Practice AP Environmental Science questions on point and nonpoint pollution sources, identifiable discharges, pesticide spraying, and urban runoff.
Researchers are studying the stream ecosystem shown in the following diagram. They have identified five different zones based on the dissolved oxygen levels and biological oxygen demand as the water flows downstream. Biological oxygen demand is the amount of oxygen needed by bacteria and other microorganisms to break down organic material in water. Some of the most common fish and macroinvertebrate species found in each zone are listed in the diagram.
Dissolved Oxygen and Biological Oxygen Demand in a Stream Ecosystem
Based on the information in the diagram, identify the zone where there is most likely point-source water pollution discharged into the stream.
The research team is interested in investigating the relationship between dissolved oxygen levels and macroinvertebrate species richness in the stream. Researchers counted the number of macroinvertebrate species in zones A, B, and C during the summer months. The researchers selected zone A to serve as the control in the investigation.