Part 3—Observe Life in Extreme Environments

Life in Extreme Environments: Exploring Underwater Volcanoes at Oceanic Spreading Centers

Tubeworms and mussels at EPR (2004)
No one expected to find abundant life in the deep-ocean bottom thriving in hot fluids along plate boundaries. The surprise discovery in 1979 of a rich biologic ecosystem in an environment of high pressure, toxic chemicals, frequent eruptions, and complete darkness completely changed our understanding of how life can exist. Research in the 30 years since the first discovery has helped us better understand how heat from Earth's interior is released through underwater hydrothermal vents, and how the complex interaction of geology and chemistry creates an environment where life can be supported through chemosynthesis.


The habitat around a hydrothermal vent is definitely extreme. Deep in the ocean under tens to thousands of meters of water, the environment is generally very cold and dark. The water emitted from the vents can be tens to hundreds of times hotter than the surrounding water. Additionally, the chemicals that seep from the vent are extremely toxic to most life forms, even in small doses. Like other volcanic features, vents are dynamic. Vents can suddenly appear and disappear and their chemical constituents can change without notice. This uncertainty of conditions makes life underwater all the more challenging. Animals that live here must be extremely specialized and resilient in order to survive.

Unlike food webs on and near Earth's surface that function via photosynthesis of green plants, chemosynthetic bacteria are the base of food webs at hydrothermal vent sites. Some of these bacteria live inside the tissues of giant tubeworms and clams providing nour­ishment to these organisms. Other chemosynthetic bac­teria float freely in the vent plume, and provide a food source for plankton. Organic materials, including the remains of bacteria and plankton, drift in the cooler water beneath the plume and are a food source for deposit-feeding organisms such as polychaete worms and small shrimp-like amphipods. These animals then become the food source for predators such as crabs, fishes, and octopi who can move easily among vent communities. Most species found in vent communi­ties are very unique and not found anywhere else. Scientists who explore new vents have an excellent chance of discovering new creatures never before known to science.

Images of Life in Extreme Environments

It is a great opportunity for a scientist to travel in person to the bottom of the ocean to visit hydrothermal vents. Observe the images on this page and explore these spectacular views of life in extreme environments. Click on the images to see an enlarged image on its own page.

Anenome
Here is a sea anemone.

Anemone on lava Pillar
Here is a sea anemone on a lava pillar. This lava cooled underwater, forming a habitat for an anemone. Anemones are filter feeders and live on the plankton and bacteria that is found in the water.

Tube worms and Mussels
Tube worms and mussels coexist around hydrothermal vents. Mussels can filter feed if there is a lack of activity around the vent for several days.

Tube Worms neart vents
Here is a typical vent community. Note the life forms seen in this image, including tube worms (Riftia pachyptila), and several colorful mussels (Bathymodiolus thermophilus). The image is located in the axial trough and appears to contain at least 60 tube worms, two mussels, and one crab. There is no black smoker chimney visible in this image, but there is a distinct shimmer of dilute hydrothermal fluid present. The shimmer is caused by the warmth of the water. Tube worms live in hard shells made of chitin. It protects them from chemicals and predators, such as crabs and fish. Tube worms use the chemicals, such as hydrogen sulfide, that are emitted from the hydrothermal vents to make their own food through a process known as chemosynthesis.

Observe Additional Images and a Movie of Life around a Vent