Source: Journal of Geophysical Research: Biogeosciences
Deep water neighborhoods around hydrothermal hotspots are a part of productivity, especially compared to the majority of the seabed. The heat, minerals, dissolved gases, and pressures found in these hot spots provide rich environments in which microbial communities can thrive.
Under these harsh conditions with swirling chemicals, organic compounds can form from inorganic materials, releasing energy along the way, which is the opposite of the more familiar conditions on the Earth’s surface, in which energy is consumed to form organic materials. Bacteria gain energy by reducing carbon dioxide with hydrogen to produce methane and water, a process called autotrophic methanogenesis.
In a new study by cock and shock, the researchers investigated where else energy might be released in ultramafic and hydrothermal ecosystems and what this might mean for life in these complex biogeochemical environments. They examined hydrothermal vents in the Mid-Atlantic Ridge (the vent field called Rainbow which is hosted in ultramafic rocks) and a vent on the Juan de Fuca border in the Pacific (a vent field hosted in basalt called Endeavor). Researchers examined nearly 1,800 proteins for Methanocaldococcus jannaschii, a member of the Archaea found in hydrothermal vents, and analyzed autotrophic methanogenesis reactions and global amino acid synthesis reactions in both stack locations.
They found that methanogenesis was due to the large imbalance of chemicals resulting from the mixing of hydrothermal fluids and seawater. The team found that in ultramafic systems, energy is released during protein synthesis on a wide temperature range. However, the same was not found for vents hosted in basalt, where the temperature ranges were smaller for methanogenesis and protein synthesis does not release energy.
Based on these results, the researchers note that some hydrothermal systems are hot spots for microbial overgrowth. They note that in very small systems, the way proteins are synthesized and energy released can tell researchers a lot about how biogeochemical cycles may have led to the emergence of deep-sea life. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2021JG006436, 2021)
—Sarah Derouin, science writer