CHANGES IN THE TROPHIC STRUCTURE OF BENTHIC MACROINVERTEBRATE COMMUNITIES ASSOCIATED WITH FOOD AVAILABILITY AND STREAM-FLOW VARIATIONS

Macroinvertebrate communities were studied in relation to food (partic ulate organic matter and periphyton) availability and hydrologic regim e in two reaches (autotrophic and heterotrophic) of the Aguera stream (Northern Spain). The structure of macroinvertebrate community reflect ed the trophic characteristics (main food sources) at each site. From a temporal point of view both food availability and hydrologic regime seem to be the main factors that determine the dynamics and structure of the community. In the autotrophic reach, shredder density showed si gnificant relationship with CPOM, and scrapers with periphyton both in terms of density and biomass.