What are the harmful effects of eutrophication on the aquatic ecosystem ?
Please take a look at this useful link.
http://iosrjournals.org/iosr-javs/papers/Vol9-Issue10/Version-1/Q0910018996.pdf
The main effects caused by eutrophication can be summarized as follows (Mason, 2002):
1. Species diversity decreases and the dominant biota changes
2. Plant and animal biomass increase
3. Turbidity increases
4. Rate of sedimentation increases, shortening the lifespan of the lake
5. Anoxic conditions may develop
Because of the high concentration of organisms in a eutrophic system, there is often a lot of competition for resources and predator pressure. This high degree of competition and the sometimes-high chemical or physical stress make high the struggle for survival in eutrophic systems. As a result, the diversity of organisms is lower in eutrophic than in oligotrophic systems.
Oxygen depletion, or hypoxia, is a common effect of eutrophication in water. The direct effects of hypoxia include fish kills, especially the death of fish that need high levels of dissolved oxygen. Changes in fish communities may have an impact on the whole aquatic ecosystem and may deplete fish stocks.
general deterioration of water quality and other effects that reduce and preclude use”.
Eutrophication leads to algal blooms. The algal blooms may initially increase the amount of Dissolved Oxygen but subsequently lower it. Microbial action on dead algae in the water is responsible for sudden depletion of DO in the water which causes hypoxia- oxygen depletion. This can sometimes be severe enough to kill the water organisms such as fishes. Eutrophication is also very unpleasant to look at and has significant costs on tourism and residential potential of the area
Low oxygen level, which might possibly lead to reduction in aquatic organisms
Please also see the following RG link.
Chapter Eutrophication: Threat to Aquatic Ecosystems
By eutrophication the water body is dead totally because of lessening in oxygen levels in water
The elements of eutrophication on lakes summarised by Hazim Jumaa Mahmood apply also to marine ecosystems, particularly in semi-enclosed seas, such as the Baltic or the Gulf of Mexico. More than 500 marine dead zones have been registered world-wide, often driven by nutrient and pesticide run-off from agro-industrially managed regions or untreated or poorly treated waste waters from urban zones. Low or zero oxygen has the biggest impact on the affected ecosystem. As oxygen is essential to most organisms from zooplankton to the top of the trophic pyramid - exceptions are bacteria and other specialised organisms capable of using H2S, manganese or other energie sources for their metabolism - it is now well established that this is the strongest growth limiting factor in gill breathing organisms, such as fish. See e.g. https://www.int-res.com/book-series/excellence-in-ecology-books/ee22/
It goes without saying that these effects will be exasperated in an ocean and in lakes warming under the effects of climate change. Cheung et al. have already estimated that at least another 10% of the world's already shrinking marine harvests will be attributable to smaller fish in warmer water - which can hold less dissolved oxygen compared to cooler water. Eutrophication is by no means a stressor to be taken lightly. However, remedies exist to reduce agricultural runoff and clean up domestic wastewater, incl. through (constructed wetlands) and attenuate the negative effects at least close to the shore through clever aquaculture designs, such as a first stage of filter feeders in the current to clean up the worst (they may even be edible if not affected by excess heavy metals), followed by finfish cages (optional, preferably not carnivores that require feeding with protein rich feeds) and brown algae to clean up the rest. For more info see the SPEAR project (open access book): Book SPEAR: sustainable options for people catchment and aquatic resources
Best, Cornelia
There are many harmful effects. I work specifically about climate change and GEI emissions. Thes publicationes can be useful.:
Eutrophication will increase methane emissions from lakes and impoundments during the 21st century
Methane emissions from natural wetlands ( Z Wang - 1996 )
Eutrophication accelerates algal bloom in the aquatic systems. Oxygen depletion or hypoxia is a common effect of eutrophication in water bodies which directly kills the fishes, especially those fishes which need high levels of dissolved oxygen. Eutrophication also leads to the availability of light and certain nutrition in the water bodies which causes depletion of fish stocks.
In tropical regions enclosed lagoons and bays may , because of untreated sewage, become eutrophic. The increase in nutrients from bacterial action on dead organisms, not only accelerates oxygen depletion, but allows the rapid growth of macro algae species that can smother corals by covering them.
F. Bouteldjaoui algal bloom is a common phenomenon. Rest are covered in the previous comments. Thank you!
F. Bouteldjaoui
Oxygen depletion, or hypoxia, is a common effect of eutrophication in water. The direct effects of hypoxia include fish kills, especially the death of fish that need high levels of dissolved oxygen. Changes in fish communities may have an impact on the whole aquatic ecosystem and may deplete fish stocks.
http://www.coastalwiki.org/wiki/Possible_consequences_of_eutrophication
Eutrophication accelerates algal growth and reduce the oxygen level in the environment. Some times the sudden algal blooms toxic to the environment and kill the organisms in the environment including fishes. The similar impact also noticed if oxygen level is low.
Please have a look at the following link:
Chapter Eutrophication: Threat to Aquatic Ecosystems
Eutrophication (Algae blooming) which causes reducing dissolved oxygen and increase ammonia and the depth of the water body as a dead zone for all living organisms.
Too much algae floating on water let little sunlight inside water body.
Fish kill, oxygen depletion, little sunlight which reduces the activities of phytoplantons thereby affecting the entire ecosystem.
Typical treated sewage (2ndary treatment) does not remove nutrients well, especially nitrogen (with excess N being main cause of eutrophication in marine waters). Removal of dissolved inorganic nitrogen (NH4, NO3 etc) in sewage requires a 3rd step - tertiary treatment through denitrification process. So typical 2ndary treated sewage effluents are still associated with eutrophication, especially in poorly flushed marine waters.
Eutrophication is the nutrient enrichment of water body which results in algal blooms thereby depleting the dissolved oxygen and reducing the penetration of sunlight inside the layer of water body.Hence, resulting in the death of aquatic organisms living inside a water body .
During evening fishes are suffering from eutrophication. Due to less Dissolved oxygen ( ppm ) living organisms are suffering from eutrophication. Supply of aerator in pond or beels or lake will improve the situation, even supply of new water will improve the situation in confined pool.
Eutrophication can also be a natural process that takes thousands of years and ends up with silting. Because of anthropogenic impacts, eutrophic lakes can become polytrophic in a much shorter time, (in very short), because they accumulate (and release) nutrients and gazes in and from sediments accelerating the process. The many possible consequences have already been described. In your case, I would propose to establish the definition of eutrophication first and then to analyse from time to time water quality in the different water layers, to check the trophic state and, if countermeasures are needed.
Principally a decrease in light penetration, which causes a decrease of photosynthetic activity. This will allo to low oxygen concentration, which is harmful for the respiration of all organisms leaving in the water.
Eutrophication causes:
1. Results in imbalance in biodiversity, with dominance of few species.
2. Appearance of algal blooms, causing oxygen deficiency at night/ early morning, becomes major cause of fish mortality.
3. Ultimately leads to death of a water body.
I would summarize eutrophication is that nutrient-induced excess of primary production which cannot be processed by primary consumers and accumulate in aquatic ecosystems with the consequences already commented.
I would like to add that consequences of eutrophication are not only of o local nature (lakes, ponds) as have been here commented, but can also be suffered in ecosystems that are distant to the nutrient load point. This is the case of the so called coastal "dead zones" that import the excess algae biomass from eutrophic estuaries. That biomass decomposes in in the coast generating severe anoxia that seriously condition local fisheries.
One of the criteria of eutrophic lakes is anaerobia in the Hypolimnion (depth zone) caused by the degradation of phytoplankton. During the stagnation period, this can lead to the formation and accumulation of NH4 and sometimes also to H2S as noted by @Abhijit. Besides anaerobic bacteria, several species of Metazoa (e.g. Chironomus sp.) can live for some time without oxygen, even in organic sediments (mud).
Eutrophication is organic pollution, which manifests itself in the case when an excessive amount of nutrients accumulates in the water of a lake or stream. As a result, the reservoir is overgrown with excessive amounts of algae and air-aquatic plants, which cannot be utilized in food chains due to toxicity (blue-green) or too significant biomass of primary producers. The prerequisite is the shallowness of the reservoir and unfavorable hydrodynamics. Practice shows that phosphorus is the main factor for the emergence of "blooming" of water, since nitrogen compounds in modern conditions are almost everywhere. Not utilized plants die and decompose, consuming oxygen dissolved in the water, as a result of which life in the water of this reservoir becomes more difficult.
I disagree with some colleagues who believe that eutrophication is only the result of the accumulation of organic matter in the ecosystem due to an excess of nutrients. The reason for eutrophication is deeper and lies in the imbalance of the ecosystem as a whole. Violation of this balance can have natural causes (aging of the reservoir), or be the result of economic activity (runoff from agricultural land), or household pollution. I would like to note that man artificially creates highly trophic conditions for obtaining high productivity in aquaculture.
Eutrophication literally chokes the biodiversity from the lakes and other freshwater environments. Only drastic removal of the flora will help abate this common phenomenon.
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