If you analyzed the invertebrates in a stream and found and
abundant supply of caddisflies and dragon fly larvae, what minimum
concentration of dissolved oxygen might be present in the stream.
The survive with much less oxygen
To determine the minimum concentration of dissolved oxygen in the stream with an abundant supply of caddisflies and dragonfly larvae, it is important to understand the oxygen needs and tolerance levels of these organisms.
Caddisflies and dragonfly larvae are aquatic invertebrates that have different oxygen requirements. Caddisflies belong to the order Trichoptera, and their larvae are well adapted to living in streams and rivers. These larvae have gills that extract oxygen from the water. Dragonfly larvae, on the other hand, belong to the order Odonata and also have gills to obtain oxygen.
While there may not be a specific minimum concentration of dissolved oxygen that guarantees the presence of caddisflies and dragonfly larvae, it is likely that the stream would need to have sufficient oxygen levels for their survival. Generally, a dissolved oxygen concentration of at least 5 mg/L (milligrams per liter) is considered suitable for most aquatic organisms.
However, caddisflies and dragonfly larvae have developed adaptations that allow them to tolerate lower dissolved oxygen concentrations compared to other organisms. They can withstand oxygen levels as low as 3 mg/L or even less, depending on the species and their stage of development.
It is important to note that the presence of these organisms alone does not provide an exact measurement of the dissolved oxygen concentration. Monitoring the dissolved oxygen levels directly using field meters or conducting laboratory tests is necessary for accurate measurements.
Therefore, to determine the precise dissolved oxygen concentration in the stream, it is recommended to use an oxygen probe, perform water sampling, and measure the dissolved oxygen levels in the laboratory.