Which of the following is NOT commonly used to deal with the side effects of eutrophication in lakes?

The correct answer is that adding nitrates is not commonly used to deal with the side effects of eutrophication in lakes. Eutrophication occurs when excessive nutrients, primarily phosphorus and nitrogen, enter a water body, leading to algal blooms and subsequent depletion of oxygen, which can harm aquatic life. Adding nitrates would only exacerbate the problem, as it would contribute to the nutrient overload that causes eutrophication in the first place.

In contrast, applying herbicides can directly target and manage the growth of nuisance plant species that flourish due to nutrient overload. Dredging lakes helps remove accumulated organic material and sediment that can contain nutrients, improving water quality and habitat conditions. Pumping oxygen into the deeper layers of water can alleviate hypoxia (low oxygen levels) which is a result of decomposition of dead algae after blooms, helping to create a more balanced ecosystem for aquatic organisms. Thus, adding nitrates would not help but rather worsen the situation, making it a solution that is not used to mitigate eutrophication impacts.