Methane dynamics in a seasonally hypoxic coastal marine basin

Versatile methanotrophs form an active methane biofilter in the oxycline of a seasonally stratified coastal basin

“…Here, methane production outpaces methane consumption, likely because of the high sedimentation rate in the Scharendjike basin (∼13 cm yr -1 (Egger et al ., 2016)). Calculated diffusive fluxes of methane from the sediment to the water column range from 0.2–1.0 mol m -2 yr -1 and the potential for ebullitive flux is high (Egger et al ., 2016; Żygadłowska et al ., 2022) which explains these high bottom water methane concentrations. Furthermore, in situ methane production by methanogens could potentially add to the methane concentrations, as Methanosarcinaceae, Methanomicrobiaceae and Methanocorpusculaceae were the dominant archaeal families in the anoxic bottom water (Supplemental material, figure 1).…”

“…Despite the metabolic potential and indications for active methane oxidation by Methylomonadaceae under anoxic conditions in sediments and the water column of other aquatic ecosystems (Oswald et al, 2016; Steinsdóttir et al, 2022), the stable isotope signatures of the methane profiles in Lake Grevelingen do not indicate high in situ activity of anaerobic methane removal in the anoxic bottom water (Żygadłowska et al, 2022). However, the surviving strategies of MOB during, and their ability to re-activate methane oxidation after exposure to anoxia is potentially an important feature to mitigate methane emissions during water column turnover (Blees et al, 2014; Mayr, Zimmermann, Dey, et al, 2020).…”

“…Lake Grevelingen is a former estuary in the southwest Netherlands. The lake has a surface area of 115 km 2 with an average water depth of 5.1 m. Here, we sampled Scharendijke basin, which is part of a former tidal channel and has a depth of 45 m. A more detailed description of the system and the study site can be found elsewhere (Egger et al, 2016; Żygadłowska et al, 2022). Lake Grevelingen was chosen to investigate microbial methane cycling as previous studies indicated that methanogenesis exceeded methane oxidation in the sediment during summer stratification, resulting in a periodic release of methane into the water column (Egger et al, 2016).…”