Carbon Transformations in a Perennially Ice-Covered Antarctic Lake

Priscu, John C.; Wolf, Craig F.; Takacs, Cristina D.; Fritsen, Christian H.; Laybourn‐Parry, Johanna; Roberts, Edward; Sattler, Birgit; Lyons, Berry

doi:10.2307/1313733

Cited by 83 publications

(69 citation statements)

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“…Land, Antarctica, contains a number of perennially ice-covered lakes, each home to complex and diverse microbial communities (1). Unusual properties of these lakes, which are sustained by the year-round ice cover, include the absence of wind-induced turbulence and persistent, salinity-dependent density gradients, which often encompass a significant proportion of the lake water columns (2).…”

Section: T He Mcmurdo Dry Valleys (Mdv) Region Of Southern Victoriamentioning

confidence: 99%

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

Jungblut

Hawes

Mackey

et al. 2016

Appl Environ Microbiol

135

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Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter ؊1 to undetectable over one vertical meter from 8.9-to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro-and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations.

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Section: T He Mcmurdo Dry Valleys (Mdv) Region Of Southern Victoriamentioning

confidence: 99%

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

Jungblut

Hawes

Mackey

et al. 2016

Appl Environ Microbiol

135

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“…In support of the latter hypothesis, we have observed heavy recruitment and colonization of bacteria on dead and dying algal cells in our enrichment cultures, an interaction that would have been excluded in the FACS analysis. There is also evidence that natural bacterioplankton communities obtain a significant fraction of organic carbon from ancient relict pools of organic matter (94).…”

Section: Isolation and Description Of Two Key Photosynthetic Protistsmentioning

confidence: 99%

Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake

Podar

Morgan‐Kiss

2016

Appl Environ Microbiol

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The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescenceactivated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (Flavobacteria and Methylobacteriaceae) were independently associated with two key MCM lake microalgae (Isochrysis and Chlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite of Chlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake. IMPORTANCESingle-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment. The microbial loop links the transfer of nutrients and carbon between the microorganisms of the food web and includes complex ecological interactions between microbial eukaryotes, bacteria, archaea, and viruses. Microbial activity is influenced by bottom-up (e.g., availability of nutrient and energy sources) and top-down (e.g., predation, parasitism, and viral lysis) controls, as well as microbe-microbe interactions (e.g., bacterial consortia). Interaction partnerships between microorganisms lead to combinations of win, loss, or neutral outcomes for each microbial partner. Parasitism and predation are examples of win-loss outcomes (1), while mutualistic interactions within biofilms and syntrophic interactions (cross-feeding of metabolic products between two species) between an alga and a heterotrophic bacterium are examples of win-win partnerships (2). ...

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“…As refilling began *1 kyr ago and the ice cover returned to the lake, diffusion of solutes from the saturated brine at depth began and continues today (McKnight et al 1991;Lyons et al 1998b). Aquat Geochem (2009) The MCM lakes are dominated by microbial processes and planktonic food webs incorporate a series of microbial trophic levels (Laybourn-Parry 1997; Priscu et al 1999). Mixotrophy, the condition where organisms can assimilate both carbon dioxide and organic compounds in light and darkness, is an important strategy among protists (Laybourn-Parry 1997).…”

Section: Physical and Chemical Structure And Evolution Of Lake Fryxellmentioning

confidence: 99%

“…Autotrophic organisms must deal with low light levels and low nutrient concentrations, as well as months of no sunlight at all. Given these harsh conditions, these lakes nonetheless contain a ''complex consortium of interacting organisms'' (Priscu et al 1999). In Lake Bonney, primary production and chlorophyll concentrations follow the profiles of photosynthetically available radiation (PAR), with the bottom of the photosynthetic zone situated at 20 m, where light penetration is only *0.5% (Priscu et al 1999).…”

Section: Physical and Chemical Structure And Evolution Of Lake Fryxellmentioning

confidence: 99%

The Saline Lakes of the McMurdo Dry Valleys, Antarctica

Green

Lyons

2008

Aquat Geochem

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The McMurdo Dry Valleys of Antarctica are among a rare group of ice-free regions lying along the coast of an otherwise ice-burdened continent. For Antarctica, these are highly atypical regions of exposed rock and barren soils. Within their 4,000 km 2 expanse, the valleys contain a number of permanently ice-covered, closed-basin lakes, which range from freshwater to highly saline environments. This paper examines the physical structure, geochemistry, nutrient and trace metal dynamics, biology, and hydrologic history of saline Lake Bonney (both east and west lobes), Fryxell, Vanda, and Joyce and provides an update to recently published volumes on these pristine systems.

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Carbon Transformations in a Perennially Ice-Covered Antarctic Lake

Cited by 83 publications

References 0 publications

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake

The Saline Lakes of the McMurdo Dry Valleys, Antarctica

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