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Oceans on the edge

Marine Ecosystem

Oceans cover two-thirds of our planet and are home to marine ecosystems which include all plants and animals linked to parts of the local physical environment.

Coral Reefs

  • Coral reefs are home to 25% of all marine fish species in the world while only covering less than 1% of the world's surface giving it a high level of biodiversity.
  • They are made up of colonies of coral organisms, including coral animals known as polyps which produce a hard calcium carbonate exoskeleton where they live.
  • Coral reefs are found in tropical oceans close to the shore where the sea temperature is between 24oC and 26oC
  • They cannot grow in water deeper than 25m
  • 20% of coral reefs in the last 50 years have been destroyed
  • 25% are under threat of destruction
  • The major areas where coral has been lost are:
    • the Caribbean and Central America
    • the islands of Indonesia and the Philippines
    • the coastlines in India, Thailand, Vietnam and China
    • the Red Sea and Persian Gulf
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Threats to coral reefs

Global Warming
Global warming is leading to a temperature rise in the oceans, which in turn will result in the bleaching of the coral and the algae living in the corals are unable to survive, disrupting the feeding cycle of the coral. Also, a rise in sea waters may result of the extinction of some marine species which can't adapt to the rising temperatures

With population increase, and fish being a crucial part of the diet for people living in tropical areas, this is going to be an increasing pressure on the coral reefs and marine species. Also, the fishing methods are also very destructive, such as using explosives (blast fishing), and unless very carefully controlled, fishing for aquarium species is likely to disrupt the food web.

Tourism is a major income source for developing countries, but what the tourists do on their visit is not necessarily helping the coral reefs. Activities such as water skiing, scuba diving and surfing all cause disturbance to the coral reef, but the resorts the tourists stay in are often involved in coastal redevelopment and increase the pollutants in lagoons.

Coastal Development
Sediment in rivers is almost always seen when coastal development is taking place. Reefs that thrive in clear water will be negatively impacted by the disturbed ground, erosion of loose soil and the washing off of pollutants.

Marine food webs
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  • Energy is transferred through an ecosystem through a food web
  • Food webs are highly interconnected - a small change in one place can easily cause a change somewhere else
  • They link together the plants and animals in an ecosystem
  • Energy is lost at each stage of the chain
  • There are more organisms at the bottom of the web than at the top
  • Predators at the top of a food web, such as the shark, will often need a lot of energy to survive and will also use a lot of that energy to catch its prey.
  • Food webs also balance the nutrients in the ecosystem as they are used and reused by different organisms

Disruption to food webs

Because food webs are so complex and interconnected, any small change can cause larger knock-on effects else where in the food webs. Changes which can disrupt the food web include:
  • Overfishing - when fishing more than what is sustainable. E.g.: Overfishing of tuna can increase mackerel numbers while decrease shark numbers. Some species have even been fished to extinction, e.g. Baiji white dolphin
  • Eutrophication - The run off of fertilisers, nitrate fertiliser for example can cause overfeeding and algae bloom. However, the large presence of algae uses up all the oxygen in the waters and other species begin to suffocate.
  • Siltation - when plants near the coast die because they get buried in silt from the soil which has been washed down to the sea.

Climate change and the oceans

Climate change has begun to create a warmer world, however this is having some unwanted effects on our oceans.
Warming of ocean waters
  • Temperatures in the tropics have increased by almost 1oC over the past 100 years
  • Temperatures could rise by 2-3oC by 2100
  • These temperatures rises are having effects on:
    • Coral bleaching - zooxanthella algae in coral polyps will die along with the rest of the coral. It is known as bleaching because the coral turns white
    • Species migration - As some species need certain conditions, they will move to other areas disrupting fishing and food webs. E.g. cod who need cold water will need to migrate
Higher sea levels
  • Between 1961-2003, sea levels rose by about 7cm
  • They could rise by another 50-100cm because of thermal expansion, melting ice glaciers and melting ice caps
  • These rise are having effects on:
    • Light levels - As water becomes deeper, there will be less light in the deeper parts of the oceans resulting in some plant species being unable to photosynthesise and will die out. Coral reefs close to 25m may begin to die out.
    • Coastal flooding - Increasing erosion could destroy some coastal ecosystem such as sand dunes, salt marshes and mangrove swamps
  • Increasing levels of CO2 in the atmosphere is making the oceans more acidic as the oceans are absorbing this CO2.
  • Ocean pH has decreased from 8.25 to 8.14 between 1750 and 2000
  • This is having an effect on:
    • Coral and shellfish health - Marine animals with calcium carbonate shells, such as shellfish and coral, could be at risk from increasing acidity of the water as calcium carbonate dissolves in acid.

Sustainable management - Case Study: Soufriere Bay

You will often find that the local populations near marine ecosystems are supported by the marine ecosystem, however the pressure on these areas is increasing for the following reasons:

Growing Population
  • The island population of St Lucia grew from 130,000 to 170,000 between 1990-2010.
  • The increase in people will mean
    • there are more people fishing
    • more waste being produced
    • more pressure to turn forests into farmland
  • Tourism makes up 45% of the country's GDP and is the main industry providing income and jobs
  • Tourists come to see the coral reefs and enjoy watersports, snorkelling, diving and fishing, but some of these activities can cause damage to the corals
  • Tourists will often leave litter on the reef and remove coral for souvenirs.
Runoff and waste
  • An increase in the number of tourist and urban areas means more coastal development
  • Waste such as sewage and farm runoff ends up travelling into the sea and damaging the coral reef.
  • Fish is an important part of the diet in St Lucia
  • Because it is a developing country, the fishermen are unable to afford the necessary equipment to deep in deep waters
  • A growing population will mean more people fishing in the shallow coral reefs threatening the food web.
Local views on management of the coral reefs
Local Fishermen
  • The coral reefs provide a source of food and income for the local fishermen
  • They want to be able to continue fishing and provide for the growing demand from local people and tourists
  • Problems: However, this may be damaging and unsustainable, reducing the fish supply
  • Tourists will often want to use the same the same areas of the reef as the fishermen
Local businesses
  • Tourism from Soufriere Bay provides the important business for these local businesses
  • They want to keep their tourists while also wanting to protect the the sea and the reefs
  • Problems: Tourists could still easily damage the reefs and conflict with the local fishermen
  • The reefs along with the sea provide and water sports and other activities such as diving for the tourists
  • Tourists are going to want a high-quality reef with colourful coral and fish species
  • Problems: High numbers of tourists can still damage the delicate ecosystem
Yacht owners and cruise ships
  • Yacht owners and cruise ships use the bay to anchor in the bay
  • Problems: Boat propellers, anchors and waste thrown overboard can damage the reef
  • Potential oil spills damaging the reef
Marine management
  • In 1992, the Soufriere Marine Management Area (SMMA) was set up
  • They brought together lots of different groups of people to resolve the conflicts
  • Through the zoning of the bay, conflicting activities were given their own areas of the bay separate from others
  • Marine reserve areas with no access to the public were created for young fish to grow
  • Funds from tourist taxes are used to pay for the area's management
  • Locals were trained to police the area

Sustainable management - Case Study: Firth of Clyde

The Firth of Clyde is 60km stretch of sea water along Scotland's west coast. 40,000 animal and microbe species live in these waters, which is why people often catch a glimpse of seals, harbour porpoises and large basking sharks. These waters and the wildlife which live in them are under pressure:

  • Fishing remains a vital source of income for the local people
  • Commercial fish levels are still very high, thanks to the Gulf Stream - a warm ocean current
  • There are still some overfishing on certain species, such as cod, causing the numbers to plummet
  • Overfishing has been a particular problem in Lamlash Bay where Scallops used to thrive. The heavy dredging machinery has destroyed the maerl - a pink-coloured cousin of coral. 
Tourism and leisure
  • Local businesses are trying more to gain income from tourism and the leisure activities available
  • The Firth of Clyde is currently the UK's second-largest yachting centre
  • Other water activities are very popular too, such as kayaking and snorkelling
  • Unfortunately, some of these activities disturb the wildlife
Sewage disposal
  • Previously, waste would simply flow into the sea due to the lack of on-land sewage treatment facilities
  • However, due to new tougher laws, this is now less of a problem
Military Testing
  • The sea-floor of the Firth of Clyde were deeply eroded by the last ice age creating seafloor valleys - a perfect testing ground for the Royal Navy's nuclear submarines
  • A serious accident would devastate the ecosystem
Local views on management
  • Locals want to see the water in the Firth of Clyde treated well and have no commercial exploitation in order to enjoy the sea views
  • Some fishermen disagree with no-fish zone in Lamlash bay as a wrong move as they rely on it for their livelihoods
Future plans for the Firth of Clyde
  • There has been a recent introduction of a no-fish zone in Lamlash Bay
  • Stretches of Scottish could become a Coastal and Marine Park (CMP), ensuring coastal and maritime-based activities are managed sustainably. If introduced, it will run along side Britain's existing national parks.
  • Big offshore tidal and wind farm developments could be developed to meet Scotland's government intention to reach 31% of electricity to come from renewable resources. These offshore developments could be a scar on the landscape and potentially make ship navigation more difficult.

Local sustainable management

Case Study - Coral Triangle

Case Study - Shetland Islands

Location: South Pacific
Threats: - acidified seawater from tourist vessels and agricultural run-off
- growing population leading to other pressures, e.g. overfishing
- pollution
- It is estimated 70% of the world's coral reefs will be destroyed by 2050
Management plan: - Marine protection areas
- sustainable fishing rules
- protection of threatened species
- planning for climate change

The coral triangle is 6 million km2 making it very difficult to enforce these rules
Location: North Sea
Threats: overfishing due to improvements in technology, e.g. factory ships, sonar, etc.
Management plan: Introduce aquaculture - fish farms where fish are intensively farmed in caged enclosures away from the rest of the ecosystem.

This industry employs 1200 people and since it was established in 1984, production of has expanded from 50 tonnes to 50,000 tonnes today.

However, this intensive farming makes it easy for fish diseases to spread quickly.

Global sustainable management
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Protecting whales
There are 3 main global agreements which protect whales, these are:
International Whaling Convention (IWC)
  • Established in 1946
  • Oversees management of the whaling industry
  • Issued an indefinite ban on commercial whale hunting in 1986
United Nations Convention on the Lay of the Sea (UNCLOS)
  • 156 nations have signed it
  • Requires those nations to follow the IWC guidelines
Convention on International Trade in Endangered Species (CITES)
  • Offers global protection to all of the great whales
Problems around protecting whales
International agreements aren't always fully effective...
  • Japan has a long track record of it defying international whale laws and are known to continue to slaughter whales
  • Norway has objected plans to make the south pacific a whale sanctuary
  • In the Faroe Islands, pilot whales are commonly massacred after they run aground in shallow water. Around a thousand pilot whales are massacred which local people think is an important part of their culture
  • Iceland hunts whales commercially and for scientific research
Marine debris on Kamilo Beach, Hawaii, washed up from the
Great Pacific Garbage Patch
Tackling pollution
  • 90% of all trade between countries involves sea travel, making shipping an enormous industry
  • Illegal activities and sub-standard ships cause marine pollution
  • There is currently a global phase-out of old tankers which should make a big improvement in maintaining ocean health.
  • Previously, oil tankers used to use sea water to wash out their tanks, causing significant oil pollution. However this is now illegal
  • There are large regions of of floating rubbish in the North Pacific known as the Pacific Garbage Patches. Unfortunately, nobody is taking the responsibility to clear it up leaving one million pieces of floating plastic per sqaure mile floating in the sea. Fortunately, countries are passing new laws to limit the use of 'throwaway' bags.