In situ photochemical activity of the phytobenthic communities in two Antarctic lakes

Kudoh, Sakae; Tanabe, Yukiko; Matsuzaki, Masahiro; Imura, Satoru

doi:10.1007/s00300-009-0660-z

Cited by 11 publications

(10 citation statements)

References 20 publications

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“…Since the Wrst description of the pillars by Imura et al (1999), research has included moss pillar growth rate using radiocarbon dating , component moss species and attached algae (Ohtani et al 2001), distribution of aquatic mosses around Syowa Station (Imura et al 2003), carbon, nitrogen, and chlorophyll a levels in apical and basal parts of pillars (Kudoh et al 2003a;Imura 2006), temperature and light environment of the moss habitat (Kudoh et al 2003b;Tanabe et al 2008;Kimura et al 2010), photochemical activity of apices and sides of pillars (Kudoh et al 2003c(Kudoh et al , 2009, and characteristics of lake sediments (Iwasa et al 2000;Matsumoto et al 2006). Since the discovery of the pillars, the Research on Ecology and Geohistory of Antarctic Lakes (REGAL) Project was organized in Japan and the shape and water quality of many lakes have been investigated.…”

Section: Introductionmentioning

confidence: 99%

Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Nakai

Abe

Baba³

et al. 2011

Polar Biol

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Aquatic mosses in the genera Bryum and Leptobryum form unique tower-like "moss pillars" underwater in some Antarctic lakes, in association with algae and cyanobacteria. These are communities with a two-layer structure comprising an oxidative exterior and reductive interior. Although habitats and photosynthetic properties of moss pillars have been reported, microXoral composition of the two-layer structure has not been described. Here we report fatty acid analysis of one moss pillar and molecular phylogenetic analysis, based on the 16S rRNA gene, of this and one other moss pillar. Cluster analysis of the phospholipid fatty acid composition showed three groups corresponding to the exterior, upper interior, and lower interior of the pillar. This suggested that species composition diVered by section, with the exterior dominated by photosynthetic organisms such as mosses, algae, and cyanobacteria, the upper interior primarily containing gram-positive bacteria and anaerobic sulfate-reducing bacteria, and the lower interior dominated by gram-negative bacteria. Molecular phylogenetic analysis revealed that Proteobacteria dominate the moss pillar as a whole; cyanobacteria were found on the exterior and the gram-positive obligate anaerobe Clostridium in the interior, while gram-positive sulfatereducing bacteria were present in the lowest part of the interior. Nitrogen-Wxing bacteria and denitrifying bacteria were found in all sections. Thus, fatty acid analysis and genetic analysis showed similar patterns. These Wndings suggest that microorganisms of diVerent phylogenetic groups inhabit diVerent sections of a single moss pillar and form a microbial community that performs biogeochemical cycling to establish and maintain a structure in an oxidation-reduction gradient between exterior and interior.

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Section: Introductionmentioning

confidence: 99%

Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Nakai

Abe

Baba³

et al. 2011

Polar Biol

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“…In this sense, the floating assemblages represent ruined benthic mats. If photosynthetic oxygen production generates positive buoyancy that can result in the Pearce and Galand (2008), the floating assemblages may experience a loss of photosynthetic activities when they become suspended in the lownutrient water column, strong light, and UVR of the lake surface conditions (Tanabe et al 2008(Tanabe et al , 2010Kudoh et al 2009). A similar suggestion was made by Pearce and Galand (2008) regarding ecological matter cycling and the nourishment role of the mats that became detached from the lakebeds.…”

Section: Discussionmentioning

confidence: 99%

Possible ecological implications of floating microbial assemblages lifted from the lakebed on an Antarctic lake

Tanabe

Kudoh

2012

Ecological Research

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Microbial assemblages can be found drifting/floating in lake water and being washed ashore in continental Antarctica. Two field studies in early and late January 2008 measured the light utilization properties and photosynthetic responses of these assemblages, which were then compared with those of pelagic and benthic microbial communities to evaluate the ecological implications of this phenomenon. The nutrient concentrations were low in the lake water, indicating oligotrophic conditions. Based on microscopic and pigment analysis, both the floating and benthic communities were mainly composed of Oedogonium sp. (Chlorophyceae), followed by cyanobacteria, diatoms, and dinoflagellates. Floating assemblages had a firmer and denser structure, and possessed more rich carotenoids than the benthic community. Measurements of photosynthesis conducted in early January indicated that the activities of the floating assemblages were considerably low. In late January almost all floating assemblages on the lakeshore turned white because of freezing and drying by the ambient temperature decrease, and had no photosynthetic signals. These results suggest that the floating assemblages could spontaneously lift off from the lakebed because of the bubbles created by photosynthesis and then repeatedly roll, flip, sink, or float depending on buoyancy. In addition, this phenomenon seemed to greatly change the cycling of matter by transporting the lake's photosynthetic products to the surrounding ecosystems, then give the benthic subsurface communities in dark regions a chance to reactivate such as gap regeneration in the case of climax forest, and also allow the floating assemblages to restart photosynthesis at the top of the lakebed by resinking.

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“…A BLAST search for the RuBisCO genes of known isolates revealed that ORU2 found in this study was most closely related in nucleotide sequence to the sulfur-oxidizing bacteria genus Thiohalophilus RuBisCO gene (GQ888587) with 82 % ND , and in amino acid sequence to the sulfur-oxidizing bacteria genus Acidithiobacillus RuBisCO gene (P0C917) with 89 % AA . Hydrogen sulfide gas was undetected in the water column and at the surface of the phytobenthos in Lake Hotoke-Ike, but C1 lg g -1 (wet weight) of hydrogen sulfide gas was detected from deeper than 5 mm within the phytobenthos mat samples (Kudoh et al 2009). The low concentration at the surface is assumed due to the rapid oxidation of hydrogen sulfide by sulfur-oxidizing bacteria.…”

Section: Diversity Of Form Ia Rubisco Genes From Proteobacteriamentioning

confidence: 92%

“…Moreover, biologically harmful levels of solar radiation may penetrate through the ice cover and shallow water column (Vincent et al 1998) because of low concentrations of UV-absorbing material (Morris et al 1995). Benthic microbial communities in the lake produce carotenoids, xanthophyll, scytonemin, and mycosporine-like amino acids (Vincent et al 1993a;Quesada et al 1999;Hodgson et al 2004;Tanabe et al 2010), presumably to protect against intense light conditions (Kudoh et al 2009). Despite this extreme environment, large pillar communities of aquatic mosses have been found in on the lake-bed near the Syowa Station located in East Antarctica (Imura et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Diversity of RuBisCO gene responsible for CO2 fixation in an Antarctic moss pillar

et al. 2012

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Antarctic ''moss pillars'' are lake-bottom biocenoses that are primarily comprised of aquatic mosses. The pillars consist of distinct redox-affected sections: oxidative exteriors and reductive interiors. Batteries of SSU rRNA genotypes of eukaryotes, eubacteria, and cyanobacteria, but no archaea, have been identified in these pillars. However, rRNA-based phylogenetic analysis provides limited information on metabolic capabilities. To investigate the microorganisms that have the potential for CO 2 fixation in the pillars, we studied the genetic diversity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO, EC 4.1.1.39)-an enzyme involved in CO 2 fixation. PCR clone libraries targeting all forms of the RuBisCO large subunit-encoding gene were constructed and 1,092 clones were randomly sequenced. Phylogenetic analysis indicated that proteobacterial form IA operational RuBisCO units (ORUs) were detected at the same frequency as the cyanobacterial form IB ORUs. Surprisingly, the form IA ORU, which was closely related to the sequences from deep-sea environments, was detected from all moss pillar sections. The form IB ORU related to Bryophyta, considered to be derived from moss, was identical to the sequence of Leptobryum sp. isolated from Lake Hotoke-Ike where the pillars were found. Moreover, certain cyanobacterial ORUs were found exclusively in the exterior of the pillar, whereas form II ORUs related to chemolithoautotrophic sulfur oxidizers and purple sulfur bacteria were found exclusively in the interior. No forms IC, ID, or III RuBisCO genes were detected. This is the first report demonstrating that bacteria with the potential for CO 2 fixation and chemoautotrophy are present in the Antarctic moss pillar ecosystem.

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In situ photochemical activity of the phytobenthic communities in two Antarctic lakes

Cited by 11 publications

References 20 publications

Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Microflorae of aquatic moss pillars in a freshwater lake, East Antarctica, based on fatty acid and 16S rRNA gene analyses

Possible ecological implications of floating microbial assemblages lifted from the lakebed on an Antarctic lake

Diversity of RuBisCO gene responsible for CO2 fixation in an Antarctic moss pillar

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