Seasonal Dynamics of Microbial Processes in Bottom Sediments of the Sevastopol Coastal Area

Comparison of methane distribution in bottom sediments of shallow lagoons of the Baltic and Black Seas

“…The diffusion flux of methane at the water-bottom boundary in the Sevastopol Bay varied from 0.004 at point 2 to 0.132 mmol/(m 2 day) at point 9 (see Table 4). The results are comparable with studies in 2011, when the methane flow in the open part of the Sevastopol Bay varied from 0.001 to 0.544 mmol/(m 2 day) [Malakhova et al, 2012]. Moreover, the maximum values both in 2011 and in 2015 were observed in the central part of the bay, characterized by the finest surface sediments.…”

“…At the same time, at points 9 and 2, acoustic anomalies in the water column were observed, similar to bubble outgassing (see Figure 2A, Figure 2B). Stream gas emissions were repeatedly recorded earlier in the coastal waters of the Heracles Peninsula, including the Sevastopol Bay [Egorov et al, 2011;Malakhova et al, 2015;Pimenov et al, 2013a]. It has been established that the mechanism of formation of biogenic methane seeps can be different.…”

“…It has been established that the mechanism of formation of biogenic methane seeps can be different. Bubble gas can form directly in the upper layers of bottom sediments due to intense microbial pro-cesses, such as in Kazachya Bay; and in deeper layers of the sedimentary layer, as in the case of the estuarine part of the Sevastopol Bay [Malakhova et al, 2015].…”

“…The formation of bubble methane in these areas is already possible at a depth of several tens of centimeters, where the methane concentration becomes higher than the gas solubility in pore water. The presence of increased methane concentrations in the sediments of the central part of the bay compared with the peripheral parts can be explained by the peculiarities of sedimentation processes [Malakhova et al, 2018]. The sedimentary matter of the central part of the bay is characterized by a finer granulometric composition of sediments (60-65 % of aleuropelites), and its supply is associated with allochthonous matter [Malakhova et al, 2018], such as rainfall drains, emergency releases of untreated water, which can be a significant Figure 8.…”

“…The presence of increased methane concentrations in the sediments of the central part of the bay compared with the peripheral parts can be explained by the peculiarities of sedimentation processes [Malakhova et al, 2018]. The sedimentary matter of the central part of the bay is characterized by a finer granulometric composition of sediments (60-65 % of aleuropelites), and its supply is associated with allochthonous matter [Malakhova et al, 2018], such as rainfall drains, emergency releases of untreated water, which can be a significant Figure 8. Dependencies of methane solubility on the depth of the station for the Sevastopol Bay ( = 18 o / oo ) and the Vistula Lagoon (average depth 2.7 m, = 3.8 o / oo ) at a water temperature of 22 ∘ C. source of organic matter.…”