What are indicators of herbicide over-application in aquatic environments?

Herbicide over-application in aquatic environments can lead to serious ecological issues, with algal blooms and fish kills being primary indicators of such detrimental effects. When herbicides are excessively applied, they not only target the intended aquatic plants but can also disrupt the water's chemical balance, resulting in nutrient overload. This nutrient surge often leads to algal blooms—massive growths of algae that can deplete oxygen levels in the water as they die and decompose. The subsequent drop in oxygen can lead to fish kills, as aquatic life struggles to survive in hypoxic conditions.

In contrast, increased fish populations would not typically be associated with herbicide over-application; instead, herbicides are more likely to harm the aquatic ecosystem. No significant changes in the ecosystem would suggest that herbicides are being used appropriately and not in excess. Rapid plant growth could occur in some cases, but this would generally depend on the specific circumstances and does not directly indicate over-application. Thus, observing algal blooms and fish kills is a clear sign of an unhealthy approach to herbicide application in aquatic environments.