Which Ocean Has the Most Marine Life?

Written by on May 5, 2014 in Editor's Choice, Other News

I recently received an interesting question on Twitter that required a lot more than 140 characters to answer.

Question: Which world oceans have the most/least marine life?
Short Answer: It’s complicated because there really are no concrete borders between oceans. But if we had to pick, it would probably be the Pacific because it’s the largest and contains the most coral reefs.

Long Answer: It’s easier to determine where the most life is by separating the oceans into different zones. The pelagic zone contains everything except for the coast and the sea floor and is divided into five parts. The Epipelagic zone extends from the surface to 200m down. It receives plenty of sunlight and therefore contains the most biodiversity in the ocean. Next comes the mesopelagic zone which extends from 200m to 1,000m. It is also called the twilight zone because of the limited light that can filter through these waters. It is too dark for photosynthesis so life in this area is limited. The bathypelagic zone extends from 1,000m to 4,000m and receives no sunlight at all. Sperm whales can reach this zone in search of food! The only light here comes from some organisms that can produce their own light. The abyssopelagic (or abyssal) zone continues to 6,000m where very few creatures can be found due to the lack of light and near freezing temperatures. The deepest a fish was ever found was here in the abyss at 8,372m down! Finally, the hadalpelagic zone extends from 6,000m to the very deepest parts of the ocean in deep trenches and canyons. Some starfish, tube worms and other invertebrates can be found way down here.

Longest Answer: Check out the following facts about our oceans!

Pacific Ocean

Pacific White-Sided Dolphin (Lagenorhynchus obliquidens). Photo credit: NMFS Southwest Fisheries Science Center.

Pacific White-Sided Dolphin (Lagenorhynchus obliquidens). Photo credit: NMFS Southwest Fisheries Science Center.

Atlantic Ocean

Indian Ocean

Beautiful view of the Indian Ocean.

Beautiful view of the Indian Ocean. Photo credit: -RejiK via photopin cc.

Southern Ocean

Arctic Ocean

Polar bear.

Polar bear. Photo credit: NOAA.

So, based on global fisheries and the overall biodiversity of coral reef ecosystems, the Pacific Ocean wins for most marine life.

Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of MarineScienceToday.com. She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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  1. Tom Shilson says:

    I just want to complain that things change When I was a young’un there were 7 oceans — North and South Atlantic, North and South Pacific, Indian, Arctic and Antarctic. These seven oceans are different from, but often confused with, the Seven Seas. I recently read a book on oceanography and I found that there are only 3 oceans, the Atlantic, Pacific, and Indian. The Arctic is considered part of the Atlantic and the Antarctic is split among the surviving oceans. Why can’t things stay the same?! End Rant, no response necessary.