What is the primary purpose of using turbidity in water quality assessments?

The primary purpose of using turbidity in water quality assessments is to evaluate light penetration in water. Turbidity refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. High turbidity levels can significantly reduce light penetration, which is essential for aquatic plants, particularly those that require sunlight for photosynthesis.

When light penetration is impaired, it can adversely affect the growth of aquatic vegetation and disrupt the entire ecosystem. This, in turn, has implications for the organisms that rely on these plants for habitat and food. Thus, measuring turbidity provides crucial information about the conditions of the water, which helps in understanding the health of the aquatic environment.

While the other options involve important aspects of water quality, they do not relate directly to turbidity's main role in assessing light availability. Temperature, oxygen levels, and sediment composition are relevant factors in water quality, but they are measured through different parameters and instruments.