title: When a habitat freezes solid: microorganisms over-winter within the ice column of a coastal Antarctic lake.
abstract: A major impediment to understanding the biology of microorganisms inhabiting Antarctic environments is the logistical constraint of conducting field work primarily during the summer season. However, organisms that persist throughout the year encounter severe environmental changes between seasons. In an attempt to bridge this gap, we collected ice core samples from Pony Lake in early November 2004 when the lake was frozen solid to its base, providing an archive for the biological and chemical processes that occurred during winter freezeup. The ice contained bacteria and virus-like particles, while flagellated algae and ciliates over-wintered in the form of inactive cysts and spores. Both bacteria and algae were metabolically active in the ice core melt water. Bacterial production ranged from 1.8 to 37.9 μg CL(-1) day(-1). Upon encountering favorable growth conditions in the melt water, primary production ranged from 51 to 931 μg CL(-1) day(-1). Because of the strong H(2) S odor and the presence of closely related anaerobic organisms assigned to Pony Lake bacterial 16S rRNA gene clones, we hypothesize that the microbial assemblage was strongly affected by oxygen gradients, which ultimately restricted the majority of phylotypes to distinct strata within the ice column. This study provides evidence that the microbial community over-winters in the ice column of Pony Lake and returns to a highly active metabolic state when spring melt is initiated.
authors.affiliation: Department of Land Resources and Environmental Sciences, Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA. cforeman@montana.edu
authors.forename: Christine M
authors.initials: CM
authors.lastname: Foreman
authors.forename: Markus
authors.initials: M
authors.lastname: Dieser
authors.forename: Mark
authors.initials: M
authors.lastname: Greenwood
authors.forename: Rose M
authors.initials: RM
authors.lastname: Cory
authors.forename: Johanna
authors.initials: J
authors.lastname: Laybourn-Parry
authors.forename: John T
authors.initials: JT
authors.lastname: Lisle
authors.forename: Christopher
authors.initials: C
authors.lastname: Jaros
authors.forename: Penney L
authors.initials: PL
authors.lastname: Miller
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Chin
authors.forename: Diane M
authors.initials: DM
authors.lastname: McKnight
mesh_terms: D000864:Antarctic Regions; D001419:Bacteria / Q000235:genetics / Q000254:growth & development*; D058645:Denaturing Gradient Gel Electrophoresis; D017753:Ecosystem; D005615:Freezing; D007053:Ice; D058086:Microalgae / Q000235:genetics / Q000254:growth & development*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012621:Seasons; D014871:Water Microbiology
chemical_list: D007053:Ice; D012336:RNA, Ribosomal, 16S