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Effects of local land-use on riparian vegetation, water quality, and the functional organization of macroinvertebrate assemblages

Land-use change is a principal factor affecting riparian vegetation and river biodiversity. In Chile, land-use change has drastically intensified over the last decade, with native forests converted to exotic forest plantations and agricultural land. However, the effects thereof on aquatic ecosystems are not well understood. Closing this knowledge gap first requires understanding how human perturbations affect riparian and stream biota. Identified biological indicators could then be applied to determine the health of fluvial ecosystems. Therefore, this study investigated the effects of land-use change on the health of riparian and aquatic ecosystems by assessing riparian vegetation, water quality, benthic macroinvertebrate assemblages, and functional feeding groups. Twenty-one sites in catchment areas with different land-uses (i.e. pristine forests, native forests, exotic forest plantations, and agricultural land) were selected and sampled during the 2010 to 2012 dry seasons. Riparian vegetation quality was highest in pristine forests. Per the modified Macroinvertebrate Family Biotic Index for Chilean species, the best conditions existed in native forests and the worst in agricultural catchments. Water quality and macroinvertebrate assemblages significantly varied across land-use areas, with forest plantations and agricultural land having high nutrient concentrations, conductivity, suspended solids, and apparent color. Macroinvertebrate assemblage diversity was lowest for agricultural and exotic forest plantation catchments, with notable non-insect representation. Collector-gatherers were the most abundant functional feeding group, suggesting importance independent of land-use. Land-use areas showed no significant differences in functional feeding groups. In conclusion, anthropogenic land-use changes were detectable through riparian quality, water quality, and macroinvertebrate assemblages, but not through functional feeding groups. These data, particularly the riparian vegetation and macroinvertebrate assemblage parameters, could be applied towards the conservation and management of riparian ecosystems through land-use change studies.

Composición y sobreposición dietaria de Pinguipes chilensis (Perciformes: Pinguipedidae), Cheilodactylus variegatus (Perciformes: Cheilodactylidae) y Aplodactylus punctatus (Perciformes: Aplodactylidae) en el litoral costero valdiviano, Chile

Pinguipes chilensis, Cheilodactylus variegatus y Aplodactylus punctatus son especies comunes de ser registradas a lo largo de la costa chilena, no obstante informacion sobre su alimentacion es escasa para la zona sur de nuestro pais. Por ello, se analizo la composicion y sobreposicion dietaria de estas especies para la costa Valdiviana. Los resultados senalan que para el periodo primaveral del ano 2010, en P. chilensis (n=41) se identificaron 20 presas, todas caracterizadas por ser invertebrados de gran tamano, principalmente crustaceos (55%) y moluscos (40%), siendo la especie Homalaspis plana la mas representativa (IRI 70%). En Ch. variegatus (n=38) se identificaron 37 presas, mayoritariamente pequenos invertebrados, principalmente crustaceos (49%), moluscos (31%) y anelidos (10%). Dentro de estos ultimos dominaron los poliquetos de la Familia Nereidae (IRI 23,2%). En A. punctatus (n=32) la diversidad de algas rojas (50%) predomino sobre las pardas (41%) y verdes (9%), siendo identificadas 34 especies presa, donde Colpomenia sp. (Phaeophyta) fue la mas representativa (IRI 32,4%). El analisis de sobreposicion de dieta entre las tres especies mostro una baja similitud entre las dietas. Las tres especies analizadas en este estudio, se caracterizan por compartir un mismo habitat. P. chilensis y Ch. variegatus se muestran ambas como depredadores carnivoros generalistas, ya que las dos especies presentan un amplio espectro alimentario sin embargo la morfologia y el tamano de su boca influirian en el tamano de la presa que consumen. En cambio, A. punctatus se confirma como una especie herbivora especialista, ya que consume preferentemente algas rojas.

Macroinvertebrates and Fishes as Bioindicators of Stream Water Pollution

Freshwater ecosystems worldwide have been progressively deteriorated during the past decades due to an increasing human pressure that has lead to a decrease in aquatic biodiversity. Among the human activities of high impact on freshwater ecosystems is the land-use change, principally from native forests to agriculture. To evaluate the impacts of human activities on water quality, a traditional approach has considered the use of single physical-chemical parameters. However, this approach may be insufficient to fully assess the impact of these human activities on freshwaters. Therefore, there is a need for alternative tools such as the indices of biotic integrity that may provide a complement to traditional approaches. In the literature, there are several examples of biotic indicators that have shown promising results in evaluating water quality including the use of macroinvertebrates and fish diets. Here, we provide a review of the indicators of biotic integrity that included fish assemblages as well as macroinvertebrates as bioindicators. We identify pros and cons of using aquatic communities as indicators of water quality. Finally, we develop a procedure that combines fish and macroinvertebrate assemblages as bioindicators and discuss their effectiveness using illustrative examples from streams under several agricultural uses in the Mediterranean region of Chile.

Estructura de macroinvertebrados acuáticos y grupos funcionales tróficos en la cuenca del río Lluta, desierto de Atacama, Arica y Parinacota, Chile

espanolEl objetivo de este estudio fue determinar la estructura comunitaria de macroinvertebrados dulceacuicolas y caracterizar los grupos funcionales troficos en la cuenca del rio Lluta ubicado en el desierto de Atacama. Para esto se muestreo con una red Surber en 12 estaciones, abarcando desde la cabecera del rio hasta su desembocadura en la costa maritima durante noviembre de 2011. En este estudio se registraron 66 taxa de macroinvertebrados, correspondiendo en su mayoria a larvas de insectos (46). Los grupos con mayor riqueza fueron Diptera (20 taxa), Coleoptera y Trichoptera (ambos con 7 taxa). Respecto de la abundancia, Chironomidae fue la familia mas abundante del area de estudio. El grupo de los colectores-recolectores fue el mas representativo en 10 de las 12 estaciones, mientras que el grupo de los ramoneadores dominaron en las dos estaciones mas cercanas a la desembocadura. Nuestros resultados son los primeros en describir la fauna de macroinvertebrados dulceacuaticos en la cuenca mas extrema del norte de Chile, conteniendo una riqueza faunistica mucho mayor que otras cuencas deserticas. Ademas la gran representatividad de los colectores-recolectores que se alimentan de fragmentos organicos menores a 1 mm depositados en el fondo, demuestran la importancia de este recurso alimentario en rios del desierto de Atacama. EnglishThe aim of this study was to determine the community structure of freshwater macroinvertebrates and characterize trophic functional groups in the Lluta river basin located in the Atacama Desert. To this was sampled with Surber sampling in 12 stations, in extension from the source to its mouth on the coast during November 2011. In this study 66 taxa of macroinvertebrates were recorded, corresponding mostly insect larvae (46). The groups with the greatest wealth were Diptera (20 taxa), Coleoptera and Trichoptera (both with 7 taxa). On abundance, Chironomidae was the most abundant family of the study area. The group of collectors-gatherers was the most representative in 10 of the 12 stations, while the group of browsers dominated the two closest stations to the mouth. Our results are the first to describe the fauna of macroinvertebrates dulceacuaticos in extreme northern Chile basin, containing a much higher than other rich fauna desert basins. Besides the great representative of the collectors-gatherers that feed on organic fragments under 1 mm deposited on the bottom, showing the importance of this food source in the Atacama desert rivers.