Importance of environmental factors over habitat connectivity in shaping bacterial communities in microbial mats and bacterioplankton in an Antarctic freshwater system

Abstract

Freshwater ecosystems are considered hotspots of biodiversity in Antarctic polar deserts. Anticipated warming is expected to change the hydrology of these systems due to increased meltwater and reduction of ice cover, with implications for environmental conditions and physical connectivity between habitats. Using 16S rRNA gene sequencing, we evaluated microbial mat and planktonic communities within a connected freshwater system in the McMurdo Wright Valley, Antarctica, to determine the roles of connectivity and habitat conditions in controlling microbial assemblage composition. We examined communities from glacial Lake Brownworth, the perennially ice-covered Lake Vanda, and the Onyx River, which connects the two. In Lake Vanda, we found distinct microbial assemblages occupying sub-habitats at different lake depths, while the communities from Lake Brownworth and Onyx River were structurally similar. Despite the higher physical connectivity and dispersal opportunities between bacterial communities in the shallow parts of the system, environmental abiotic conditions dominated over dispersal in driving community structure. Functional metabolic pathway predictions suggested differences in the functional gene potential between the microbial mat communities located in shallower and deeper water depth. The findings suggest that increasing temperatures and meltwater due to future climate change will affect bacterial diversity and functioning in Antarctic freshwater ecosystems.

A possible unique ecosystem in the endoglacial hypersaline brines in Antarctica

“…Differently from East Bonney Lake, where Bacteroidetes and Actinobacteria were predominant 26 , Proteobacteria dominated within the bacterial communities of BC brines. The dominance of Proteobacteria (and Cyanobacteria) was also reported by Ramoneda et al 33 in Lake Vanda. However, this result referred to microbial mats, whereas water under the ice cover of the lake was characterized by a high relative abundance of Actinobacteria.…”

Bacterial community structure and metabolic potential in microbialite‐forming mats from South Australian saline lakes

“…The PICRUSt2 algorithm was employed to predict the metabolic potential of the microbialite‐associated bacterial communities and their corresponding roles in the bioprecipitation of carbonate. Although this is an indirect method for estimating microbial metabolic functions and therefore, has some limitations (Douglas et al, 2020; Langille et al, 2013; Sun et al, 2020), it has been demonstrated to accurately predict the functional complexity of microbial communities across a wide range of ecosystems, including microbialite‐forming mats and other microbial mats from geothermal springs (Coman et al, 2015), freshwater (Iniesto et al, 2021; Ramoneda et al, 2021), marine and hypersaline environments (Casaburi et al, 2016; DiLoreto et al, 2019; Louyakis et al, 2017; Saona et al, 2021).…”

Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica

“…Hydrological variance is noted in several desert ecology studies as the primary driving factor of microbial community relative to temperature, nutrients and other local environmental conditions [ 21 , 33 , 75 ]. Impact of stream flow, temperature and niche filtering has been associated with changes in community structure, and more recent data using functional metabolic pathway prediction analyses is suggestive of overall functional profiles changes in these communities [ 76 ]. Here, we establish clear transcriptional disparities occurring with hydrological change in the meltwater stream communities.…”