Do scrapers increase downstream? Patterns in southeastern Australian streams

Abstract

We measured scraper biomass and relative abundance and epilithic chlorophyll and organic matter on a single occasion at 17 sites ranging from order 1 to order 4 on five streams in southeastern Australia. Biomass of invertebrate scrapers was not related to chlorophyll concentration and was negatively related to epilithic organic matter. Neither scraper biomass nor relative proportion of scrapers increased downstream as predicted by the river continuum concept, and a power analysis indicated a greater than 90% probability that there was no relationship between either parameter and either stream order and upstream catchment area. We conclude that scraper biomass does not depend on algal standing crop as predicted by the RCC but is more likely to be influenced by total epilithon.

Keywords: stream, invertebrate scraper, epilithon, functional feeding group

Journal of Aquatic Sciences Vol. 21(1) 2006: 33-41