Eutrophication
Some pollutants affect the environment by disrupting the equilibrium in food chains.
Sewage
If untreated sewage gets into rivers, micro-organisms decompose it. They dramatically increase in number and use oxygen from the water for Respiration that requires oxygen.. As a result there is less oxygen dissolved in water, so aquatic organisms such as fish and insects may be unable to survive.
Nitrate fertilisers
These are soluble, and when sprayed on crops they can be easily washed into waterways, this is called The washing of chemicals into the soil or waterways by rain.. The process can be outlined as follows:
- increased nitrates in the water increase the growth of algae and plants
- the algae form a bloom over the water surface, preventing sunlight reaching other water plants
- these plants die because they are unable to carry out A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic. without light
- microbes such as bacteria increase in number as they If a substance decomposes, it breaks down into simpler compounds or elements. the dead plants, using and reducing the oxygen content in the water during respiration as they do so
- the low oxygen levels can cause aquatic insects and fish to suffocate, and eventually the lake may be left completely lifeless
Question
A farmer sprays nitrate fertiliser on his land around a lake. Can you put these steps in order to describe how the fish and other organisms in the lake could be killed as a result of his actions?
- Dead plants are decomposed by bacteria, which use up the oxygen in the water during respiration.
- Algae blooms prevent sunlight reaching other plants. The plants begin to die.
- Excessive nutrients (nitrates) from fertilisers are flushed from the land into rivers by rainwater.
- Oxygen levels reach such a low point that fish and other organisms suffocate.
- These nutrients cause increased aquatic plant growth of algae and other plants.
- Excessive nutrients (nitrates) from fertilisers are flushed from the land into rivers by rainwater.
- These nutrients cause increased aquatic plant growth of algae and other plants.
- Algae blooms prevent sunlight reaching other plants. The plants begin to die.
- Dead plants are decomposed by bacteria, which use up the oxygen in the water during respiration.
- Oxygen levels reach such a low point that fish and other organisms suffocate.
Indicator species
An indicator species is an organism whose presence or absence is used by scientists to determine if an area is polluted.
Air pollution
An organism that is part fungus and part algae or cyanobacteria. Lichen grow in exposed places such as rocks and can be used as an indicator species for air pollution. are commonly used to determine air pollution as many species will only grow in areas which are free of air pollutants such as those produced by traffic.
Water pollution
Freshwater An animal without a backbone. are used to determine the levels of pollution in freshwater. Some organisms can tolerate high levels of pollution, whereas others will not be found in polluted areas.
Pollution is also indicated by acidic Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline. or lack of oxygen in water.