coupled device (CCD) camera (DP30-BSW,
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Diagnostic Instruments, USA) on an epifluorescence microscope with a 50-W mercury lamp
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(BX61, Olympus, Japan). Interference from cyanobacteria was calibrated for accurate
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enumeration of AAPB.
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Calculation of energy flux through different phototrophic pathways. The number of
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photosynthetic unit (mol/L) in the environment was calculated from BChla or Chla concentrations
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through the formula n=BChla*NA/911 /36, or n= Chla*NA/893/300, respectively.(Blankenship et
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al., 1995) The unit for BChla concentration is g/L, NA represent the Avogadro constant, 911 is the
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molecular weight of chlorophyll molecule with the unit g/mol and 893 is the molecule weight of
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bacterio-chlorophyll with same unit. 36 BChla molecules for one bacterial photosynthetic unit
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(LH1+RC)(Hu et al., 1998; Rathgeber et al., 2004) and 300 Chla molecules for one phytoplankton
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photosynthetic unit were assumed (Falkowski and Raven, 1996). The electron transport rate (ETR)
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per reaction center (unit: µmol quanta s-1) was calculated with the formula ETR=E×σRC×Fv/Fm,
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where E is PAR (unit: µmol quanta m-2 s-1), σRC (unit: m2) is relative functional cross section of
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reaction center, Fv/Fm (dimensionless ratio unit) is the photochemical efficiency (Koblizek et al.,
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2003). The energy flux of BChla based phototrophy or Chla based phototrophy in the field were
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calculated by multiplying the corresponding ETR with the number of photoreaction centers. The
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photosynthetic electron flux was transformed to ATP flux in ATP/m3/day by multiplying a factor
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of 0.5 with 12 hours irradiance period (Koblízek et al., 2003). A factor of 30.54×103 J/mol ATP
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(Shen and Wang, 2002；Koblízek et al., 2003) was employed to convert ATP to energy with the
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unit J/m3/day. A factor of 5×105 J/mol carbon was employed for the estimation of the saved
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organic carbon by BChla phototrophic energy (Kolber et al., 2001).
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References
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Blankenship, R. E., Madigan, M. T., and Bauer, C. E. (1995). Anoxygenic Photosynthetic Bacteria.
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Falkowski, P. G. and Raven, J. A. (1997). Aquatic Photosynthesis. Blackwell Publishers,
Blackwell Science, Oxford, England
Goericke, R. (2002). Bacteriochlorophyll a in the ocean: Is anoxygenic bacterial photosynthesis
important? Limnol Oceanogr 47:290-295.
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Gorbunov, M. and Falkowski, P. (2004). Fluorescence Induction and Relaxation (FIRe) Technique
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and Instrumentation for Monitoring Photosynthetic Processes and Primary Production in
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Microscopic
(TIREM)
approach
for
accurate
enumeration
of
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Kolber, Z. S., Plumley, F. G., Lang, A. S., Beatty, J. T., Blankenship, R. E., VanDover, C. L.,
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Vetriani, C., Koblížek, M., Rathgeber, C., and Falkowski, P. G. (2001). Contribution of
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aerobic photoheterotrophic bacteria to the carbon cycle in the ocean. Science
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Shen, T., and Wang J.Y. (2002). Biochemistry. Higher Education Press, Beijing ,China.
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Rathgeber, C., Beatty, J. T., and Yurkov, V. (2004). Aerobic phototrophic bacteria: new evidence
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for the diversity, ecological importance and applied potential of this previously
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overlooked group. Photosynth Res 81:113-128.
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Supporting Data
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Supporting Figures
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Figure S1
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the shelf and oceanic surface waters
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Comparison of concentrations of BChla, Chla (a) or BChla proportion (b) between