How do fertilizers affect aquatic environments?

Fertilizers primarily contain nutrients such as nitrogen and phosphorus, which, when washed into aquatic environments, can stimulate excessive growth of algae, a process known as eutrophication. This rapid increase in algal blooms can deplete oxygen levels in the water, as the decay of the algae consumes oxygen from the water, leading to hypoxic or anoxic conditions. Such low oxygen levels can result in negative impacts on aquatic life, causing fish kills and reducing biodiversity. Therefore, the impact of fertilizers on aquatic ecosystems is closely linked to the phenomenon of eutrophication and the subsequent changes in oxygen levels, making it the most accurate choice.