A biological methane filter on the seafloor can form much faster than scientists previously believed, according to a study published in National Science Review. An international research team, including a University of Bremen microbiologist, observed this process over six years at a newly formed methane seep in the South China Sea, located at a depth of 1,766 meters. The site was previously untouched, with no detectable methane flow or significant life on the seafloor before a drilling operation in 2018 explored gas hydrates—frozen deposits of methane and water. Between 2018 and 2023, the team used a variety of tools, including echo sounders, underwater cameras, chemical sensors, sediment samples, and genetic analysis, to track the development of the ecosystem. Microorganisms that consume methane, even in oxygen-free conditions, are key to the biofilter. These microbes usually grow slowly because their metabolic processes yield little energy. However, at the new seep, they multiplied far more rapidly than expected, with their numbers doubling every 21 to 38 days during the early stages—much faster than the previously estimated 100 to 200 days. "Within just one to two years, an effective methane-consuming ecosystem had already formed," said Emil Ruff, the microbiologist from the University of Bremen. Within two to three years, microorganisms and newly arriving animal life had merged into a complex biofilter. Burrowing worms helped break down methane as the microbes grew, and bristle worms colonized the previously barren seafloor. These worms mixed the sediment to a depth of more than 50 centimeters, likely helping to transport oxygen, nitrate, and sulfate into deeper layers. Oxygen-free zones also remained, allowing different microorganisms to break down methane with or without oxygen. In turn, the worms benefited from the microbes, which likely served as a food source, creating a cooperative system for methane breakdown. Within just a few years, the young ecosystem was breaking down methane as effectively as older, established methane seeps with similar methane supplies. According to the team's calculations, the new system reached 60% to 100% of the methane-degrading capacity of a decades-old, mature ecosystem. However, this rapid development came at a cost: the original ecosystem changed significantly. Within a 20-meter radius, the diversity of bacteria and other microorganisms dropped by more than 50% within two years. Even 500 meters away, methane concentrations increased, and microbial diversity fell by more than 30%. The study highlights two parallel developments: the seafloor quickly gained a strong ability to break down methane, but the original biological community was significantly altered in the process. These findings are important for understanding how methane leaks might evolve in response to ocean warming and human activities. They also suggest that models predicting methane breakdown should account not only for microbial growth but also for the interactions between microorganisms, animals, and the chemical conditions of the seafloor.