Which nutrient, when found in excessive amounts in water bodies, can lead to algal blooms?

Nitrogen is a key nutrient that, when present in excessive amounts in aquatic environments, can lead to significant ecological problems such as algal blooms. These blooms occur because nitrogen acts as a fertilizer, stimulating the rapid growth of algae. Algal blooms can deplete oxygen levels in the water when the algae die and decompose, leading to hypoxic or anoxic conditions which are detrimental to aquatic life. Furthermore, some algal species produce toxins that can be harmful to fish, other wildlife, and even humans, contributing to water quality issues and impacting recreational activities.

Potassium and calcium are essential nutrients for aquatic organisms but do not typically cause algal blooms in the same way nitrogen does. Selenium, while also a trace element required by organisms, primarily poses toxicity concerns at certain concentrations rather than being linked to algal proliferation. Thus, nitrogen is specifically associated with the phenomenon of algal blooms due to its role in promoting excessive growth in aquatic systems.