Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen, phosphorus, or both. It leads to increased plant growth in a lake or pond. In time, eutrophication may cause plants to completely fill in the area where a lake or pond once stood.
The word "eutrophic" is of Greek origin, meaning "truly nourished." Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-20th century.
Why should I be aware of this?
The eutrophication of freshwater bodies results in depletion of oxygen and deteriorating living conditions for many organisms. It tends to occur in low-lying areas, particularly near settlements and agricultural land. Inputs of nitrogen via acid rain further aggravate the nutrient surplus.
How does this affect us?
- Nutrient run-offs from agriculture and municipal drains often cause hygenic problems, as such sources normally contain fresh excrement from livestock or man. Contamination with intestinal bacteria can carry a disease risk from pathological bacteria, virus or parasites.
- It has an adverse impact on acquatic life.
All about eutrophication
Modest inputs of nutrients has a positive effect on biodiversity as well as the total production of the ecosystem. But too much of it leads to the accumulation of excessive biomass. Eutrophication is a form of nutrient pollution in ecosystems. It can result in
- Water bodies gradually ageing and becoming more productive. Any natural process like this might take thousands of years to progress but human activities accelerate this process tremendously.
- The presence of excessive plant nutrients causes pollution of water bodies.
Causes of eutrophication
Plant nutrients are supplied primarily in the form of phosphorus, nitrogen and carbon to water bodies in various ways.
- Sewage -- When detergents containing large amounts of phosphates are drained during washing through the household sewage system, it finds its way into ground water and fresh water bodies.
- Pollution from agriculture -- Soil erosion from fertilised fields causes high levels of phosphorus to reach rivers with the displaced soil.
- Fish farms - Discharge of nutrients from fish farms also causes eutrophication. This can be corrected to some extent through feed qualities and feeding routines.
- Discharges from industry --Indutsial waste also increase the flux of both inorganic nutrients and organic substances.
- Fossil fuels -- The burning of fossil fuels releases phosphorus and nitrogen compouds in the atmosphere. These acumalate and then precipitate as raindrops and snowflakes.
The effect of eutrophication and excessive nutrients is most visible during hot summer months.
Impact of eutrophication
- Massive algae blooms -- Blooms of toxic blue-green algae severely restrict the use of the water. This leads to consumption of the oxygen dissolved in water. This can suffocate and kill fish and other forms of acquatic life.
- It cause odour and increases pathogenic animals.
- Reduced light penetration in the water affects the distribution of attached algae and other water plants.
Eutrophication and environment
Once oxygen levels are low, phosphates and other salts will leak out of the bottom sediments, reinforcing the eutrophication process. In extreme situations, the water will contain toxic hydrogen sulphide gas, causing fish to die and bottom areas to rot.
Eutrophication feeds poisonous, foul-smelling algae in bathing water. Dead fish that appear to have “suffocated” are a sign that algae have consumed most of the oxygen. In nitrogen enriched soils some endangered plants cannot survive.
- Norway has taken action to reduce discharges of phosphorus and nitrogen to the Skagerrak coast. Discharges of phosphorus have been reduced by more than 60 per cent since 1985, while discharges of nitrogen have been reduced by around 40 per cent. Coastal areas and many lakes are still affected by eutrophication.