Hidden worlds of darkness
You might expect the deep seafloor to be drab and featureless but it is not in many places. Cold seeps are special. In some cases, the visible abundance of life around a seep can rival our local tide-pools.
Most living things depend ultimately on sunlight for food. Most of us are familiar with the common process of photosynthesis. The seeps we hope to find however are located over two miles below the surface of the ocean, out of the sun's reach in total darkness. Some of the organisms that live under these circumstances have unusual sources of food. They ultimately do not depend on sunlight like most living things do. Instead, some members of cold seep communities depend on energy contained within the molecules of seeping methane and hydrogen sulfide gas. The primary biological process of harvesting energy from chemicals to make food is called chemosynthesis.
Discoveries
Earlier expeditions to places such as Monterey Bay and the Gulf of Mexico have revealed very unusual and sometimes-lush biological communities bathed in cold waters at great depths. This was a surprise since similar deep-sea communities had only been found in areas where hot water, not cold, seeped out of the seafloor near mid-ocean ridges with volcanic activity. The hot water seeping out of these areas carried dissolved methane and hydrogen sulfide gases. These communities associated with hot water were called hydrothermal vent communities. Most oceanography texts describe hydrothermal vents, but not cold seeps. Cold seep communities, which exist in the absence of volcanic activity and heat, were discovered in 1984 by Dr. Charles Paull. Hydrothermal vent communities were discovered 7 years before in 1977.
Figure 1: Where cold seeps have been found.
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A C T I V I T I E S
• Activity 1.3a
What do you know about food webs?
In the ocean
Flash animation by Antonio Michel
• Activity 1.3b
Photosynthesis
Test your knowledge about this crucial process.
Photosynthesis game
Flash animation by George Ruiz and Wes Bellanca
• Link
Hydrothermal vent discovery
Read a short history of the discovery of hydrothermal vents at this USGS site:
"Exploring the deep ocean floor: Hot springs and strange creatures"
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