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Eutrophication is when the environment becomes enriched with nutrients. All living things need specific nutrients to live. Because too many or too few can cause problems, nature does a good job of providing the right amount of nutrients. This is true in aquatic ecosystems because aquatic ecosystems are so dynamic. the water is oligotrophic when too few nutrients are present. It makes sense that serious problems will arise when there is not enough nutrition available for the variety of organisms living in an aquatic environment.

However, problems can also arise when the aquatic system has an overabundance of nutrients. We get eutrophication when this happens. When too many nutrients, like nitrogen and phosphorous, are present a eutrophic stream, river or lake occurs. usually as a result of runoff from the surrounding land. Algae, plankton and other microorganisms love these types of nutrients, and when they are plentiful, these aquatic organisms can take over. It can have serious negative effects on other organisms like birds, fish and even people, when river, lake or other aquatic system becomes eutrophic.

How it happens:

Excess of fertiliser from agriculture land washed away by the rain water to the nearby pond or water. The nutrient level in water increases when accumulation of fertilisers in the water happens. This phenomena is called eutrophication. This causes phytoplankton to grow and reproduce more rapidly. This will result in algal blooms. The aquatic plants cannot carry out photosynthesis because the sunlight is blocked by the algae. Sediment at the bottom of the pond is formed when the aquatic plants and the algae die. This effects the pond’s ecosystem and encourage the growth of detritus. All the oxygen the water s used up by the detritus by carrying out decomposition. This causes the biochemical oxygen demand(BOD) increases. Lack of oxygen in water causes many aquatic organisms to die. Toxic bi-product that can poison the ecosystem of the pond are produce by some species of algae.

How to determine bod:

1. A sample of water is taken from a pond.
2. If the amount of oxygen required for the decomposition of organic matter in the sample is high, then BOD is high. This means the water sample from the pond is very highly polluted.
3. BOD increases when the water is very highly polluted by bacteria pollution.
4. BOD decreases when the water is very highly polluted by toxic pollution.

Causes:

1. Fertilizers

Human actions causes eutrophication. Human likes to depend on the usage of nitrate and phosphate fertilizers. Lawns, golf courses, farm and other fields are to be heavily fertilized by people. These fertilizers run off into streams, rivers, lakes and oceans when it rain. The hungry algae, plankton and other aquatic plant life are fed well. This increases the rate of photosynthesis activity. This causes dense growth of plant life such as the water hyacinths and algal blooms in the aquatic environments.

2. Concentrated animal feeding operations

Main contributor of nitrogen and phosphorus nutrients responsible for eutrophication is the concentrated animal feeding operations (CAFOs). The concentrated animal feeding operations normally discharge high scores of the nutrients. It somehow finds way into lakes, streams, rivers, and oceans where they accumulate in very high concentrations. By recurring cyanobacterial and algal blooms, thereby plaguing the water bodies.

3. Direct sewage discharge and industrial waste into water bodies

In the developing nations, sewage water is directly channel into water bodies such as oceans, lake, and rivers. This results in, high amounts of chemical nutrients introduced. This stimula the dense growth of other aquatic plants and algal blooms which threatens survival of aquatic life in a lot of ways.

4. Aquiculture

A technique of growing fish, aquatic plants without soil and shellfish in water containing dissolved nutrients is known as aquiculture. Aquiculture it also qualifies a top ranking contributor to eutrophication as it is highly practice in the recent times. The unconsumed food particles together with the fish excretion will increase the levels of phosphate and nitrogen in the water if aquiculture is not properly managed. This will result in dense growth of microscopic floating plants.

5. Natural events

Eutrophication can also cause by natural events. If a lake, river, or stream flood, it may wash away any excess nutrients off the land and into the water. However, in areas that are not surrounded by fertilized lands, eutrophication is less likely to occur.

Example:

Lake Erie was the most publicized example of eutrophication in the 1960s and 1970s. it was called the “dead lake”. From heavily developed agricultural and urban lands, the smallest and shallowest of the five Great Lakes was swamped for decades with nutrients. Plant and algae growth choked out most other species living in the lake as a result. It left the beaches unusable because of the smell of decaying algae that washed up on the shores. (refer appendix 8)

Effects:

1. Threatens the survival of other aquatic life forms and fish

The other photosynthetic plants and phytoplankton grow explosively when aquatic ecosystems experience increase in nutrients. This is commonly known as algal blooms. This causes the algal blooms to limit the amount of oxygen dissolved which is required for respiration by other plant and animals species in the water. When the algae or plant life die and decompose, oxygen depletion will occur. When hypoxic levels is reached by the dissolve oxygen, the plant and animal species under the water such as fish, shrimp, and other aquatic species suffocate to death. In extreme cases, the growth of bacteria is encouraged by the anaerobic conditions that produces toxins which are dangerous to the marine bird and mammals. Light penetration into the lower depths of the water is reduced because of the growth of phytoplankton. This causes loss of aquatic life, aquatic dead zones and it also lessens biodiversity.

2. Limits access to safe drinking water and deterioration of water quality

Algal blooms are highly toxic. The growth of more toxic bacterial is promoted when the water reaches the anaerobic condition. This causes decline in the availability of clean drinking water and extensive deterioration of water quality. Water systems is block because of the dense growth of photosynthetic bacteria and algal bloom on the surface of water. Hence, this limit the availability of piped water. Toxic algal blooms have shut down many water supply systems across the world. For example, in 2007, more than 2 million residents of Wuxi, China could not access piped drinking water for more than a week because of the severe attack by algal blooms on Lake Taihu. (refer appendix 9)

3. Endangers fishing

Increased growth of minute floating plants such as photosynthetic bacteria and algae and the growth of extensive and dense mats of floating plants such as water hyacinths and Nile cabbage is one of the main characteristic of eutrophication. Fishing is endangered whenever this happens on a water body. It will become difficult to set the fishing nets in water when the plants are floating on water. This will also limit the mobility of boats and other fishing vessels.

4. Degradation of recreational opportunities

The blooming of other aquatic plants and algal that float on an extensive area of the water surface is the main problem of eutrophication. It reduces the navigation and transparency in the water which lessens the recreational values and opportunities of the lakes, especially for swimming and boating. Water hyacinth, algal blooms, and Nile cabbage can spread over an extensive area along the shores. It can sometimes float over the whole surface into the land area.

5. Poisoning and impact on human health

Dinoflagelates which generates red tide is also referred as cyanobacteria, which release very powerful toxins with high poison levels in the water. Explosive plant growth in the water create anaerobic conditions which also results in the doubling of the toxic compounds. Even at the least concentration when ingested in drinking water, it causes death in animals and humans. Various negative health impacts such as cancers can be cause when the toxic compounds can also make their way up the food chain. Biotoxins are linked to increased diarrhoetic shellfish, paralytic and incidence of neurotoxic in humans. This can lead to death. The poison is accumulated in their muscles by shellfish and then poison humans upon consumption. The ability of inhibiting blood circulation in infants is associated with high nitrogen concentration in drinking water. This is a condition known as blue baby syndrome.

Ways to overcome:

1. Composting

Use of nitrate and phosphate fertilizers is the main cause of eutrophication. Composting can be used as a solution, in a bid to address the phenomenon. The practice of converting organic matter such as decaying vegetation and food residues into compost manure is known as composting. The high concentration of phosphates and nitrates that feed the other microbes and algae in water bodies are the deficient caused by the nutrients present in the compost manure. All the essential elements are synthesized and broken down by the plants in compost fertilizer thereby not creating the cycle of eutrophication. Nutrient limitation is a term for this method of controlling eutrophication.

2. Reducing pollution

Limiting pollution is an effective and easy method of cutting back on the amount of phosphate and nitrogen discharged into water systems. Municipalities and big manufacturing companies ought to desist from discharging waste into water systems and reduce pollution. So this will reduce the amount of nutrients and toxins ending up in the waters that feed the other microscopic organisms and algae. Nutrient content will be reduced in the water systems if municipalities and industries can cap their waste discharge and pollution to a lower level which can subsequently control eutrophication.

Keep in mind:
This is only a sample.

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3. Ultrasonic Irradiation

The use of ultrasonic irradiation is one such mechanism which has been exploited as an alternative solution to manage and control algal blooming when it comes to eutrophication. Cavitations is used to produces free radicals that destroy algae cells in this process. To determine the uniqueness of its use in controlling the eutrophication problem, research is still underway.