Publication Date:
2021-05-19
Description:
Research Group: Applied Microbiology Unit, Department of Botany, Faculty of Science, University of Dares Salaam, P.O. Box 35060, Dar es Salaam, Tanzania
Description:
Mangrove forest sediments were investigated with respect to organic matter content, bacterial numbers, methane emission, sulphide concentration and redox potential profiles. The sediments had characteristically high organic matter content (varying from 8 to 30 % of dry weight) and high bacterial numbers (varying from 5 to 20 x 10〈sup〉8〈/sup〉 cells/g fw). Both values decreased with depth (0-30 cm). Methane emission, sulphide and redox profiles on the other hand, showed remarkable differences between and among sampling sites. In areas with a high abundance of leaf litter and few trees very high sulphide concentrations were encountered: increasing from about I mM at the surface to 25 mM at 30-40 cm depth. Redox values were consistently low; from -150 to -200 mV. Near trees, in between the roots, a remarkably lower sulphide concentration was observed in the top 5-30 cm of the sediment. Methane emission varied from 0 to 500µmo/m〈sup〉2〈/sup〉/h. In vitro incubations showed that methanogenic activity extended down to at least 30 cm depth. In other areas where there was no visible leaf litter accumulation and with many aerial roots the sulphide concentration was much lower ( I µM) in the top 30 cm layer with correspondingly higher redox values ( + I 00 m V to -150 m V). Below 30 cm sulphide concentrations increased to a maximum of 2 mM. Methane emissions from these areas were very low or even negative (-I to 8 µmo/m〈sup〉2〈/sup〉/h). In vitro measurements showed CH〈sub〉4〈/sub〉 production in the top layer occurring at a rate much higher than estimated from the emissions. The results clearly demonstrate the importance of the anaerobic microbial activity in mangrove sediments and indicate that aerial roots are responsible for a major input of oxygen into the sediment, which speeds up oxidation.
Description:
Published
Keywords:
Mangroves
;
Sediments
;
Organic matter
;
Methanogenesis
;
Sulphate reduction
;
Redox potential
;
Bacteria
;
Biomass
;
ISW, Tanzania
Repository Name:
AquaDocs
Type:
Journal Contribution
Format:
116547 bytes
Format:
application/pdf
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