oceans on the edge

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dead zones and some of the threats to our ocean

Dead zones are areas which ecosystems have collapsed completely

-our supplies of lobster, shellf fish and crabs could die out by 2050

-hundreds of dolphins are killed each year by sprawling

-coral reefs and mangrove forests are at risk

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why are coral reefs important

-provide homes for 4000 fish species, which are food for local communities

-reefs provide shoreline protection from storms and tsnumi and wave erosion

-reefs can grow with rising sea level and prevent impacts from climate change

-supply tropical fish for aquarium trade e.g seahorses

-tourisum in places like the caribean provide half of its income from reef tourisum

-can help us research the different fish species which live there

-source of medicimne, provide lime for cement and can be used in jewellry

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what are global factors affecting coral reefs

-gobal warming, will increase sea temps by 1-2 degrees which can cause coral bleaching

-el nino events (events which occur every 3-7 years) which cause bleaching

-ocean acidification will stop corals from growing

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what are local factors that affect coral reefs

-blast fishing using dynamite destroys coral reefs

-coral mining by taking lime which is used for cement

-diseases such as black band disease or unwanted predators such as parrot fish which eat the algae off coral reefs

-pollution from sewage, oil spills and chemicals kills coral reefs

-heavy rain which washes pollution from land onto sea, hurricans which cause huge waves break coral reefs

-siltation- when reefs become covered by a blanket of silt which is washed into rivers then the sea from farms. This stops light getting into the sea, which prevents corals from living and growing

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how does tourisum affect coral reefs

-damage from boat anchors

-trampelling by snorkelers and divers

-sewage and pollutants such as sun screen from hotels

-beach enhancement

-coastal infilling, which causes sedimentation to run off into the sea

-heavy demand for reef sea food e.g lobster

-construction of hotels which leads to a loss and degradtion of mangroves

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whats happening to krill?

Krill is very important to a food web.

-tiny shrimp like animals

-they are under threat from suction harvesting- a method which grabs huge amounts of tiny creatures

-they feed on algae and plankton at the bottom of the food chain

-they are eatten by penguins, whales and fish

-however they have declined by 80% since the 1980s because :

-used in omega 3 health substances

-used in fish farms as food

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what is the nutrient cycle

FISH eat algae so take in NITRATES

they EXCRETE so BACTERIA converts waste it into AMMONIA and NITRATES

ALGAE AND PLANTS absorb these nitrates and the cycle continues again

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eutrophication and siltation

EUTROPHICATION- this is when nitrogen from fetrilisers is washed into rivers, causing a rapid growth of algae. This algae blocks sunlight and oxygen from getting to the fish. The fish die

SILTATION- increased cloudiness of water from sediment. This is caused by deforestation, which causes sediment to run off into rivers and seas. This clouds water preventing sun light reaching into the ocean. Which damages corals

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direct and indirect impacts

DIRECT IMPACTS- climate change

-climate change leads to extreme weather e.g storms and floods which damage oceans by increasing pollution and siltation

-as temps rice glaciers will melt, which increase fresh water going into oceans making it less salty which affects ocean temps


-warmer water temps will make the ocean expand

-sea levels rise due too melting ice glaciers, which damages mangroves and erodes land areas

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what is coral bleaching

-corals are animals called POLYP

-they live in shells and combine together to form coral reefs

-they feeod on algae within the ocean

-algae gives coral reefs its colour and produce oxgen which polyps rely on

-when ocean temperatures rise, algae cant survive and polyps die, making coral turn white- this is known as coral bleaching

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species migration


-cold water species like cod are moving north and being replaced by sardines

-diseases like new englands lobster disease are increasing in warmer temps

-jelly fish plagues have been linked to nurtrient pollution and warming waters as they seem to be able to adapt quickly

-dangerous species like warm water such as portugese o war jelly fish have increased in north atlantic

-alien species like chinese mitten crab have been spread around more as seas get warmer

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management in st lucia

-management for coral reefs


-most fishermen arent able to afford boats, so use dynamite and place pots over coral reefs which is very damaging

--20% of people live below poverty line so use mangroves to get charocoal and coral reefs to hunt wild life

-forests are cut down so they can grow bannanas, which causes siltation to run off into oceans

-more tourists- which leads to more tourist activities e.g snorkeling which damages coral reefs


-are being polluted by wasteland -contain mosquitos -largest magrove

-site of rubbish disposal -important because it provides charcoal, honey and salt


soufriere have given fishermen modern boats and refrigerated ice houses to improve fish processing


-land has been set aside as a woodlot for fuel and charcoal (taking pressure of mangroves)


-established a marine conservation area

-provides jobs for local people who guard the area

-educated the people


-rapid development in sourfriere has encouraged siltation and poltutution

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managing fish stocks in the north sea

trying to save species such as cod by:

-ensuring mesh of nets wont catch baby fish

-quota managements

-discard management

-setting up marine reserves


-plankton which are eaten by baby cod do not like cold water, so are being replaced by warmer water species, so num of cod is decreasing

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sea laws

The law of the sea

-prevent nations taking unfair shares of the oceans wealth

- they have done this by addressing the main areas of pollution e.g stopping sea bed mining, ocean dumping and pollution of ships

-conserved areas


-oil spills are reduced

-ships are designed not to pollute

-dumping rubbish and sewage has reduced, but is hard to monitor


-by setting up areas which are monitored and managed, however is costly

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