The Pacific Ocean

The Pacific Ocean is the largest, deepest and oldest of the ocean basins. It is bordered by five of the seven continents, with the Americas to the East, Antarctica to the South and Oceania and Asia to the west.

With an area of 155, 000, 000 square kilometres, it is larger than the entire land mass of the Earth. The average depth of the Pacific is 4 km. The deepest point is located at the Challenger Deep, within the Mariana trench, where it is submerged to 10.9 km. For reference – Mount Everest’s height is just short of 9km.

The Pacific Ocean has been sailed countless times from the earliest seafaring humans 50 000 years ago as they spread further and further out of Africa. While there is some debate as to whether or not these migrants travelled far enough east to reach South America by boat, they were the first to explore Earth’s biggest ocean.

At the beginning of the 16th century, European navigators first reached the Pacific. In the centuries thereafter imperialistic aims led various countries to continue exploring. Many of the famous scientific expeditions, such as the three voyages of James Cook, that of Charles Darwin, and the Challenger Expedition made crucial scientific discoveries during the late 1700 and 1800s.

The biota of the deep Pacific Ocean is extensive, with there being many environmental gradients. As such, there are high levels of endemism. Much of the animal biota is found in localised regions, especially surrounding hydrothermal vents (e.g. the Nafanua volcanic cone) and deep sea food falls, such as whale carcasses. In the deep sea (benthic environments) there is little to no light and very high pressure, and so animals have specialised adaptations and low energy lifestyles. Species such as Tube worms (Tevnia jerichonana, and Riftia pachyptila) are commonplace around hydrothermal vents and utilise vital symbionts to survive in the harsh, light limited environment. Other groups, like deep sea fish (e.g. Deepwater slipskin (Lycodapus endemoscotus)) are found in often more open, bathypelagic waters.

Cold water corals are distributed across the Pacific Ocean. Most studies on cold water corals take place in the North Atlantic Ocean and so the distribution within the Pacific is not well documented. Seamounts, which are underwater mountains, tend to hold the largest biodiversity of corals and other organisms. Within the Pacific there is an estimated 30,000 to 50,000 seamounts. Of these, very few have been studied, however those that have appear to show high endemism. For example, up to 34% of species on SW Pacific seamounts were newly discovered and potentially endemic. Because there were few common species between seamounts in this region, it is possible that, seamounts may be analogous to island groups. There is no legislation in the US to protect these regions.

Within the vast Pacific Ocean, two particular Island chains have been added as in depth case studies. Follow the links to find out more:

The Aleutian Islands

New Zealand