oceans and fisheries

Where is the majority of Earth's water distributed?

Oceans hold ~97.5% (saltwater). Fresh water makes up ~2.5%, mostly frozen in ice sheets and glaciers, followed by groundwater, lakes, rivers, and the atmosphere.

What are the main processes in the water cycle?

Evaporation, transpiration, condensation, precipitation, interception, infiltration, surface run-off, through-flow, and ground water flow.

What are the main fresh water sources used by humans?

Aquifers (groundwater wells), rivers, lakes, artificial reservoirs, and desalinated seawater.

What are the three main sectors of global fresh water usage?

1. Agricultural (irrigation) 2. Industrial (cooling and manufacturing) 3. Domestic (drinking, sanitation, cooking).

Why does water availability vary globally, leading to potential conflict?

Unequal natural rainfall distribution divides regions into water-rich and water-poor; rising demand, contamination, and transboundary rivers create political tension/conflict over water rights.

What is a multipurpose dam project and what are its key advantages?

A large barrier built across a river that provides electricity (HEP), flood control, water storage for irrigation, domestic supply, and recreation.

What are the main environmental and social disadvantages of multipurpose dams?

Environmental: Flooding natural habitats, blocking fish migration, altering sediment flow. Social: Displacement of local communities and risk of catastrophic dam failure.

What are the primary sources of fresh water pollution?

Domestic sewage, industrial wastewater/toxic chemicals, and agricultural runoff (fertilisers, pesticides, animal waste).

What is bioaccumulation in aquatic food chains?

The accumulation of non-biodegradable toxic substances (like heavy metals) in an organism's body, which increases in concentration at higher trophic levels.

How does nutrient enrichment lead to eutrophication in rivers and lakes?

1. Runoff containing nitrates/phosphates enters water. 2. Rapid algae growth (algal bloom) blocks sunlight. 3. Submerged plants die. 4. Decomposers multiply and consume dissolved oxygen. 5. Aquatic life suffocates and dies.

How does acid rain affect aquatic ecosystems?

Acid rain lowers the pH of lakes and rivers, leaching toxic aluminium ions into water, which damages fish gills and kills aquatic life.

What strategies are used to improve fresh water quality and sewage management?

Building modern sewage treatment plants, improving municipal sanitation, enforcing industrial discharge laws, and creating water protection zones.

What is the life cycle of the malaria parasite and how is it transmitted?

Transmitted to humans by the female Anopheles mosquito vector; the Plasmodium parasite infects human liver and red blood cells, causing recurring fever and illness.

What are the main strategies used to control and eradicate malaria?

Antimalarial drugs (treatment), vector control (insecticide-treated bed nets, spraying interiors, draining standing water where mosquitoes breed), and introducing biological predators.

How can cholera be controlled and prevented?

Ensuring access to safe potable water, proper sewage disposal/sanitation, boiling or chlorinating drinking water, and practicing good personal hygiene.