Agriculture and development are the activities that contribute most to the nutrients loading. Nutrients in the form of fertilizers are applied on the fields in order to maximize the production but presently farmers are using fertilizers in excess of crops need. So, these excess nutrients are lost by leaching or runoff into ground water and by volatilization (vaporization of nitrogen in the form of ammonia). Phosphorus binds to the soil and generally lost through soil erosion, through all these processes nutrients mainly nitrogen and phosphorus are ultimately supplied to river and lakes where they cause eutrophication
Cleaning of land and building of towns and cities accelerates the land runoff through which more nutrients such as nitrogen and phosphorus are supplied to water resources that stimulate growth of algae. These algae bloom disrupts normal functioning of ecosystem. Death and decomposition of these algae uses a lot of oxygen resulting in hypoxia that kills water bodies.
Construction and Industrial sites:
Release of construction debris and dirt and other harmful chemicals from different construction sites are major source of water pollution. Addition of these wastes into waterways causes poisoning of aquatic life as well as of every animal that drink this water.
Industrial sources of eutrophication are considered as “point sources” of nutrient pollution as they directly discharge nutrients into water resources via pipes or other distinct routes. Fossil fuel combustion in different industries releases nitrogen oxide in atmosphere and contribute to the formation of smog and acid rain. Atmospheric deposition of nitrogen oxide is significant source of nitrogen into the water bodies and cause severe symptoms of eutrophication. As a point sources these are typically the easily controllable sources of nutrients and can be regulated.
Mainly fertilizers are composed of nitrogen, phosphorus, and potassium compounds. Addition of fertilizers in order to increase primary productivity, density and biomass of economically important fishes results in eutrophication of water as over abundance of nutrients from fertilizers causes Algae blooms. Through soil erosion, leaching of land fertilizers results in addition of nitrogen and phosphorus into the river and lakes that ultimately stimulate algae growth just as they stimulates plant growth in garden. Algae growth causes oxygen deficiency that leads to the death of aquatic inhabitants.
Decentralized septic system:
Septic systems are considered as a safe and effective treatment of wastewater but due to mismanagements in these systems they have become one potential source of water pollution. Mainly wastewater is composed of water along with nutrients, pathogens and other potential pollutants. Excessive dumping of macronutrients such as nitrogen and phosphorus-based compounds in water resources lead to eutrophication which stimulates the disproportionate growth of algae that ultimately results in hypoxia and overall deterioration of water quality.