Role of sulfur-oxidizing bacteria on the ecology in tropical mangrove sediments

Mangroves are unique ecological niches for microorganisms which play major roles in biogeochemical cycles and in nutrient recycling. Sulfur compounds are primarily utilized by sulfur-oxidizing bacteria (SOB) and sulfate-reducing bacteria (SRB) which play an important role in mangrove metabolism. Besides, SOB oxidizes the toxic sulfide produced by SRB to inorganic sulfate utilized by mangroves and other microorganisms. Since the understanding of SOB role in mangrove ecosystem is scarce, the following questions are postulated. (1) Does the seasonal pattern influence abundance of SOB and sulfur-oxidation activity (SOA) in the mangrove sediments? (2) Which environmental variables support SOB and SOA? For this, sediments were sampled monthly for 13 months at Chorao, Goa, (southwest coast of India) for analysis of physicochemical, bacterial and sulfur related parameters. The average SOB population during pre-monsoon, monsoon and post-monsoon season was 1.99 x 10(5) g(-1), 2.0 x 10(5) g(-1) and 2.51 x 10(5) g(-1) respectively. The average SOA during pre-monsoon was 1.66 mMd(-1), 0.92 mMd(-1) in monsoon and 2.09 mMd(-1) during post-monsoon season. Though the SOB did not have significant seasonal influence, SOA varied with season significantly. During the monsoon season SOB (r(2) = 0.550, p<0.001) and SOA (r(2) = 0.467, p<0.001) were influenced by total inorganic carbon. However, during the post-monsoon season SOA contributed to decrease in sulfide concentrations (r(2) = 0.408, p<0.01). Maximum carbon-fixation through SOA was in post-monsoon and least in pre-monsoon. Thus, SOB and SOA contribute by mineralization and detoxification to maintain homeostasis in the mangrove ecosystem. (c) 2019 Elsevier B.V. All rights reserved.