Effects of composition of labile organic matter on biogenic production of methane in the coastal sediments of the Arabian Sea

Abstract

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sediments from different environmental niches to measure methane production. The methane production rates were examined in relationship to the sediment biochemistry, i.e., carbohydrates, proteins, and lipids. The gas production measured by head space method ranged from 216 ng g( -1) day( -1) in the mangrove sediments to 3.1 μg g( -1) day( -1) in the shallow Arabian Sea. LOM ranged from 1.56 to 2.85 mg g( -1) in the shallow Arabian Sea, from 3.35 to 5.43 mg g( -1) in the mangrove estuary, and from 0.66 to 0.70 mg g( -1) in the sandy sediments with proteins contributing maximum to the LOM pool. Proteins influenced methane production in the clayey sediments of shallow depths of the Arabian Sea (r = 0.933, p < 0.001) and mangrove estuary (r = 0.981, p < 0.001) but in the sandy beach sediments, carbohydrates (r = 0.924, p < 0.001) governed the net methane production. The gas production was more pronounced in shallow and surface sediments and it decreased with depth apparently governed by the decrease in lability index. Thus, the lability index and protein content are important factors that determine methane production rates in these coastal ecosystems.

Global regulation of methane emission from natural lakes

“…The subsequent sinking and decay of algal blooms can have direct effects on methanogenesis - providing a greater supply of substrate - as well as indirect effects, due to a reduction in dissolved oxygen concentration, especially in the hypolimnion 34 . Thus the trophic state impacts CH 4 concentrations in water and sediment 16,34–36,37 as well as the CH4 emission to the atmosphere 16,18 . However, it is important to note that lakes grouped by the first split in Fig.…”

A synthesis of methane emissions from shallow vegetated coastal ecosystems

“…The abundance of labile OM in VCEs is thought to be the driver for CH 4 emissions from these systems. For example, there is a positive linear relationship between CH 4 production rates and concentration of labile OM in salt marsh and mangrove sediments (e.g., Giani, Bashan, Holguin, & Strangmann, 1996; Gonsalves, Fernandes, Fernandes, Kirchman, & Bharathi, 2011; Xiang, Liu, Ding, Yuan, & Lin, 2015). Additionally, in these same ecosystems, experimental manipulations show increasing CH 4 production when labile OM is added to sediments (e.g., Oremland, Marsh, & Polcin, 1982; Zhuang et al, 2018).…”

Methane emissions partially offset “blue carbon” burial in mangroves

“…Water CH 4 evasion rates were significantly higher (40 to 91%) in the wet season compared to the dry season ( Table 1 ). Higher flux rates in the wet season (>17%) were also found in the mangrove waters of the Andaman Islands ( 24 ) and may be driven by freshwater riverine inputs that increase nutrient loading, increase the supply of labile organic matter, and reduce the supply of sulfate (and therefore inhibit sulfate reduction), all of which can enhance CH 4 production rates ( 19 , 28 ).…”