Volcanoes of the Deep

Student Handout

Lean on Me

Life at 2,286 meters (7,500 feet) below the ocean surface is harsh. To survive, some organisms living near hydrothermal vents have formed close associations. These kinds of relationships between organisms occur in many ecosystems, not just near hydrothermal vents. Find out more by investigating the organisms in this activity.


  1. Your group will be assigned the names of two organisms. Using resources in the library and on the Internet, research information about the relationship between these two organisms.


  1. On a separate sheet of paper, describe the relationship between the two organisms.

    • Which organism(s) benefits from the relationship? How?

    • Is either organism harmed by the relationship? How?

    • Could both organisms survive without this relationship? Explain.

  2. Consider the relationship between the tubeworms you saw in the program and the microbes that live inside them. How is this relationship similar to or different from the relationship between your organisms?

Tubeworms and Bacteria
Sulfur-oxidizing bacteria and tubeworms living at hydrothermal vents share a symbiotic association. The microbes make their home in special cells inside the worm. (Quite a few microbes live here: an estimated 285 billion bacteria per ounce of tissue.) In exchange for a safe, cozy place to live, they give the worm all the nourishment it needs. They do this by absorbing three ingredients—oxygen, carbon dioxide and hydrogen sulfide—and then changing those ingredients to make food for the worm.