Which organisms indicate good water quality in streams?

Organisms that indicate good water quality in streams are typically sensitive to pollution and require well-oxygenated, clean water to thrive. Scuds and crane flies are excellent bioindicators of healthy aquatic ecosystems. Scuds, also known as amphipods, are small crustaceans that live in clean environments, while crane flies, which resemble large mosquitoes, have larvae that develop in unpolluted water with adequate oxygen levels. Their presence suggests a balanced ecosystem rich in biodiversity.

In contrast, other groups such as roaches and leeches may tolerate a range of water quality conditions, including polluted environments. Algae and moss can thrive in both good and poor conditions, making them less reliable indicators. Catfish and frogs can be found in a variety of habitats, not all of which indicate high water quality, as they can often survive in less ideal conditions. Thus, scuds and crane flies stand out as indicators of good water quality due to their sensitivity to environmental changes.