Oceans on the edge


Threats to the oceans include:

  • Overfishing- humans now use sonar to pin point the location of fish. Then using huge nets they catch vast numbers. This has led to collapsing fish populations.
  • Ocean acidification- more acidic water may erode shells of sea creatures and damage coral reefs
  • Ocean pollution- water quality in oceans is declining fast due to pollution from coastal cities, rivers, oil spills and illegal dumping of waste
  • Building out to sea (land reclamation)- In many coastal countries, new developments are now being built out to sea such as palm in Dubai
  • Fish farming (aquaculture)- To meet globak demand for fish we are now farming our own fish. However fish need to be fed fish so populations still fall
  • Resource extraction (such as oil and gas)- As we run out of oil, companies are increasing looking to marine areas to extract it from deep under the ocean bed. This had led to big disasters such as Deepwater Horizon in which oil spills occur
  • Cyanide fishing- Highly destructive forms of fishing which involve either causing an explosion that knock fish out which can then be easily caught or spraying water with cyanide. This knowcks them out so they can be caught but also kills nearby coral reef habitats
  • New alien species- As conditions and habitats in oceans change new species are appearing such as the giant squid
  • Climate change- As sea temperatures rise it is causing coral bleaching
  • Tourism- may involve coastal developments, cutting down of mangrove forests, releasing of pollutants, and damage to corals reefs.

What is coral?

Coral is made up of massive colonies of tiny animals called polyps which produce a hard, protective, limestone crust around their solft bodies. When they die their empty crusts remain as a platform for more reefs growth. An algea called zooxanthellae lives within the polyps tissue to give it it's colour. Coral reefs are home to 25% of marine fish species even though they only cover less than 1% of the earths surface- has a high biodiversity. They grow  1c every 2 years.

Coral reefs need special conditions to grow:

  • Shallow water (no deeper than 25m)
  • Warm water (22-26 degrees)
  • Clear water (for sunlight)
  • Clean water

This makes coral reefs an indicator ecosystem as it indicates a clean environment.

Why are coral reefs important?

  • Reefs provide shoreline protection from storms and act as natural barriers to help 15% of the worlds coastlines from wave damage. As they form in shallow water they dissipate the waves energy to protect coastlines and reduce erosion
  • Reefs provide jobs for some poeple in th poorest countries in the world- souvenirs, fishing trips, snorkelling and diving,
  • Reefs provide building materials for some of the worlds poorest countries such as Tuvalu- limestone
  • Reefs make a huge contribution to the carbon cycle- they take in carbon dioxide as they are formed in shallow water so photosynthesise and and store that carbon.
  • They are a source of medicine. Some HIV drugs and anti-biotice drugs originate from coral reefs…


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