ESS Topic 4: Water, aquatic food productions systems and societies

Hydrological cycle

Hydrological cycle

movement of water between three storages

Role of oceans

74% total precipitation falls over oceans, 84% total evaporation comes from oceans

Evapotranspiration

Loss of water through evaporation + transpiration

Sublimation

Ice to water vapor

Condensation

Water vapor to liquid

Evaporation

Liquid to water vapor

Advection

Wind-blown movement of water

Precipiration

Movement of water from atmosphere to land and oceans

Melting

Solid snow and ice to liquid water

Freezing

Liquid form to solid form

Water on the surface may cause

Flooding, surface runoff, infiltration, percolation, currents

Flooding

Too much water to drain

Surface runoff

Movement of water over land’s surface

Infiltration

Movement of water from surface to soil

Percolation

Movement of water from soil to rocks

Currents

Movement of water in streams and rivers

Human impacts

Agriculture, deforestation, urbanisation

Deforestation impacts

Decline in vegetation cover, less interception, more ground compaction, more overland runoff, likelihood of floods

Interception

Because of grass water can’t reach soil

Ocean circulation systems

Are driven by differences in temperature and salinity

Salinity

How much salt there is

Ocean conveyor belt

Transports heat and energy around the world, affecting climate

Ocean conveyor belt role

Responsible for the transfer of heat from tropics to colder regions

Access to freshwater

Varies considerably, as some areas have year-round rainfall while others have water shortages

Physical water scarcity

water development is approaching, or exceeded unsustainable levels

Economic water scarcity

Where water is available locally but not accessible for most people for financial reasons

Effects of global warming

Many areas will become drier

Increasing demand for water is caused by

Population growth, societies becoming richer

Contamination and over-extraction of water

Overusing freshwater results in decline in quality because some water resources are non-renewable

How to conserve water

Construction of dams, water transfer schemes, desalination

Water resources and conflict

Conflict may arise over the use of water because of reduced availability of resources in lower basin countries

Lower basin

all precipitation flows to the same river

Example of water resources and conflict

Egypt and Ethiopia over the nile river

Demand for aquatic food resources

Continue to increase as the human population grows and as standards of living rise

Photosynthesis and aquatic food webs

Highest rate of productivity through photosynthesis is found in shallow seas

Comparison between terrestrial system and aquatic system

In terrestrial, most food is harvested from low tropic levels. In aquatic, most food is harvested in higher tropic levels.

Maximum sustainable yield

Largest amount of species that can be harvested without reducing annual replacement of biomass

Indigenous populations and sustainable yields

Hunts whales & seals within sustainable levels

Effects of developing modern fishing industry / technology

Falling fish stocks

Example of reducing impacts of modern fisihing

EU’s Common Fisheries Policy

EU’s Common Fisheries Policy

Set out regulations for size of catch permitted, size of fish allowed to be caught, size of nets, etc

Aquaculture

Cultivating aquatic organisms for food

Issues with aquaculture

Loss of habitat, pollution caused by the use of fish feed, antibiotics, spread of diseases within farmed fish

Freshwater pollution sources

Runoff, sewage, industrial discharge, solid domestic waste

Marine pollution physical sources

Rivers, pipelines, atmosphere, activities at sea

Types of aquatic pollutants

Organic material, inorganic plant nutrients, toxic metals, synthetic compounds, hot water, oil, radioactive pollution, invasive species, floating debris

Ways to test water quality

Dissolved oxygen, phosphate, nitrate, ammonia

Biodegradation of organic material

Utilizes oxygen, can lead to anoxic conditions

Anoxic

Oxygen-less

Results of biodegradation of organic material

Formation of methane, hydrogen sulfide, ammonia

Biochemical Oxygen Demand (BOD)

Measure of the amount of dissolved oxygen need to break down the organic material in water, can used to assess water pollution levels

Indicator species

Indirect measure of pollution and environmental degradation

Biotic indices

Indirect method of measuring pollution

What does biotic indices involve

Levels of tolerance, diversity, abundance of organisms

Trent biotic index

Based on the disappearance of certain indicator species as pollution increases

Eutrophication

The process by which a body of water, such as a lake or river, becomes enriched with nutrients, especially with nitrogen and phosphorus

Eutrophication can be caused by both human and natural causes

Yes

Process of eutrophication

Increase of nitrates or phosphates, rapid growth of algae, accumulation of dead organic matter, high rate of decomposition, lack of oxygen

Natural causes of eutrophication

Nutrients added from decomposing biomass, runoff from surrounding areas

Human causes of eutrophication

Runoff of fertilisers from agricultural land, domestic wastewater, untreated sewage

Positive feedback of eutrophication

Algae grow, block light, underwater plants die, create more nutrients as they decompose, more algae, further divergence from equilibrium

Negative feedback of eutrophication

Underwater plants die, dead organic matter increase, decomposers increase, faster decomposition, same quantity of dead organic matter

Impacts of eutrophication on ecosystem

Increase in biomass of algae, less light penetration to underwater plants, increase in bacteria and oxygen levels, decrease in biodiversity, length of food chain decreases

Impacts of eutrophication on society

Nitrate-enriched water = higher rates of stomach cancer, cost of treating nitrate-enriched water is expensive

Pollution management for altering human activity

Avoid spreading fertilisers in the winter, use organic fertilisers on agricultural fields, do not apply fertilisers to fields that are next to streams and rivers

Pollution management for regulating at point of emission

Sewage treatment processes that remove nitrates and phosphates from waste, only use washing machines with full load, reduce use of fertilisers

Pollution management for cleaning up and restoring

Pump air through lakes to avoid low-oxygen, reintroduce plant and animal species

Methods to reduce unsustainable fishing

International policies (EUCFP), national governments may establish marine parks and protected areas, consumers can make sure they buy certified fish

Dead zones

when there is not enough oxygen to support aquatic and marine life, can be result of eutrophication