Some Like it Hot: Extreme lifestyles in the deep sea

If you're anything like me, the phrase "marine life" probably brings to mind those creatures which typically appear on our dinner plates, such as fish, shrimp, and lobster. Charles Fisher, host of this Wednesday's Research Unplugged conversation "Some like it hot: Extreme lifestyles in the deep sea," had a few more, lesser-known—and much less edible—marine animals to add to that list.

Fisher, who has participated in more than fifty oceanographic expeditions, researches the physiology and ecology of hydrothermal vent and cold-seep animals. Addressing Wednesday's crowd of over 40 attendees, he presented colorful photos and explanations of the complex and, at times, puzzling world of deep-sea biology.

undersea off-white vents

Animals have adapted to the deep-sea hydrothermal vents.

Though his lecture title calls the deep-sea environment "extreme"—its denizens exist in total darkness, after all, some 2,500 meters below the ocean surface, in a place where frigid (2 degrees C) ocean is met by plumes of water as hot as 350 degrees C—Fisher argued that much of the time our own habitat is less hospitable than those below the sea. "Think about it—we have storms and fluctuating temperatures," explained Fisher. "These factors simply don't exist in the deep sea."

What does exist on the ocean's floor are hydrothermal vent systems, the focal point of Fisher's research. Discovered less than 30 years ago, these hydrothermal hot springs occur in spots where tectonic plates overlap, and present unique challenges and opportunities for marine animals and bacteria. Scientists once believed that the low oxygen, high temperatures and pressures, and toxicity of vent environments precluded the development of life. But explorations by Fisher and colleagues over the last decades have uncovered a major biological secret: Despite the considerable environmental challenges, animals from every phylum have been drawn to the vents by their abundant food supplies, and have successfully adapted to the environment.

Fisher is particularly interested in the symbiotic relationships that exist between some of these marine animals and the bacteria that live inside them, a partnership that has turned toxic vent chemicals into usable food energy. One such animal, a large tube worm named Riftia pachyptila, is colonized by dense populations of bacteria that feed upon sulfide. The tube worm's blood contains a special type of hemoglobin that—in addition to binding oxygen—also binds the toxic sulfide and passes it along to the hungry bacteria without harming the host organism.

bacteria growing on maroon tubeworms

The bacteria living inside the tube worm provides its main source of energy.

R. pachyptila and other animals that host chemosynthesizing bacteria are of special interest to researchers in other fields. For one thing, their unusual hemoglobin may prove useful in the advancement of artificial blood substitutes for humans.

More broadly, the unique mode of life represented by these animals has provided new insights into a variety of basic biological, geochemical, and oceanographic phenomena. And, says Fisher, new associations and communities are constantly being discovered and reported. "For all we currently know, there is so much more to learn about the fascinating life forms around these hydrothermal vents."

Chuck Fisher, Ph.D., is professor of biology and chair of the NSF-funded Ridge 2000 research initiative. He can be reached at Anne Marie Toccket is an undergraduate communications student and intern for Research Unplugged. She can be reached at

Last Updated October 19, 2005