The importance of meiofauna to lotic ecosystem functioning

1. Although meiofauna occur in large numbers in many streams, almost nothin g is known about their functional role. 2. In other systems, meiofauna influence microbial and organic matter dynam ics through consumption and bioturbation. Given that these are important pr ocesses in streams, meiofauna have the potential to influence lotic functio n by changing the quality and availability of organic matter as well as the number and biotic activity of benthic microbes. Selective feeding by meiof auna has the potential to alter the availability of nutrients and organic c arbon. 3. Meiofauna generally contribute only a small amount to metazoan productio n and biomass in streams, although exceptions occur. Within a stream, the r elative importance of meiofauna may reflect whether the temporary or perman ent meiofauna dominate the meiobenthos as well as the season when samples a re collected. 4. We suggest stream conditions (small sediment grain size, restricted inte rstitial flow) under which meiofauna have the greatest likelihood of influe ncing stream ecosystem function. 5. Important areas for future research include addressing whether meiofauna feed selectively, whether meiofauna are links or sinks for carbon in strea ms, and whether bioturbation by meiofauna influences stream ecosystem proce sses in a predictable manner.