Seasonal Viral Loop Dynamics in Two Large Ultraoligotrophic Antarctic Freshwater Lakes

• Published in: Microbial Ecology
• Main Authors: Sawstrom, C, Anesio, AM, Graneli, W, Laybourn-Parry, J
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer New York LLC 2007
• Subjects: Biological Sciences; Microbiology; Microbial ecology; Antarctic; Crooked Lake; Lake Druzhby; Vestfold; Vestfold Hills; Antarc*; Antarctica
• Online Access: http://www.springerlink.com; https://doi.org/10.1007/s00248-006-9146-5; http://www.ncbi.nlm.nih.gov/pubmed/17075732; http://ecite.utas.edu.au/49040

The effect of viruses on the microbial loop, withparticular emphasis on bacteria, was investigated overan annual cycle in 2003-2004 in Lake Druzhby andCrooked Lake, two large ultraoligotrophic freshwaterlakes in the Vestfold Hills, Eastern Antarctica. Viralabundance ranged from 0.16 to 1.56 109 particles _1and bacterial abundances ranged from 0.10 to 0.24 109cells _1, with the lowest bacterial abundances noted inthe winter months. Virus-to-bacteria ratios (VBR) wereconsistently low in both lakes throughout the season,ranging from 1.2 to 8.4. lysogenic bacteria, determinedby induction with mitomycin C, were detected on threesampling occasions out of 10 in both lakes. In LakeDruzhby and Crooked Lake, lysogenic bacteria made upbetween 18% and 73% of the total bacteria populationduring the lysogenic events. Bacterial production rangedfrom 8.2 to 304.9 106 cells _1 day_1 and lytic viralproduction ranged from 47.5 to 718.4 106 viruslikeparticles _1 day_1. When only considering primaryproduction, heterotrophic nanoflagellate (HNF) grazingand viral lysis as the major contributors to the DOC pool(i.e., autochthonous sources), we estimated a highcontribution from viruses during the winter monthswhen 960% of the carbon supplied to the DOC pooloriginated from viral lysis. In contrast, during thesummer G20% originated from viral lysis. Our studyshows that viral process in ultraoligotrophic Antarcticlakes may be of quantitative significance with respect tocarbon flow especially during the dark winter period.