Artificial construction of the biocoenosis of deep-sea ecosystem via seeping methane

Deep-sea ecosystems, such as cold seeps and hydrothermal vents, have high biomass, even though they are located in the benthic zone, where no sunlight is present to provide energy for organism proliferation. Based on the coexistence of the reduced gases and chemoautotrophic microbes, it is inferred that the energy from the reduced gases supports the biocoenosis of deep-sea ecosystems. However, there is no direct evidence to support this deduction. Here, we developed and placed a biocoenosis generator, a device that continuously seeped methane, on the 1000-m deep-sea floor of the South China Sea to artificially construct a deep-sea ecosystem biocoenosis. The results showed that microorganisms, including bacteria and archaea, appeared in the biocoenosis generator first, followed by jellyfish and Gammaridea arthropods, indicating that a biocoenosis had been successfully constructed in the deep sea. Anaerobic methane-oxidizing archaea, which shared characteristics with the archaea of natural deep-sea cold seeps, acted as the first electron acceptors of the emitted methane; then, the energy in the electrons was transferred to downstream symbiotic archaea and bacteria and finally to animals. Nitrate-reducing bacteria served as partners to complete anaerobic oxidation of methane process. Further analysis revealed that viruses coexisted with these organisms during the origin of the deep-sea biocoenosis. Therefore, our study mimics a natural deep-sea ecosystem and provides the direct evidence to show that the chemical energy of reduced organic molecules, such as methane, supports the biocoenosis of deep-sea ecosystems.