Open AccessSulfate reduction and sulfide oxidation in extremely steep salinity gradients formed by freshwater springs emerging into the D ead S ea
Author(s) -
Häusler Stefan,
Weber Miriam,
Siebert Christian,
Holtappels Moritz,
NoriegaOrtega Beatriz E.,
De Beer Dirk,
Ionescu Danny
Publication year - 2014
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12449
Subject(s) - sulfide , sulfate , salinity , sulfate reducing bacteria , sulfur , microbial mat , sulfur cycle , environmental chemistry , sediment , seawater , halophile , biology , ecology , bacteria , chemistry , paleontology , cyanobacteria , organic chemistry
Abundant microbial mats, recently discovered in underwater freshwater springs in the hypersaline D ead S ea, are mostly dominated by sulfur‐oxidizing bacteria. We investigated the source of sulfide and the activity of these communities. Isotopic analysis of sulfide and sulfate in the spring water showed a fractionation of 39–50‰ indicative of active sulfate reduction. Sulfate reduction rates ( SRR ) in the spring sediment (< 2.8 nmol cm −3 day −1 ) are too low to account for the measured sulfide flux. Thus, sulfide from the springs, locally reduced salinity and O 2 from the D ead S ea water are responsible for the abundant microbial biomass around the springs. The springs flow is highly variable and accordingly the local salinities. We speculate that the development of microbial mats dominated by either S ulfurimonas/ S ulfurovum‐like or T hiobacillus / A cidithiobacillus‐like sulfide‐oxidizing bacteria, results from different mean salinities in the microenvironment of the mats. SRR of up to 10 nmol cm −3 day −1 detected in the D ead S ea sediment are surprisingly higher than in the less saline springs. While this shows the presence of an extremely halophilic sulfate‐reducing bacteria community in the D ead S ea sediments, it also suggests that extensive salinity fluctuations limit these communities in the springs due to increased energetic demands for osmoregulation.