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Soda lake environments are known to be variable and can have distinct differences according to geographical location. In this study, we investigated the effects of different environmental conditions of six adjacent soda lakes in the Pantanal biome (Mato Grosso do Sul state, Brazil) on bacterial communities and their functioning using a metagenomic approach combined with flow cytometry and chemical analyses. Ordination analysis using flow cytometry and water chemistry data from two sampling periods (wet and dry) clustered soda lakes into three different profiles: eutrophic turbid (ET), oligotrophic turbid (OT), and clear vegetated oligotrophic (CVO). Analysis of bacterial community composition and functioning corroborated this ordination; the exception was one ET lake, which was similar to one OT lake during the wet season, indicating drastic shifts between seasons. Microbial abundance and diversity increased during the dry period, along with a considerable number of limnological variables, all indicative of a strong effect of the precipitation-evaporation balance in these systems. Cyanobacteria were associated with high electric conductivity, pH, and nutrient availability, whereas Actinobacteria, Alphaproteobacteria, and Betaproteobacteria were correlated with landscape morphology variability (surface water, surface perimeter, and lake volume) and with lower salinity and pH levels. Stress response metabolism was enhanced in OT and ET lakes and underrepresented in CVO lakes. The microbiome dataset of this study can serve as a baseline for restoring impacted soda lakes. Altogether, the results of this study demonstrate the sensitivity of tropical soda lakes to climate change, as slight changes in hydrological regimes might produce drastic shifts in community diversity. [ABSTRACT FROM AUTHOR]

The volcanic and tectonic lakes of the eastern branch of the African Great Rift Valley are exposed to multiple stressors and characterised by different levels of hydrological connectivity. Past volcanic activity generated endorheic basins, in which the nature of the bedrock, its connection with groundwater, and local climatic conditions, favoured the formation of highly alkaline soda waters. While little is known about their nutrient dynamics, most lakes in this area experience considerable microbial blooms and harbour diverse and specifically adapted microbial populations, some of which could embody novel biotechnological potential. Here we review the geochemical and (micro)biological features of a cluster of lakes distributed within the East African Rift, ranging from fresh to hypersaline, under different levels of hydrological connectivity. Possibly no other location on Earth has a comparable range of lake types in close proximity to each other and representing such a remarkable microbial biodiversity. Environmental heterogeneity and habitat connectivity among adjacent aquatic ecosystems may have positive implications in terms of regional environmental stability by enhancing the overall carrying capacity, i.e. the resilience to various forms of impact, contributing to biodiversity protection. Within these ecosystems, microbial processes encompass the entire basis of their primary production, in particular those driven by cyanobacteria. Combining a multi-disciplinary ecohydrological approach with a biogeochemical investigation of the principles underlying their functioning, our study can contribute to the development of appropriate environmental protection measures to effectively maintain their natural capital. [ABSTRACT FROM AUTHOR]

Abstract: Lake Bogoria is a saline–alkaline lake in the Kenyan Rift Valley, known for supporting dense blooms of cyanobacteria and large flocks of up to 1million Lesser Flamingos (Phoeniconaias minor). An algorithm for the remote sensing of chlorophyll-a (Chl-a), as an indicator of cyanobacterial biomass, has been developed using a time series of Landsat images and in situ measurements. In situ measured reflectance spectra were resampled to Landsat bands, and the near infrared (NIR) band, R 835, was found to be well represented by a linear relationship to Chl-a (R 2 =0.847; Standard error, SE =55μgl−1; Samples, N =14) for concentrations up to 800μgl−1. The band ratio R 835/R 660 also showed a strong linear relationship with Chl-a (R 2 =0.811; SE =61μgl−1, N =14). Similar relationships were derived using Landsat satellite imagery and monthly in situ Chl-a data for the period Nov 2003–Feb 2005. The NIR:Red ratio gave a better fit to Chl-a than a single NIR band algorithm when applied to satellite imagery, and the ratio performed best when based on TOA reflectance rather than atmospherically corrected data. Hence an algorithm for Chl-a was derived based on the TOA Landsat reflectance ratio, R 835/R 660, which showed a strong fit against Chl-a (R 2 =0.801; SE =69μgl−1, N =33) despite the limitations of time coincidence for the available satellite-in situ matches (less than 8days). Lesser Flamingos feed on cyanobacteria in saline–alkaline lakes, therefore the algorithm can be used to monitor changes in their food supply, providing valuable information for their future conservation. The study also allowed characterisation of the optical properties in Lake Bogoria and provides insight into the changes occurring during cyanobacterial bloom and die-off events. [Copyright &y& Elsevier]