Which of the following is most a source of nitrogen that can lead to eutrophication of aquatic ecosystems?
a. runoff of fertilizer from yards b. treated sewage
c. runoff of manure from farms d. all of these

Answer:

All of these are the most important source of  of nitrogen that can lead to eutrophication of aquatic ecosystems

Explanation:

Eutrphication is process where the amount of nutrients in the aquatic system  increases. The two major source of nutrients or minerals that causes eutrophication is Nitrogen and Phosphorus. The nitrogen or Phosphorus promotes the growth of phytoplanktons. These phytoplanktons covers the surface of the aquatic system thereby leading to decrease in the amount of oxygen  in the system. The runoff from the agricultural lands contains the particles of fertilisers used  for the crops.Usually those fertilizers like Urea  are made up of Nitrogen and phosphorus. Also the sewage water too contains nitrogen in it.

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answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.