Which environmental concern is primarily associated with algal blooms in water bodies?

The primary environmental concern associated with algal blooms in water bodies is oxygen depletion in the water. When algae proliferate excessively, often due to nutrient overload from sources such as agricultural runoff, they can lead to significant changes in the aquatic ecosystem. As these algae die and decompose, the decomposition process consumes a large amount of dissolved oxygen in the water. This reduction in oxygen levels can create a hypoxic environment, which is detrimental to aquatic life, including fish and other organisms that rely on oxygen for survival.

In contrast, increased fish spawning rates, decreased water temperature, and improved clarity of water sources do not align with the consequences of algal blooms. In fact, algal blooms can detrimentally affect fish reproduction, contribute to warming due to reduced light penetration, and cause water clarity to decrease, making them significant environmental hazards rather than beneficial phenomena.