The problem of malnutrition arises when household waste,

 agricultural waste or industrial waste is mixed with water flows and accumulates in a lake, river or lake.  This waste accumulates in the aquifer and provides nutrition to aquatic plants as they contain some of the major problems of the aquatic ecosystem (Eutrophication) elements (nitrogen-phosphorus compounds).  As a result, growth of water hyacinth, duckweed, algae etc. starts accelerating.  The result is a decrease in dissolved oxygen in the water.  Therefore, the amount of saturated oxygen in the water (Biological Demand For Oxygen - BOD) increases.  The decomposition of aquatic plants continues.  The use of water-soluble oxygen in this decomposition process leads to a deficiency of apoxy.  So the life of other som organisms, fish, etc. also ends. 

 Decomposition of dead plants produces odors as well as changes the color of water.  When there is a sudden increase in vegetation due to increase in nutrients in the water, it is called water bloom or algal bloom.  The same phenomenon found in aquatic ecosystems is Eutrophication।