The concentration of nitrogen and phosphorus in agricultural runoff can significantly affect the growth of harmful algal blooms HABs in nearby bodies of water. These nutrients, primarily in the form of nitrates and phosphates, are essential for the growth and reproduction of algae. When there is an excess of these nutrients in the water, it can lead to a rapid increase in algal populations, resulting in algal blooms.Harmful algal blooms can have detrimental effects on aquatic ecosystems, as they can deplete oxygen levels in the water, release toxins, and block sunlight from reaching submerged aquatic vegetation. This can lead to the death of fish and other aquatic organisms, as well as pose risks to human health and the economy.There are several chemical treatments that can be used to remediate the issue of harmful algal blooms caused by agricultural runoff:1. Phosphorus precipitation: Adding chemicals like alum aluminum sulfate or ferric chloride can help precipitate phosphorus in the water, making it unavailable for algal growth. This process can help reduce the overall phosphorus concentration in the water and limit the growth of HABs.2. Nitrogen removal: Denitrification, the process of converting nitrates to nitrogen gas, can be facilitated by adding chemicals like sodium nitrate or calcium nitrate to the water. This can help reduce the overall nitrogen concentration in the water and limit the growth of HABs.3. Algaecides: Chemicals like copper sulfate or hydrogen peroxide can be used to directly target and kill algae in the water. However, these chemicals can also have negative effects on non-target organisms and should be used cautiously.4. Oxygenation: Increasing the oxygen levels in the water can help promote the growth of beneficial bacteria that can outcompete algae for nutrients. This can be achieved by adding chemicals like hydrogen peroxide or potassium permanganate to the water.It is important to note that these chemical treatments should be used in conjunction with other management practices, such as reducing nutrient inputs from agricultural runoff through the implementation of best management practices BMPs like buffer strips, cover crops, and nutrient management plans. This can help prevent the occurrence of harmful algal blooms and protect the health of aquatic ecosystems.