Effect of salinity changes on the bacterial diversity, photosynthesis and oxygen consumption of cyanobacterial mats from an intertidal flat of the Arabian Gulf

Abstract

The effects of salinity fluctuation on bacterial diversity, rates of gross photosynthesis (GP) and oxygen consumption in the light (OCL) and in the dark (OCD) were investigated in three submerged cyanobacterial mats from a transect on an intertidal flat. The transect ran 1 km inland from the low water mark along an increasingly extreme habitat with respect to salinity. The response of GP, OCL and OCD in each sample to various salinities (65 per thousand, 100 per thousand, 150 per thousand and 200 per thousand) were compared. The obtained sequences and the number of unique operational taxonomic units showed clear differences in the mats' bacterial composition. While cyanobacteria decreased from the lower to the upper tidal mat, other bacterial groups such as Chloroflexus and Cytophaga/Flavobacteria/Bacteriodetes showed an opposite pattern with the highest dominance in the middle and upper tidal mats respectively. Gross photosynthesis and OCL at the ambient salinities of the mats decreased from the lower to the upper tidal zone. All mats, regardless of their tidal location, exhibited a decrease in areal GP, OCL and OCD rates at salinities > 100 per thousand. The extent of inhibition of these processes at higher salinities suggests an increase in salt adaptation of the mats microorganisms with distance from the low water line. We conclude that the resilience of microbial mats towards different salinity regimes on intertidal flats is accompanied by adjustment of the diversity and function of their microbial communities.

Microphytobenthic dynamics in a Wadden Sea intertidal flat – Part II: Seasonal and spatial variability of non-diatom community components in relation to abiotic parameters

“…The presence of filamentous cyanophytes all year round, with the highest abundances of Microcoleus chthonoplastes in autumn, is also in good agreement with results of similar studies in other intertidal flats (e.g. Stal & Krumbein, 1985;Zehr et al, 1995;Omoregie et al 2004;Abed et al, 2007;Gerdes & Wehrmann, 2008). The number of phototrophic flagellates in the sediments of the Soltho¨rn tidal flat showed a seasonal cycle, with blooms in spring and autumn.…”

Determining the specific microbial populations and their spatial distribution within the stromatolite ecosystem of Shark Bay

“…These gradients result in the presence of microbial species adapted to different ranges of salinity and could result in a reduction in the diversity of bacterial and archaeal communities at higher salinities (Benlloch et al, 2002;Jungblut et al, 2005). High levels and fluctuations in salinity also result in an increase in biodiversity and favour the growth of halophilic microorganisms (Wieland and Kuhl, 2006;Abed et al, 2007). It is evident from this study, and regardless of time and the type of stromatolite, that certain phenotypic groups, such as both unicellular and filamentous cyanobacteria and halophilic archaea, are consistent components of these environments and therefore likely to be intrinsic to the development of the stromatolites at Shark Bay.…”

Mechanisms of damage to corals exposed to sedimentation

“…From those samples, six then were analyzed, constructing 16S rRNA clone libraries. The nucleic acid extraction, PCR (750-800 bp), DGGE (300-550 bp), phylogenetic analysis, and calculation of diversity and richness indices (log e) from the obtained sequences were conducted as previously described (60,61). The PCR for the DGGE samples and for the excised bands was done with 10 ng DNA using the primers GM5F (with GC clamp) and 970RM.…”