NOAA Ocean Explorer and Life in the Mariana Trench
A Mysterious Habitat
The Mariana or Marianas Trench is the deepest place in the ocean. In 2016, a NOAA expedition examined the trench and took some fantastic photos and videos of its inhabitants. This article shares some of the expedition's discoveries and also explores the biology of the mysterious and often beautiful creatures in the trench.
The Mariana Trench is located in the western Pacific Ocean to the east of the Mariana Islands, which are in turn located to the east of the Philippines. The islands include Guam, a U.S. territory. The NOAA expedition's headquarters was the Okeanos Explorer, a converted navy ship. The trench was explored by a remotely operated vehicle, which was controlled by scientists on the ship. Guam serves as the port for the Okeanos Explorer.
NOAA stands for National Oceanic and Atmospheric Administration. The organization is a government agency in the United States.
Location of Guam and the Mariana Trench
The Mariana Trench is the arc-shaped curve that lies to the north, east and south of the letter A, which represents the location of Guam.
The Mariana Trench
The Mariana Trench gets its name from the nearby archipelago known as the Mariana Islands. The islands are in turn named after Mariana of Austria (1634 - 1696), the second wife of King Philip of Spain. Mariana's given name was Maria Anna, but this was changed to the Spanish form when she became Queen. Spanish vessels arrived at the arc-shaped archipelago in the sixteenth century. The indigenous people of the islands are the Chamoru. They are also known as the Chamorro.
The trench was formed by the collision of two of the plates that make up the Earth's crust. The Pacific plate moved - and is still moving - underneath the Philippine plate in a process known as subduction. The downward movement of the plate created the trench. Hot magma and volcanoes that were produced as a result of the movement created the islands.
Researchers at various organizations have made the following measurements. They may be updated as equipment and techniques improve.
- The trench is approximately 10,944 metres (36,069 feet or 6.831 miles) deep at its deepest point. This area is known as Challenger Deep.
- Challenger Deep is located 332 km (206 miles) southwest of Guam.
- The trench is about 2,500 metres (1,500 miles) long.
- It's also 43 miles wide, on average.
- At the bottom of the trench, the pressure is more than a thousand times greater than air pressure at sea level.
Although the Mariana Trench is the deepest part the ocean, its bottom is not the closest surface to the centre of the Earth. Because the Earth bulges at the equator, some areas of the Arctic seabed are actually closer to the Earth's centre.
An Exploration of the Mariana Trench
A Strange Acorn Worm
Acorn Worms: Phylum Hemichordata
The body of an acorn worm has three sections, as shown in the diagram below. The first section is the proboscis, the middle one is the collar and the last and longest section is the trunk. The proboscis and collar look somewhat like an acorn, which gave the worms their name.
The proboscis is used to burrow through the sediment on the seabed. Some acorn worms take in sediment through their mouth and then digest organic materials and microbes in the sediment. Others filter nutrient particles and microorganisms out of the water via their gills. The gills are also used for respiration. As in a fish, water enters the worm's mouth, flows over its gills and then out of the body through the gill slits. The gills absorb oxygen from the water and send it into the bloodstream. Carbon dioxide moves in the opposite direction.
Deep-Sea Acorn Worms
Unlike acorn worms living in shallow water, the ones discovered in deep water are very long. Their body may be more than eight feet in length. In addition, the worms are seen stretched out over the seabed. The ones at shallow depths build a U-shaped burrow and stay in it with most of their body hidden from view. As at least one researcher has said, the bodies of the deep water animals look too delicate to dig a burrow. Shallow water acorn worms are often dull in colour. The vibrant colour of deep water forms was a surprise for scientists.
Basket stars are classified in the class Ophiuroidea. They belong to the phylum Echinodermata, like starfish (also called sea stars), sea urchins, sea cucumbers and sand dollars.
Basket Stars: Phylum Echinodermata
Basket stars resemble starfish but have five long, slender and flexible arms instead of relatively thick and stiff ones. Each arm branches repeatedly, forming narrower branches as it does so. The terminal branches are very fine and are often curled at their tips.
The central disk of a basket star is more distinct than that of a starfish. The design created by the branches around the disk often looks like lace or a mesh. The arms are not always arranged neatly as in the animal above, however. Basket stars sometimes have an untidy and very strange appearance.
Locomotion and Feeding
Basket stars move over their substrate by wriggling their arms. The animals curl into a ball if they are threatened. The arms are used to catch prey as well as move the animal. A basket star positions itself in a water current when it feeds. The spines, hooks and coils on the arms are very useful for catching small prey like krill, other crustaceans and zooplankton.
Once the prey is caught, it's gradually moved towards the mouth, which is located on the underside of the central disk. The rows of small tube feet under the arms help in the process of transporting the food. Unlike the case in starfish, the tube feet don't have suction cups and aren't useful in locomotion.
A Basket Star Eating Krill in the Seattle Aquarium
At least some of the starfish in the Mariana Trench are unusual, as the photos below show. The orange animal has soft arms, most of which are folded up. The bumps on the surface are spines. Each spine contains tiny claws called pedicillariae, which protect the animal. Pedicillariae are found in other starfish as well.
Brisingid sea stars are found in deep water. Unlike typical starfish that move over a substrate to find food, brisingids extend their arms upwards to trap tiny prey creatures being carried by water currents. This process is known as suspension feeding.
Jellyfish: Phylum Cnidaria
Like starfish, jellyfish are creatures that don't deserve the word fish in their name but are nevertheless very interesting animals. Some researchers and organizations use the word "jellies" to refer to the animals, but the word jellyfish is still very popular.
Jellyfish are actually one stage in the life cycle of the organism. The other stage is the polyp stage, which gives rise to the jellyfish stage. A jellyfish consists of a gelatinous bell which contains the internal organs and contracts or pulsates in order to move the animal. Tentacles dangle from the bell. These tentacles contain stinging cells that kill prey animals.
The stinging cells of a jellyfish are known as cnidocytes. (The initial c in the words Cnidaria and cnidocytes is silent.) A cnidocyte contains a capsule called a nematocyst. The capsule contains a harpoon-like structure that shoots venom into the prey. In some species of jellyfish, the "harpoon" can penetrate human skin and the venom is strong enough to hurt a person.
A Beautiful and Unusual Jellyfish
Deep-Sea Anglerfish: Class Osteichthyes
Anglerfish catch their prey with a fishing technique, as theIr name suggests. They actually have the equivalent of a fishing rod attached to their head. When a prey animal is nearby, the anglerfish lowers its rod, which has a lure at the tip. The lure is technically known as an esca. When a curious animal approaches the esca, the anglerfish swallows the animal.
A famous species of deep-sea anglerfish is Melanocetus johnsoni. Its common name is the humpback anglerfish or the black sea devil. It has a fearsome expression, sharp teeth and a long fishing rod with a bioluminescent lure. When it swims through dark water, its glowing lure is very noticeable. The fish photographed in the Mariana Trench looks very different, however, and has a shorter fishing rod.
The genus and species of the fish below wasn't identified on the NOAA website, but I found a YouTube video of a deep-sea anglerfish with a similar appearance. This fish has been seen in deep water off the coast of California and is shown in the video below. Scientists believe that the fish is blue when it's young and then turns rose and finally red as it matures. It has the scientific name of Chaunacops coloratus.
A Deep-Sea Anglerfish in California
Effects of Human Activity on the Mariana Trench
In addition to interesting information, the NOAA Ocean Explorer website contains two sad images of trash in the Mariana Trench - an empty beer can at 3,780 metres depth and an empty food can at 4,947 metres depth. The website says that other items of trash were found in the 2016 exploration of the trench, including several plastic bags, a piece of rope and an item of clothing. Even the deepest part of the ocean is not immune to the action of humans.
The Mariana Trench is not a silent place. For three weeks in early 2016, a protected hydrophone recorded sounds in the Challenger Deep section of the trench. Many of the sounds that were detected were caused by near and distant earthquakes. The "moans" of distant baleen whales were also heard, as well as noise created by a category 4 typhoon overhead. In addition to these natural sounds, however, there was a lot of noise created by the propellers of ships. Scientists hope to repeat their recordings over time so that they can monitor the sound that humans are adding to the trench environment.
There was also a lot of noise from ship traffic, identifiable by the clear sound pattern the ship propellers make when they pass by. Guam is very close to Challenger Deep and is a regional hub for container shipping with China and The Philippines.— Robert Dziak, NOAA scientist
The First Sighting of a Fish Species
Despite the high pressure and the darkness in the Mariana Trench, many different invertebrates and fish have been found there. The 2016 exploration revealed animals that have never been seen before or which have never been seen alive. It also showed us strange and unusual forms of animals that we see in other parts of the ocean. Every time researchers explore the trench, new discoveries are made. It's a fascinating place.
References and Further Reading
© 2016 Linda Crampton
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