Aim Little is known about factors affecting the elevational and longitudinal zonation of tropical Andean stream communities. We investigated epilithon, macroinvertebrate and fish assemblages along a 4100-m elevational-longitudinal gradient in an Andean headwater of the Amazon Basin. We interpret our results within the context of environmental factors, emphasizing temperature, as well as ecological theory relating shifts in metazoan functional feeding groups to shifts in basal resources along the fluvial continuum.Location Araz a-Inambari-Madre de Dios watershed, south-eastern Peru.Methods We sampled water physicochemistry, epilithon and macroinvertebrate diversity and abundance, and fish diversity at 18 main-stem and 14 tributary sites from high puna grasslands (4300 m a.s.l.) to Amazon Basin lowlands (200 m a.s.l.). ResultsWater physicochemical parameters and the taxonomic and ecological structure of invertebrate and fish assemblages displayed mostly nonlinear responses to elevation: water temperature and percentage of macroinvertebrate taxa identified as leaf shredders had U-shaped responses; dissolved oxygen and percentage of macroinvertebrate taxa identified as grazers had hump-shaped responses. Epilithon richness increased slightly with elevation whereas macroinvertebrate and fish richness decreased.Main conclusions Elevational gradients in physicochemical parameters are insufficient to explain abrupt and nonlinear shifts in community taxonomic and functional structure. Rather, trophic interactions, including predation and longitudinal turnover in basal food resources, seem to exert a stronger influence on the distributions of Andean aquatic organisms. A steep elevational decline in relative taxonomic diversity of leaf-shredding (versus algae-grazing) insects supports the hypothesis that temperature affects the functional composition of insect assemblages via its influence on microbial decomposition rates. This relationship, and the distributions of several insect and fish species across narrow elevational bands, suggests that Andean stream communities may be sensitive to global warming. Placer mining and road building impacts have already altered stream community structure, including the absence of many benthic species from low-elevation habitats.

Peru is one of the megadiverse countries worldwide, displaying a great diversity of ecosystems due to its tropical location, marine currents, and complex relief, which jointly define environments differentiated by altitude and climatic conditions. The arid and semi-arid ecosystems comprising xeric and Andean shrublands, coastal deserts, and coastal hills, illustrate this diversity of ecosystems; these stretch over 177 358 km2, representing 13.8% of the Peruvian territory. Several studies on aquatic macroinvertebrates are being conducted in these ecosystems; although not so numerous yet, have shown a rise in recent years. The objective of this work was to determine the composition and distribution of aquatic macroinvertebrates in the arid and semi-arid ecosystems of Peru. To this end, we conducted a literature survey; the articles and theses found were reviewed and analyzed. The following keywords were used: macroinvertebrates, macrozoobenthos, bioindicators, diversity of aquatic organisms, and water quality; we used the Google Academic search engine, Scopus, Web of Science, ResearchGate and the thesis repositories of Peruvian universities, additionally a thesis from the University of Barcelona. Of a total of 53 sources of information, 38 are theses and 15 are scientific articles conducted from 1992 to 2020, referring to studies conducted at elevations ranging from 0 to 3,831 m asl. Most studies were conducted at the Lima and La Libertad departments, resulting in 20 and 10 publications, respectively. The topics addressed most frequently were bioindication, biodiversity, taxonomy, and distribution. Most theses were carried in the Universidad Nacional de Trujillo and the Universidad Nacional Mayor de San Marcos, with 12 and 10 theses, respectively. The period 2011–2020 records the largest number of publications (40). According to the type of aquatic ecosystem, rivers (38) were the systems most intensively studied, followed by coastal wetlands (14) and lagoons (2); to note, one thesis studied two types of ecosystems. Specimens were collected mainly with the Surber and D nets; as a result, seven phyla, 10 classes, 39 orders, and 118 families were reported. The highest richness of families corresponds to rivers (110), followed by coastal wetlands (57), and lagoons (12). The western hydrographic slope recorded the highest richness at phylum, class, order, and family levels, likely because most investigations were conducted in this slope. On the other hand, the phyla Cnidaria, Nematoda, and Nematomorpha were not recorded in the eastern slope, which showed fewer orders (19) relative to the western slope (39). A similar trend is observed at the family level: of the 118 families recorded, 59 were reported for the eastern slope. The most common families at both sides were Chironomidae, Baetidae, Simuliidae, Elmidae, Hydrophilidae, Libellulidae, Physidae, Dytiscidae, Ceratopogonidae, Coenagrionidae, Hydroptilidae, Hydropsychidae, and Tipulidae. Separately, the most common families in all types of aquatic ecosystems were Chironomidae, Baetidae, and Dytiscidae. It is recommended to further promote studies on macroinvertebrates living in the eastern slope, addressing taxonomic, and ecological topics, as well as broadening the approach to an integral ecosystem view. Finally, the biotic indices should be calibrated and validated for the main hydrographic basins. This work is an initial effort to review, systematize, analyze, and gather the results of studies on aquatic macroinvertebrates in Peru, particularly in arid and semi-arid ecosystems.

Se evaluaron 10 cuerpos de agua en los Humedales de Ventanilla ubicados en la región Callao, en Perú, en los meses de marzo y agosto del 2018. Se tuvo como objetivo el estudio de la comunidad de macroinvertebrados acuáticos y su aplicación para determinar la calidad de agua. Para ello se registraron parámetros fisicoquímicos in situ y para la colecta biológica se utilizó una red D-net de 500µm. Los valores de los parámetros fisicoquímicos estuvieron de acuerdo con lo recomendado en la normativa nacional, con excepción de la conductividad eléctrica, que superó el límite en los cuerpos de agua cercanos al mar. Los macroinvertebrados acuáticos estuvieron representados por 17 taxones entre gasterópodos y artrópodos de los cuales los primeros fueron los más abundantes (85,5% en marzo con 2555 organismos/m2 y 74,2% en agosto con 4422 organismos/m2), y los segundos, los más diversos. El Índice Biótico con Macroinvertebrados para los Humedales de Wisconsin (WWMBI por sus siglas en inglés) categorizó los cuerpos de agua como de calidad “muy pobre” y “pobre” debido probablemente a la presencia de materia orgánica, dominancia de gasterópodos o contaminación por metales pesados. Finalmente se reportó que la conductividad eléctrica influyó en la distribución de los macroinvertebrados acuáticos. Asimismo, se sugiere elaborar índices bióticos para humedales costeros de nuestro país.

con lombrices Eisenia fetida y la aplicación del protocolo CERA con macroinvertebrados, con el objetivo de evalua r el estado ecológico del río Chonta en sus partes alta y media. Pa ra ello se establecieron cinco estaciones de monitoreo: cuatro de contro l (M-1, M-3, M-4, M-5) y una de referencia (M-2). Cabe menciona r que la estación M1 presenta impactos por la actividad minera. L o s metales analizados en sedimentos fueron: As, Cd, Pb, Hg, Ni, Z n, Cu y Cr, cuyos resultados fueron comparados con los valores umbra les establecidos en los estándares canadienses de calidad para sedimentos, valores TEL (ECA canadiense). Los resultados obtenidos fueron los siguientes: Al ser analizadas por las tres técnicas, las estaciones con mayor grado de contaminación fuero n M-1, M-4 y M-5; asimismo las concentraciones promedio de metales en sedimentos más altas obtenidas durante las 4 campañas fuero n para el Zn: 24.084 mg/kg, As: 12.15 mg/kg y Cd: 0.579 mg/kg en M-1. La estación M-1 presentó la mayor concentración en casi todos lo s metales analizados; en esta estación el As y Cd superaron los estándares canadienses para sedimentos valores TEL en todas la s campañas. También tenemos que el Cd excedió los ECA canadienses de sedimentos en M-1 (primera campaña: 0.974 mg /kg y cua rta campaña: 1.017 mg/kg), M-2 (cuarta campaña: 0.847 mg/kg), y M -3 (cuarta campaña: 0.959 mg/kg). Ninguno de los siguientes meta les superó los ECA canadienses para sedimentos: Ni, Zn, Cr, Cu, Pb y Hg. Por otro lado, el test de supervivencia determinó que los meta les tóxicos influyen en el crecimiento de las lombrices, así tenemos que la mayor pérdida de peso se registró en M-1 con -34.9%. Finalmente, las valoraciones del Protocolo CERA arrojaron calidades ecológica s que van de pésimas en todas las campañas para M-1, M-4 y M-5 a sí como malas para M-3, y regular en promedio para M-2.