Learn more: What are marine habitats?

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From the surface, the sea can look like one homogeneous single habitat. In fact, the ocean has a huge diversity of habitats. There are many different types of marine habitats that serve as homes for different types of organisms.

A few examples of marine habitats:

  • Intertidal zones
  • Sandy and rocky shores
  • Salt marshes
  • Estuaries
  • Mangroves
  • Coral reefs
  • Kelp forests
  • Seagrass meadows
  • Sea mounts
  • Deep sea wents
  • Abyssal plains

Grouping habitats

Sometimes scientists talk about habitats in terms of the layer of water that they lie in:

  • Pelagic or open ocean habitats lie in the water near the ocean’s surface.
  • Demersal and deep sea habitats lie near the bottom, towards the benthic layer or sea floor.

They also talk about how far habitats are from the shore:

  • Coastal, shoreline or shallow sea habitats are near the shore, where the water is often more shallow.
  • Deep ocean habitats are further out, where the water is often very deep.

Factors affecting marine habitats

Many factors affect what a marine habitat is like. The major abiotic, or non-living factors, that affect marine habitats are:

  • Amount of light
  • Temperature
  • Amount of oxygen and carbon dioxide
  • Amount of nutrients in the water
  • Pressure

These factors are affected by three things:

  1. Depth of the water
  2. Distance from the shore
  3. Ocean currents and tides

Impact of depth

  • It gets darker
  • It gets colder
  • There is less oxygen
  • There is more carbon dioxide
  • There are more nutrients
  • The pressure gets much higher

Impact of distance from shore

Generally, if you stay at the same depth, as you get further from shore:

  • The amount of nutrients can vary
  • The other factors don’t really change

But, as you get further from shore, because the distance to the sea floor increases and it makes things darker, it’s harder for plants that live on the sea floor to grow.

Impact of currents

Currents are interesting because they can mix up the water. Currents and tides mean that marine habitats are always changing and they often don’t have clear boundaries.

Perhaps the most important type of currents to marine diversity are the ‘upwelling currents’. These bring cooler, nutrient-rich waters to the surface near the coast. This means that not only can the plants get lots of light and carbon dioxide in a fairly warm environment, but they can also get lots of nutrients. Most marine life lives in coastal habitats, because the conditions tend to be more favourable than the open ocean.

There are also many organisms that rely on currents to move them through the water. For instance, plankton are the many different types of very small organisms (animals, algae, bacteria, etc.) that drift along with the current.

Our Ocean Planet Science Geography Thumb

Science / Geography | Ages 7-11

Our Ocean Planet

Our Ocean Planet Science Geography ages 7-11 unit is a KS2 teacher resource. Students discover marine topics across both the UK and globally, developing ocean literacy.