Diversity and distribution of cyanobacteria in coastal saline soils

Abstract:

[Objective] Little is known about the diversity and distribution of cyanobacteria in salinized soils. In this study, we determined soil properties (pH, salinity and water contents, ammonium, nitrite, nitrate, total organic carbon and nitrogen), and investigated the molecular diversity and distribution patterns of soil cyanobacteria at 12 sites near the mouth of Yellow River and in the southern coastal plain of Laizhou Bay (Shandong province), typical salinized coastal regions in China. Salinity gradients were devided into three ranges: low (0.63%?1.27%), medium (1.55%?2.00%), and high saline (2.39%?5.11%). [Methods] Automated ribosomal intergenic spacer analysis (ARISA), clone libraries and real-time quantitative PCR were used to determine the cyanobacterial community structure, composition and abundance, respectively. [Results] Based on ARISA fingerprints, we found cyanobacterial phylotype richness increased with salinity; multiple dimensional scaling and hypothesis testing (ANOSIM) indicated that the community structure of cyanobacteria generally clustered by salinity (P=0.03) more than by water content (P=0.09). Biota-Environment correlation (BEST) analysis further revealed that a combination of two factors, salinity and water content of soils, could mostly explain the changes in cyanobacterial community structure (P=0.02). Clone libraries of 16S rRNA gene were constructed for 3 representative samples. Sequencing and classification following phylogenetic analysis showed that Halomicronema and Acaryochloris dominated in the low saline samples, whereas Leptolyngbya was the most abundant in both medium and high saline soils. Another two taxa, Arthrospira and Geitlerinema, were only found in the samples of low salinity, while Oscillatoria was detected once from the high salinity. Cyanbacterial 16S rRNA genes were much more abundant in low salinity (2.14×105 copies/g dry soil) than in medium (1.25×105 copies/g dry soil) and high salinity samples (1.20×105 copies/g dry soil). [Conclusion] This study demonstrates that salinity shapes the diversity, community structure and abundance of cyanobacteria in the saline soils, which has implications for carbon and nitrogen cycling contributed by these microorganisms in coastal terrestrial ecosystems.

Key words:Cyanobacteria, Saline gradient, Community structure, Molecular diversity, Abundance