S1 GEOGRAPHY MODULE 1 OCEANS IN TROUBLE - Notes

2024-2025 HKUGA COLLEGE S1 GEOGRAPHY MODULE 1 OCEANS IN TROUBLE

Learning Objectives

  • Understand the ecological and socio-economic importance of oceans.

  • Identify ocean problems and discuss the causes and impacts.

  • Know how to deal with ocean problems on a global and local basis.

1.1. Continents, Oceans, and Seas

Round-up

  • There are seven continents and five oceans on Earth.

  • Continents are surrounded by oceans.

Ocean and Sea

  • Similarities between oceans and seas:

    • Both are water bodies.

    • Found on Earth.

    • Homes to marine animals.

    • Saltwater.

  • Differences between oceans and seas:

    • Oceans are larger.

    • Some seas are landlocked, while oceans are not.

    • Oceans do not have boundaries, while seas do.

    • Seas exist near the shore, where land and oceans meet.

    • Oceans are deeper.

1.2. Marine Ecosystem

Food Chains

  • A pathway showing the feeding relationships between marine organisms is a food chain.

  • Example food chain: Kelp -> Sea urchin -> Sea otter and Sheepshead wrasse.

  • If the sea otter population declines:

    • Sea urchin population increases.

    • Kelp forest may collapse because sea urchins graze on kelp.

  • Trophic levels:

    • Sea otter: Secondary consumer

    • Kelp: Producer

    • Sea urchin: Primary consumer

    • Sheepshead wrasse: Secondary consumer

  • Moray eels eat sea otters; thus, their trophic level is Tertiary consumer.

Round-up

  • Marine organisms are linked by the food they feed on, forming a food chain.

  • A food chain starts from producers, which are eaten by consumers.

  • The trophic level is the position of an organism in a food chain.

  • Trophic levels and organisms:

    • 5th (Apex predator): shark (feeds on tertiary consumers)

    • 4th (Tertiary consumer): bigger fish (feeds on secondary consumers)

    • 3rd (Secondary consumer): small fish (feeds on primary consumers)

    • 2nd (Primary consumer): zooplankton (eats plants/producers)

    • 1st (Producer): phytoplankton (produces its own food with sunlight by photosynthesis)

  • In reality, organisms feed on more than one kind of food, forming a food web.

Marine Energy Flow

  • Energy is transferred along the food chain, decreases in population with increasing trophic level

  • Only about 10% of energy is transferred from one trophic level to the next higher one.

  • Energy is lost through respiration and excretion of organisms.

Percentage \, of \, energy \, transferred = \frac{Energy \, at \, higher \, level}{Energy \, at \, lower \, level} \times 100

Practice Corner

  • Producers produce food through photosynthesis.

1.3. Fishing & Overfishing

Where do we fish?

  • Fishing is a human activity.

  • Major fishing grounds are located near the shore at continental shelves.

  • Continental shelves are shallow regions with a gentle slope at the edge of a continent.

  • They have an adequate supply of nutrients from the land.

  • Sunlight can pass through the water easily, supporting phytoplankton growth, which provides a rich source of food for fish.

  • A large number of fish are nourished on continental shelves, making them good fishing grounds.

Overfishing

  • Overfishing occurs when fish are caught faster than they can reproduce, leaving not enough mature fish to reproduce.

  • Possible reasons behind overfishing: tragedy of the commons, advanced fishing strategies.

  • Ocean problem: Overfishing.

  • Percentage change in fish catch between peak and 2010:

    • Bluefin tuna: -72%

    • Salmon: -86%

    • Cod: -91%

  • Bottom trawling contributes to overfishing due to unselective trawling methods, which yield a lot of bycatch that dies and is thrown back, increasing the catching rate and destroying seabed habitats vital for fish growth and reproduction.

  • Adverse impacts of overfishing on the marine ecosystem:

    • Decline in species numbers, leading to extinction and loss of biodiversity.

    • Depletion of large fish stocks, forcing fishermen to target smaller fish, upsetting the food web's balance.

Grand Banks

  • Grand Banks was a popular fishing ground because it is located on the continental shelf with abundant nutrients for plants and fishes to nourish.

  • The decline in cod capture in the Grand Banks, particularly in the 1970s indicates overfishing there.

  • The development of more advanced and effective fishing technology such as gas-powered ships with refrigeration and processing facilities extends fishing time and range which increased in total fish catch leading to overfishing.

  • Socio-economic impact of overfishing: Competition for limited fish stocks or fishing areas may cause conflicts, which increases international tension.

  • Measures to alleviate overfishing:

    • Set up a fish ban.

    • Set up catch shares / individual fishermen or groups share the allowable catch quota.

    • Set up more marine protection areas (MPAs) / conservation areas where fishing is restricted or only allowed seasonally.

    • Encourage fishermen to adopt sustainable fishery practices / increase the mesh size of the fishing net / ban destructive fishing methods such as bottom trawling / fishermen are allowed to catch big fish only.

Round-up – What is overfishing?

  • Definition: Overfishing occurs when fish are caught at a rate faster than they can reproduce.

  • Causes:

    • Rapid population growth: Increased demand for seafood.

    • Technological improvement: Large fishing boats extend fishing time and range.

  • Impacts on the marine ecosystem:

    • Decrease in biodiversity: Overfishing causes certain species to decrease in population and increases bycatch.

    • Disruption to food web: Fishing down the food chain disrupts the food chain.

    • Damage to marine habitats: Bottom trawling destroys the seabed.

  • Impacts on society and the economy:

    • Decline of fisheries: Fishing industries decline rapidly when fish stocks are depleted, resulting in economic losses.

    • Threat to food supply: The depletion of fish stocks causes a reduction in food supply and protein intake.

    • International conflicts: The competition for fishery resources often leads to territorial disputes between countries.

How to stop overfishing?

  • Practice sustainable fisheries: regulating and improving fishing practices, fishing ban, catch share program.

  • Marine protected areas (MPAs).

  • Education: Increase public knowledge of local fisheries and raise public’s awareness of marine conservation.

Practice Corner

  • The change in fishing technology worsen the problem of overfishing, Technological advancement from manual fishing to mechanical work, gas-powered ship - extend the fishing range - increase the total fish catch - Catching rate > Reproduction rate.

  • Socio-economic impact brought by overfishing is that the fishing rate will be significantly affected, which involves many people's professions; there are also cultural elements, etc.

1.4. Marine Pollution

Dead zone

  • Dead zones are areas where most forms of life cannot survive.

  • The problem of dead zones is getting serious in the Gulf of Mexico because the size of the dead zones in 2013 was almost twice as that in 2012.

  • The common source of phosphorus and nitrogen in the Gulf of Mexico is intensive farming.

Photograph

  • Adverse socio-economic impacts of dead zones:

    • Coral bleaching: decline in the number of tourists and hence the tourism industry.

    • No fish: a decrease in income of the fishing industry/ worsening the livelihood of fishermen.

  • How to alleviate the problem of dead zones:

    • Treat the sewage before discharging it into rivers/seas.

    • Raise the sewage charges to encourage farmers to produce less sewage.

    • Adopt sustainable farming such as intercropping / green manure to reduce the use of chemical fertilizers.

Oil spill

  • Oil harms seabirds because it increases the weight of their feathers, making it harder for them to fly.
    They are also more vulnerable to temperature fluctuations.

  • Geographical enquiry steps:

    • 1. Planning and hypothesis setting

    • 2. Data collection

    • 3. Data processing and presentation

    • 4. Data interpretation and conclusion

    • 5. Evaluation

  • Hypothesis for cleaning the ocean from oil spills: The best way to clean the ocean from oil spills is by absorption, removal, or dissolving.

Round-up – How are the seas polluted?

  • (1) Improper disposal of sewage, Sewage washed into the sea - Increasing nutrient in the sea - Explosive growth of algae - Sunlight blocked for sea plants - Death of plants/algae - No oxygen among algae - Use up the oxygen by bacteria - Fishes die in dead zone.

  • (2) Oil spill: Oil tanker crashes and oil drilling accidents cause large oil spills. Oil from land is washed into the seas through sewers and rivers.

  • (3) Disposal of Solid waste: Different types of solid waste are brought from the land to the oceans by sewers and rivers. Plastics are one of the major solid wastes found in the oceans.

  • (4) Improper disposal of Radioactive materials: The dumping of radioactive waste and conduction of nuclear tests in the oceans increase the risk of radiation pollution.

Impacts of marine pollution

  • (1) Threatening marine life: Solid waste, especially plastics, may trap or choke marine animals. Seawater polluted with heavy metals, oil and other chemicals can poison marine life and destroy marine habitats.

  • (2) Food web contamination: Heavy metals and toxic chemicals are absorbed by marine life and build up along the food chain, and spread to food web. When people consume the contaminated seafood, they may become sick.

Socio-economic impacts

  • (1) Economic loss

  • (2) Health risk: Marine pollution increases the risk of food poisoning. The government expenditure on medical services will increase.

  • (3) Loss of recreational resources: Recreational activities will be suspended when the coastal areas are polluted.

1.5. The importance of Oceans to the Natural Environment

Maintain water cycle

  • Oceans facilitate the water cycle by holding most of the world’s water. They form a major component of the water cycle through the processes of evaporation, condensation and precipitation.

  • Without water in oceans, the water remaining is not enough to sustain the water cycle.

Regulate the climate

  • Coastal cities:

    • Total annual precipitation: 1386 mm

    • Lowest average temperature: 4 °C

    • Highest average temperature: 19 °C

    • Annual range of temperature: 15 °C

  • Inland cities:

    • Total annual precipitation: 421 mm

    • Lowest average temperature: -8 °C

    • Highest average temperature: 24 °C

    • Annual range of temperature: 32 °C

  • Coastal cities have higher annual precipitation than inland cities.

  • Coastal cities have a smaller annual range of temperature than inland cities.

  • Onshore wind from the ocean brings lots of moisture to the coast, which results in a higher rainfall in coastal city.

  • Water absorbs and loses heat more slowly than land, smaller annual range of temperature in the coastal city.

  • The type of climate enjoyed by the coastal regions is the maritime climate.

Other Points

  • Warm ocean currents move from lower latitudes to higher latitudes (Poleward), while cold ocean currents move from higher latitudes to lower latitudes (Equatorward).

  • Figure 1.5d: Winter with warm ocean current, The coastal city is warmer than the inland city.

  • Figure 1.5e: Summer with cold ocean current, The coastal city is cooler than the inland city.

  • Maritime climate is when coastal areas have relatively cool summers, warm winters, and a small annual range of temperature.

1.6. The Importance of Oceans to Human

  • Oceans provide various types of energy resources.

  • X: oil / fossil fuels. The seabed is drilled to obtain the energy.

  • Y: wind power. Prevailing winds drive the wind turbines to produce electricity.

  • Z: tidal power. The rising and falling tides move the turbines to produce electricity.

  • Across:

    • 3. Recreation

    • 6. Mineral

    • 7. Seafood

  • Down:

    • 1. Transportation

    • 2. Trading

    • 4. Waste treatment

    • 5. Tourism

Round-up

  • Oceans provide:

    • (1) Fish, shellfish, and plants for food: Major fishing grounds are located in the shallow coastal waters on continental shelves. It is because they receive plentiful sunlight and nutrients from land.

    • (2) Different types of energy resources:

      • (a) Oil / fossil fuels and natural gas

      • (b) Wind power

      • (c) Tidal power

    • (3) Mineral resources

      • (a) Salt

      • (b) Sand and gravel

      • (c) Precious metal and gemstones

    • (4) Recreation and tourism

    • (5) Trade and transport

    • (6) Waste storage and treatment

1.7. International Cooperation in Ocean Protection

  • The dispute stated in Source 1.7a would occur because The South China Sea contains abundant oil and natural gas reserves. All neighbouring countries claim that it is part of their territories in order to control as many resources as possible.

  • The dispute stated in Source 1.7a concern homeland security and resource security.