ESTRUCTURA TRÓFICA DE LA COMUNIDAD DE MACROINVERTEBRADOS ACUÁTICOS EN ARROYOS DE LA ORINOQUÍA COLOMBIANA.

A characterization of the trophic groups of the invertebrate communities in three streams and channels of the alluvial plains of the Colombian Orinoquia is presented. The sampling of the communities was carried out in three streams during July (2016), October (2016), and January (2017). Physicochemical [temperature (°C), dissolved oxygen (mg l-1 O2), pH, conductivity (μS cm-1), ammonia (μg l-1 NH4+), and phosphates (μg l-1PO4-)] and hydrological (flow m3 s-1) variables were measured. In 50 m reaches of each sampling site, five samples of macroinvertebrates were taken in rocky substrates. Organisms were identified, and diversity was determined using the Shannon index. The comparison between sampling points was made using the Morisita-Horn index and the multivariate analysis between temporality, physicochemical variables, and organisms was performed with the Redundancy Analysis (RDA). The stomach contents of the collected individuals were identified for the more representative genera, and each genus was assigned to a specific trophic group according to their intestinal contents and mouthparts. The Collectors-Gatherers were the most abundant group in the three streams, and their high number was maintained during all the samplings. However, their abundance and richness reached their maximum peak during the dry season. The RDA indicated that water flow and temperature partially explain the temporal variation in the occurrence and abundance of the different trophic groups. In general, the findings show that organisms adapt their diet to the offer available in their environment, and therefore it is important to classify them trophically in the different ecosystems. [ABSTRACT FROM AUTHOR]