9 Types of Marine Ecosystems

Underwater view of a coral reef ecosystem teeming with aquatic life.

Francesco Ungaro/Pexels

An ecosystem is made up of the living organisms, the habitat they live in, the non-living structures present in the area, and how all of those relate to and influence each other. Ecosystems may vary in size, but all the parts of the ecosystem depend upon each other. If one part of the ecosystem is removed, it affects everything else.

marine ecosystem is any that occurs in or near salt water, which means that marine ecosystems can be found all over the world, from a sandy beach to the deepest parts of the ocean. An example of a marine ecosystem is a coral reef, with its associated marine life — including fish and sea turtles — and the rocks and sand found in the area.

The ocean covers 71 percent of the planet, so marine ecosystems make up most of the Earth. This article contains an overview of major marine ecosystems, with types of habitat and examples of marine life that live in each. 

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Rocky Shore Ecosystem

Sea stars in a tide pool on a rocky beach under an orange sunset sky.

Doug Steakley/Getty Images

Along a rocky shore, you may find rock cliffs, boulders, small and large rocks, and tide pools (puddles of water that can contain a surprising array of marine life). You will also find the intertidal zone, which is the area between low and high tide. 


Rocky shores can be extreme places for marine animals and plants to live. At low tide, marine animals have an increased threat of predation. There may be pounding waves and lots of wind action, in addition to the rising and falling of the tides. Together, this activity has the ability to affect water availability, temperature, and salinity. 

Marine Life

Specific types of marine life vary with location, but in general, some types of marine life you'll find at the rocky shore include:

  • Marine algae
  • Lichens
  • Birds
  • Invertebrates such as crabs, lobsters, sea stars, urchins, mussels, barnacles, snails, limpets, sea squirts (tunicates), and sea anemones.
  • Fish
  • Seals and sea lions
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Sandy Beach Ecosystem

Gull on the beach with a crab in its beak with a second gull flying toward the first, ocean waves in soft focus in the background.

Alex Potemkin/Getty Images

Sandy beaches may seem lifeless compared to other ecosystems, at least when it comes to marine life. However, these ecosystems have a surprising amount of biodiversity. 

Similar to the rocky shore, animals in a sandy beach ecosystem have had to adapt to the constantly changing environment. Marine life in a sandy beach ecosystem may burrow in the sand or need to move quickly out of reach of the waves. They must contend with tides, wave action, and water currents, all of which may sweep marine animals off the beach. This activity can also move sand and rocks to different locations. 

Within a sandy beach ecosystem, you'll also find an intertidal zone, although the landscape isn't as dramatic as that of the rocky shore. Sand generally is pushed onto the beach during summer months, and pulled off the beach in the winter months, making the beach more gravelly and rocky at those times. Tide pools may be left behind when the ocean recedes at low tide. 

Marine Life

Marine life that are occasional inhabitants of sandy beaches include:

  • Sea turtles, who may nest on the beach
  • Pinnipeds, such as seals and sea lions, who may rest on the beach

Regular sandy beach inhabitants:

  • Algae
  • Plankton
  • Invertebrates such as amphipods, isopods, sand dollars, crabs, clams, worms, snails, flies, and plankton
  • Fish — including rays, skatessharks, and flounder — can be found in shallow waters along the beach
  • Birds such as plovers, sanderlings, willets, godwits, herons, gulls, terns, whimbrels, ruddy turnstones, and curlews
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Mangrove Ecosystem

First person photo of a mangrove forest as seen from a small boat.


Mangrove trees are salt-tolerant plant species with roots that dangle into the water. Forests of these plants provide shelter for a variety of marine life and are important nursery areas for young marine animals. These ecosystems are generally found in warmer areas between the latitudes of 32 degrees north and 38 degrees south. 

Marine Species Found in Mangroves

Species that may be found in mangrove ecosystems include:

  • Algae
  • Birds
  • Invertebrates such as crabs, shrimp, oysters, tunicates, sponges, snails, and insects
  • Fish
  • Dolphins
  • Manatees
  • Reptiles such as sea turtles, land turtles, alligators, crocodiles, caimans, snakes, and lizards
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Salt Marsh Ecosystem

Salt Marsh in Cape Cod, Massachusetts on a gray day.

Walter Bibikow/Getty Images

Salt marshes are areas that flood at high tide and are composed of salt-tolerant plants and animals.

Salt marshes are important in many ways: they provide habitat for marine life, birds and migratory birds, they're important nursery areas for fish and invertebrates, and they protect the rest of the coastline by buffering wave action and absorbing water during high tides and storms.

Marine Species

Examples of salt marsh marine life:

  • Algae
  • Plankton
  • Birds
  • Fish
  • Occasionally marine mammals, such as dolphins and seals. 
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Coral Reef Ecosystem

Underwater view of a coral reef with tropical fish swimming around.


Healthy coral reef ecosystems are filled with an amazing amount of diversity, including hard and soft corals, invertebrates of many sizes, and even large animals, such as sharks and dolphins.

The reef-builders are the hard (stony) corals. The basic part of a reef is the skeleton of the coral, which is made of limestone (calcium carbonate) and supports tiny organisms called polyps. Eventually, the polyps die, leaving the skeleton behind.

Marine Species

  • Invertebrates may include: hundreds of species of coral, sponges, crabs, shrimp, lobsters, anemones, worms, bryozoans, sea stars, urchins, nudibranchs, octopuses, squid, and snails
  • Vertebrates may include a wide variety of fish, sea turtles, and marine mammals (such as seals and dolphins)
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Kelp Forest

Underwater view of a habor seal swimming through a kelp forest.

Douglas Klug/Getty Images

Kelp forests are very productive ecosystems. The most dominant feature in a kelp forest is — you guessed it — kelp. The kelp provides food and shelter for a variety of organisms. Kelp forests are found in cooler waters that are between 42 and 72 degrees Fahrenheit and in water depths from about six to 90 feet. 

Marine Life in a Kelp Forest

  • Birds: seabirds such as gulls and terns, and shorebirds such as egrets, herons, and cormorants
  • Invertebrates such as crabs, sea stars, worms, anemones, snails, and jellyfish
  • Fish, including sardines, Garibaldi, rockfish, seabass, barracuda, halibut, Halfmoon, jack mackerel and sharks (e.g., horn shark and leopard shark)
  • Marine mammals, including sea otters, sea lions, seals, and whales
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Polar Ecosystem

Polar bear swimming underwater looking at camera.

Detroitzoo/Wikimedia Commons/CC BY 4.0

Polar ecosystems are found in the extremely cold waters at the Earth's poles. These areas have both cold temperatures and fluctuations in the availability of sunlight. At some times in polar regions, the sun doesn't rise for weeks. 

Marine Life in Polar Ecosystems

  • Algae
  • Plankton
  • Invertebrates: One of the most important invertebrates in polar ecosystems is krill.
  • Birds: Penguins are well-known inhabitants of polar ecosystems, but they live only in the Antarctic, not the Arctic.
  • Mammals: Polar bears (known for living only in the Arctic, not the Antarctic), a variety of whale species, plus pinnipeds such as seals, sea lions, and walruses
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Deep Sea Ecosystem

Close up of deep sea coral underwater.

NOAA's National Ocean Service/Flickr/CC BY 2.0

The term "deep sea" refers to parts of the ocean that are over 1,000 meters (3,281 feet). One challenge for marine life in this ecosystem is light and many animals have adapted so that they can see in low light conditions, or don't need to see at all. Another challenge is pressure. Many deep-sea animals have soft bodies so they aren't crushed under the high pressure that is found at extreme depths.

Deep Sea Marine Life

The deepest parts of the ocean are more than 30,000 feet deep, so we're still learning about the types of marine life that live there. Here are some examples of general types of marine life that inhabit these ecosystems:

  • Invertebrates such as crabs, worms, jellyfish, squid, and octopus
  • Corals
  • Fish, such as anglerfish and some sharks
  • Marine mammals, including some types of deep-diving marine mammals, such as sperm whales and elephant seals
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Hydrothermal Vents

Hydrothermal vents underwater.

NOAA Photo Library/Flickr/CC BY 2.0

While they are located in the deep sea, hydrothermal vents and the areas around them make up their own unique ecosystem.

Hydrothermal vents are underwater geysers that spew mineral-rich, 750-degree water into the ocean. These vents are located along tectonic plates, where cracks in the Earth's crust occur and seawater in the cracks is heated up by the Earth's magma. As the water heats and pressure rises, the water is released, where it mixes with the surrounding water and cools, depositing minerals around the hydrothermal vent.

Despite the challenges of darkness, heat, ocean pressure, and chemicals that would be toxic to most other marine life, there are organisms that have adapted to thrive in these hydrothermal vent ecosystems.

Marine Life in Hydrothermal Vent Ecosystems

  • Archaea: Bacteria-like organisms that perform chemosynthesis (which means they turn the chemicals around the vents into energy) and form the base of the hydrothermal vent food chain
  • Invertebrates: Including tubeworms, limpets, clams, mussels, crabs, shrimp, squat lobsters, and octopuses
  • Fish: Including eelpouts (zoarcid fish)
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Kennedy, Jennifer. "9 Types of Marine Ecosystems." ThoughtCo, Feb. 16, 2021, thoughtco.com/types-of-marine-ecosystems-2291779. Kennedy, Jennifer. (2021, February 16). 9 Types of Marine Ecosystems. Retrieved from https://www.thoughtco.com/types-of-marine-ecosystems-2291779 Kennedy, Jennifer. "9 Types of Marine Ecosystems." ThoughtCo. https://www.thoughtco.com/types-of-marine-ecosystems-2291779 (accessed March 30, 2023).