Concentrated fluid and gas releases occur in prac- tically all seas and oceans in the form of cold seeps (for example, in the Sea of Okhotsk) and mud volcanoes (the Black and Caspian seas and the Gulf of Cádiz in the Atlantic Ocean). Like hot underwater springs (vents), cold hydrothermal springs (seeps) maintain the life activity of the colossal biomass of sludge worms, shrimps, and giant sulfur bacteria [1]. In regions of gas hydrate releases in marine ecosystems, specific biological chemosynthesis-sustained commu- nities were found. In places of intense methane ingresses, bacterial mats were discovered, largely con- sisting of colorless sulfur bacteria of the Beggiatoa genus, mollusks, worms, and other organisms. One of the main energy and carbon sources in such zones is methane [2], which is involved in food webs in several ways. Invertebrates can consume anaerobic and aero- bic methanotrophs [3], as well as sulfate-reducing bac- teria, which participate in anaerobic methane oxida- tion, and chemoautotrophic sulfur-oxidizing bacteria, which can assimilate 13C isotope–depleted dissolved inorganic carbon, forming as a result of methane oxi- dation [4].
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