Supratidal Extremophiles—Cyanobacterial Diversity in the Rock Pools of the Croatian Adria

Abstract

Hardly any molecular studies have been done on euendoliths of marine coastal environments, especially along the supratidal ranges of carbonate coasts. In our study, we provide a comparative sequence analysis using 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene combined with extensive microscopy of the endolithic community from rock pools of the Croatian Adria. Molecular diversity indices and richness estimates showed high level of diversity, particularly in high-salinity samples. The most common cyanobacteria belong to the order Pleurocapsales, similar to observations on limestone coasts in other parts of the world. Using single-cell amplification sequences of Hormathonema spp., Hyella caespitosa, and Kyrtuthrix dalmatica was for the first time introduced to the public GenBank.Microscopic investigations did not show qualitative variances in diversity among sites with different salinity but clear differences in prevalent organisms from similar environments suggesting that most of them are adapted to inhabit extreme, marine endolithic habitats and that similar species inhabit geographically separated but ecologically similar environments. This is a remarkable concordance rather seldom seen in molecular community studies in support of the hypothesis that endolithic ecosystems are seeded from a global meta-community.The relative diversity of the community is greater than those described from harsh endolithic habitats of cold and hot deserts. The maximum likelihood phylogenetic tree consisting of 166 operational taxonomic units (OTUs) at 96 % sequence similarity revealed 11 distinct clusters. Three clusters contained only epilithic or endolithic taxa, and five clusters contained mixed epilithic and endolithic taxa. Organisms clustered according to their taxonomic affiliations and not to their preferences to salt concentrations.

Latitudinal gradient of cyanobacterial diversity in tidal flats

“…Although all of the Croatian sequences classified as Pleurocapsales stayed unclassified on genus level (96%), their high sequence abundance (Fig 4, S7 Table) was in line with other studies at this limestone coast [129; 130]. The nearly complete absence of sequences classified as filamentous Oscillatoriales and Nostocales in the well-stabilized Croatian sample is surprising and may be explained by the extraordinary local settings (limestone coast with sandy rock pools) that may favor unicellular species [129; 130]. Also biases during sample preparation could not be excluded, since microscopic investigations (not shown here) detected high amounts of filamentous species (with and without heterocysts) wrapped within thick sheaths, which may have withstood the lysis process during the DNA isolation.…”

“…Unicellular taxa (Chroococcales, Chroococcidiopsidales, Pleurocapsales, and Synechococcales) are often described in marine and freshwater environments, and are also known to dominate harsh and unfavorable environments from deserts to rocky shores and tidal flats across latitudes [64; 117; 123; 124; 125; 126; 127; 128; 129; 130]. RDA indicated a strong influence of grain size for the distribution of OTUs classified as Chroococcales or Pleurocapsales (Fig 3).…”

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

“…Microbial fossils of cyanobacteria, morphologically similar to modern forms, could be recognised in up to 2.1 Ga (×10 9 years) old deposits [3][4][5][6][7], while traces of photosynthetic microorganisms preserved as laminated mats and stromatolites influenced the carbonate sediments throughout most of the early history of Earth [8][9][10]. Today, cyanobacteria continue to play a central role in promoting carbon and nitrogen cycling in marine and freshwater environments, while especially dominating in extreme habitats [11][12][13]. The study of modern forms helps in the interpretation of fossil records [5].…”

Microbial communities of the Mediterranean rocky shore: ecology and biotechnological potential of the sea‐land transition

“…Regarding marine environments, the microbial ecology of rocky shores has previously been analysed (Chan et al ., ; Langenheder and Ragnarsson, ; Pinedo et al ., ; Brandes et al . ), including its links with oil spills and biodegradation (Alonso‐Gutiérrez et al ., ). However, and in contrast with the well‐studied microbial ecology of the intertidal zone (for a review, see Mitra et al ., ), a holistic study on the microbial ecology of the marine supralittoral Mediterranean rocky shore has not been addressed previously.…”

“…The aquatic to land transition has been reported to be linked to a narrow gradient in species distribution in function of the distance to the water line, as for example in cyanobacteria in an English lake (Pentecost, 2014). Regarding marine environments, the microbial ecology of rocky shores has previously been analysed (Chan et al, 2003;Langenheder and Ragnarsson, 2007;Pinedo et al, 2007;Brandes et al 2015), including its links with oil spills and biodegradation (Alonso-Guti errez et al, 2009). However, and in contrast with the wellstudied microbial ecology of the intertidal zone (for a review, see Mitra et al, 2014), a holistic study on the microbial ecology of the marine supralittoral Mediterranean rocky shore has not been addressed previously.…”