Global metrics of land cover and land use provide a fundamental basis to examine the spatial variability of human-induced impacts on freshwater ecosystems. However, microscale processes and site specific conditions related to bank vegetation, pollution sources, adjacent land use and water uses can have important influences on ecosystem conditions, in particular in smaller tributary rivers. Compared to larger order rivers, these low-order streams and rivers are more numerous, yet often under-monitored. The present study explored the relationship of nutrient concentrations in 150 streams in 57 hydrological basins in South, Central and North America (Buenos Aires, Curitiba, São Paulo, Rio de Janeiro, Mexico City and Vancouver) with macroscale information available from global datasets and microscale data acquired by trained citizen scientists. Average sub-basin phosphate (P-PO4) concentrations were found to be well correlated with sub-basin attributes on both macro and microscales, while the relationships between sub-basin attributes and nitrate (N-NO3) concentrations were limited. A phosphate threshold for eutrophic conditions (>0.1 mg L-1 P-PO4) was exceeded in basins where microscale point source discharge points (eg. residential, industrial, urban/road) were identified in more than 86% of stream reaches monitored by citizen scientists. The presence of bankside vegetation covaried (rho = –0.53) with lower phosphate concentrations in the ecosystems studied. Macroscale information on nutrient loading allowed for a strong separation between basins with and without eutrophic conditions. Most importantly, the combination of macroscale and microscale information acquired increased our ability to explain sub-basin variability of P-PO4 concentrations. The identification of microscale point sources and bank vegetation conditions by citizen scientists provided important information that local authorities could use to improve their management of lower order river ecosystems.
Primer registro de Cloeon dipterum (L.) (Ephemeroptera: Baetidae) en Buenos Aires, Argentina RESUMEN. Cloeon dipterum (L.) (Ephemeroptera: Baetidae) está ampliamente distribuido en las zonas templadas de Eurasia, sin embargo, está restringido en América del Norte a tres estados de Estados Unidos y Canadá, y en América del Sur a Chile. Con el fin de confirmar nuestra hipótesis de que se introdujo recientemente en Argentina, el objetivo del presente estudio fue identificar la especie en base a análisis moleculares y caracteres morfológicos. Para ello se recolectaron ninfas de tres hábitats artificiales en diferentes localidades de la provincia de Buenos Aires y de dos arroyos afluentes del Río Luján, al noreste de Buenos Aires (Argentina). Todas las ninfas fueron identificadas como C. dipterum, lo que confirma la presencia de la especie en Argentina. La distribución de C. dipterum en Buenos Aires junto a su ausencia en los sitios previamente muestreados de manera regular, indicarían que los individuos registrados son introducidos y están bien establecidos en la zona de estudio. PALABRAS CLAVE. Cuerpos de agua neotropicales. Especie exótica. Insectos acuáticos. ABSTRACT. Cloeon dipterum (L.) (Ephemeroptera: Baetidae) is widely distributed in temperate areas of Eurasia, whereas, in North America, it is restricted to three states of the USA and Canada, and, in South America to Chile. To confirm our hypothesis that C. dipterum has been recently introduced in Argentina, the aim of the present study was to identify the species based on molecular analyses and morphological features. To this end, nymphs were collected from three artificial habitats located in different localities of Buenos Aires province and two tributary streams of the Luján River, northeast of Buenos Aires, Argentina. Nymphs were all identified as belonging to C. dipterum thus confirming the presence of the species in Argentina. The distribution of C. dipterum in Buenos Aires, together with its absence from previously sampled sites, would indicate that the individuals recorded are introduced and already well established in the study area.
Indicators of ecosystem health are effective tools to assess freshwater ecosystem impairment. However, they are scarcely used as a monitoring tool by local environmental agencies in Argentina. Here, we review the literature to analyze the use of ecosystem health indicators in freshwaters from Argentina. We found 91 scientific articles relating to the use of ecological indices to assess the impact of different environmental stressors in aquatic environments published between 1996 and 2019. We generated Google Earth map where we deployed the sampling sites and type of indices reported by each article. As biological indices were the most used, we also surveyed bioindication experts to gather information on their application. We found that most studies were concentrated mainly in Pampas (34%), Dry Chaco (20%), Espinal (12%), and Patagonian Steppe (10%) ecoregions. Biological indices (mainly with invertebrates) were more used than geomorphological or physico-chemical indices. Indices resulted useful to evaluate the impact of stressors in 63% of cases, being land use the most studied stressor. However, sampling design varied greatly among studies, making their comparison difficult. The information compiled here could help to the design of monitoring protocols, the adoption of regional indices, and the creation of a national inventory of ecosystem health status, which are mandatory to propose well-grounded conservation and management policies for freshwaters in Argentina.
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