RESUMEN La laguna de Baconao es una laguna tropical costero-litoral, con constantes perturbaciones antrópicas y naturales; escenario que favorece la eutrofización, con tendencia a la proliferación del fitoplancton. El desarrollo de esta investigación comienza con un registro de muerte masiva de peces en la laguna, en mayo de 2017, siendo el objetivo principal documentar la implementación de un protocolo de gestión del riesgo por contaminación con ficotoxinas, adaptado a las condiciones del ecosistema, a partir de la caracterización de la situación de riesgo, enfocado a la mitigación y prevención de impactos negativos. Se confirma la existencia de una Floración Algal Nociva (FAN) mixta en remisión, con implicaciones negativas en todo el ecosistema, así como la presencia de células vivas de Gymnodinium sp., Karlodinium micrum, y abundantes restos de células de otros dinoflagelados; altos valores de clorofila a, con una concentración máxima de 20,37 ± 0,04 µgL-1; bajos valores de oxígeno disuelto y elevada contaminación bacteriana, con predominio de cianobacterias. Se documenta la implementación de un protocolo de gestión del riesgo con importantes pautas metodológicas a seguir para el manejo de similares eventos de riesgo, donde la alianza intersectorial constituyó un factor clave de éxito.

ABSTRACT The Baconao Lagoon is a tropical, coastal and littoral ecosystem which receives continuous natural and human perturbations; favoring the eutrophication process, and consequently, the phytoplankton proliferation. The starting point of this research begins with a massive fish kill report into the lagoon on May 2017, being the main objective to document the implementation of a risk management protocol for the phycotoxin presence, adapted to the ecosystem conditions, considering the characterization of the risk event, focusing on mitigation and prevention of negative impacts. The presence of a mix Harmful Algal Bloom (HAB) in remission was confirmed, with negative implications to the entire ecosystem. It was identified the presence of abundant motile cells of Gymnodinium sp., Karlodinium micrum and dinoflagellate cells rests, as well as high values of chlorophyll a, being the highest concentration 20.37 ± 0.04 µgL-1; low values of dissolved oxygen, and an important bacterial contamination, with the dominance of cyanobacteria. The implementation of a risk management protocol was documented with important methodological guidelines to follow to the management of similar risk events, where the intersectoral alliance performs a key success factor.

Se presentan datos recabados entre los meses de junio a agosto, 2016 de la floración algal nociva (FAN) ocurrida en la laguna Alalay (Cochabamba, Bolivia), que en marzo del mismo año causó la muerte masiva de peces y aves. Esta FAN estuvo dominada continuamente por Arthrospira fusiformis, Anabaenopsis milleri y Aphanocapsa sp., tres cianobacterias que se reportan en la literatura como altamente tóxicas y cuyas adaptaciones morfológicas, autecología, uso efectivo de nutrientes, espacio y luz, y las consecuencias de su actividad fisiológica en el ecosistema determinaron su prevalencia en la laguna. Los resultados físicos y químicos denotan el estado hipereutrófico de la laguna y un cambio en la limitación de la productividad en el ecosistema del nitrógeno hacia el fósforo. La incorporación de nitrógeno atmosférico y el reciclaje de nutrientes en la columna de agua y sedimentos así como la reutilización de la materia orgánica producida por las algas han resultado en una densidad algal pocas veces reportada en la literatura. Los análisis multivariados muestran que aunque solo poco más del 77% de la varianza en la abundancia algal es explicada por los parámetros físicos y químicos medidos durante el estudio, nitratos, fósforo total, carbonates, sulfatos y conductividad son las variables que determinan en mayor grado los patrones de variación espacio-temporal observados en los tres puntos de muestreo estudiados. Estas variaciones confirman resultados anteriores obtenidos con variables ambientales y comunidades de diatomeas que muestran que la laguna está afectada de manera distinta en los tres puntos de estudio por las actividades antrópicas en la cuenca. La identidad confirmada de Arthrospira fusiformis y Anabaenopsis milleri, su alta abundancia durante marzo y meses subsecuentes, las características del deceso masivo de animales y los datos físicos y químicos históricos, sugieren que ese deceso fue producido por cianotoxinas y no así por descensos en el tenor de oxígeno disuelto o la presencia de sulfuro de hidrógeno en la columna de agua. Los resultados aquí reportados tienen implicaciones para el desarrollo de protocolos de recuperación y manejo de la laguna, aspecto que se discute en el contexto de los datos recabados y de la literatura.

We present data collected during June to August, 2016 for the harmful algal bloom (HAB) developing in Alalay shallow lake, Cochabamba Bolivia; bloom that caused the massive kill of fish and birds early in March of the same year. The bloom was continuously dominated by Arthrospira fusiformis, Anabaenopsis milleri and Aphanocapsa sp., three cyanobacteria reportedly highly toxic and which morphological and autecological adaptations, effective use of nutrients, space and light, and the ecological consequences of their physiological activities determined their prevalence in the lake. Atmospheric nitrogen fixation and the recycling of nutrients from the water column and sediments, as well as the reuse of organic matter produced by photosynthetic organisms resulted in algal densities that are seldom reported in the literature. Water chemistry shows that the lake is hypereutrophic and that it has shifted from a nitrogen to a phosphorus limitation. Multivariate analyses showed that although only about 77% of the algal abundance variance is explained by measured water chemistry variables, nitrates, total phosphorus, carbonates, sulfatos, and conductivity are the parameters explaining observed variation in algal abundance in the three selected sampling sites. Such variations confirm previous results obtained by analysis of environmental variables and diatom assemblages, showing that the three sampling points are affected differently by anthropic activities in the drainage basin. The confirmed identity of Arthrospira fusiformis and Anabaenopsis milleri, their high abundance during March and subsequent months, the features of the fish and bird kills, and the historical water chemistry data suggest that the kills were produced by cyanotoxins and not by low dissolved oxygen and presence of hydrogen sulfide, as reported in the local and national press. The results shown here have implications for the development of recuperation and management protocols, aspects that are discussed in the context of our data and reports in the literature.

<p>A fauna de peixes do Rio dos Sinos vem sendo exposta a uma poluição grave desde os anos 70 do século passado. Descargas contínuas de esgotos industriais e urbanos causaram hipóxia e recorrentes mortandades de peixes. Os objetivos do presente estudo são: avaliar os efeitos de longo prazo da poluição sobre a comunidade de peixes e investigar a recuperação da ictiofauna após uma mortandade severa em 2006. Para avaliar os impactos de longo prazo, foram realizados amostragens sazonais entre setembro de 2007 a março de 2009 em quatro locais que foram investigados em 1998/99 com a mesma metodologia. Os efeitos da mortandade de peixes foram investigados comparando a fauna no trecho afetado pela mortandade com o que não foi afetado. As propriedades coletivas da comunidade íctica riqueza e diversidade de Shannon aumentaram durante o intervalo de 10 anos em todos os pontos de amostragem, porém os valores da abundância ficaram estáveis. A análise da constância das espécies e a análise de agrupamento mostraram que as diferenças encontradas entre os estudos 1998-1999 e 2007/09 são pouco expressivas. A comparação dos trechos afetados e não afetados pela mortandade de peixes mostrou uma rápida recuperação da fauna que ocorreu em um ano. A ictiofauna do Rio dos Sinos sofreu provavelmente os impactos mais graves nos anos 70 do século passado, contudo, não documentado por este estudo. Depois de um declínio inicial a comunidade exibiu padrões relativamente estáveis com tendências de recuperação. Após as mortandades de 2006 a recuperação da fauna foi rápida, provavelmente favorecida pela proximidade de áreas de fonte não poluídas e pela integridade física dos habitats do Rio dos Sinos.</p>

<p>The fish fauna of the Sinos River has been subjected to severe pollution since the 1970´s. Continuous discharges of industrial and municipal sewage cause hypoxia and often even fish kills. The objectives of the present study are to assess long-term effects of pollution on the fish community over a time scale of approximately ten years and to investigate recuperation of the fish fauna after a massive fish kill in 2006. To assess the long-term impacts, seasonal sampling was conducted from September 2007 to March 2009 in four sites which were investigated in 1998/99 with the same methodology. The effects of the fish kill were investigated by comparing the present fauna in the affected river stretch with the fauna of an unaffected adjacent river stretch. The collective community properties richness and Shannon diversity changed during the ten year interval in a consistent pattern. Richness and Shannon diversity increased significantly in all sites, abundance values, however, did not. Analysis of species constancy and cluster analysis showed that the differences between the 1998/99 and 2007/09 studies were relatively small. The comparison of the reaches affected by the 2006 fish kills showed a rapid recovery within one year. Probably the Sinos fish fauna suffered the most severe impacts in the 70s of the last century, which could not be documented by this study. After an initial decline, the community displays relatively stable patterns with a tendency of recovery. After a severe fish kill, faunal recovery was rapid, probably favoured by the proximity of unpolluted source areas and physical habitat integrity of the Sinos River.</p>

A retrospective diagnosis of a massive fish mortality in an aquaculture facility was performed following a cattle waste effluent spill to a river used as source for the fish farm. The level of suspended solids and non-ionised ammonia (NH3) reaching the farm were estimated based on concentrations in the animal waste and the dilution factor in the river. The calculations indicate that both concentrations were higher in the fish farm after the leakage than the lethal concentrations reported in water quality criteria for freshwater fish. Therefore, these calculations tie the cattle waste leakage to the fish kills observed.

Se presenta un diagnóstico retrospectivo de la mortalidad masiva de truchas ocurrida en una piscifactoría tras el derrame accidental de un vertido de purines aguas arriba de dicha piscifactoría. Se calcularon las concentraciones de amoníaco no ionizado (NH3) y de sólidos en suspensión en el agua de la piscifactoría tras el vertido, considerando su concentración en el purín y el factor de dilución del vertido. Estos cálculos indicaron que las concentraciones de sólidos en suspensión (6541.1 mg/L) y de NH3(1.26 mg/L) eran superiores a las concentraciones letales descriptas en los criterios de mortalidad para peces, indicando que el vertido de purines estaba implicado en la mortalidad ocurrida en la piscifactoría.