Chapter 6 · Try it yourself
Vent Food Web
In 1977 the submersible Alvin dropped 2,500 m onto the Galápagos Rift and found something nobody expected: hot springs crowded with clams, tubeworms, crabs and fish, in total darkness. Every food web anyone had studied started with sunlight. This one starts with chemicals. Build it one link at a time, then pull the plug.
A hydrothermal vent, 2,500 m down
Arrows show which way the energy flows: from the food to whoever eats it. Dashed boxes with a question mark are links you have not added yet.
Build the web
Step 1 of 5
What if…
Switching the vent off cuts the chemical supply at the bottom of the web.
1 · Hot vent fluid
Two ways to make food
| Compare | Vent: chemosynthesis | Reef: photosynthesis |
|---|---|---|
| Energy source | Chemical energy in hydrogen sulfide (the rotten-egg gas) gushing out of the vent | Sunlight |
| Who makes the food | Bacteria and archaea, free-living or inside tubeworms, mussels and clams | Algae, phytoplankton and seagrass, some living inside corals |
| The recipe (simplified) | carbon dioxide + hydrogen sulfide + oxygen → sugar + sulfur + water | carbon dioxide + water + light → sugar + oxygen |
| Where it works | In total darkness, wherever vent chemicals flow | Only where light reaches, roughly the top 200 m |
Simplified model: five levels and a handful of representative animals; real vent webs have hundreds of species, and plenty of animals eat at more than one level. The first vents were found on 17 February 1977 on the Galápagos Rift, about 2,500 m deep, by scientists diving in Alvin (WHOI); they saw giant white clams, mussels, tubeworms, white crabs, a purple octopus and a pink fish. Black smoker temperature: NOAA Ocean Exploration measured 339 °C at one vent. Riftia facts: WHOI. The eelpout’s diet and taste for larger limpets: published predation studies at East Pacific Rise vents. Tubeworm colonies die when a vent stops and larvae colonize new vents within about a year: Smithsonian Ocean. Equations: NOAA Ocean Exploration.