First record of picophytoplankton diversity in Central European hypersaline lakes

Abstract

Our survey has revealed that the phytoplankton in the anthropo-hypersaline lakes of the Transylvanian Basin (Romania) was often dominated by photoautotrophic picoplankton (PPP, cells with a diameter <2 μm). Therefore, the aim of this study was to identify PPP members both in the summer and the winter communities using molecular biological techniques, denaturing gradient gel electrophoresis (DGGE) and sequence analysis. The applied PCR-DGGE methods were highly specific to cyanobacteria and green algae. A total of 11 different plankton taxa were identified that were related to several distant taxonomic groups. PPP were represented by a simple community and consisted of two major genotypes, one from the green algal species Picochlorum oklahomense and the other related to marine Synechococcus isolates (Cyanobacteria). These marine PPP species were recorded for the first time in inland saline lakes from Europe. Besides picoplankton, several additional marine taxa (e.g. cryptophytes and haptophytes) were detected among the nanoplankton species. The presence of the identified marine and hypersaline species could be explained by wind, precipitation or waterfowl transfer; however, this latter could have smaller importance.

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

“…We consider that the accumulated organic carbon might be subsequently metabolized by both heterotrophic aerobic (Actinobacteria, Bacteroidetes, Gammaproteobacteria and Planctomycetes) and anaerobic Bacteria (Halanaerobiales and Clostridiales) as well as Archaea (Halobacteriales). In comparison with Ursu Lake, the photic zone of Fara Fund Lake hosts smaller communities of phototrophic microorganisms as shown by the low chlorophyll a content reported in this study (see Table 1) and by previous works (Keresztes et al, 2012). Thanks to our microscopy and molecular analyses (doi: 10.5061/dryad.2gm06), we consider that oxygen levels in the euphotic zone of Fara Fund Lake were mostly generated by the photosynthetic activity of Dunaliella algae (see also Somogyi et al, 2014).…”

Protist diversity along a salinity gradient in a coastal lagoon

“…Beside the known halophilic genera Fabrea and Dunaliella, our hypersaline samples were highly represented by reads from the diatom Amphora and the heterotrophic dinoflagellate Oxyrrhis, which were occasionally observed in hypersaline waters (Buskey et al 1998, Caric et al 2011, Keresztes et al 2012. Moreover, the brackish libraries were dominated by some taxa such as Scuticociliata, Sphaeropleales and Chrysophyceae-clade C, which have a likely freshwater origin but can include halotolerant species previously found in inland and coastal hypersaline lakes (Elloumi et al 2006.…”

“…Similar to estuarine communities, hypersaline microbial eukaryotes are highly diverse and can include high proportions of novel taxa . For example, at least one-quarter of the 18S rRN A gene sequences recovered from Spanish coastal and inland ponds (Triadó-Margarit & Casamayor 2013) as well as Spanish (Triadó-Margarit & Casamayor 2012), Tibetan (Wu et al 2009) and Romanian (Keresztes et al 2012) hypersaline lakes shared < 97% similarity with known sequences. Both estuarine and hypersaline environments can thus harbour diverse and partially unexplored microbial communities.…”

Unique picoeukaryotic algal community under multiple environmental stress conditions in a shallow, alkaline pan

“…An approximately 1000 nt length fragment of the 18S rRNA gene was amplified by PCR using primers Euk328F and Chlo02R as described in Somogyi et al (2013, accepted Sequence analysis was performed with clones having different restriction pattern generated with the endonucleases Csp6I and Hin6I (Fermentas, Vilnius, Lithuania). A Chlorophytaspecific denaturant gradient gel electrophoresis analysis (DGGE) with a gradient of denaturants from 40 to 70% was also carried out using a shorter fragment (approximately 400 nt length) amplified with primers Euk528F and Chlo02R as described by Keresztes et al (2012). Sequencing reaction and capillary electrophoresis were performed by Biomi Ltd.…”