The Census of Marine Life: Making Waves on Earth’s Final Frontier

Julie Marentette
30 January 2013

Above: One of the largest and most colorful new species collected by the Census of Coral Reef Ecosystems, this purple sea star is about a foot long and very conspicuous. Unlike its close relatives, this species is out during the day, perhaps a reflection that there are relatively few predators in the French Frigate Shoals ecosystem (Gustav Paulay, Florida Museum of Natural History)

Outer space might be considered the “final frontier.” But the world’s oceans, which cover 71% of Earth’s surface, also remain largely unexplored. In fact, some people say that scientists know more about space than they do of the deep ocean. However, a better understanding of life in the ocean will be key to helping endangered marine life survive and recover.

So what lives in the oceans, and where? How has this life changed over time? And what changes does the future hold? Between 2000 and 2010, a team of 2700 scientists working in over 80 countries sought answers to these questions. The project was dubbed the Census of Marine Life, or CoML. Over the course of the decade, these scientists were involved in over 500 expeditions. They collected millions of samples from coastal areas, the open ocean, the deeps, coral reefs, and at the poles.

The CoML made use of a lot of techniques, including:

Genetic (DNA) barcoding

DNA, the “blueprint of life,” contains molecular sequences that are unique to each species. Scientists can identify species by reading these sequences. This method is faster than “traditional” visual methods of identifying species based on anatomy (or body shape).

Did You Know? So far, only about 250,000 of the estimated 1 million species living in the ocean have been identified. That means three out of four marine species are waiting to be discovered.


Scientists can attach electronic tags to an animal. These tags emit signals, and these signals are then followed by satellites. This way, scientists know where the animal travels. They can learn how deep and how far the animal ranges.

Acoustic or side-scan SONAR

A device uses sound waves off objects, like fish. Then, scientists can examine the signals received in return. This can tell researchers how many animals live in very large areas or deep below the ocean surface.

The only specimen known of the second species of Glypeids, Laurentaeglyphea neocaledonica (Richer de Forges, 2006), from the Coral Sea. (Lai/Richer de Forges)

The CoML has also produced some interesting results:

Living fossils

Laurentaeglyphea neocaledonica is a species of crustacean found living off the northeastern coast of Australia. It belongs to a group of animals previously thought to have gone extinct 50 million years ago.

Fish city

A group of approximately 20 million fish was located in the Atlantic Ocean, off the coast of New Jersey. These fish covered an area of around 60 km2. This is the size of some cities!

Extreme travelers

The sooty shearwater is a seabird that flies an average of 64,000 km each year. It can cover between 200 and 900 km a day as it travels between the North and South Poles!

By helping to understanding what species exist (biodiversity), how abundant they are, and where they live (distribution), the CoML is allowing researchers determine how climate change, overfishing, and pollution are affecting the ocean. In fact, the census was conducted and its results are being analyzed at a time when many marine organisms are facing the threat of extinction.

Did You Know? Microbes, like bacteria, represent the greatest degree of biodiversity in the ocean. Tens of thousands of different species can be found in a single litre of seawater!

So the CoML is much more than a collection of interesting facts about some sea creatures. It will help scientists and governments identify areas of the ocean that need to be given special protection. At the same time, it will help with targeting other areas for help and repair. The census will also help researchers identify when these areas start to recover.

This article was updated by Let's Talk Science staff on 2016-08-26 to improve readability by reducing the reading grade level.

Julie Marentette

Dr. Marentette is a Canadian scientist working on national environmental monitoring issues. She is a toxicologist and a behavioural ecologist who enjoys researching how animals, including people, are affected by toxic chemicals. Mostly, she really likes fish.

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