8.4.2

Water

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Ocean Acidification

The process where the oceans become more acidic can have disastrous impacts on the ecosystems that exist there.

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What is ocean acidificaition?

  • Ocean acidification refers to the process of more CO2 being absorbed into the ocean, which means the pH decreases (becomes more acidic).
  • When there is a higher concentration of CO2 absorbed into the ocean, it converts largely into carbonic acid (H2CO3 ).
  • But if there are lower concentrations of carbon dioxide when the CO2 is absorbed, the carbonate ions promote healthy coral growth.
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Impacts on coral reefs

  • Algae, which live in the tissues of corals, provide carbohydrates to the corals through photosynthesis. A by-product of the algae gives the coral brilliant bright colours.
  • Corals can only survive between 23-29oC (never below 18oC).
  • Coral bleaching happens when the water is too warm, causing the algae to be ejected and leaving the coral white.
  • Climate change is the leading cause of coral bleaching because the ocean temperatures continue to rise.
  • Additionally, acidic water makes coral disintegrate.
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Impacts on other life

  • If coral reefs are lost, there are many other animals that are dependent on them.
  • Coral reefs provide shelter for 25% of marine species.
  • Coral reefs can provide shorelines protection from storms and large waves.
  • The fish that live in the reefs can support local fishing industries.
  • Tourism can thrive around coral reefs, especially where scuba diving and snorkelling are possible.

Effect of Temperatures on Water and Carbon Stores

Increased temperatures are likely to cause the most impact to cold regions, like those found within the Arctic Circle.

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Increased evaporation rates

  • Changes in global temperatures result in increased evaporation rates.
  • This is simplified into the phrase ‘wet get wetter and dry get drier’.
  • Changes to temperature could lead to changes in the air circulation system. This could result in tropical storms moving further away from the equator as sea surface temperature reaches 27oC in places further away from the equator.
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Drainage basin stores

  • With increased temperature, there is a rise in the rate of evaporation and so in water vapour.
  • But due to warmer temperatures, the precipitation falls as rainfall rather than as snow.
  • The higher temperatures also mean that snowmelt begins earlier.
  • This can alter the river regimes. With higher river discharge in the winter because of higher amounts of rainfall and spring snowmelt happening earlier.
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Drainage basin stores cont.

  • Thawing of permafrost regions can lead to water infiltrating and percolating deeper. Before, this water would have been unable to infiltrate the frozen ground and instead been surface runoff.

Threats to Ocean Health

Ocean environments provide food, protection and income for the communities that develop around them. To keep these goods and services, the health of the ocean is of the utmost importance.

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Developing nations

  • The poorest nations will be most dependent on their oceans as food supply and income.
  • Climate change results in changes to coastal environments, which leads to changes in the location and amount of species with knock-on impacts for the rest of the food chain.
  • The North Atlantic has increased in temperature and the plankton that is used to cooler waters dies. This has a knock-on impact on the rest of the food chain.
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Tourism

  • Tourism surrounding coral reefs have always included scuba divers and snorkelling to see the beautiful colours and fish.
  • Coral bleaching has been seen in Australia’s Great Barrier Reef which can impact the tourism industry of these regions and can lead to a spiral of decline.
  • Oil spills, though less common, are devastating to coral and marine ecosystems.
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Coastal protection

  • Mangroves provide significant coastal protection and are found along tropical coasts. They bind together sediment with their extensive root network, protecting the shore from storm surges and preventing erosion.
  • 50% of all mangroves have been lost since the 1950s. This is largely because of tourism, as the mangroves can be cleared for tourist-friendly beaches and hotel developments. But this leaves the coasts exposed, as seen in Northern Sri Lanka in the 2004 Boxing Day Tsunami.

Jump to other topics

1Tectonic Processes & Hazards

2Option 2A: Glaciated Landscapes & Change

3Option 2B: Coastal Landscapes & Change

4Globalisation

5Option 4A: Regenerating Places

6Option 4B: Diverse Places

7The Water Cycle & Water Insecurity (A2 only)

8The Carbon Cycle & Energy Security (A2 only)

9Superpowers (A2 only)

10Option 8A: Health & Human Rights (A2 only)

11Option 8B: Migration & Identity (A2 only)

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