Life at the Bottom of the Seafloor

Up until the 1970s, life was thought to have been dependent on energy from the sun.  With the first discovery of a hydrothermal vent system, this notion was shattered.  Hydrothermal vents are fissures, or volcanic vents, on the floor of the ocean where geothermally heated water is released.  Compared to the 2(DEG)C water in the deep sea, these vents expel water ranging from 6(DEG)C up to 464(DEG)C.  The critical ingredient for life at these depths is sulfur, which is emitted from the vents most abundantly as hydrogen sulfide.  Bacteria use heat, methane, and sulfur products to produce energy in a process known as chemosynthesis.  This method of energy uptake is unlike almost every other organism on the planet that is dependent directly or indirectly on sunlight, by plants that undergo photosynthesis or other organisms that consume plants.











Image Courtesy of University of Victoria

The energy produced by these chemosynthetic bacteria support a whole ecosystem and many trophic levels of organisms.  The bacteria grow into a thick mat and are consumed by the grazers: amphipods and copepods.  A food web is formed by larger organisms including snails, tube worms, crabs, octopi, clams, and fish that feed on the grazers and each other.  The hydrothermal vent community supports surprising levels of biodiversity including 400 species of gastropods and a few species unique to the vents themselves and found nowhere else.

One cool community was discovered in 2005 in the Nafanua volcano in American Samoa to be dominated by eels, and thus dubbed “Eel City” pictured below.  It has not yet been determined whether the eels are feeding on the bacterial mats or feeding elsewhere and inhabiting this area, but it will be an interesting insight into the adaptability of eels either way.











Image Courtesy of Scripps Institute of Oceanography

-Kelsie DiPerna


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