Cold Seeps
Cold seeps are areas where methane, hydrogen sulfide, and other hydrocarbon-rich fluids slowly seep through the seafloor without the extreme temperatures of hydrothermal vents. They occur along continental margins, often associated with subduction zones, oil and gas deposits, or methane hydrate deposits. Unlike vents, which are ephemeral (decades to centuries), cold seeps can persist for thousands to millions of years, supporting long-lived communities. Seep organisms are similar to vent fauna—tube worms, mussels, and clams hosting chemosynthetic bacterial symbionts—but seep tube worms (Lamellibrachia) can live for over 250 years, making them among the longest-lived animals known. Dense mussel beds, bacterial mats, and carbonate rock formations (produced by microbial methane oxidation) characterize seep landscapes. Cold seeps are far more widespread than vents, found on virtually every continental margin.