Oceans on the Edge

A set of revision cards for the topic of oceans on the edge.

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Marine eco-systems

Coral reefs - cover less than 1% of the earth's surface and are located in areas with:
- shallow water of 25m or less to ensure lots of light,
- tropical water temperature of 24-26 degrees C,
- areas of saline water.

The values of coral reefs include:
Tourism - a magnet for world's tourists, countries in the Caribbean get over half their income from reef tourism.
Exploitation for fishing - 4000 species of fish provide food, 25% of world's commercial fish catch comes from coral reefs,
Education and research - learn about marine life,
Other uses - medical source, making decorative objects such as jewellery, a source of lime for cement and building,
Shoreline protection - provides protection from storms, tsunamis and wave erosion. Can grow with rising sea levels, protect against climate change.
Aquarium trade - supply tropical fish, sea horses and plants for our fish tanks.

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Marine eco-systems

Mangroves are swampy areas found in estuaries and long marine shorelines - tolerate daily tidal flooding and high salinity.

The values of mangroves include:
Habitats - mangroves are home to many animals who use them as a nursery for their young, e.g. tigers, crocodiles, snakes, dolphins and birds.
Exploitation for fishing - Prawns found here are in huge global demand (£30 billion a year), mangroves are often removed and replaced with prawn aquaculture to increase yield.
Shoreline protection -provides protection against tsunamis, the 2004 Asian tsunami shows that where mangroves still existed they protected people and property,
Carbon store - carbon dioxide is stored over the centuries in the rick mud beneath the swamp - this is released once they're removed. 

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Human impacts on coral reefs

Population growth - most coral reefs are located in developing countries with populations growing at 3% per year. People also migrate to these areas for jobs in tourism or fishing.
Land development - building work disrupts the land and causes soil erosion, the oil is then washed in to the sea and clouds the water which means less sunlight is able to reach the coral.
Pollution from cars and industry.
Coral mining for sand and lime for urban development as coral is often the only local building material.
Blast fishing using dynamite or trawling reefs all cause damage.
Overfishing disrupts the food webs of the coral reefs.
Tourism - demand for reef jewellery, damage from boat anchors, recreational fishing by tourists, trampling by snorkellers and divers breaks the coral. 

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How humans can damage marine food webs and nutrien

Food web disruption:
Over fishing interferes with the natural balance of ocean animal population e.g. excessive hunting of a particular species such as tuna. This triggers a series of impacts. If humans reduce the number of tuna it will indirectly impact sharks as they cannot find enough tuna to feed on. This leads to a decrease in the number of sharks and an increase in organisms lower down in the food chain such as mackerel and they are no longer being eaten by the tuna.

Nutrient cycle disruption:
Excessive amounts of nutrients are added to a body of water such as fertilisers carried by rain run off from farmland into rivers (eutrophication). The nutrient rich waters cause an explosion of marine life known as algal bloom, the algae uses up most of the waters oxygen causing fish to suffocate in the water. 

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How climate change might damage marine eco systems

Direct impacts include -
Increases in temperature causing coral reefs to become vulnerable to bleaching,
Extreme weather events such as storms and flooding leading to damaged ocean ecosystems.
Increases in temperature causes glaciers to melt meaning there is more fresh water in the oceans. The sea becomes less salty and less dense and there is an impact on the sea currents which distribute heat.
Higher sea levels lead to mangrove swamps and salt marshes becoming submerged.
Coral reef islands such as Maldives would be completely submerged.
Low lying countries would disappear and increasing sea level would lead to higher rates of erosion.

Indirect impacts include -
Warmer water temperatures causing oceans to expand, this combined with melting glaciers will cause sea levels to rise between 20 cm and 1 metre.

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Impact of climate change on developed/developing c

Developed - USA
Sea level causes increased coastal erosion and flooding. Risk of storm surges in Florida, threats to coastal wetlands.

Developed - Europe
Low lying countries such as Denmark and the Netherlands will be submerged.

Developing - Asia
Increasing intensity of tropical cyclones could displace people in low lying coastal areas. Threatens mangroves and coral reefs.

Developing - Bangladesh
Storm surges will increase and grow in strength. Sea level rise of 45cm would displace 5.5 million people.

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Firth of Clyde - 60km stretch of sea water along S

Threats facing the ecosystem include:
Fishing - important source of local income due to the Gulf Stream having made commercial fishing sizes very high. Over fishing of species like cod have caused the numbers to crash.

Tourism - Falling income from fishing and farming have led to local businesses to try and make more of tourism and leisure along the coastline. Now the 2nd largest yachting centre which disturbs wild life.

Sewage disposal - In the past on-land sewage treatments were limited, so waste from toilets flowed straight into the sea. This is now less of a problem.

Military testing - Perfect testing ground for the Royal Navy's nuclear submarines. A serious accident would have terrible effects on the ecosystem.

Local peoples views on their ecosystems can lead to conflict because many outsiders have moved to coasts to enjoy the views and they want to see the water treated well and free from exploitation. Local fisherman rely on the Firth of Clyde for their income. The coastal aims provide conflict themselves, government aims such as 31% electricity from renewable sources by 2011 means off-shore wind resources can be exploited but could interfere with navigation for ships and ruin the local landscapes. 

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Local divers formed a group called COAST (Community of Arran Seabed Trust) which campaigned for a no-take zone to be established in Lamlash bay. It aimed to improve marine environment and reverse fish decline, sustain the livelihoods of people dependant on tourism as well as fishing, increase the popularity of the area as a tourist and diving destination.
2008 the Scottish government made part of Lamlash bay a no-take zone, the rest of the bay is a management area where scallops can be fished but only in less destructive ways.
Will soon be designated a Coastal and Marine park (CMP) to ensure that coastal and marine-based activities are managed in a sustainable way to bring long term economic benefits to people, whilst protecting the environment.
Scottish Marine Bill is a new set of laws to help manage future conflicts in Scottish waters.

Sustainable management is a balancing act between ecosystem conservation and helping local people make a living without over harvest resources. This involve using fishing equipment which doesn't harm habitats, using marine resources at a rate that won't destroy them for future generations, allowing poor people to use resources of subsistence activities and local people to be involved to decide how fishing and other uses should be managed.

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Shetland Islands Aquaculture

Reasons for problems: Increased longlining - ships can now lay 150km length of baited hooks on the seabed, sonar is now used to detect shoals of fish which may have otherwise been missed, factory ships now have freezers which allow them to stay out in the sea for longer.

Solution - Aquaculture,
Intensively farmed salmon and cod are now raised in enclosures along the northern European coastlines. Shetland aquaculture is an association established in 1984 and provides an alternative to traditional unsustainable methods of fishing.
1200 residents of the Shetland Islands now work in the aquaculture sector.
Production expanded from 50 tonnes in 1984 to 50 000 tonnes today,
Now introduced more varieties of fish such as tout and mussels,
Own hatchery and supplies both fish and eggs to help commercial firms become established,
Around half of fish eaten in the UK is farmed in Shetland Islands,
Outbreaks of diseases are common among caged fish in cramped conditions,
100, 000's of salmon escape from farms each year threatening wild populations.

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Global solutions

CITES - The Convention of International Trade in Endangered Species of Wild Fauna and Flora gives global protections to all of the greatest whales as many species were hunted almost to extinction during the 25th century. CITES also helped protect other species such as sturgeon fish whose eggs were used to make caviar.
Problems - Japan has a long history of defying international whaling laws and continues to kill them. Norway objected to plans for the South Pacific to be made into a whale sanctuary.

Law of the sea was developed to prevent certain nations from taking an unfair share of the oceans wealth. Treaty was established in 1994 and 40% of the ocean was placed under the law of adjacent coastal states. It also addresses issues such as fisheries, navigation, continental shelves, the deep sea, scientific research and pollution of the marine environment. 

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Frances Cox


Sarah-Jane Williams

Thanks a massive help :)

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