Effects of metal contamination with physicochemical properties on the sediment microbial communities in a tropical eutrophic-hypereutrophic urban reservoir in Brazil.

We investigated the effects of metals and physicochemical variables on the microbes and their metabolisms in the sediments of Guarapiranga reservoir, a tropical eutrophic-hypereutrophic freshwater reservoir located in a highly urbanized and industrialized area in Brazil. The metals cadmium, copper, and chromium showed minor contribution to changes in the structure, composition, and richness of sediment microbial communities and functions. However, the effects of metals on the microbiota are increased when taken together with physicochemical properties, including the sediment carbon and sulfur, the bottom water electrical conductivity, and the depth of the water column. Clearly, diverse anthropic activities, such as sewage discharge, copper sulfate application to control algal growth, water transfer, urbanization, and industrialization, contribute to increase these parameters and the metals spatially in the reservoir. Microbes found especially in metal-contaminated sites encompassed Bathyarchaeia, MBG-D and DHVEG-1, Halosiccatus, Candidatus Methanoperedens, Anaeromyxobacter, Sva0485, Thermodesulfovibrionia, Acidobacteria, and SJA-15, possibly showing metal resistance or acting in metal bioremediation. Knallgas bacteria, nitrate ammonification, sulfate respiration, and methanotrophy were inferred to occur in metal-contaminated sites and may also contribute to metal removal. This knowledge about the sediment microbiota and metabolisms in a freshwater reservoir impacted by anthropic activities allows new insights about their potential for metal bioremediation in these environments.

Spatial Variation and Environmental Parameters Affecting the Abundant and Rare Communities of Bacteria and Archaea in the Sediments of Tropical Urban Reservoirs.

Microbial communities in freshwater sediments play an important role in organic matter remineralization, contributing to biogeochemical cycles, nutrient release, and greenhouse gases emissions. Bacterial and archaeal communities might show spatial or seasonal patterns and were shown to be influenced by distinct environmental parameters and anthropogenic activities, including pollution and damming. Here, we determined the spatial variation and the environmental variables influencing the abundant and rare bacterial and archaeal communities in the sediments of eutrophic-hypereutrophic reservoirs from a tropical urban area in Brazil. The most abundant microbes included mainly Anaerolineae and Deltaproteobacteria genera from the Bacteria domain, and Methanomicrobia genera from the Archaea domain. Microbial communities differed spatially in each reservoir, reflecting the establishment of specific environmental conditions. Locations with better or worst water quality, or close to a dam, showed more distinct microbial communities. Besides the water column depth, microbial communities were affected by some pollution indicators, including total phosphorus, orthophosphate, electrical conductivity, and biochemical oxygen demand. Distinct proportions of variation were explained by spatial and environmental parameters for each microbial community. Furthermore, spatial variations in environmental parameters affecting these communities, especially the most distinct ones, contributed to microbial variations mediated by spatial and environmental properties together. Finally, our study showed that different pressures in each reservoir affected the sediment microbiota, promoting different responses and possible adaptations of abundant and rare bacterial and archaeal communities.

Eutrophication effects on CH4 and CO2 fluxes in a highly urbanized tropical reservoir (Southeast, Brazil).

Shallow urban polluted reservoirs at tropical regions can be hotspots for CO2 and CH4 emissions. In this study, we investigated the relationships between eutrophication and GHG emissions in a highly urbanized tropical reservoir in São Paulo Metropolitan Area (Brazil). CO2 and CH4 fluxes and limnological variables (water and sediment) were collected at three sampling stations classified as hypereutrophic and eutrophic. Analysis of variance (ANOVA) and the principal component analysis (PCA) determined the most significant parameters to CO2 and CH4 fluxes. ANOVA showed significant differences of CO2 and CH4 fluxes between sampling stations with different trophic state. The hypereutrophic station showed higher mean fluxes for both CO2 and CH4 (5.43 ± 1.04 and 0.325 ± 0.167 g m-2 d-1, respectively) than the eutrophic stations (3.36 ± 0.54 and 0.060 ± 0.005 g m-2 d-1). The PCA showed a strong relationship between nutrients in the water column (surface and bottom) and GHG fluxes. We concluded that GHG fluxes were higher whenever the trophic state increases as observed previously in temperate and tropical reservoirs. High concentrations of nutrients in the water column in the studied area support the high production of autotrophic biomass that, when sedimented, ends up serving as organic matter for CH4 producers. These outcomes reinforce the necessity of water quality improvement and eutrophication mitigation in highly urbanized reservoirs in tropical regions.

Higher Abundance of Sediment Methanogens and Methanotrophs Do Not Predict the Atmospheric Methane and Carbon Dioxide Flows in Eutrophic Tropical Freshwater Reservoirs.

Freshwater reservoirs emit greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2), contributing to global warming, mainly when impacted by untreated sewage and other anthropogenic sources. These gases can be produced by microbial organic carbon decomposition, but little is known about the microbiota and its participation in GHG production and consumption in these environments. In this paper we analyzed the sediment microbiota of three eutrophic tropical urban freshwater reservoirs, in different seasons and evaluated the correlations between microorganisms and the atmospheric CH4 and CO2 flows, also correlating them to limnological variables. Our results showed that deeper water columns promote high methanogen abundance, with predominance of acetoclastic Methanosaeta spp. and hydrogenotrophs Methanoregula spp. and Methanolinea spp. The aerobic methanotrophic community was affected by dissolved total carbon (DTC) and was dominated by Crenothrix spp. However, both relative abundance of the total methanogenic and aerobic methanotrophic communities in sediments were uncoupled to CH4 and CO2 flows. Network based approach showed that fermentative microbiota, including Leptolinea spp. and Longilinea spp., which produces substrates for methanogenesis, influence CH4 flows and was favored by anthropogenic pollution, such as untreated sewage loads. Additionally, less polluted conditions favored probable anaerobic methanotrophs such as Candidatus Bathyarchaeota, Sva0485, NC10, and MBG-D/DHVEG-1, which promoted lower gaseous flows, confirming the importance of sanitation improvement to reduce these flows in tropical urban freshwater reservoirs and their local and global warming impact.

Corrigendum: Higher Abundance of Sediment Methanogens and Methanotrophs Do Not Predict the Atmospheric Methane and Carbon Dioxide Flows in Eutrophic Tropical Freshwater Reservoirs.

[This corrects the article DOI: 10.3389/fmicb.2021.647921.].

Phosphorus removal in a pilot scale free water surface constructed wetland: hydraulic retention time, seasonality and standing stock evaluation.

Constructed wetlands (CWs) are decentralized wastewater treatment systems considered to be green and low cost. They have the potential to effectively remove pollutants and recycle nutrients with plant composting. However, they need large areas to implement them due to the usual high Hydraulic Retention Times (HRT), reaching up to 50 days. The main objective of the present study was to evaluate the influence of HRT (HRT = 3, 7, and 10 days), and seasonality on Total Phosphorus (TP) removal, and standing stock in a pilot scale free water surface CW (FWS CW). Unplanted and planted (Eichhornia crassipes) tanks were evaluated in wet and dry seasons. The FWS CW was set up as a complementary treatment to a secondary level wastewater treatment plant. The system was monitored weekly for ten months, totalizing 29 replicate samplings (n = 58). Planted tanks were harvested every week to keep free space for plant reproduction (∼40%). The mean removal efficiency of TP ranged between 82% and 95% without a significant difference between HRT (pvalue > 0.05). However, when the effects of the sedimentation of the unplanted tanks were disregarded, the lowest HRT (3 days) tank presented the highest standing stock of TP. The wet season presented a significant difference in TP removal results (pvalue < 0.05), associated with higher macrophyte growth rate due to more intense solar irradiation and incorporation of TP by E. crassipes. The results point out advances in P removal and recycling by a low-cost ecological engineering system.

Avaliação ecotoxicológica de efluentes tratados por alagados construídos / Ecotoxicological evaluation of effluents treated by constructed wetlands

RESUMO O objetivo deste trabalho foi avaliar o desempenho de alagados construídos com fluxo subsuperficial horizontal cultivados com as macrófitas aquáticas Eleocharis sp. (junco) e Typha sp. (taboa) na redução da toxicidade de efluentes domésticos. Para isso, foram utilizados ensaios ecotoxicológicos com o microcrustáceo Daphnia similis, a dicotiledônea Lactuca sativa (alface), a monocotiledônea Sorghum vulgare (sorgo) e as macrófitas aquáticas Lemna sp. (lentilha-d'água) e Azolla sp. O efluente doméstico mostrou-se tóxico à Daphnia similis com média de EC50 de 1,3%. Os tratamentos com macrófitas reduziram significativamente a toxicidade do efluente, com médias de EC50 de 73% para o tratamento com junco, 53,17% para o com taboa e 78,25% para o com taboa + junco. O controle (sem macrófitas) também reduziu significativamente a toxicidade, com média de EC50 de 63,13%. Nos ensaios de fitotoxidade, a alface e o sorgo não se mostraram sensíveis ao efluente analisado, embora sejam para outros tipos de efluentes. A macrófita Lemna sp. também não foi sensível ao efluente estudado, no entanto, observou-se a capacidade de identificar, com essa espécie, o potencial eutrofizante do efluente, já que esta se desenvolveu melhor no efluente bruto do que nos tratados. Com a macrófita Azolla sp., foi possível verificar que o efluente bruto apresenta maior potencial eutrofizante se comparado com os tratamentos com junco, taboa e controle, nos quais houve remoção de nitrogênio e fósforo. No entanto, evidenciou-se efeito tóxico para Azolla sp. nos efluentes tratados.

ABSTRACT The research objective was to evaluate the performance of wetlands constructed with vertical sub-surface flow cultivated with Eleocharis sp. (Junco) and Typha sp. (Taboa). For this, ecotoxicological tests were used with the microcrustacean Daphnia similis, with the dicotyledon Lactuca sativa (alface), the monocotyledon Sorghum vulgare (sorgo) and the aquatic macrophytes Lemna sp. (Duckweed) and Azolla sp. The domestic effluent was toxic to Daphnia similis with a mean EC50 of 1.3%. Macrophyte treatments significantly reduced effluent toxicity with EC50 averages of 73% for junco treatment, EC50 53.17% for taboa treatment, and EC50 78.25% for taboa + junco treatment. The control (without macrophytes) also significantly reduced toxicity, with a mean EC50 of 63.13%. In the phytotoxicity tests, lettuce and sorgo were not sensitive to the analyzed effluent, although they were for other types of effluents. The macrophyte Lemna sp. was also not sensitive to the effluent studied. However, it was possible to identify the eutrophic potential of the effluent with this species, since it was better developed in the raw effluent than in treated ones. With the macrophyte Azolla sp., it was possible to verify that the raw effluent has greater eutrophic potential when compared to the treatments with junco, taboa and control, where nitrogen and phosphorus removal was observed. However, toxic effect was observed for Azolla sp. in treated effluents.

Conflitos hídricos na gestão dos reservatórios Billings e Barra Bonita / Water conflicts in the management of the Billings and Barra Bonita reservoirs

Este trabalho tem como objetivo analisar criticamente a gestão pública do reservatório Billings e a gestão privada do reservatório de Barra Bonita, buscando compreender os conflitos que envolvem o uso dos reservatórios e analisar os fatores que resultam nos principais passivos ambientais. A hipótese geral sustenta a ideia de que a análise dos conflitos pelo uso da água em reservatórios pode contribuir na compreensão da gestão das empresas. Como metodologia, foram aplicadas entrevistas a representantes da Emae, Cetesb, Sabesp, AES-Tietê e CFTP visando compreender os conflitos e os fatores que resultam nos principais passivos ambientais. Os resultados identificaram dificuldades em conduzir uma gestão compartilhada entre os usuários e operadores. (AU)

This paper is a critical analysis of the public management of the Billings reservoir and of the private management of the Barra Bonita reservoir, and attempts to understand the conflicts involved in the use of these reservoirs as well as the factors that result in major environmental damage. The general hypothesis supports the idea that analyses of conflicts over the use of water in reservoirs may contribute to the understanding of business management. As methodology, representatives from Emae, Cetesb, Sabesp, AES-Tiete and CFTP were interviewed to understand better the conflicts and the factors that result in major environmental damage. The results identified difficulties in shared management between users and operators.(AU)