Deep Ocean Trenches: Formation & Examples

There is an abundance of xenophyophores in the Mariana Trench, a type of foraminifera protist. Protist is a phylogenic kingdom and consists of single-celled organisms. Under this category is foraminifera which can be benthic, meaning they live on the bottom of the ocean, or planktonic, meaning they live throughout the water column. The xenophyophore nestles into the sediment and begins to create its casing using materials that surround it. These unique casings are called tests where other organisms can live. Scientists are still trying to learn more about these organisms, which is difficult due to their fragile frame and living in an isolated environment.

Located in the Horizon Deep area of the Tonga Trench are Alicella gigantea, the largest of all amphipods under the phylum Arthropoda and are crustaceans. Arthropods have segmented bodies, hard exterior skeletons, and molt to grow larger. They use an antenna to sense (taste, feel, smell, etc.) their surroundings; this is helpful in the dark benthic areas of the ocean. Little is known about the Alicella gigantea and its behaviors because it lives in such an isolated environment.

Survival

The environmental conditions in a trench vary but are extremely different from waters closer to the surface. Organisms that are benthic dwellers have evolved differently to adapt to their unique surroundings. Trench environments are cold, dark, is high in pressure, and low in oxygen. One way organisms have adapted to darkness in the trenches is bioluminescence, a chemical reaction within an organism that produces light. Bioluminescence can be used for many different things in marine life, such as mating or luring prey. Food or how organisms receive their sustenance is unique as well. Some organisms have adapted to feed off the particles and nutrients dispersed from underwater ocean vents, such as dissolved sulfide. Other organisms have evolved together to create a unique food web that operates in the deep ocean, while some organisms feed on marine snow or organic material made up of organisms from higher in the water column. The pressure in the ocean grows further down you go. At the bottom of the Mariana trench, the pressure is equal to 8 tons per square inch. Organisms have adapted to this immense pressure in many ways. Some evolved without gas-filled organs; others have evolved exteriors that can withstand high pressure.

Importance to Humans

Life began on earth around 3.7 billion years ago. There are many different theories on how this occurred; however, current research suggests that we can learn a lot about the beginning of life from organisms and how they live deep in the ocean trenches. Early life on planet earth was hostile and quite similar to the harsh conditions in the Mariana trench. Some scientists believe that studying the life patterns and organisms in these environments can help us better understand how life evolved. Some recent research indicates that because of the harsh conditions of early earth, the organisms that survived did so by living far beneath the ocean's surface. Today, we have found traces of those organisms living at the deepest parts of the ocean in areas such as the Mariana trench, which scientists are still trying to decode and piece into the bigger picture.

Lesson Summary

An ocean trench is an indentation in the ocean floor and is the deepest area of the ocean. Trenches are formed through subduction, which occurs when tectonic plates collide and push one plate beneath the other. Trenches can be found all over the surface floor of the ocean at subduction zones. The Mariana trench is the deepest known point in the ocean at over 35,000 feet deep. Life in these deep areas has evolved to survive in high-pressure, low-oxygen environments. We are still learning so much about trenches and the organisms that live there; however, recent studies suggest these organisms can help us better understand the evolution of life on earth.