At the end of the year, we make traditional review of research output on studies of saline lakes and salinity related questions. The Web of Science Core Collection is used as a database. The combined list of papers for topics “salt lakes”, saline lakes” and “salinity and lake” is the research output of the year.
This year the list is compiled of 668 papers that is more or less the same output that we analyzed previous year.
The most active country is USA, followed by China, Germany, Canada and Spain.
The most popular Web of Science Research Category is Geosciences Multidisciplinary.
The most active organization is Chinese Academy of Sciences.
The most popular journal – International Journal of Systematic and Evolutionary Microbiology.
This year the Web of Science introduced new metric – usage count. The Usage Count is a measure of the level of interest in a specific item on the Web of Science. The count reflects the number of times users click link to the full-length article at the publisher’s website (via direct link or Open-Url) or save the article for use in a bibliographic management tool (via direct export or in a format to be imported later).
The most frequently used paper of this year is the research by Erik Jeppesen with several coauthors who studied ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and related changes in salinity. Based on long-term data from seven lakes and reservoirs at the Mediterranean climate zone authors discuss how changes in water level and salinity related to climate change and water abstraction affect the ecosystem structure, function, biodiversity and ecological. All case study lakes in the semi-arid Mediterranean region showed an increase in salinity/conductivity associated with a decline in lake water levels, increased hydraulic residence time and evaporation. Review shows that the biodiversity of most lake organism groups also declines with increasing salinity, and if the salinity increase is high (e.g. from freshwater to brackish levels) its effects may in some cases override all other environmental and pressure factors such as temperature or eutrophication. Finally, authors highlight research required to improve knowledge of the impacts of anthropogenically induced changes on lake water level and consequent changes in salinity.
The top five papers for the year 2015 were selected based on impact factor of journal and my preferences.
Gary King from Louisiana State University study microbes from salty soil in the Atacama desert in Chili, the Bonneville Salt Flats in Utah and a part of the big island in Hawaii. He found that the soil pull carbon monoxide out of the air and held onto it. Species responsible for this are two microbes (Halorubrum str. BV1 and Alkalilimnicola ehrlichii MLHE-1) that use carbon monoxide as an energy source. He suggests the same process could occur on Mars, as its atmosphere has more carbon monoxide in it than does ours. The point is that in order for life to have existed on Mars it would need an energy source. King suggests that carbon monoxide may hold the key to life on Mars. Thus, the salt tolerant earth bacteria that actively uptake CO in salt-saturated medium establishes the potential for microbial CO oxidation under conditions that might obtain at local scales on contemporary Mars and at larger spatial scales earlier in Mars’ history.
Aharon Oren from The Hebrew University of Jerusalem discussed the microbial processes in high-salt environments. The progress in this area is due to application of state-of-the-art culture independent techniques of high-throughput sequencing and metagenomics and studies of unusual and previously unexplored hypersaline environments in Australia, Antarctica and in the deep sea. Studies of the metabolic potentials of different halophilic microorganisms, Archaea as well as Bacteria, shed light on the possibilities and the limitations of life at high salt concentrations, and also show their potential for applications in bioremediation.
Dimitry Sorokin from Winogradsky Institute of Microbiology in Russia with coauthors reviewed functional microbiology of soda lakes. Despite the harsh conditions, soda lakes are inhabited by abundant, mostly prokaryotic, microbial communities. The review summarizes results of studies of main functional groups of the soda lake prokaryotes responsible for carbon, nitrogen and sulfur cycling, including oxygenic and anoxygenic phototrophs, aerobic chemolithotrophs, fermenting and respiring anaerobes. Even though the intensive microbiology and molecular ecology studies of the last years made the soda lakes one of the best-studied saline systems, there are still many questions to be answered. The most obvious include a possibility of anaerobic methane (ANME) and ammonium (anammox) oxidation, anaerobic CO conversions, aerobic methane and ammonium oxidation in hypersaline soda lakes, polymer hydrolysis in hypersaline soda lakes, syntrophism, and nitrogen fixation under aerobic conditions.
Tyler Lewis from University of Alaska Fairbanks in USA with coauthors studied chemical response of Subarctic lakes to climate-driven losses in surface area. Research documented changes in nutrients and ions (calcium, chloride, magnesium, sodium) over a 25 year interval in shrinking, stable, and expanding Subarctic lakes of the Yukon Flats, Alaska. Concentrations of different solutes increased in shrinking lakes over the last 30 years, while simultaneously undergoing little change in stable or expanding lakes. This created a present-day pattern in which shrinking lakes had higher solute concentrations than their stable or expanding counterparts. The most conservative ion, chloride, increased >500% in shrinking lakes. Overall, the substantial increases of nutrients and ions may shift shrinking lakes towards overly eutrophic or saline states, with potentially severe consequences for ecosystems of northern lakes.
Adrian-Stefan Andrei from Babes-Bolyai University in Romania with coauthors described contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes. Meromictic lakes are extreme environments in which water stratification is associated with physicochemical gradients and high salt concentrations. Authors compare the prokaryotic assemblages from Ursu and Fara Fund hypersaline meromictic lakes (Transylvanian Basin, Romania) and infer their role in elemental cycling by matching taxa to specific biogeochemical functions. The analyses showed that the lakes harbored multiple and diverse prokaryotic communities. Microbial populations indigenous to each lake pointed to similar physiological functions within carbon degradation and sulfate reduction. In spite of the high salinity, the Bacteria were found to be more diverse than Archaea, indicating that the current view on microbial diversity in hypersaline ecosystems needs to be broadened. Genetic sequencing of prokaryotic communities revealed a large proportion of operational taxonomic units with no close relatives, showing that these poorly investigated environments are potential sources of novel microorganisms. Further functional studies are needed to describe nutrient cycles near the thermodynamic limits of life.
The six mentioned papers (top five and the paper with highest usage count) covers two major topics that are traditionally important for saline lake studies. The first one is microbial diversity and variety of biogeochemical processes that can be studied at salt lakes. From extraterrestrial life to bioremediation of highly polluted waters – the saline bacteria can give answers and help. The second urgent topic is the sensitivity of saline lakes to climate change and water balance. Traditionally the topic was hot for shrinking saline lake. This is still the alarming problem for many lakes (e.g. Urmia Lake in Iran). However, the papers I select for this year review actually describe freshwater lakes (lakes in the semi-arid Mediterranean region, Subarctic lakes) that can shift towards saline state. It demonstrates that problems widely discussed by saline lake scientists soon might become relevant for wider circle of limnologists. I discussed earlier that freshwater and saline lake limnology are actually separate wings of the inland lake research. The global threat for lake ecosystems can bring these areas of research closer.
King GM (2015). Carbon monoxide as a metabolic energy source for extremely halophilic microbes: implications for microbial activity in Mars regolith. Proceedings of the National Academy of Sciences of the United States of America, 112 (14), 4465-70 PMID: 25831529
Andrei AŞ, Robeson MS 2nd, Baricz A, Coman C, Muntean V, Ionescu A, Etiope G, Alexe M, Sicora CI, Podar M, & Banciu HL (2015). Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes. The ISME journal, 9 (12), 2642-56 PMID: 25932617
Oren, A. (2015). Halophilic microbial communities and their environments Current Opinion in Biotechnology, 33, 119-124 DOI: 10.1016/j.copbio.2015.02.005
Sorokin, D., Banciu, H., & Muyzer, G. (2015). Functional microbiology of soda lakes Current Opinion in Microbiology, 25, 88-96 DOI: 10.1016/j.mib.2015.05.004
Jeppesen, E., Brucet, S., Naselli-Flores, L., Papastergiadou, E., Stefanidis, K., Nõges, T., Nõges, P., Attayde, J., Zohary, T., Coppens, J., Bucak, T., Menezes, R., Freitas, F., Kernan, M., Søndergaard, M., & Beklioğlu, M. (2015). Ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and related changes in salinity Hydrobiologia, 750 (1), 201-227 DOI: 10.1007/s10750-014-2169-x
Lewis TL, Lindberg MS, Schmutz JA, Heglund PJ, Rover J, Koch JC, & Bertram MR (2015). Pronounced chemical response of Subarctic lakes to climate-driven losses in surface area. Global change biology, 21 (3), 1140-52 PMID: 25294238