Destratification of a lake will often reduce:

• A. Fish populations
• B. Algae
• C. Water temperature variation
• D. Oxygen levels

Answer: (B)

Destratification of a lake primarily involves mixing the water layers to promote uniform temperature and oxygen distribution throughout. In many cases, this process is intended to combat issues associated with stratified layers that can lead to anoxic conditions, especially in the deeper waters of the lake.

When a lake is stratified, warmer water sits above cooler, denser water, which can limit the mixing that typically replenishes oxygen at lower depths. This stratification can result in an increase in nutrients and algae blooms, particularly in the warmer upper layer. By destratifying the lake, you can reduce the prevalence of conditions that favor algae growth. The more even distribution of temperature and nutrients can help limit excessive algal blooms that often deplete oxygen and deteriorate water quality.

In this sense, destratification serves as a means to improve overall water quality and directly impacts the productivity of algae in the water column. Other factors, like fish populations, water temperature variation, and oxygen levels, may see changes as a result of destratification, but the primary effect relates to algae, making this the most accurate choice in the context of the question.