What are marine habitats?
‘Marine’ is a word that describes oceans and seas, where water is salty. Over 70% of the Earth’s surface is covered water, and nearly all of that is saltwater from oceans and seas.
Marine habitats can be very different from each other depending on how warm the water is. Warm, tropical water has coral reefs full of tiny, colourful fish, while chilly waters in the polar regions have fewer species that have adapted to water that can be colder than the temperature that water normally freezes at (0°C)!
Top 10 facts
- Marine habitats include oceans and seas, which both have saltwater.
- Marine creatures also live in estuaries – where rivers and oceans meet and the water is still salty.
- Saltwater is water that has 35g of salt for every kilogram of water. It’s not something we humans can drink as it will just make us more thirsty!
- Oceans and seas cover over 70% of the Earth’s surface.
- There are five oceans across the planet, and over 100 different seas.
- Having salt in the water means that it takes a lower temperature for the water to freeze (it normally freezes at 0°C). So, some marine animals have adapted to living in waters that are below 0°C, especially around polar regions.
- Waters around the polar regions have fewer species of fish than waters in the tropics (near the equator) and temperate zones.
- About three-fifths of all the fish species that we know about live in marine habitats.
- About one-third of marine species live in coral reefs, which are located in the tropics, on the eastern side of continents and around islands.
- Some marine life can be found in very deep places in the ocean – this can be over 5 kilometres down from the surface.
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Did you know?
- Over 70% of the Earth’s surface is covered by water, and most of that includes marine habitats.
- Marine habitats have water that contains a lot of salt – we call it saltwater. Oceans, seas and estuaries (where rivers and oceans meet) all have saltwater.
- Temperatures in marine habitats are different depending on where in the world they are. Water can be below 0°C (its normal freezing point) around polar regions, but up to 30°C in the tropics.
- The different water temperatures mean that fish and plants have had to adjust to living in those different conditions. If you suddenly moved them from cold polar water to warm tropical water, they wouldn’t be happy.
- The five oceans on the Earth are:
- Arctic Ocean
- Atlantic Ocean
- Pacific Ocean
- Indian Ocean
- Southern Ocean (around Antarctica)
- Creatures who live in marine habitats can breathe underwater (for example, using gills) or can hold their breath for a long time and just come up to the surface every now and then for air.
- Most marine life depends on plankton, which are tiny organisms that are all over the ocean and provide perfect meals for larger fish.
- Some of the strangest looking fish are those that live in the very deepest parts of the ocean, where the ocean has dips like valleys. These can be more than 5 kilometres below the surface, and the fish have adapted to be able to stand all that water pressure above them as well as living in darkness.
- There are sea grasses and plants, and even different creatures that live on the ocean floors rather than swimming around closer to the surface.
- An example of the food web in marine habitats
- Underwater life
- Sea urchin
- Sea anemone
- Green turtle
- A discus fish
- Coral reef
The saltwater in marine habitats has 35g of salt for every kilogram of water. It’s a lot more salt than is healthy for us to have in our drinking water, which is why we can’t drink water from the ocean.
There are just five oceans in the world, but over 100 seas. This is because a sea is a body of water that is closed off a bit by land, but usually connected with oceans. Seas include anything with the name ‘bay’ or ‘gulf’ too.
Marine creatures in polar waters include:
- Beluga whale
- Ice fish
- Krill (food for larger creatures)
- Sperm whale
Marine creates in temperate waters include:
- Right whale
- Sea urchin
Marine creatures in tropical waters include:
- Bottlenose dolphin
- Green turtle
- Sea cucumber
Marine creatures that live in very deep parts of the sea include:
- Football fish
- Lantern fish
- Stoplight loosejaw
- Viper fish
Just for fun...
- Play lots of marine biology games and find out more about the ocean's depths
- Marine habitat colouring sheets and activities
- Complete some marine habitat wordsearches
- Test your knowledge of marine biology in a CBBC quiz
- Design a fish with the right adaptations to survive and thrive
- Find ocean games, sea stories and underwater fact files on the WWF's Go Wild site for children
- Follow a humpback whales migration game and find out more about how we can protect them
- Show off your knowledge with a BBC quiz about ocean life
Children's books about marine habitats
Find out more about marine habitats:
- Look through WWF Ocean Fact Files
- Watch BBC Bitesize videos about ocean habitats, animals that live in the sea and how fish are adapted to live in water
- The DK FindOut! guide to oceans and seas
- See a cross-section of the coral reef
- Saltwater habitats
- Discover the secrets of seagrass meadows and why they're so important
- Download information sheets about sandy shore habitats and rocky shore habitats
- Underwater facts for kids: oceans
- Understand more about how fish breathe underwater
- Read National Geographic Kids fact files about marine creatures: great white sharks, dolphins, turtles and blue whales
- Follow a migration route map and understand how animals (including blue whales) move around our planet
- Watch a coral reef at night
- See how different types of fish work together to keep clean!
- Understand more about how we can care for the ocean
- Factsheets about different marine species
- Digital Ocean School from Surfers Against Sewage offers lessons and resources about all aspects of marine life