Sediments from ocean trench walls also have very low levels.

A team of deep-sea oil drillers search for a lost submarine in an ocean trench, where they encounter mysterious marine monsters.

A new species of deep-sea fish has been discovered in an ocean trench previously thought to be uninhabited.

One example, xenophyophores, have been found in the deepest ocean trench, 6.6 miles (10,541 meters) below the surface.

Major habitat types are identified: polar, temperate shelves and seas, temperate upwelling, tropical upwelling, tropical coral, pelagic (trades and westerlies), abyssal, and hadal (ocean trench).