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RESUMEN La interpretación de la diversidad biológica puede resultar muy compleja, ya que existe una dinámica basada en el origen y en la diversificación de las especies, así como en los efectos antrópicos, tales como la introducción de especies invasoras, cuya consecuencia puede conducir a la extinción local de especies nativas. El objetivo de este trabajo fue analizar la variación temporal (2012 y 2017), tanto en composición como en distribución de la ictiofauna a lo largo del río Atacames, noroccidente del Ecuador. En 2012 se registró: 1) la presencia de Astyanax ruberrimus que se extinguió localmente para el 2017; y 2) la presencia de la tilapia (Orechromis niloticus) como única especie introducida a la que se sumó el guppy (Poecilia gillii) para el 2017. Adicionalmente, el aumento en las actividades humanas condujo a un arreglo en la diversidad, abundancia y distribución de peces a lo largo del cauce, lo que determinó además que algunas especies se dispersaran hacia la zona alta de la cuenca.

ABSTRACT The interpretation of biological diversity can be very complex, as it exists a dynamic based on the origin and diversification of species, in addition to anthropogenic effects, such as the introduction of invasive species, which can result in the local extinction of the native ones. The aim of this study was to analyze the temporal variation (2012 and 2017), in composition and distribution of the ichthyofauna along the Atacames River in northwestern Ecuador. In 2012 we recorded: 1) the presence of Astyanax ruberrimus, which was reported locally extinct by 2017; and 2) the tilapia (Orechromis niloticus) as the only introduced fish species present until 2017, when the addition of the non-native guppy (Poeciliagillii) occurred . In addition, the increase in human activities conduced to change in diversity, abundance and distribution of fish along the watercourse, which resulted in dispersing of some species towards the upper reaches of the river basin.

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In November 2015, two iron ore tailing dams collapsed in the city of Mariana, Brazil. The dams' collapse generated a wave of approximately 50 million m3 of a mixture of mining waste and water. It was a major environmental tragedy in Brazilian history, which damaged rivers, and cities 660 km away in the Doce River basin until it reached the ocean coast. Shortly after the incident, several reports informed that the concentration of metals in the water was above acceptable legal limits under Brazilian laws. Here the microbial communities in samples of water, mud, foam, and rhizosphere of Eichhornia from Doce River were analyzed for 16S and 18S rRNA-based amplicon sequencing, along with microbial isolation, chemical and mineralogical analyses. Samples were collected one month and thirteen months after the collapse. Prokaryotic communities from mud shifted drastically over time (33% Bray-Curtis similarity), while water samples were more similar (63% Bray-Curtis similarity) in the same period. After 12 months, mud samples remained with high levels of heavy metals and a reduction in the diversity of microeukaryotes was detected. Amoebozoans increased in mud samples, reaching 49% of microeukaryote abundance, with Discosea and Lobosa groups being the most abundant. The microbial communities' structure in mud samples changed adapting to the new environment condition. The characterization of microbial communities and metal-tolerant organisms from such impacted environments is essential for understanding the ecological consequences of massive anthropogenic impacts and strategies for the restoration of contaminated sites such as the Doce River.

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o Introduction: Freshwater research in Latin America has been increasing in recent years, with a large participation of scientists based on local institutions. However, researchers in the region are facing diverse challenges, and we lack a regional overview of the status of freshwater research. Objective: To address this, we surveyed researchers in the region to assess the current activity and challenges faced by the scientific community. We were interested in understanding (1) the type of research currently taking place in the region, (2) the major research gaps, as viewed by local researchers, and (3) the main limitations or obstacles slowing the development of freshwater science in the region. Methods: We prepared a questionnaire with 26 questions regarding the background of participants, their ongoing research priorities, the products generated from their research, and the major limitations they are facing as researchers. Results: We obtained 105 answers from researchers in 19 Latin American countries. Some of the important trends identified included: (1) a focus on stream ecosystems under agricultural and natural forest; (2) emphasis on biodiversity assessment and species inventories; (3) limited ecological research, mostly centered on litter decomposition and food web studies; and (4) communicating research in the form of peer-reviewed papers and reports in gray literature. Major limitations to the scientific activity included: (1) language, with a majority of respondents considering their handling of English a handicap; (2) limited access to research equipment; (3) lack of tools, such as taxonomic keys; and (4) limited research funding. Research needs and priorities resulted in three major areas in need of attention: (1) developing taxonomy and systematics; (2) improving our current understanding of ecology and natural history; and (3) understanding species distributions and biodiversity patterns. Conclusions: Latin America has an active community of scientists. There is a need to diversify research topics, without abandoning traditional research areas (e.g., taxonomy, species distribution). We advocate for more collaboration among scientists with similar research goals, regardless of their affiliation. Improving communication and collaboration among universities and countries within Latin America will certainly facilitate overcoming obstacles and will help shaping a brighter future for freshwater research, and sciences in general, in the region.

o Introducción: las investigaciones en ecosistemas de agua dulce en América Latina han aumentado en los últimos años, con gran participación de científicos establecidos en instituciones locales. Los investigadores en la región se enfrentan a una variedad de desafíos y carecemos de una descripción regional del estado de la investigación en agua dulce. Objetivo: para abordar esto, encuestamos a investigadores de la región para evaluar las líneas de investigación y los desafíos que enfrenta la comunidad científica. Estábamos interesados ​​en comprender (1) el tipo de investigación que se está llevando a cabo actualmente en la región, (2) las principales brechas de investigación, según lo visto por los investigadores locales, y (3) las principales limitaciones u obstáculos que retrasan el desarrollo de la ciencia del agua dulce en la región. Métodos: preparamos un cuestionario con 26 preguntas sobre los antecedentes de los encuestados, sus prioridades actuales de investigación, los productos generados a partir de su investigación, y las principales limitaciones que enfrentan como investigadores. Resultados: obtuvimos 105 respuestas de investigadores en 19 países latinoamericanos. Algunas de las tendencias más importantes incluyeron: (1) un enfoque en ecosistemas fluviales, principalmente bajo los usos de tierra agrícola y de bosque; (2) énfasis en la evaluación de la biodiversidad y los inventarios de especies; (3) la limitada investigación ecológica está centrada en la descomposición de hojarasca y los estudios de la red alimentaria; y (4) la comunicación de la investigación se da a través de artículos científicos revisados por pares e informes técnicos en literatura gris. Las principales limitaciones de la actividad científica incluyen: (1) lenguaje, con la mayoría de los encuestados que consideran que su manejo del inglés es una desventaja; (2) acceso limitado a equipos de investigación; (3) falta de herramientas, tales como claves taxonómicas; y (4) financiamiento de investigación limitado. Las necesidades y prioridades de investigación dieron como resultado tres áreas principales que requieren atención: (1) desarrollar la taxonomía y la sistemática; (2) mejorar nuestra comprensión actual de la ecología y la historia natural; y (3) comprensión de la distribución de especies y patrones de biodiversidad. Conclusiones: América Latina tiene una comunidad activa de científicos. Identificamos la necesidad de diversificar los temas de investigación, sin abandonar áreas tradicionales (e.g., taxonomía, distribución de especies). Abogamos por una mayor colaboración entre los científicos con los objetivos de investigación similares, independientemente de su afiliación. Mejorar la comunicación y la colaboración entre universidades y países de América Latina ciertamente facilitará la superación de obstáculos y ayudará a forjar un futuro más prometedor para la investigación del agua dulce y las ciencias en general en la región.

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Harmful algal blooms (HABs) have been recorded in the Chubut Province, Argentina, since 1980, mainly associated with the occurrence of paralytic shellfish poisoning (PSP) toxins produced by dinoflagellates of the genus Alexandrium. PSP events in this area impact on fisheries management and are also responsible for severe human intoxications by contaminated shellfish. Within the framework of a HAB monitoring program carried out at several coastal sites along the Chubut Province, we analyzed spatiotemporal patterns of PSP toxicity in shellfish during 2000-2011. The highest frequency of mouse bioassays exceeding the regulatory limit for human consumption was detected in spring and summer, with average values of up to ≈70% and 50%, respectively. By contrast, a lower percentage of positive bioassays (2-8%) or no toxicity at all was usually detected during autumn and winter. The most intense PSP events were usually observed between November and January, with values of up to 4,000 µg STX eq 100 g-1, and showed a marked interannual variability both in their magnitude and location. In addition, a severe PSP outbreak was recorded during autumn, 2009, at Camarones Bay, with toxicity values of up to 14,000 µg STX eq 100 g-1. The scallop Aequipecten tehuelchus showed significantly higher toxicity values compared to other shellfish species in SJG and SMG, suggesting a lower detoxification capacity. Our results contribute to the understanding of HABs dynamics on the Argentine Patagonian coast.

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Changes in diet of Laetacara araguaiae Ottoni and Costa, 2009 were evaluated in the Sucuriú River (Upper Paraná basin, Brazil) in an area with a small hydroelectric power plant, both before and after the formation of the reservoir, in order to answer: Did the construction of the reservoir affected the diet of this species? The results showed greater change of diet composition in the upstream section of the reservoir. It was observed that before the formation of the reservoir and the first year after, the individuals from upstream section formed a group characterized by an insectivorous diet. With the dam construction and habitat change we observed that aquatic plant material, sediment, and algae predominated in the diet. These results show the opportunistic feeding habit of L. araguaiae and contribute to the understanding of how the impoundment of rivers can influence the trophic dynamics of the ichthyofauna.

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Most Latin American demands for drinking water are in or near urban areas. However, population growth and untreated sewage disposal degrade water quality, with negative effects for biodiversity and ecosystem services. Mobilizing society to monitor quality of urban watercourses facilitates training and allows diagnosis that may further help implement mitigation and management strategies. Therefore, our research was conducted in a > 4000 km2 metropolitan region of high human influence. Urban water body assessments were conducted by 1965 teachers and students and their consistency validated by rigorous scientific methods. The assessments revealed degradation of physical habitat, water quality, or biology in 91% of the evaluated urban stream sites. Increased knowledge concerning environmental stressors and biological responses by local citizens may increase their participation in public policy development and implementation. We conclude that participatory scientific monitoring is a viable way for improving science education, increasing social participation, and improving the ecosystem services provided by urban watercourses.

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Changes in diet of Laetacara araguaiae Ottoni and Costa, 2009 were evaluated in the Sucuriú River (Upper Paraná basin, Brazil) in an area with a small hydroelectric power plant, both before and after the formation of the reservoir, in order to answer: Did the construction of the reservoir affected the diet of this species? The results showed greater change of diet composition in the upstream section of the reservoir. It was observed that before the formation of the reservoir and the first year after, the individuals from upstream section formed a group characterized by an insectivorous diet. With the dam construction and habitat change we observed that aquatic plant material, sediment, and algae predominated in the diet. These results show the opportunistic feeding habit of L. araguaiae and contribute to the understanding of how the impoundment of rivers can influence the trophic dynamics of the ichthyofauna.(AU)

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