Dear Dr. Fadhel,

I'll try to answer it in a nutshell as follows:

1. Presence of higher concentrations of dissolved inorganics viz. nitrates, phosphates and silicates (primarily for diatoms) and carbon through natural advection or upwelling and/or anthropogenic influences (sewage, irrigation). Intertidal injection also introduces copious amount of nutrients. In the freshwater regime dissolved orthophosphates serve as the limiting nutrients for bloom while in marine environments it is generally dissolved nitrates that limit the algal growth. In estuarine set up however, both can play significant roles depending on the section of the estuary and the species concerned.

2. A rise in temperature, dearth of dissolved oxygen, rapid fluctuation in pH-resulting in the absence of higher trophic level consumers, zooplankton to fish, leading to unchecked phytoplankton bloom.

3. Presence of condition amicable for all organisms, especially spring bloom, after a phase of tiding over adverse conditions may also lead to explosion in numbers of microalgae.

4. Absence of competitive macrophytes in the waterways, leading to monopolization by the phytoplankters in exploitation of the available resources.

5. Ability of certain species under some genera to withstand or adapt to adverse conditions and resultantly out-competing other in terms of dominance.

6. Natural catastrophes such as flood through excess release from dams, torrential downpour, flood, cyclones etc can and does introduce land wash or churned sediment bed-released nutrients into the water column that might and do favour microalgae.

7. Introduction of nuisance species/non-native species through ballast discharges which might find the ambient conditions ripe for the picking and may end up becoming the dominant species causing multiple blooms year round. Best example:: Odontella in Bay of Bengal.

8. Seawater incursions into the aquifer or the rupturing/fissuring of bedrock resulting in admixing of waters with higher nutrient load and ultimately causing enrichment of the surrounding water bodies. Sedimentary rocks with higher nutrients can and do leach huge quantities of inorganic load into the water.

9. Presence of certain microbes trigger the enrichment of certain nutrients, such as phosphate solubilizing bacteria help to release phosphates from apatite minerals through synthesis of low molecular weight organic acids etc, can lead to eutrophication and exploitation by certain algal communities causing blooms.

There are various other more beautifully intricately woven factors responsible for eutrophication but to keep it simple the aforementioned points should suffice.

I hope this helps you,

Regards,

Dr. Abhishek Mukherjee

Dear Dr Abhishek Mukherjee

Very helpful answer , thank you very much. In your experience sir , what is the first step for solution ! And please I need more details about the competition absence in such ecosystem ( rivers ecosystem) !

https://www.nature.com/scitable/knowledge/library/eutrophication-causes-consequences-and-controls-in-aquatic-102364466

Dear,

Above publication hopefully address all your Questions:)

good luck!

First of all, you will need do a scientific study of the nutrient content of both the water and sediment. This will help in both monitoring and evaluation purposes as well as in determining the course of action to be taken.

Secondly, you will need to identify the source of the nutrients and take actions to minimize further pollution from the nutrients. It is easier to stop point source pollution such as discharge from sewer pipes than non point source such as leacheates from agricultural fields. Whatever the case the nutrient discharge into the water must be reduced to the bearest minimum. For non point source pollution such as leacheates from agricultural fields, establishment of green belts as buffer along the river together with reduction in fertiliser use or a change in the mode of application will help. But it is also possible that nutrients in the sediment would still be mobilised into the water even if all these steps are taken and this would require a very long recovery time.

Worse case scenario will require dredging.

Eutrophication is triggered by the excess of macro-nutrients, with phosphorus and nitrogen being the key ones. I am attaching a number of good review papers that will shed some light on this complex topic. The reference sections in papers by Yao et al 2018 and Yuan et al 20918 will give you access to many relevant past papers on the subject.

Tomas

Dear Safdar Bashir

Thank you very much for your helpful answer.

Dear Francis Gbogbo

Thank you very much for your helpful answer.

Dear Tomas

Thank you very much for your helpful answer, also for very useful papers.

Very good explanatory notes by Dr. Mukhergee. Thank you. As requested by Mazin, may be solutions to each situation would have been more interesting and useful.

Thank you Dr. Tomas for providing so many interesting references.

Dear Dr. Fadhel,

Eutrophication is, in all honesty, a natural phenomenon off-late being more readily catalyzed by the increased human activities and a penchant for better living by altering the existing best. Eutrophication and the follow-up explosion in floral and faunal lives are all part of the natural rhythmicity comprising enrichment and mitigation through mineralization and demineralization of the inorganic/organic compounds. The ameliorative efforts should only and always focus on the issues created by us since one cannot stop natural upwelling or advection or any such matters. And as for the anthropogenized issues, the addressed causes often are rhetorical and the solution lies in reverse engineering the cause.

Thanking you,

Dr. Abhishek Mukherjee

The major cause of eutrophication in rivers is excessive introduction of nitrogen and phosphorus (excessive nutrient load) into the water body. And this can be due to uncontrolled anthropogenic activities going on along the catchment area of the river such as agriculture, untreated wastewater discharge from both domestic and industrial areas.

It requires an integrated approach to handle this problem. Firstly, identification of pollution types and sources; treatment of wastewater before discharge into the river. The links others provided above will give you greater insight to the approach to apply.

You can also read my previous work on this link:

Article Water Quality Characterisation and Restoration Measures of U...

I wish you good luck in your study.

Dear Dr. Abhishek Mukherjee

Thank you very much for your help , your efforts may be reflected on the health of 3 million citizenship in Mosul city.

Dear Dr Doris Ogueri

Thank you very much for your explanation and for useful paper.

Many thanks to you Dr Malcolm

More Live Photo’s about river eutrophication In Mosul city. This photos was taken today in the middle of the city .

River eutrophication is primarily caused by the excessive inflow of nutrients from the river catchment. These depend largely on the nature of the river catchment, the type of human activities, soil type, topography and the hydrographic factors. I think the various suggestions above have answered your question. Thank you.

Tank you Dr Nwonumara for your help.

Further information on trophic cascades & biomanipulation can be found here (downloadable at https://www.researchgate.net/publication/270352982):

Vadas, R.L. Jr. 1989. Food web patterns in ecosystems: a reply to Fretwell and Oksanen. Oikos 56: 339-343 (cf. http://www.jstor.org/pss/3565618).

When food-web impacts occur to throw off trophic-level structure, eutrophication can result. Perhaps strategic predatory-fish stocking might help?

-Bob

Entry of untreated sewage into the river.

Well,

High concentration of Nutrients coming with wastewater, with shallow water depth, in a hydrostatic condition (low water velocity and low water discharge).

Sincerely