Stream Bryophyte Group. 1999. Journal of the North American Benthological Society 18:151–184.
Aquatic bryophytes are a common but often overlooked component of a wide variety of stream ecosystems. Although stream environments present a number of challenges for bryophyte reproduction and survival, some bryophytes have characteristics that allow them to persist in a wide variety of stream types (e.g., adaptations to low light and temperature, rapid nutrient uptake, resistance to scouring and spates). Primary production by aquatic bryophytes can equal or exceed that by epilithic and periphytic algae, which have been much more widely studied. Also, it is clear that bryophytes can profoundly influence both the abundance and community structure of stream invertebrates. However, a number of fundamentally important roles of bryophytes in stream ecosystems remain unexamined. Very little is known, for example, about the dynamics of nutrient uptake by bryophytes. The dynamics of nutrient regeneration from decomposing bryophyte tissues are essentially unknown. Nor is it known whether bryophytes increase or decrease the habitat quality for stream trophic levels other than stream invertebrates. For example, ecological interactions between bryophytes and epiphytic microorganisms are potentially important but unknown. Similarly, it is not clear whether fish benefit from the increased abundance of insects often observed when bryophytes are present in streams. The purpose of this review is to summarize the existing literature on the functions of bryophytes as important ecosystem components, rather than as simple environmental indicators. We hope that this information will foster a greater appreciation for the potential functions of these organisms, and will stimulate additional research that will improve our knowledge of whole-stream ecosystem dynamics.