Rio Doce Acoustic Surveys of Fish Biomass and Aquatic Habitat.

Following the failure of the Fundão mine tailings dam in Brazil, approximately 32 million cubic meters of Fe ore tailings were released into the downstream riverine system. The postevent monitoring surveys implemented the use of noninvasive acoustic methods to improve the understanding of the fish biomass distribution patterns and aquatic habitat condition of the impacted reaches of the Rio Gualaxo do Norte, Rio do Carmo, and Rio Doce. The primary focus of the program was to collect hydroacoustic measurements of fish biomass, which was accompanied by sonar imaging of aquatic habitats using high-resolution side scan and downward imaging sonar at each site visited. The biannual surveys began in April 2017 and were fundamentally a multiple control-impact design because before data (prior to the dam failure event) were not available. Up to 22 sites were visited for each survey, including reservoir and river sites. Results indicate similar levels of instream habitat between control and impact river and reservoir sites. Average volumetric biomass was not significantly different between impact sites and their corresponding controls in the August 2018 survey (latest to date). Preliminary temporal analysis of the biomass data set collected indicates that either stable or increasing levels of biomass are detected at tailings impacted sites within the Rio Doce. Integr Environ Assess Manag 2020;16:615-621. © 2020 Hydrobiology QLD Pty Ltd. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Após o rompimento da barragem de rejeitos da mina do Fundão no Brasil, cerca de 32 milhões de metros cúbicos de rejeitos de minério de Fe foram libertados no sistema fluvial a jusante. Monitoramentos pós-evento foram implementados com a utilização de métodos acústicos não invasivos visando ampliar a compreensão dos padrões de distribuição da biomassa de peixes e condições dos habitat aquáticos em trechos impactados do Rio Gualaxo do Norte, Rio do Carmo e Rio Doce. A aquisição de medições hidroacústicas sobre a biomassa de peixes foi o foco principal do programa, seguido pela obtenção de imagens dos habitats aquáticos através da utilização de um sonar de varredura lateral de alta resolução e um sonar de imagem vertical, em cada local visitado. Os levantamentos de campo semestrais tiveram início em Abril de 2017 e seu design amostral foi baseados na concepção "trechos controle - trechos impactados" uma vez que não existem dados disponíveis para o período anterior ao evento (rompimento da barragem). Em cada levantamento foram visitados até 22 pontos de amostragem, incluindo vários reservatórios e rios. Os resultados indicaram níveis de habitat similares entre os pontos controle e impacto, de rios e reservatórios. No monitoramento mais recente (Agosto/2018) a biomassa volumétrica média não foi significativamente diferente entre os locais de impacto e os seus correspondentes pontos controles. A análise temporal preliminar do conjunto de dados sobre a biomassa indicou níveis estáveis ou crescentes deste parâmetro nos locais impactados pelos rejeitos, no Rio Doce. Integr Environ Assess Manag 2020;16:615-621.

Evaluation of criteria used to assess the quality of aquatic toxicity data.

Good quality toxicity data underpins robust hazard and risk assessments in aquatic systems and the derivation of water quality guidelines for ecosystems. Hence, an objective scheme to assess the quality of toxicity data forms an important part of this process. The variation of scores from 2 research papers using the Australasian ecotoxicity database (AED) quality assessment scheme was evaluated by 23 ecotoxicologists. The results showed that the quality class that the assessors gave each paper varied by less than 10% when compared with a quality score agreed a priori between the authors of this study. It was determined that the majority of the variation in each assessment was due to ambiguous or poorly written assessment criteria, information that was difficult to find, or information in the paper that was overlooked by the assessor. This led to refinements of the assessment criteria in the AED, which resulted in a 16% improvement (i.e., reduction) in the mean variation of scores for the 2 papers when compared with the a priori scores. The improvement in consensus among different assessors evaluating the same research papers suggests that the data quality assessment scheme proposed in this article provides a more robust scheme for assessing the quality of aquatic toxicity data than methods currently available.