Cyanobacteria and Diatoms in Biofilms of Two Karstic Streams in Germany and Changes of Their Communities Along Calcite Saturation Gradients

Abstract

Biofilms microscopically dominated by cyanobacteria and diatoms of two CO 2 degassing karst-water creeks in Germany were investigated for their diversities along a gradient of calcification using SSU rRNA gene cloning and sequencing from environmental samples. The recovered totals of 731/413 cyanobacteria/diatom clones were grouped at 97/98% similarity levels into 28/29 molecular OTUs widely spread over their corresponding sequence phylogenies forming mostly monophyletic subclades. Sequence comparisons with named reference strains from NCBI/GenBank as well as newly determined references from the SAG culture collection left about half of the cyanobacteria OTUs still unidentified. Most of the diatom OTUs could be identified at least at the generic level. To improve identification also cultures of cyanobacteria and diatoms were established that allowed even species identification of some diatoms, but also revealed additional cyanobacteria hard to identify which were not recovered in the clone libraries. A significant correlation of the relative OTU abundances in clone libraries with values of SI calcite was found and, therefore, redundancy analysis distinguished highly calcified sites far from the spring from those less calcified closer to the spring. The noncalcified spring sites were clearly distinct from all other sites by the presence of four cyanobacteria OTUs exclusively retrieved and that no diatoms could be recovered from there. Four cyanobacteria and three diatom OTUs were recovered whose increasing relative abundance per clone library was correlated with increasing calcification. This may indicate that not only cyanobacteria, but also diatoms are more directly involved in the biogenic impact on tufa formation than assumed previously.

Cyanobacterial Contribution to Travertine Deposition in the Hoyoux River System, Belgium

“…Our isolates 3 and 2a appear to belong to their OTU5, which is related to the type strain of Tychonema bourrellyi CCAP 1459/11 [59]. The phylogenetic tree of Brinkmann et al [36] did not include the clones identical to our dominant strain, and therefore, we can only guess that it belongs or is closely related to their clade B. This would also correspond to the Tychonema/ Phormidium/Microcoleus clade found with a metagenomic study by Schneider et al [60].…”

“…The Hoyoux sequences are in bold and the travertine and tufa sequences from elsewhere are printed in italics. The OTU numbers are taken from Brinkmann et al [36] and the 'Unid.' number from Arp et al [17] Phormidium tubules are broken and exposed to the environmental water so that the carbonate precipitation takes place inside the tubules as well (Fig.…”

“…cme.msu.edu/seqmatch/seqmatch_intro.jsp). The sequences from Arp et al [17], Cousin and Stackebrandt [35] and Brinkmann et al [36] were added when they belonged to the clade B of the latter authors, where our sequences are positioned, plus two thin Oscillatoriales. The sequence of Leptolyngbya boryana PCC73110 was selected as outgroup.…”

“…However, many sequences obtained in those studies were unidentified or found to belong to phylotypes of ambiguous taxonomic identification. Cultivation attempts yielded relatively few strains, of which seven were deposited in a culture collection [36]. Therefore, to date, a direct link between a cultured isolate and natural populations of cyanobacteria involved in the carbonate precipitation in a travertine habitat has not been established.…”

What do we really know about early diagenesis of non-marine carbonates?

“…), dissolution Lopez et al (2017), Westaway (1993), Pentecost et al (1997), Kele et al (2011), De Filippis et al (2012, Özkul et al (2013), Van Noten et al (2013), Lebatard et al (2014), Claes et al (2015Claes et al ( , 2017aClaes et al ( , 2017b Sorey and Colvard (1997), Fouke et al (2000Fouke et al ( , 2003, Kharaka et al (2000), Chafetz and Guidry (2003), Kandianis et al (2008), Veysey et al (2008) Cipriani et al (1977), Barazzuoli et al (1988), Guo and Riding (1992, Pentecost (1995), Minissale et al (2002), Brogi et al (2007), Brogi and Capezzuoli (2008), Pedley (2009), Gandin and Capezzuoli (2014) Arp et al (2001Arp et al ( , 2010, Shiraishi et al (2008aShiraishi et al ( , 2008b, Brinkmann et al (2015) (continued on next page) et al, 2012; Nielsen et al, 2014). Lab and field studies report ACC phases found in close association with crystalline CaCO 3 (Jones and Peng, 2012a;Pedley, 2014) and/or organisms (cyanobacteria) or organic substances (Couradeau et al, 2012;Benzerara et al, 2014;Martignier et al, 2017).…”