Marine Life Definition and Examples

Definition of Marine Life, Including Types of Marine Life and Career Information

Crabeater seal in Antarctica
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To understand marine life, you should first know the definition of marine life. Below is information on marine life, types of marine life and information on careers working with marine life.

Definition of Marine Life

The phrase 'marine life' refers to organisms that live in salt water. These can include a diverse array of plants, animals and microbes (tiny organisms) such as bacteria and archaea.

Marine Life Are Adapted to Life in Saltwater

From the perspective of a land animal like us, the ocean can be a harsh environment. However, marine life are adapted to live in the ocean. Characteristics that help marine life thrive in a saltwater environment include the ability to regulate their salt intake or deal with large quantities of salt water, adaptations to obtain oxygen (e.g., a fish's gills), being able to withstand high water pressures, living in a place where they can get enough light, or being able to adjust to a lack of light. Animals and plants that live on the edge of the ocean, such as tide pool animals and plants, also need to deal with extremes in water temperature, sunlight, wind and waves.

Types of Marine Life

There is a huge diversity in marine species. Marine life can range from tiny, single-celled organisms to gigantic blue whales, which are the largest creatures on Earth. Below is a list of the major phyla, or taxonomic groups, of marine life.

Major Marine Phyla

The classification of marine organisms is always in flux. As scientists discover new species, learn more about the genetic makeup of organisms, and study museum specimens, they debate how organisms should be grouped. More information about the major groups of marine animals and plants is listed below.

Marine Animal Phyla

Some of the most well-known marine phyla are listed below. You can find a more complete list here. The marine phyla listed below are drawn from the list on the World Register of Marine Species.

  • Annelida - this phylum contains segmented worms. An example of a segmented marine worm is the Christmas tree worm.
  • Arthropoda - Arthropods have a segmented body, jointed legs and a hard exoskeleton for protection. This group includes lobsters and crabs.
  • Chordata - Humans are in this phylum, which also includes marine mammals (cetaceans, pinnipeds, sirenians, sea otters, polar bears), fish, tunicates, seabirds and reptiles.
  • Cnidaria - This is a diverse phylum of animals, many of whom have stinging structures called nematocysts. Animals in this phylum include corals, jellyfish, sea anemones, sea pens and hydras.
  • Ctenophora - These are jelly-like animals, such as comb jellies, but they don't have stinging cells.
  • Echinodermata - This is one of my favorite phylums. It includes such beautiful animals as sea stars, brittle stars, basket stars, sand dollars and sea urchins. 
  • Mollusca - This phylum includes snails, sea slugs, octopuses, squids, and bivalves such as clams, mussels and oysters.
  • Porifera - This phylum includes sponges, which are living animals. They can be very colorful and come in a diverse array of shapes and sizes.

Marine Plant Phyla

There are also several phyla of marine plants. These include the Chlorophyta, or green algae, and the Rhodophyta, or red algae. 

Marine Life Terms

From adaptation to zoology, you can find an often-updated list of marine life terms in the glossary here.

Careers Involving Marine Life

The study of marine life is called marine biology, and a person that studies marine life is called a marine biologist. Marine biologists may have many different jobs, including working with marine mammals (e.g., a dolphin researcher), studying the seafloor, researching algae or even working with marine microbes in a lab.

Here are some links that may help if you're pursuing a career in marine biology:

References and Further Information

  • Marine Education Society of Australasia. Marine Phyla. Accessed August 31, 2014.
  • WoRMS. 2014. Animalia. Accessed through: World Register of Marine Species on August 31, 2014.
  • WoRMS 2014. Plantae. Accessed through: World Register of Marine Species on August 31, 2014.
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Your Citation
Kennedy, Jennifer. "Marine Life Definition and Examples." ThoughtCo, Aug. 26, 2020, Kennedy, Jennifer. (2020, August 26). Marine Life Definition and Examples. Retrieved from Kennedy, Jennifer. "Marine Life Definition and Examples." ThoughtCo. (accessed March 20, 2023).

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