Traditionally, at the end of the year we summarize what was published in peer-reviewed journals on the research topics related to saline lakes. “Salt lake or saline lake” and “salinity and lake” basic searches in Web of Science Core Collection result in almost 800 papers published in 2018.

• Research areas are dominated by Environmental Sciences Ecology (22%), Geology (20%) and Microbiology (11%).
• The top 5 countries are USA (27%), China (25%), Germany (8%), Russia (7%) and Spain (5%).
• Journals that most frequently published papers on salt lakes are Frontiers in Microbiology, Science of the Total Environment, International Journal of Systematic and Evolutionary Microbiology.
• Chinese Academy of Sciences, Russian Academy of Sciences and University of Utah are the most active organizations.

The difficult task is to select best papers. The simple criterion is the impact factor of the journal. Also some personal preferences influence the final selection.

Top 5 papers of the year 2018

• Lakes on the Tibetan Plateau as Conduits of Greenhouse Gases to the Atmosphere. Journal of Geophysical Research, 2018, 123: 2091–2103

In this study, scientists measured the partial pressures of carbon dioxide, methane, and nitrous oxide in the littoral zones of 17 lakes on the Tibetan Plateau. Carbon dioxide exchange with the atmosphere from saline lakes was found to be higher than from freshwater lakes. Therefore, further study with enhanced spatiotemporal resolution and breadth is needed to better understand the role played by saline lakes in global carbon cycles.

• A metagenomics roadmap to the uncultured genome diversity in hypersaline soda lake sediments. Microbiome, 2018, 6:168

Scientists report two important advances that were obtained by the first sequencing effort of hypersaline soda lake sediment metagenomes. First, they obtained the first genomes of haloalkaliphilic members of the Candidate Phyla Radiation (a recently described expansion of the tree of life) and several hundred other novel prokaryote lineages. Second, they found evidence for the presence of organisms that use hydrogen as an electron donor, and carbon dioxide as an electron acceptor and as a building block for biosynthesis in many more taxonomic groups than those encompassing known homo-acetogens, sulfate-reducers, and methanogens. Since only few environmental metagenomics studies have targeted sediment microbial communities and never to this extent, authors expect that findings are relevant not only for the understanding of haloalkaline environments but can also be used to set targets for future studies on marine and freshwater sediments.

• Sharp water column stratification with an extremely dense microbial population in a small meromictic lake, Trekhtzvetnoe. Environmental microbiology, 2018, 20: 3784-3797

Located on the shore of Kandalaksha Bay (the White Sea, Russia) and previously separated from it, Trekhtzvetnoe Lake (average depth 3.5 m) is one of the shallowest meromictic lakes known. Despite its shallowness, it features completely developed water column stratification with high-density chemocline community of Chlorobium phaeovibrioides which almost completely intercepts diffusion of hydrogen sulfide from the anoxic monimolimnion. Anoxygenic photosynthesis rate exceeds the oxygenic photosynthesis rate in the mixolimnion. Metagenomic analysis demonstrated that the Chl. phaeovibrioides population in the bacterial plate layer had nearly clonal homogeneity. These features make the ecosystem of the Trekhtzvetnoe Lake a valuable model for studying regulation and evolution processes in natural high-density microbial systems.

• NaCl-saturated brines are thermodynamically moderate, rather than extreme, microbial habitats. FEMS microbiology reviews, 2018, 42: 672-693

Authors survey the evidence that NaCl-saturated brines are biologically permissive, fertile habitats that are thermodynamically mid-range rather than extreme. NaCl-saturated environments contain biomass-dense, metabolically diverse, highly active and complex microbial ecosystems; and this underscores their moderate character. Were NaCl sufficiently soluble, some halophiles might grow at concentrations of up to 8 M. It may be that the finite solubility of NaCl has stabilised the genetic composition of halophile populations and limited the action of natural selection in driving halophile evolution towards greater tolerance of dry conditions.

• Global Pattern of Microplastics (MPs) in Commercial Food-Grade Salts: Sea Salt as an Indicator of Seawater MP Pollution. Environ. Sci. Technol., 2018, 52: 12819–12828

Study was based on the hypothesis that commercial sea salts can act as an indicator of microplastic pollution in the surrounding environment. A total of 39 different salt brands produced at geospatially different sites, including 28 sea salt brands, 9 rock salts and 2 lake salts from 21 countries/regions on six continents, were investigated. Relatively high MP content was identified in sea salts produced in Asian countries/regions. The abundance of MPs in unrefined sea salts exhibited significant linear correlations with plastic emissions from worldwide rivers and with the MP pollution levels in surrounding seawater. The results indicate that sea salt can be a good indicator of the magnitude of MP pollution.