Sub-Ice Microalgal and Bacterial Communities in Freshwater Lake Baikal, Russia

Abstract

The sub-ice environment of Lake Baikal represents a special ecotope where strongly increasing microbial biomass causes an "ice-bloom" contributing therefore to the ecosystem functioning and global element turnover under low temperature in the world's largest freshwater lake. In this work, we analyzed bacterial and microalgal communities and their succession in the sub-ice environment in March-April 2010-2012. It was found out that two dinoflagellate species (Gymnodinium baicalense var. minor and Peridinium baicalense Kisselew et Zwetkow) and four diatom species (Aulacoseira islandica, A. baicalensis, Synedra acus subsp. radians, and Synedra ulna) predominated in the microalgal communities. Interestingly, among all microalgae, the diatom A. islandica showed the highest number of physically attached bacterial cells (up to 67 ± 16 bacteria per alga). Bacterial communities analyzed with pyrosequencing of 16S rRNA gene fragments were diverse and represented by 161 genera. Phyla Proteobacteria, Verrucomicrobia, Actinobacteria, Acidobacteria, Bacteroidetes, and Cyanobacteria represented a core community independently on microalgal composition, although the relative abundance of these bacterial phyla strongly varied across sampling sites and time points; unique OTUs from other groups were rare.

Ecology under lake ice

“…While the available winter limnology literature provides evidence that lakes can support an abundance of algae under ice as demonstrated by genetic (e.g. Bashenkhaeva et al 2015), pigment (e.g. Catalan et al 2002) and cell count (e.g.…”

Microbial life under ice: Metagenome diversity and in situ activity of Verrucomicrobia in seasonally ice‐covered Lakes

“…However, Verrucomicrobia have been observed in the oxic hypolimnion of the Tous and Amadorio reservoirs (Cabello-Yeves et al, 2017a). Moreover, studies of the sub-ice microbial communities of deep Lake Baikal have shown Verrucomicrobia are among the most dominant groups at the surface (Cabello-Yeves et al, 2017b) and that their abundances are linked to diatom blooms (Bashenkhaeva et al, 2015). Hence, it appears that Verrucomicrobia populations represented by our MAGs are resident members of the microbial community in icecovered periods in northern lakes, and knowledge of their genomic and metabolic traits can contribute to our understanding of lake metabolism and nutrient cycling in winter.…”

Freshwater ice as habitat: partitioning of phytoplankton and bacteria between ice and water in central European reservoirs

“…Moreover, Betaproteobacteria, especially members of the metabolically versatile (Zeng et al, 2012) R-BT subcluster embedded within genus Limnohabitans are reported to be abundant taxa (> 10%) during spring and summer in fish ponds of South Bohemia located nearby the ponds of the TBBR surveyed in the present study (Šimek et al, 2010). Given recent evidence supporting a role for Gammaproteobacteria in partitioning phytoplankton to the ice phase in winter (D'souza et al, 2013) together with recognition that they are dominant members of sea-ice microbial communities (Bowman et al, 2012) as well as important members of the ice-associated communities in Russian (Rozmarynowycz, 2014;Bashenkhaeva et al, 2015) and North American Great Lakes (Rozmarynowycz, 2014), it is tempting to speculate that the apparent high abundance of this class might be related to an active role in biological ice nucleation during the early stages of ice formation that were represented in our survey. Consistent with this, gammaproteobacterial orders containing potential ice-nucleating members (Xanthomonadales and Pseudomonadales) comprised > 35% of total bacterial reads and a single Pseudomonas sp.…”

“…Notable in this context are under-ice blooms of the cyanophyte Aphanizomenon flos-aquae reported from Lake Stechlin, Germany (Üveges et al, 2012;Bižić-Ionescu et al, 2014) as well as expansive blooms of the diatom Aulacoseira spp. in Lakes Erie and Baikal (Hampton et al, 2008;Bashenkhaeva et al, 2015). Whereas there is growing consensus on the suitability of the under-ice environment as habitat for phototrophs, only limited information is available on the sympagic (ice-associated) habitat in freshwater ecosystems (Felip et al, 1995;Priscu et al, 1999;Frenette et al, 2008;Bondarenko et al, 2012;Twiss et al, 2012;Bazhenova and Korzhova, 2014;Rozmarynowycz, 2014).…”