Which of the following statements about algal blooms is true?

Algal blooms can indeed be of relatively short duration, which is a significant characteristic of these phenomena. Typically, environmental conditions such as nutrient availability, water temperature, and light influence the growth of algae. When these conditions are favorable, algae can proliferate rapidly, leading to a bloom. However, once the conditions change—such as a depletion of nutrients or changes in temperature—these blooms can dissipate quickly, re-emphasizing their potentially transient nature.

While certain algal blooms can be harmful or toxic to aquatic life, they are not universally harmful, making the first statement misleading. Additionally, while soil erosion can contribute to an excess of nutrients that may lead to algal blooms, it is not the sole cause; therefore, the third statement oversimplifies the issue. Lastly, algal blooms do not improve water quality; in many cases, they can lead to degradation of water quality, especially when they deplete oxygen levels or produce toxins. Thus, the choice correctly identifying that algal blooms can occur over a relatively short time frame stands out as the accurate statement.