oceans on the edge revision notes

7/30/2019 Oceans on the Edge Revision Notes

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Module 1 – Topic 7 – Oceans on the edge

7.1 How and why are some ecosystems threatened with destruction?

The term ecosystem describes a grouping of plants and animas that is linked with its local physical

environment. The oceans, covering two-thirds of our planet, are home to distinctive marine ecosystem

communities composed of fish, aquatic plants and sea birds.

1. Coral reefs

Coral reefs are found in the tropical

zone of our oceans. They over less

than 1% of the earth’s surface, but

are home to 25% of all marine fish

species. They only form in warm,

shallow waters that have low nutrient

levels.

Coral belongs to the same family as jelly fish but it has a

solid skeleton of limestone. Coral reefs are alive. Although

they have the appearance of rocks, they are made of living

animals. Each piece of coral contains a polyp. These marine

animas (ranging from 1mm to 20cm) live alongside others,

forming large colonies.

Fresh water, silt, sewage pollution, marine pollution and

disease can kill coral. High temperatures and strong

sunlight cause massive coral death. It is estimated that

70% of the world’s coral reefs will be destroyed by 2050.

500 million people rely on coral reefs for their food and livelihood - 20% of the world’s population.

However, some of the ways people use corals reefs can cause damage, such as –

• Tourism: Coral reefs attract large number of tourist who scuba dive to see the species.

Careless use of equipment and people touching reefs causes damage. Also, tourist vessels can

cause pollution in the water.

• Poison fishing: Using cyanide to kill fish also kills the coral

• Dynamite fishing instantly kills all fish and other living creatures within 25-20 metres.

• Over- exploitation can alter the food chain.

• Pollution from sewage and nitrogen from fertilisers cause an overgrowth of algae. This

smothers the reef by cutting out sunlight.• Coral mining for use in road building, house construction or souvenirs for tourists removes live

coral. Coral reef products have been used to treat cancer, ulcers, cardiovascular diseases and

HIV. The limestone coral skeletons can be used for human bone grafts.

• Sedimentation along coasts caused by farming, soil erosion and mining smother reefs by

blocking sunlight.

2. Mangrove Swamps

Mangroves are areas of swampy forest, found in

estuaries and along marine shorelines in around 120

tropical and subtropical countries

Mangrove plants have evolved to tolerate daily tidal

flooding and high salinity. Long twisting roots anchor



the trees against a constant ebbing and flowing tide. The roots trap mud, making a habitat for lobsters

and prawns.

Mangrove swamps have been destroyed around the world to be turned into

prawn farms. In Vietnam’s Mekong Delta large areas of mangrove trees have

been removed, leaving a flat muddy plain studded with blue plastic-lined

ponds. Prawn aquaculture can also cause serious pollution problems.

Antibiotics and pesticides used in the prawn pools frequently leak into the

delicate ecosystem.

Mangrove removal creates problems of coastal erosion and loss of nursery grounds for fish. Crocodiles,

snakes, tigers, deer, otters, dolphins and birds all lose an important habitat. Carbon dioxide stored over

centuries in the rich mud beneath the swamp is released when the trees are removed.

Mangrove swamps are also natures defence against tsunamis and coastal flooding.

3. Unsustainable use and disturbance of marine ecosystems

Food webs can be used to show the

relationship between species in an

ecosystem. The animals and plants are

all dependent on each other. Energy

enters the system from the sun, where

primary producers take the suns energy

through the process of photosynthesis.

This energy is transferred up the food

web as species are consumed. There are

always more top predators (quaternary

consumers), such as sharks, compared

to secondary consumers, such as tuna.

This is because big hunting sharks use alot of energy chasing prey, so must eat

a large number of tuna to stay healthy.

Food webs can be disrupted by humans

interfering with the natural balance.

Overfishing will impact directly on that

species numbers, but reducing the

number of consumers above, who will

have less to eat and organisms lower

down the food chain, who might

increase. For example, cod fishing in the North Atlantic has never recovered from overfishing offNewfoundland during the 1970s. The Baiji white dolphin has been hunted to extinction during the

twentieth century.

Humans also impact the marine food webs through our agricultural activities on land. Eutrophication is a

process that happens when excessive nutrients are added to water. Nitrate fertilisers from farmland

are washed into rivers and the ocean by rain water (run-off). The nutrient enriched water causes a

growth in marine life, called an algal bloom. The algae use up most of the water’s oxygen, leaving not

enough for other species, such as fish and crustaceans (crabs and prawns). Japan and the Gulf of

Mexico are particularly badly affected areas. The North Sea is another ‘nitrate hotspot’ where lobster

populations have been lost due to a lack of oxygen.

As well as nitrates being washed into the water, soil can be added, this process is called siltation. The

increased silt in the water can block sunlight and decrease photosynthesis. With reduced plant

numbers, fish populations can also decline.



4. Climate change and the oceans

Climate change could cause the oceans waters to increase in temperature. This may affect species

numbers. Also may disrupt ocean currents, which will have knock on effects on global temperatures. For

example, the UK's climate is kept relatively mild due to the warm waters of the Gulf Stream, bringing

warm water to our shores from the Gulf of Mexico.

Warmer climate may also cause the ice sheets on land to melt, causing sea level to rise. Coastal marine

ecosystems such as mangrove swamps would become permanently submerged. Additional fresh water

entering our oceans will also disrupt the salt content of the oceans and their circulation.

The majority of the world’s coral reefs are in danger of being killed off by climate change. This is

because the oceans absorb some of the extra carbon dioxide that humans are outing into the

atmosphere. Carbon dioxide dissolves in water to form carbonic acid. Small rises in acidity can seriously

damage coral reefs, which then appear bleached after losing their vibrant colour.

7.2 How should ecosystems be managed sustainably?

1. Firth of Clyde Case Study

The Firth of Clyde is a 60km stretch of sea water along Scotland’s

west coast

The area contains a large amount of species including seals, sharks,

turtles, whales and porpoises. The area is under a lot of pressure

from human activities such as-

• Fishing – This is an important source of local income, along

with kelp (seaweed) harvesting. Scallops have been overfished from these waters. Fishermen

have used heavy dredging machinery made of metal chains and rollers. This equipment scours

the seabed and destroys the maerl – a pink coloured cousin of coral. This area is used as a

nursery habitat for many fish species, so once it is destroyed these species number will decline.• Tourism and leisure – The area is the UK’s second largest yachting centre. Snorkelling and

kayaking are also popular activities. However, such activities disturb wildlife.

• Sewage disposal – In the past waste from toilets flowed straight into the sea. Tougher laws

now mean waste water has to be cleaned before entering the ocean.

• Military testing – Nuclear submarines use the area to practice, if an accident were to happen

this would devastate the ecosystem.

To help protect the ecosystem local’s people set up COAST (Community of Arran Seabed trust) to

campaign for a no-take zone to be established in Lamlash Bay. They wanted to stop fishing in the area,

to allow the natural ecosystem to reform. They believed that this would increase the popularity of

tourism to the area, with improved diving sites.

In 2008, the Scottish government made part of Lamlash Bay a no-take zone. All fishing within the

specified area has been banned while scientific trials are carried out. Local fishermen were against the

scheme, as it means that they can not earn money. Local retired residents were for the scheme as want

to protect the marine ecosystem; however they do not want increased tourist number disturbing their

peace and quiet.

To help protect this area in the future the government is considering making it a Coastal and Marine

Park (CMP), so protected like National Parks are on land. This would mean much closer monitoring of

commercial activities like fishing and sea-bed drilling for oil, gas or other minerals (which are all very

important to the Scottish economy).

Off-shore wind turbines are another threat to the ecosystem. They could interfere with navigation for

ships and be unsightly. However, they produce renewable energy, so help the environment. Oil and gas

mining under the sea-bed can cause increased pollution, so affect species habitats.



2. Sustainable management at the local scale

Coral Triangle – this is an area of the south Pacific that

contains three-quarters of all known coral species

120 million people gain their food and income from this

area of the world. The six governments of the Coral

Triangle – Indonesia, Malaysia, Papua New Guinea, the

Philippines, the Solomon Islands and Timor Leste – wantto discourage non-sustainable activities.

In 2007, they established a partnership to conserve the

coral reefs and the fishers they support. A range of

strategies are being introduced, including:

• Marine-protection areas where reef populations can remain unharvested

• New sustainable fisheries management rules (including quotas if necessary)

• Protection measures for threatened species

• Establishing climate change adaption plans

Shetland Island Aquaculture – this scheme has been set up to protect the waters of the North Seafrom overfishing. Too many fish are being caught before they have had time to reproduce and breed

the next generation. New technological methods such as longlining (up to 150km length of baited hooks

on the seabed), using sonar (to detect shoals of fish) and factory ships (with freezers onboard, allowing

them to stay out at sea longer), have increased the amount of fish caught.

In 1984 the Shetland Aquaculture was created. 50 producers based on the islands intensively farming

salmon and cod in caged enclosures. 1,200 residents now work in the aquaculture sector, producing over

50,000 tonnes of fish a day. However, fish farming can bring new dangers to marine ecosystems.

Outbreaks of parasites and disease are common among caged fish who live in cramped conditions, and

hundreds of thousands of salmon escape from North Atlantic farms each year, allowing these serious

problems to spread to wild populations.

3. Sustainable management at the global scale

Endangered species – international laws exist to protect endangered species. Many species of whale

were hunted almost to extinction during the twentieth century, bringing a public outcry in many

countries. Three global agreements have helped whales –

• IWC – The international Whaling Convention was established in 1946 to oversee the

management of the whaling industry worldwide. In 1986 it issued an indefinite ban on

commercial whaling.

• UNCLOS – The United Nations Convention on the Law of the Seas requires that the 156

nations who have signed it must follow the IWC guidelines• CITES – The convention on International Trade in Endangered Species of wild fauna and flora

gives global protection to all the great whales.

However, Japan continues to deft international whaling laws and continues to slaughter whales. Norway

has objected to proposals for the south Pacific to be made into a whale sanctuary. Each year in the

Faroe Islands, around a thousand Pilot whales are massacred after they run aground in shallow waters.

Local people see the hunt as an important part of their culture.

Pollution – Shipping can cause marine pollution. Single-hulled ships are being phased out, as they are

vulnerable to leaks. Also it is now illegal for ships that have recently delivered oil to use seawater to

wash out their tanks. Flushing water through the tanks can also bring marine species into the ships.

Flushing is banned, although monitoring what actually happens on ships out at sea is difficult.

The Pacific Garbage Patches, which are enormous rubbish-strewn regions of the north Pacific. In 1999

scientists counted one million pieces of floating plastic per square mile. The plastic mostly comes from

plastic bottles and bags captured and kept in place by a circulatory ocean current called the North

Pacific Gyre.

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