Oceans in trouble

Global Coverage

Oceans and seas cover approximately 71%71\% of the Earth's surface, leading to Earth being commonly referred to as the 'Blue Planet'.

Major Global Oceans

  1. Arctic Ocean

  2. Atlantic Ocean

  3. Indian Ocean

  4. Pacific Ocean

  5. Southern Ocean

Major Named Seas and Water Bodies

  • North and West:

    • North Sea

    • Baltic Sea

    • Black Sea

    • Caspian Sea (an inland sea)

    • Mediterranean Sea

    • Bering Sea

  • Middle East and Africa:

    • Red Sea

    • Arabian Sea

  • Asia-Pacific:

    • Bo Hai

    • Huang Hai (Yellow Sea)

    • Dong Hai (East China Sea)

    • Philippine Sea

    • Nan Hai (South China Sea)

    • Sea of Japan

    • Andaman Sea

  • Americas:

    • Caribbean Sea

Oceans vs. Seas

  • Oceans: Large areas of water. All five major oceans are connected to one another.

  • Seas: Smaller and shallower than oceans; they are considered part of an ocean.

  • Inland Sea: A sea that is almost entirely enclosed by land (e.g., Caspian Sea).

Major Seas and Geography of China

  1. Bo Hai: Located in the north-east.

  2. Huang Hai: Located in the north-east.

  3. Dong Hai: Located in the east.

  4. Nan Hai (South China Sea): Located in the south.
    These four seas all belong to the Pacific Ocean.

  • Regional Context: Hong Kong is situated nearest to the Nan Hai (South China Sea).

  • Surrounding Countries: Vietnam, Malaysia, Brunei, Philippines, North Korea, South Korea, and Japan.

Benefits and Resources Provided by Oceans

Oceans provide five primary categories of resources to human beings:

  1. Food:

    • Oceans are a major primary source of protein. Marine species caught or reared include fish, crabs, shrimps, and oysters.

    • Global Statistics: In 2018, approximately 84⋅10684\cdot10^6 tonnes of fish were caught for food consumption worldwide.

    • Fishing Grounds: Specific areas where fish are found in large numbers. Important ones include the North-west Pacific, North-east Pacific, North-west Atlantic, North-east Atlantic (Grand Banks), and the Nan Hai (the closest to Hong Kong).

  2. Energy Resources:

    • Oil (Petroleum) and Natural Gas: Huge reserves exist under the seabed. In 2015, 29%of the world's extracted oil came from offshore sources. Natural gas is used for electricity (e.g., natural gas from the Nan Hai fuels Hong Kong's Castle Peak Power Station).

    • Offshore Wind Power: Wind speeds in the open sea are steady and high. Between 2011 and 2019, offshore wind farms became increasingly important for electricity generation capacity.

    • Wave and Tidal Power: Renewable sources that use the movement of water to generate power (e.g., Rance Tidal Power Station in France). Though current scales are small, they possess rich potential.

  3. Minerals and Metals:

    • Sea Salt: Collected from salt pans (e.g., in Spain) via evaporation of seawater.

    • Metals on Seabed: Mining operations extract copper, titanium, and rare-earth elements (extracted from Monazite) for industrial use.

  4. Transport Routes:

    • Sea transport is the cheapest method for moving goods over long distances and has acted as a 'highway' for trade for thousands of years.

    • Hong Kong External Trade (2020):

      • Sea Transport: 54.8 ext{%}

      • River Transport: 36.7 ext{%}

      • Road Transport: 6.9 ext{%}

      • Air Transport: 1.6 ext{%}

  5. Recreational Sites:

    • Coastal areas and coral reefs attract tourists and provide health/relaxation benefits through activities like sunbathing, beach volleyball, windsurfing, swimming, boating, surfing, diving, and exploring coral reefs.

Climate Regulation by Oceans

Oceans regulate the climate of coastal areas to make them more suitable for habitation.

  • Coastal Mechanism: In summer, sea winds bring cool, moist air. In winter, they bring warm, moist air, resulting in a mild and wet climate.

  • Inland Comparison: Inland areas (far from the sea) experience more extreme temperatures—hotter in summer and cooler in winter—and are generally drier throughout the year.

The Marine Ecosystem: Structure and Processes

  • Definition: A marine ecosystem is formed by living things interacting with each other and their environment.

  • Components:

    1. Biotic Components (Living): Plankton (tiny plants and animals), shrimps, fish, whales, and bacteria.

    2. Abiotic Components (Non-living): Sunlight, seawater, sand/mud, and dissolved gases (e.g., oxygen).

  • Energy Flow:

    • Primary Energy Source: Sunlight.

    • Producers: Plant plankton (tiny plants) that make food through photosynthesis.

    • Consumers:

      • Primary Consumers: Animal plankton and shrimps that eat producers.

      • Secondary Consumers: Fish that eat primary consumers.

      • Tertiary Consumers: Large predators like sharks and whales that eat lower-level consumers.

    • Transfer Efficiency: Only about 10 ext{%} of the energy from one level is passed to the next level. The remaining energy is lost as heat through movement and respiration.

    • Decomposers: Bacteria that break down the remains of dead organisms.

  • Nutrient Cycling: The circulation of nutrients (e.g., Nitrogen) from seawater to living things and back to the environment via decomposers.

Challenges: Overfishing and Habitat Destruction

  • Definition of Overfishing: When the catch rate exceeds the growth/reproduction rate of the fish stock, leading to depletion.

  • Statistical Trends:

    • In 1974, 10 ext{%} of global fish stocks were overfished.

    • By 2017, this rose to 34 ext{%}.

    • Case Study: In the Mediterranean Sea, the European hake population is being lost at a rate 11 to 66 times (or even more than 66 times) faster than it can reproduce.

  • Causes of Overfishing:

    • Increasing Demand: Driven by global population growth (4.84.8 billion in 1990 to over 7.27.2 billion recently).

    • Poor Fishery Management: Lack of monitoring for illegal fishing, government subsidies for commercial fleets, and the use of modern machines to catch vast quantities.

    • Destructive Fishing Methods:

    1. Blast Fishing: Use of explosives that kills fish and destroys coral reef habitats.

    2. Bottom Trawling: Dragging huge nets across the seabed. This destroys habitats, catches baby fish/unwanted species, and stirs up mud/sand which blocks sunlight, preventing photosynthesis in marine plants.

Sustainable Fishing and Solutions

  • Sustainable Fishing: Catching seafood at a rate that conserves enough stock for future generations.

  • Practices:

    • Fishing Ban Periods: e.g., The Chinese Central Government bans fishing in the Nan Hai for at least three months every summer to allow for reproduction.

    • Fishing Quotas: Limits on total weight of fish caught or limits on the number of boats and operating hours (e.g., European Union member quotas).

    • Gear Restrictions: Banning destructive methods and requiring the