Glossary

Glossary

This glossary will be added to as the voyage continues. It will explain unfamiliar terms and describe organisms found, the layers of the ocean and instruments used on the voyage.

Instruments used on this voyage:

Argo: This is an international collaboration that collects data from a network of floats that descend to cruising depth, drift for several days, ascend while taking salinity and temperature profiles, and then transmit data to satellites.

Beam trawl: This is used to trawl along the sea floor. It is a trawl where the mouth is held by a beam. It a cone shaped body ending in a bag which retains the catch.

CTD instruments: CTD stands for Conductivity – Temperature – Depth. These measure characteristics of water such as salinity, temperature, pressure, depth and density. They are placed into the actual water that you want to measure (rather than taking a sample). If the CTD instrument is lowered through the water measurements are recorded continuously.

DTIS camera: DTIS stands for “Deep Towed Imaging System”. It is a newly developed camera system that is being used to take pictures and videos of deep sea biodiversity and seafloor habitats. It has high definition still and video cameras, and light and batteries mounted in a rectangular frame. It is attached to the ship via a conducting wire.

Epibenthic sled: This sled collects small organisms from close to the sea bed using two fine mesh nets. It is pulled short distances to collect relatively large organisms living in or on the upper few centimetres of sediment on the sea floor. Wide skids make sure that it doesn’t sink in the sediment and a video system can monitor progress.

Multi-beam sonar: This sonar sends out many beams of sound at once down to the seafloor to produce a "swath" - an image of large areas of  the seafloor. This can effectively map the sea floor.

Multicorer: These take multiple samples of sediment from the sea floor.

Sediment grabs: These are scoops that take samples of soft sediment as are found on the bottom of the ocean.

The layers of the Ocean

Profile of the Ocean

The Sunlight (Epipelagic) Zone

This surface layer extends from the surface to 200 meters deep. It is the top layer where enough sunlight penetrates for plants to carry out photosynthesis. With the light comes heating from sun and so this zone can have a wide range of temperatures, from as high as 36°C in the Persian Gulf to -2°C near the north pole.

The twilight (Mesopelagic) Zone

This zone extends from 200 - 1,000 metres. Only some light penetrates, but not enough for plants to grow. Temperature changes the greatest in this zone as this is the zone which contains the thermocline. Because of the lack of light, it is within this zone that bioluminescence begins to appear on life. The eyes on the fishes are larger and generally upward directed, so that they can see the silhouettes of other animals (for food) against the dim light.

The midnight (Bathypelagic) Zone

This zone extends from 1,000-4,000 metres. No light penetrates and the only light at this depth (and lower) comes from the bioluminescence of the animals themselves. The temperature in this zone is constant at about 4°C. The pressure is extreme and yet sperm whales can dive down to this level in search of food.

The pitch-black (Abyssal or Abyssalpelagic) Zone

This zone extends from 4,000 - 6,000 m. Three-quarters of the area of the deep-ocean floor lies in this zone. The water temperature is constantly near freezing and the presume immense and only a few creatures can be found at these crushing depths. The deepest a fish have ever been found was in the Puerto Rico Trench at 8,372 meters.

The Hadalpelagic Zone

The deepest zone of the ocean extends from 6,000 meters) to10,911 metres in the Mariana Trench off the coast of Japan. The temperature is constant at just above freezing. The weight of all the water over head in the Mariana Trench is over 8 tons per square inch (the weight of 48 Boeing 747 jets). Even at the very bottom life exists. In 2005, tiny single-celled organisms, called foraminifera, a type of plankton, were discovered in the Challenger Deep trench southwest of Guam in the Pacific Ocean.

If you want to learn more about layers of the ocean click here

Antarctic Circumpolar Current: This is a major ocean current that flows from west to east around Antarctica. It connects the Atlantic, Pacific and Indian Oceans and redistributes hear around the world. It transports the equivalent of about 135 times the water in all the world's rivers. This current is very important in determining the Earth's climate.

If you want to learn more about Antarctic Circumpolar Current click here

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