Macroinvertebrate community dynamics in the Potrerillos stream (Colombia): Response to seasonal flow changes

• Published in: Limnetica Vol. 29; no. 2; pp. 195 - 210
• Main Authors: Magnolia Longo, S, Hilldier Zamora, G, Castor Guisande, G, John Jairo Ramirez, R
• Format: Journal Article
• Language: English; Spanish
• Published: 01.12.2010
• Subjects: Colombia
• ISSN: 0213-8409

Between January and December 2006 monthly samplings of benthic macroinvertebrates in two sampling stations were conducted in the Potrerillos stream. This article presents the analysis of the spatial and temporal changes in the composition and structure of this community as a function of the seasonality of rains in a drywood tropical region. It was determined that the periods of scant and moderate rains were beneficial to processes of colonization and development of different taxa, as these periods presented the highest values of abundance, richness and diversity (H'). This last concept was related to a continuous flow of low variability, which favored the heterogeneity of habitats, favorable levels of physical and chemical variables, and the availability of higher food supply. During the dry season, the flow ceased and several isolated ponds were formed, habitats and food were lost, physical and chemical conditions were altered, many taxa disappeared and the taxa best adapted to lenitic zones and moist substrates were dominant. The abundant rains brought new hydrologic dynamics, which, though they generated unstable habitats and microhabitats, allowed for the colonization of organisms, mainly those with winged instars, which increased richness and diversity. Despite that disturbances caused by drought and abundant rains caused fluctuations in the habitats' characteristics and in the composition and structure of the community, the ecosystem was stable and resilient with reference to these community attributes.Original Abstract: Entre enero y diciembre de 2006 se Ilevaron a cabo muestreos mensuales de macroinvertebrados bentonicos en dos estaciones de muestreo en la quebrada Potrerillos. Este articulo presenta el analisis de los cambios espaciales y temporales en la composition y estructura de esta comunidad en funcion de la estacionalidad de las Iluvias en una region de bosque seco tropical. Se determino que los periodos de Iluvia escasa y moderada beneficiaron procesos de colonization y desarrollo de diversos taxa, presentando estas epocas los valores mas altos de abundancia, riqueza y diversidad (H'). Lo anterior se relaciono con un caudal continuo y poco variable, que favorecio la heterogeneidad de habitats, niveles propicios de variables fisicas y quimicas y la disponibilidad de mayor oferta alimenticia. En la epoca de sequia ceso el caudal y se formaron pozos aislados, hubo perdida de habitats y de alimento, se alteraron las condiciones fisicoquimicas, desaparecieron muchos taxa y dominaron los mejor adaptados a zonas leniticas y sustratos humedos. Las Iluvias abundantes trajeron una nueva dinamica hidrica, que aunque generaron habitats y microhabitats inestables, permitio la colonization de organismos, principalmente de aquellos con estadios alados, lo que incremento la riqueza y diversidad. A pesar que los disturbios por la sequia y las Iluvias abundantes ocasionaron fluctuaciones en las caracteristicas de los habitats y en la composicion y estructura de la comunidad, el ecosistemafue estable y resiliente en lo referente a estos atributos comunitarios.