Aquatic Fauna in the Driest Desert on Earth: First Report on the Crustacean Fauna of the Loa River (Atacama Desert, Antofagasta Region, Chile)

[The longest river in Chile, the Loa, is in fact found in the Atacama Desert in the far north of the country. Being an important resource for the dry Antofagasta region, this river experiences high anthropogenic impacts due to water use for mining, urban, and agricultural activities. Unfortunately, few biological surveys have been conducted in the Loa, and the invertebrate fauna in particular is poorly known. The aim of this study is to characterize the microcrustacean species associations at various sites of the Loa River and some of its tributaries. Unexpectedly high species richness was detected at high-altitude sites, where the amphipods Hyalella fossamanchini and H. kochi were reported. At low-altitude sites only the ostracod Heterocypris panningi was found. No significant correlation was detected between species richness and salinity, nor between richness and conductivity. Although a null model community analysis indicated that the microcrustacean species associations in the Loa are largely random, species richness and altitude were significantly and positively correlated. Potential causes of this pattern include the accumulation of nutrients and pollution along the course of the river, as well as increasing temperatures in the lower-altitude zones of the river. The biogeography of the constituent members of the Loa fauna is discussed. El rio Loa, es el mas largo de Chile, y se encuentra localizado en la region de Antofagasta, en el desierto de Atacama, este rio tiene mucha intervencion antropica debido al uso de sus aguas por industrias mineras, asi como usos domesticos y agricolas. Desafortunadamente hay pocos estudios sobre sus componentes biologicos. El objetivo del presente trabajo consistio en estudiar los ensambles de crustaceos en diferentes zonas del rio Loa y algunos de sus afluentes. Los resultados revelaron una alta riqueza de especies principalmente en zonas altas del rio, donde se reportaron principalmente los anfipodos Hyalella fossamanchini y H. kochi , mientras que en zonas bajas solo se reporto el ostracodo Heterocypris panningi . No obstante, no hubo correlaciones significativas entre el numero de especies con salinidad, hubo una correlacion debil pero no significativa entre riqueza de especies y conductividad, y una correlacion significativa entre riqueza de especies y altitud. Los resultados del modelo nulo indicaron la presencia de factores aleatorios en la regulacion de las asociaciones de especies. Una posible razon, seria la potencial acumulacion de nutrientes y contaminantes, asi como altas temperaturas en zonas bajas del rio. Se discutieron topicos ecologicos y biogeograficos. , The longest river in Chile, the Loa, is in fact found in the Atacama Desert in the far north of the country. Being an important resource for the dry Antofagasta region, this river experiences high anthropogenic impacts due to water use for mining, urban, and agricultural activities. Unfortunately, few biological surveys have been conducted in the Loa, and the invertebrate fauna in particular is poorly known. The aim of this study is to characterize the microcrustacean species associations at various sites of the Loa River and some of its tributaries. Unexpectedly high species richness was detected at high-altitude sites, where the amphipods Hyalella fossamanchini and H. kochi were reported. At low-altitude sites only the ostracod Heterocypris panningi was found. No significant correlation was detected between species richness and salinity, nor between richness and conductivity. Although a null model community analysis indicated that the microcrustacean species associations in the Loa are largely random, species richness and altitude were significantly and positively correlated. Potential causes of this pattern include the accumulation of nutrients and pollution along the course of the river, as well as increasing temperatures in the lower-altitude zones of the river. The biogeography of the constituent members of the Loa fauna is discussed. El rio Loa, es el mas largo de Chile, y se encuentra localizado en la region de Antofagasta, en el desierto de Atacama, este rio tiene mucha intervencion antropica debido al uso de sus aguas por industrias mineras, asi como usos domesticos y agricolas. Desafortunadamente hay pocos estudios sobre sus componentes biologicos. El objetivo del presente trabajo consistio en estudiar los ensambles de crustaceos en diferentes zonas del rio Loa y algunos de sus afluentes. Los resultados revelaron una alta riqueza de especies principalmente en zonas altas del rio, donde se reportaron principalmente los anfipodos Hyalella fossamanchini y H. kochi , mientras que en zonas bajas solo se reporto el ostracodo Heterocypris panningi . No obstante, no hubo correlaciones significativas entre el numero de especies con salinidad, hubo una correlacion debil pero no significativa entre riqueza de especies y conductividad, y una correlacion significativa entre riqueza de especies y altitud. Los resultados del modelo nulo indicaron la presencia de factores aleatorios en la regulacion de las asociaciones de especies. Una posible razon, seria la potencial acumulacion de nutrientes y contaminantes, asi como altas temperaturas en zonas bajas del rio. Se discutieron topicos ecologicos y biogeograficos. ]