What is the difference between cold seeps and hydrothermal vents?

Cold seeps are relatively stable, long-lived places in the ocean where hydrocarbon-rich fluid that is of a similar temperature to surrounding water seeps up from cracks in the seafloor while hydrothermal vents are volatile, short-lived openings in the seafloor created through volcanism where magma-heated, high-temperature water emerges.

Cold seeps and hydrothermal vents are similar in that the ecosystems they support are largely driven by a process called chemosynthesis, the synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight. Chemosynthetic bacteria at these sites can be found living symbiotically in or on animals, serving as the basis of the food chain in these communities. Both also represent environments with reduced oxygen availability.

There are, however, several differences between cold seeps and hydrothermal vents, as described in the table below.

Cold Seeps

Cold (or marine) seeps are locations where hydrocarbon-rich fluid seeps up from below the seafloor, often as methane or hydrogen sulfide.

  • Relatively stable and long-lasting
  • Fluid temperatures are similar to surrounding seawater
  • Emit gasses and fluids including methane, oil, and hydrogen sulfides
  • Organisms here grow slowly and can be extremely long-lived
  • Occur at tectonically active areas like the Cascadia Margin in the Eastern Pacific, and along passive (inactive) continental margins, like along the U.S. Atlantic coast and the Gulf of Mexico
  • Organisms that thrive at seep sites include slow-growing tubeworms, Lamellibrachia luymesi; those found at a seep site in the Gulf of Mexico were over 200 years old and about 2 meters (6 feet) long

Hydrothermal Vents

Hydrothermal vents are openings on the ocean floor from which magma-heated, mineral-rich water emerges, often forming large chimneys.

  • Driven by volcanism; volatile and short-lived
  • Highly acidic fluids are of extremely high temperatures (> 400°C/750°F)
  • Emit gasses comprised of hydrocarbons and hydrogen sulfide
  • Rich in minerals that precipitate out forming “white and black smokers”
  • Organisms here grow quickly
  • Occur at tectonically active areas like the mid-ocean ridges and the Pacific Ring of Fire
  • Organisms that thrive at vent sites include giant tube worms (Riftia pachyptila), the fastest growing marine invertebrates and one of the fastest growing organisms on Earth [a little less than 1 meter (~3 feet) in a year]


Published February 3, 2023