The distribution of microplankton in the McMurdo Dry Valley Lakes, Antarctica: response to ecosystem legacy or present-day climatic controls?

Roberts, Edward; Priscu, John C.; Wolf, Craig F.; Lyons, W. Berry; Laybourn‐Parry, Johanna

doi:10.1007/s00300-003-0582-0

Cited by 50 publications

(74 citation statements)

References 26 publications

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“…In agreement with previous reports (2,19,26,41), our functional analyses of a key photosynthetic gene confirmed that a stratified autotrophic community dominated by photosynthetically active protists occupies the photic zone of Lake Bonney. First, a population of stramenopiles related to Nannochloropsis was abundant throughout the water columns of both lobes.…”

Section: Discussionsupporting

confidence: 92%

Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition

Kong

Ream

Priscu

et al. 2012

Appl Environ Microbiol

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102

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ABSTRACTThe autotrophic communities in the lakes of the McMurdo Dry Valleys, Antarctica, have generated interest since the early 1960s owing to low light transmission through the permanent ice covers, a strongly bimodal seasonal light cycle, constant cold water temperatures, and geographical isolation. Previous work has shown that autotrophic carbon fixation in these lakes provides an important source of organic matter to this polar desert. Lake Bonney has two lobes separated by a shallow sill and is one of several chemically stratified lakes in the dry valleys that support year-round biological activity. As part of an International Polar Year initiative, we monitored the diversity and abundance of major isoforms of RubisCO in Lake Bonney by using a combined sequencing and quantitative PCR approach during the transition from summer to polar winter. Form ID RubisCO genes related to a stramenopile, a haptophyte, and a cryptophyte were identified, while primers specific for form IA/B RubisCO detected a diverse autotrophic community of chlorophytes, cyanobacteria, and chemoautotrophic proteobacteria. Form ID RubisCO dominated phytoplankton communities in both lobes of the lake and closely matched depth profiles for photosynthesis and chlorophyll. Our results indicate a coupling between light availability, photosynthesis, andrbcLmRNA levels in deep phytoplankton populations. Regulatory control ofrbcLin phytoplankton living in nutrient-deprived shallow depths does not appear to be solely light dependent. The distinct water chemistries of the east and west lobes have resulted in depth- and lobe-dependent variability in RubisCO diversity, which plays a role in transcriptional activity of the key gene responsible for carbon fixation.

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Section: Discussionsupporting

confidence: 92%

Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition

Kong

Ream

Priscu

et al. 2012

Appl Environ Microbiol

Self Cite

102

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“…This would be an advantageous strategy within the permanent chemocline, where potential prey would be abundant and particulate organic carbon from the upper photic zone may accumulate. In support of this suggestion, Roberts et al (24) reported that HNFs dominated heterotrophic protozoa in Lake Bonney and peaked within the permanent chemocline of the west lobe of Lake Bonney.…”

Section: Isolation and Description Of Two Key Photosynthetic Protistsmentioning

confidence: 86%

“…The majority of dissolved organic carbon is autochthonous (i.e., derived from new photosynthetic activity within the water column). Protists represent the major producers of organic matter in the MCM lake food web (21,22), while heterotrophic nanoflagellates (HNFs) and ciliates are the top predators of bacteria and smaller protists (23,24). Despite the energetic costs of maintaining and regulating both photosynthetic and heterotrophic cellular apparatuses, mixotrophy appears to be very prevalent in MCM aquatic food webs (23,25).…”

mentioning

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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“…So far, research has been carried out only with regard to ciliates dwelling in moss in east Antarctic (Foissner 1996;Petz 1997). However, the majority of ecological research on ciliates has focused on small ponds, lake and marine ecosystems rather than on habitats dominated by mosses (Laybourn−Parry et al 1991;Roberts et al 2004;Buosi et al 2011;Safi et al 2012). The investigation of relations between ciliates and environmental parameters in water ecosystems revealed that the temperature of water and concentrations of biogenic compounds have a significant effect on the abundance of these protozoans.…”

Section: Introductionmentioning

confidence: 99%

Ecology of moss dwelling ciliates from King George Island, Antarctic: the effect of environmental parameters

Mieczan¹,

Tarkowska‐Kukuryk²

2014

Polish Polar Research

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This paper presents a complex study on ciliates from the different species of mosses of King George Island, South Shetland Islands, Antarctic. Samples of ciliates were collected from Polytrichastrum alpinum, Sanionia georgico−uncinata, Sanionia uncinata and Brachythecium austrosalebrosum. The highest species richness (19 taxa) occurred in habitats from Brachythecium austrosalebrosum. The lowest number of taxa (5) was ob− served in Polytrichastrum alpinum. The greatest abundance of ciliates was found in sam− ples from Brachythecium austrosalebrosum (25-30 ind. g −1 ), while the lowest was found in samples from Polytrichastrum (4-6 ind. g −1 ). In each species of mosses, vertical differentia− tion of these protozoa assemblages was found. The number of species and abundance sig− nificantly increased in the lower samples. The upper samples of mosses were dominated by mixotrophic taxa, whereas samples from the lower part the proportions of bacterivore spe− cies increases. The RDA performed to specify the direct relationships between the abun− dance of ciliate taxa and environmental variables showed obvious differences between hab− itats studied. However, variables that significantly explained the variance in ciliate commu− nities were: dissolved oxygen, pH, and nutrients.

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The distribution of microplankton in the McMurdo Dry Valley Lakes, Antarctica: response to ecosystem legacy or present-day climatic controls?

Cited by 50 publications

References 26 publications

Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition

Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition

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

Ecology of moss dwelling ciliates from King George Island, Antarctic: the effect of environmental parameters

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