4.3, 4.4: Water, Food Production Systems and Society

4.3 - Aquatic Food production systems 

• Continental shelf: extension of continents under the seas and oceans (creates shallow water)

→ has 50% of oceanic productivity but 15% of its area

→ light reaches shallow seas so producers can be photosynthesize 

→ countries can claim, exploit, and harvest it 

• Zooplankton: single-celled animals that eat phytoplankton and their waste 
• Fishery: when fish are harvested in a certain way 

→ 90% oceans and 10% freshwater 

→ 70% of the world’s fisheries are exploited 

• Aquaculture: farming aquatic organisms (coastal and inland) involving interventions in the rearing process to enhance production 

→ Impacts of fish harms: loss of habitat, pollution, spread of diseases, escaped species may survive to interbreed with wild fish, escaped species may autocomplete native species  

• Maximum Sustainable yield (MSY):

→ SY: increase in natural capital (natural income that can be exploited each year without depleting original stock)

→ MSY: highest amount that can be taken without permanently deleting the stock

4.4 - Soil degradation and conservation 

• Pollutants can be: anthropogenic or natural, point or nonpoint source, organic or inorganic, direct or indirect 

1. Organic: 

→ pollutant: sewage, animal waste, pesticide

→ example: human waste, insecurities 

→ effects: eutrophication, loss of biodiversity 

2. Inorganic: 

→ pollutant: nitrates and phosphates radioactive material, heavy toxic material 

→ example: industry, nuclear power stations, fertilisers

→ effects: eutrophication, bioaccumulation, biomagnification 

3. Both:

→ pollutant: solid domestic waste, debris, suspended solids

→ example: silt form construction, household garage

→ effects: damage controls, plastics

• Freshwater pollution: agricultural runoff, sewage, solid domestic waste
• Marine pollution: rivers, human pollution, pipelines 

Measuring water pollution: 

1. BOD: amount of dissolved oxygen required to breakdown organic material in a given volume of water 
2. Indicator species: plants and animals that show something about the environment by their presence, absence, abundance
3. Biotic index: indirectly measures pollution by assessing the impact on species within the community according the their tolerance, diversity, and relative abundance 
4. Eutrophication: when lakes and coastal waters receive inputs of nutrients (nitrates and phosphates) that result in an excess growth of plants and phytoplankton

• The eutrophication process: 

→ Fertiliser enters rivers/lakes 

→ High level of phosphates, algae grows faster 

→ More algae, more food for zooplankton or small animals that feed on them. A lack of zooplankton animals means that these are less to eat algae 

→ Algae die and are decomposed by aerobic bacteria 

→ Not enough oxygen is present therefore everything dies and the food chain collapses 

→ oxygen levels fall lower, dead organic material sediments on the lake or the river bed and turbidity increases 

→ All life is gone and sediment settles to leave a clear blue lake. This process in which bodies of water become enriched with nutrients and minerals 

• Biochemical oxygen demand: amount of DO required to break down organic material in a given volume of water 

 → biological monitoring and indicator species can be used to determine levels of pollution 

→ strengths: stationally, sensitive and representative 

→ weaknesses: identification