Exploring the relationship between active bacterioplankton and phytoplankton in the Southern Ocean

Abstract

Bacterioplankton are a heterogenous community composed of cells with different physiological states. The consideration of the active fraction of bacterioplankton as a potential factor affecting the strength of the relationship between bacteria and phytoplankton in the Southern Ocean was evaluated in waters around the Antarctic Peninsula. We estimated active bacterioplankton from uptake of 3 H-Leucine (bacterial production [BP]) and using vital stains to estimate their proportion within the total bacterioplankton community, based on their relative nucleic acid content (high [HNA] vs. low [LNA]), and by nucleic acid double staining (NADS), based on their membrane permeability. Then we performed a comparative analysis between total and active bacterioplankton and chlorophyll a (chl a) in this area. Staining with NADS suggested that 61% of all bacteria were viable, a higher proportion of the total bacterial community than previously reported for the Southern Ocean. HNA bacteria comprised 45% of all bacteria, indicating that 16% of bacteria may be viable but with LNA. BP was more strongly related to abundance of LNA cells than NADS-viable or HNA bacteria. The relationship between chl a and bacterial abundance (BA) did not increase when considering the abundance of HNA or NADS-viable cells alone, showing that viability/activity of stains did not enhance the linkage between BA and phytoplankton biomass in the Southern Ocean. In contrast, the relationship between chl a and BP was stronger than those reported in the literature, suggesting that, in this region, BP is closely dependent on phytoplankton.KEY WORDS: Active bacteria · NADS · HNA · LNA · Bacterial production · Chlorophyll a · Southern OceanResale or republication not permitted without written consent of the publisher

Carbon fluxes in the Canadian Arctic: patterns and drivers of bacterial abundance, production and respiration on the Beaufort Sea margin

“…In the Southern Ocean, Ortega-Retuerta et al (2008), in line with our finding, observed that LNA cells were more closely related to BP than HNA cells. In the present study, HNA and LNA subpopulations were likely governed by different forcings.…”

Biogeneration of chromophoric dissolved organic matter by bacteria and krill in the Southern Ocean

“…Extrapolation of our rates to field conditions predicts a CDOM duplication time of 31-33 d, considering average BP values in the Antarctic Peninsula area during austral summer (Ortega-Retuerta et al 2008). However, in areas where high BP values were reported (e.g., in the western Weddell Sea during ice-free periods, where BP can reach 0.111 mg C h 21 L 21 ), CDOM duplication times of about 10 d are possible.…”

“…We forced the regression line to pass through the origin to avoid the effects of a high-CDOM background. To extrapolate these experimental rates to field CDOM bacterial generation rates (m 21 d 21 ), we used a mean BA of 7.14 3 10 5 cells mL 21 and a mean BP of 0.031 mg C L 21 h 21 ; these values were based on sampling and experimentation in the same area determined during the cruise ICEPOS 2005 (Ortega-Retuerta et al 2008).…”

Patterns in planktonic metabolism in the Mediterranean Sea

“…Water subsamples of 4 and 10 ml were filtered through 0.2 µm polycarbonate black filters and stained with DAPI (4, 6-diamino-2 phenylindole) to a final concentration of 1 µg ml −1 . During the cruises, BA was determined by flow cytometry by FACSCalibur Flow Cytometer (Beckton Dickinson©) as described in Ortega-Retuerta et al (2008).…”