Limnology and plankton diversity of salt lakes from Transylvanian Basin (Romania): A review

Abstract

Geography, babeş-bolyai university, 5-7 clinicilor str., 400006 cluj-napoca, romania; 2 national institute of research and development for biological sciences (nirdbs), institute of biological research, 48 republicii str., 400015 cluj-napoca, romania; 3 department of Aquatic Microbial ecology, institute of Hydrobiology, biology center of the Academy of sciences of the czech republic, na sádkách 7, 370 05 České budějovice, czech republic; 4 department of Molecular biology and biotechnology, Faculty of biology and Geology, babeş-bolyai university, 5-7 clinicilor str., 400006 cluj-napoca, romania; 5 5department of taxonomy and ecology, Faculty of biology and Geology, babeş-bolyai university, 5-7 clinicilor str., 400006 cluj-napoca, romania; 6 electron Microscopy center, babeș-bolyai university, 5-7 clinicilor street, clujnapoca, romania; 7 center for systems biology, biodiversity, and bioresources, babes-bolyai university, 5-7 clinicilor str., 400006 cluj-napoca, romania *corresponding author: gheorghe.serban@ubbcluj.ro ABSTRACTin the present work, we review the current knowledge on genesis, limnology and biodiversity of salt lakes distributed around the inner contour of eastern carpathian arc (transylvanian basin, central romania). transylvanian salt lakes formed on ancient halite (nacl) deposits following natural processes or quarrying activities. Most of these lakes are located in eastern (sovata area), southern (ocna sibiului), and western (turda-cojocna) parts of the transylvanian basin, have small surfaces (0.1-4 ha), variable depths (2-100 m), are hypersaline (>10%, w/v, total salts, mainly nacl) and permanently stratified. As consequence of steady salinity/density gradient, heat entrapment below surface layer (i.e., heliothermy) develops in several transylvanian lakes. the physical and chemical water stratification is mirrored in the partition of plankton diversity. lakes with less saline (2-10% salinity) water layers appear to harbor halotolerant representatives of phyto-(e.g., marine native Picochlorum spp. and Synechococcus spp.), zoo-(e.g., Moina salina), and bacterioplankton (e.g., Actinobacteria, Verrucomicobia), whereas halophilic plankton communities (e.g., green algae Dunaliella sp., brine shrimp Artemia sp., and members of Halobacteria class) dominate in the oxic surface of hypersaline (>10% salinity) lakes. Molecular approaches (e.g., Pcr-dGGe, 16s rrnA gene-based clone libraries, and dnA metabarcoding) showed that the o 2 -depleted bottom brines of deep meromictic transylvanian lakes are inhabited by known extremely halophilic anaerobes (e.g. sulfate-reducing delta-Proteobacteria, fermenting clostridia, methanogenic and polymer-degrading archaea) in addition to representatives of uncultured/unclassified prokaryotic lineages. overall, the plankton communities thriving in saline transylvanian lakes seem to drive full biogeochemical cycling of main elements. However, the trophic interactions (i.e., food web structure and energy flow) as well as impact of human activities and predicted climate chang...

Spatio‐temporal insights into microbiology of the freshwater‐to‐hypersaline, oxic‐hypoxic‐euxinic waters of Ursu Lake

“…Ursu Lake has a unique and complex ecology, at the same time exhibiting dynamic fluctuations and stability, and can be used as a modern analogue for ancient Introduction Meromictic lakes, permanently stratified inland water bodies, occur in a range of geological settings and can host stratified microbial ecosystems within their chemically distinctive water layers (Boehrer and Schultze, 2008;Lee et al, 2018). Those developed on ancient salt deposits of Central Romania, such as Ursu Lake, have a unique hydrology (Alexe et al, 2018). Ursu Lake has a permanently stratified halocline, from low salt (near-fresh) water at the surface to saturated bottom brine (Máthé et al, 2014;Andrei et al, 2015;Alexe et al, 2018).…”

“…Those developed on ancient salt deposits of Central Romania, such as Ursu Lake, have a unique hydrology (Alexe et al ., 2018). Ursu Lake has a permanently stratified halocline, from low salt (near‐fresh) water at the surface to saturated bottom brine (Máthé et al ., 2014; Andrei et al ., 2015; Alexe et al ., 2018). Whereas a number of deep‐sea haloclines have been well studied, their microbial ecosystem lacks primary production (e.g.…”

Influence of pycnocline on settling behaviour of non-spherical particle and wake evolution

“…the Dead Sea with N up to 0.17 s −1 27 . However, the most distinct examples are highly stratified systems: deep hypersaline anoxic basins (DHABs) such as Gulf of Mexico (the Orca Basin) 5 , brine pools in the Mediterranean Sea, the Black Sea and the Red Sea 28 , and salt lakes 29 . The increase of salinity by several dozen (psu) over one meter depth has been reported in the Orca Basin 5 and a sharp halocline has been reported in Ursu Lake (Romania) with salinity difference between homogeneous upper and lower layers about 300 (psu) over 1 m 29 .…”

Airborne particles pollution in Dej city

“…Dej is a representative city in Cluj County, Romania, mainly for exploitation of sodium chloride from medieval times. Geological layers are typical for Badenian sediments associated with halite deposits [1][2][3]. Minerals, such as quartz, calcite, and clays, are the major components of Dej soil.…”