Biology 103
2000 First Web Report
On Serendip

Ever since I was first introduced to science, I have been told the same things. All the organisms on the earth depend on each other. Plants provide us with oxygen. Living things require energy to exist. And, of course, life would be nothing without the sun. These are the kinds of definite "truths" upon which a classroom first graders can depend.

But this last statement, this idea that life cannot exist without sunlight, has recently been challenged. Scientists have found life over a mile below the surface of the sea, far from the sun. And not just one form of life, but many. There are long white tube worms with red-purple tips. There are 8- inch long clams. Giant white crabs. Shrimp without eyes (1). Scientists have discovered over 300 organisms that don't just survive, but thrive, in the dark depths of the ocean (3).

After discovering these hydrothermal vents surrounded by life, scientists first question was: how do these animals survive in such an extreme environment?

The answer is amazing in itself. These animals survive not on photons derived from the sun, but on chemicals from the inside of the Earth. Bacteria on the surface of these vents oxidize the hydrogen sulfide that the vents produce, and harness the energy from the reaction between hydrogen sulfide and oxygen, providing the base for this deep-sea food chain. Some organisms feed directly upon these bacteria while others, like the tubeworm, host these bacteria in their tissue in exchange for the nutrients they need (3).

So now these animals have food. But what about the toxic metals spewed forth from the vents into the surrounding water? Although scientists have not been able to completely understand how these organisms exist in such a toxic atmosphere, they do have some ideas. It appears that different animals cope with the metals in different ways. Some animals, like some tubeworms, seem to get rid of the metals through mucus. Other organisms have metal-binding proteins within their systems (3). These animals not only have to deal with these metals, but also with extreme acidity (a pH of about 2), and it is still not clear how they survive this.

And still there is another concern- how do these animals survive such intense pressure? More than a mile below the surface of the sea, these animals would face about 3,350 pounds of pressure on every square inch of their bodies (3). With this kind of pressure, our lungs would be crushed immediately. These animals, however, have developed so that their bodies do not have any air pockets, thus allowing them to exist in this pressurized atmosphere.

As if all these strange circumstances were not enough, the deep-sea creatures have to deal with extreme temperatures as well. The ocean water that these creatures live in is about 35 degrees Farenheit, while the fluids being spewed from the surrounding vents can get up to 750 degrees , (3).

Yet another problem is that these hydrothermal vents and "black smokers" are highly fragile and can collapse or "shut off" at any given time, cutting off the key elements to the creatures' existence. Scientists believe that these animals have learned to migrate to other vents when this occurs.

Although there is still much that we don't know about these deep-sea creatures and how they exist in such extreme circumstances, we do know that the discovery of these hydrothermal vent communities is crucial to our expanding understanding of life. Until these underwater worlds were discovered a little over two decades ago, we could not have imagined that life would exist in such circumstances- no access to sunlight, extreme and shifting temperatures, intense pressure, toxic and acidic surroundings and all based upon fragile vents. Yet these creatures do exist, and it appears that they have existed for millions of years, even despite devastating changes that occurred on Earth's surface (3).

The questions that arise from these deep-sea communities are seemingly infinite. Are these creatures a glimpse into the creatures at the Earth's very beginning? Is this proof that life can exist on other, seemingly extreme planets? What can these creatures teach us about assumptions we've made in terms of what life needs to exist? And, will these creatures go on if life on land disappeared? There is still clearly so much we have to learn about life.

WWW Sources

2)What Are Deep Sea Hydrothermal Vents?,

3)Nova Online, sea vents page.

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