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Aquatic Microbial Ecology

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AME 68:77-90 (2012)  -  DOI:

Bacterioplankton productivity in lakes of the Taylor Valley, Antarctica, during the polar night transition

Trista J. Vick, John C. Priscu*

Montana State University, Department of Land Resources and Environmental Science, 334 Leon Johnson Hall, Bozeman, Montana 59717, USA
*Corresponding author. Email:

ABSTRACT: Research on the lakes of the McMurdo Dry Valleys, Antarctica, is typically conducted during the period of 24 h sunlight (October to January) when logistical support is readily available. As part of the International Polar Year initiative, we obtained logistical support to study microbial dynamics in the permanently ice-covered lakes of the Taylor Valley during the transition from 24 h of sunlight to the complete darkness of the polar night (mid-April). Our study focused on the perennially ice-covered lakes Fryxell (FRX), East Lobe Bonney (ELB), and West Lobe Bonney (WLB), all of which are chemically stratified and have food webs dominated by microorganisms. Depth-integrated bacterioplankton productivity (BP; leucine incorporation [Leu] and thymidine incorporation [TdR]) in the lakes ranged from 1.2 to 3.4 mg C m−2 d−1. Overall, summer was characterized by relatively high rates of BP and photoautotrophic primary productivity. Rapid decreases in photosynthetically active radiation marked a subsequent transition period, which was characterized by variable cell counts and decreasing Leu:TdR ratios (ratios >1 signify a physiological shift from growth to maintenance mode). Finally, cell counts decreased and Leu:TdR increased by as much as 280% during the fall, revealing a distinct change in the physiological state of the bacterioplankton as light-mediated primary productivity ceased. Our data reveal that the shift in physiological state may result from a switch from contemporary phytoplankton-excreted carbon to other sources of dissolved organic carbon, which can support the bacterioplankton populations through the winter.

KEY WORDS: Leucine · Thymidine · Leu:TdR · Dissolved organic carbon · Winter · Loss rates · Survival · Sunlight

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Cite this article as: Vick TJ, Priscu JC (2012) Bacterioplankton productivity in lakes of the Taylor Valley, Antarctica, during the polar night transition. Aquat Microb Ecol 68:77-90.

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