Diversity and spatial distribution of autotrophic communities within and between ice‐covered Antarctic lakes (McMurdo Dry Valleys)

Abstract

We compared the spatial distribution and diversity of autotrophic microbial communities among four permanently ice-covered, chemically stratified lakes located in the Taylor (Lakes Bonney-east and west lobes, Fryxell), and Wright (Lake Vanda) Valleys of the McMurdo Dry Valleys (Victoria Land, Antarctica). Clone libraries were constructed for major carbon fixation genes (rbcL isoforms IA/B and ID; cbbM; nifJ). Real time quantitative polymerase chain reaction assays were also developed for each of these markers of autotrophy to assess the influence of lake physicochemical factors on spatial trends in major photosynthetic and chemolithoautotrophic groups. Both lobes of Lake Bonney were dominated by Ribulose-1, 5-bisphosphate carboxylase oxygenase (RubisCO) form ID rbcL (haptophytes and stramenopiles), while Lake Fryxell was dominated by rbcL form ID-harboring cryptophytes. Lake Vanda was the least productive lake and was dominated by form IA/B rbcL (cyanobacteria and chlorophytes) and form ID rbcL (stramenopiles). Autotrophic carbon fixation genes from photosynthetic organisms were generally positively correlated with light availability. Chemolithoautotrophic organisms harboring form II RubisCO were detected in only two of the four lakes (west lobe Lake Bonney and Fryxell) and were associated with the presence of either sulfide (Fryxell) or dimethylated sulfur compounds (west lobe Lake Bonney).

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

“…1, P4). The 18S rRNA sequences from these SAGs were very similar to sequences recovered from clone libraries generated from 13-m-deep waters from the east and west lobes of Lake Bonney (29), and recent reports suggested that haptophyte communities related to this organism are key primary producers in this lake (28,30,55). Communities of Isochrysis dominate the chemoclines of the east and west lobes of Lake Bonney (28).…”

“…The 18S rRNA sequences from these SAGs were very similar to sequences recovered from clone libraries generated from 13-m-deep waters from the east and west lobes of Lake Bonney (29), and recent reports suggested that haptophyte communities related to this organism are key primary producers in this lake (28,30,55). Communities of Isochrysis dominate the chemoclines of the east and west lobes of Lake Bonney (28). Several recent studies using quantitative PCR analyses to monitor the abundance of photosynthetic functional genes (rbcL and psbA) indicated that, in contrast to chlorophyte populations, the abundance (DNA) and activity (RNA) of haptophyte populations are not correlated with light availability (28,55).…”

“…Samples were collected through the ice hole located in the middle of the lake (77°42.825=S, 162°26.832=E) on 21 December 2012, during the austral summer. A sampling depth (piezometric depth of 13 m) was selected to reflect the depth of maximum phytoplankton biomass (29), which was verified by in situ chlorophyll fluorescence with a submersible FluoroProbe (BBE Moldaenke GmbH) (28). Lake water samples were collected with a 5-liter Niskin bottle (General Oceanics), transferred to 1-liter amber bottles, and stored at 4°C in the dark until processing.…”

“…Photosynthetically active radiation (PAR) is relatively low under the ice (Ͻ50 mol m Ϫ2 s Ϫ1 ), due to the attenuation of the ice cover, and declines below detectable levels at depths of Ͼ25 m (28). Recently, the diversity and spatial distribution of the planktonic microbial eukaryotic communities residing in Lake Bonney have been reported (28)(29)(30)(31). Protist populations residing in the MCM lakes are vertically stratified and exhibit lake-specific differences in distribution patterns.…”

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

“…In traversing the oxycline, we expect a change in microbial community, both functionally and compositionally, as described for planktonic communities (25). Furthermore, it is not known how the composition and dominant metabolisms of bacteria other than cyanobacteria shift with lake depth or redox gradients and how these changes might relate to observed shifts in macroscopic mat morphology with lake depth (18).…”