On November 2015, one of Brazil's most important watersheds was impacted by the mine waste from Fundão dam collapse in Mariana. The mine waste traveled over 600 km along the Doce River before ...reaching the sea, causing severe devastation along its way. Here we assessed trace element concentrations and cytogenotoxic effects of the released mine waste. Water samples were collected along the Doce River ten days after the disaster in two impacted sites and one non-impacted site. Sampling points were located hundreds of kilometers downstream of the collapsed dam. Water samples were used for trace element quantification and to run an experiment using Allium cepa to test cytogenotoxicity. We found extremely high concentrations of particulate Fe, Al, and Mn in the impacted sites. We observed cytogenotoxic effects such as alterations in mitotic and phase indexes, and enhanced frequency of chromosomal aberrations. Our results indicate interferences in the cell cycle in impacted sites located hundreds of kilometers downstream of the disaster. The environmental impacts of the dam collapse may not only be far-reaching but also very likely long-lasting, because the mine waste may persist in the Doce River sediment for decades.
•Higher concentrations of particulate metals were found in impacted sites.•Cytogenotoxic effects were found in the impacted sites.•Mining waste affected genetic aspects of Allium cepa.•Impacts of the tragedy are far-reaching and long-lasting.
Small water systems are important hotspots of greenhouse gas (GHG) emission, but estimates are poorly constrained as data are scarce. Small ponds are often constructed in urban areas, where they ...receive large amounts of nutrients and therefore tend to be highly productive. Here, we investigated GHG emissions, seasonal and diel variation, and net ecosystem production (NEP) from an urban pond. In monthly 24-h field campaigns during 11 months, diffusive water–atmosphere methane (CH₄) and carbon dioxide (CO₂) fluxes and CH₄ ebullition and oxidation were quantified. With oxygen (O₂) measurements, NEP was assessed. The pond was a net GHG source the entire year, with an emission of 3.4 kg CO₂ eq m−2 yr−1. The dominant GHG emission pathway was CH₄ ebullition (bubble flux, 50%), followed by diffusive emissions of CO₂ (38%) and CH₄ (12%). Sediment CH₄ release was primarily driven by temperature and especially ebullition increased exponentially above a temperature threshold of 15°C. The pond’s atmospheric CO₂ exchange was not related to NEP or temperature but likely to a high allochthonous carbon (C) input via runoff and anaerobic mineralization of C. We expect urban ponds to show a large increase in GHG emission with increasing temperature, which should be considered carefully when constructing ponds in urban areas. Emissions may partly be counteracted by pond management focusing on a reduction of nutrient and organic matter input.
Increased periods of prolonged droughts followed by severe precipitation events are expected throughout South America due to climate change. Freshwater sediments are especially sensitive to these ...changing climate conditions. The increased oscillation of water levels in aquatic ecosystems causes enhanced cycles of sediment drying and rewetting. Here we experimentally evaluate the effects of induced drought followed by a rewetting event on the release of carbon dioxide (CO2), methane (CH4), nutrients (nitrogen and phosphorus), and trace elements (iron, manganese, and zinc) from the sediment of a tropical reservoir in southeastern Brazil. Furthermore, we used bulb onions (Allium cepa) to assess the potential cytogenotoxicity of the water overlying sediments after rewetting. We found peaks in CO2 and CH4 emissions when sediments first transitioned from wet to dry, with fluxes declining as sediments dried out. CO2 emissions peaked again upon rewetting, whereas CH4 emissions remained unaltered. Our experiment also revealed average increases by up to a factor of ~5000 in the release rates of nutrients and trace elements in water overlying sediments after rewetting. These increased release rates of potentially toxic compounds likely explain the lower replication of Allium cepa cells (up to 22% reduction) exposed to water overlying sediments after rewetting. Our findings suggest that increased events of drought followed by rewetting may lead to a range of changes in freshwater ecosystems, including nutrient enrichment, increased toxicity following resuspension of contaminants, and higher emission of greenhouse gases to the atmosphere.
Caffeine is one of the most consumed substances, and it has been largely detected in aquatic ecosystems. We investigated the trends in caffeine consumption over three decades and its relationships ...with gross domestic product (GDP) and human development index (HDI) to understand global patterns and to identify potential hotspots of contamination. The total caffeine consumption is increasing mainly due to population growth. Moreover, caffeine consumption per capita is also increasing in some countries, such as Brazil, Italy, and Ethiopia. A high positive correlation between caffeine consumption per capita with HDI and GDP was found for coffee-importing countries in Europe, while a high negative correlation was found for coffee-exporting countries in Africa. The literature review showed that the highest caffeine concentrations coincide with countries that present an increasing caffeine consumption per capita. Also, approximately 35% of the caffeine concentrations reported in the literature were above the predicted no-effect concentration in the environment and, again, overlaps with countries with increasing per capita consumption. Despite the high degradation rate, caffeine consumption tends to increase in a near future, which may also increase the overall amount of caffeine that comes into the environment, possibly exceeding the thresholds of several species described as tolerant to the current environmental concentrations. Therefore, it is essential to prevent caffeine from reaching aquatic ecosystems, implementing sewage treatment systems, and improving their efficiency.
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•The global patterns and trends in caffeine consumption over time were investigated.•Caffeine concentration in the aquatic ecosystems may increase in the coming years.•Positive correlations between caffeine consumption and time were found in Europe.•Negative correlations between caffeine consumption and time were found in Africa.•Increasing caffeine consumption coincides with high environmental concentrations.
Caffeine concentrations in the environment may increase in the near future due to increasing consumption, especially in countries lacking sanitation.
Caffeine is a contaminant frequently detected in water bodies. Growth trends in both human population and caffeine consumption per capita are expected to exacerbate the occurrence of caffeine in ...freshwaters. Yet the effects of caffeine on native fish fauna are poorly understood. We exposed larvae of an endemic Neotropical catfish (
Rhamdia quelen
) to a range of caffeine concentrations for 30 days. We found that larvae exposed to the highest concentration (16 mg L
−1
) showed skeletal deformations and reduced growth. We further compiled measured environmental concentrations of caffeine in surface freshwater globally and performed a risk assessment. Our analysis points to a low risk to
R. quelen
and equally sensitive fish species in ~90% of the freshwater ecosystems considered in our analysis. The risk quotient is higher in freshwater ecosystems of South and Central America, where
R. quelen
is endemic. Although the ecotoxicological risk is currently low in most places, increased caffeine consumption, exacerbated by the lack of sanitation, is expected to increase caffeine concentrations in many parts of the world, posing a threat of sublethal morphological effects to local fish species.
The incorrect disposal of medicines can be harmful to the environment. Here, we aim to understand the consumption and disposal of medicines in Brazil using online forms. 64% of the respondents have ...the habit to self-medicate. 66% of respondents dispose the disused or expired medicines in the garbage. 71.9% of respondents never receive any information about correct disposal of medicines. 95.2% of respondents believe that residues of medicines can be harmful to the environment. Environmental education can provide information to the population and help to mitigate pharmaceuticals pollution.
The most important pathways for pharmaceuticals to the environment considering human disposal in the present study case. Display omitted
•The incorrect disposal of medicines may represent a risk to the environment.•Investigate how people are disposing unused medicines is crucial.•Online questionnaires were spread out in Brazil.•66% of the respondents discard unused or expired medicines in common garbage.•Environmental education may help to mitigate pharmaceuticals pollution.
The importance of viruses in aquatic ecosystem functioning has been widely described. However, few studies have examined tropical aquatic ecosystems. Here, we evaluated for the first time viruses and ...their relationship with other planktonic communities in an Amazonian freshwater ecosystem. Coupling between viruses and bacteria was studied, focusing both on hydrologic dynamics and anthropogenic forced turbidity in the system (Lake Batata). Samples were taken during four hydrologic seasons at both natural and impacted sites to count virus-like particles (VLP) and bacteria. In parallel, virus-infected bacteria were identified and quantified by transmission electron microscopy (TEM). Viral abundance ranged from 0.5 x 10⁷ ± 0.2 x 10⁷ VLP ml⁻¹ (high-water season, impacted site) to 1.7 x 10⁷ ± 0.4 x 10⁷ VLP ml⁻¹ (low-water season, natural site). These data were strongly correlated with the bacterial abundance (r² = 0.84; P < 0.05), which ranged from 1.0 x 10⁶ ± 0.5 x 10⁶ cells ml⁻¹ (high water, impacted site) to 3.4 x 10⁶ ± 0.7 x 10⁶ cells ml⁻¹ (low water, natural site). Moreover, the viral abundance was weakly correlated with chlorophyll a, suggesting that most viruses were bacteriophages. TEM quantitative analyses revealed that the frequency of visibly infected cells was 20%, with 10 ± 3 phages per cell section. In general, we found a low virus-bacterium ratio (<7). Both the close coupling between the viral and bacterial abundances and the low virus-bacterium ratio suggest that viral abundance tends to be driven by the reduction of hosts for viral infection. Our results demonstrate that viruses are controlled by biological substrates, whereas in addition to grazing, bacteria are regulated by physical processes caused by turbidity, which affect underwater light distribution and dissolved organic carbon availability.
Large storage dams have widely documented impacts on downstream aquatic environments, but hydroelectric dams with little or no capacity for storage of water inflows (i.e., run-of-river) have received ...less attention. Two of the world’s largest run-of-river hydropower dams (Jirau and Santo Antônio, Brazil) are located on the Madeira River, the largest tributary to the Amazon River. Here we examine whether the Madeira dams have affected downstream seasonal flood pulses and short-term (daily and sub-daily) flow dynamics. We show that the combined effects of these dams on seasonal flood pulses were modest. However, dam operations significantly increased day-to-day and sub-daily flow variability. The increase in short-term flow variability is largely explained by rapid, short-term variations in river flow caused by fluctuations in energy demand (hydropeaking). Both the magnitude of hydropeaking and the mean absolute day-to-day change in discharge downstream of the dams doubled after dam closure. In addition, the median hourly rate of water level change downstream of the dams was three times higher than upstream. Our findings highlight that even run-of-river dams on very large rivers such as the Madeira—whose average discharge at the dam site is larger than that of the Mississippi River at its mouth—can alter downstream hydrology through hydropeaking. Although little studied in tropical floodplain rivers, hydropeaking by large run-of-river dams may be detrimental to downstream aquatic organisms and human populations that utilize the river for navigation and fisheries.
Understanding how species are structured in space and time and how they are functionally related to environmental conditions is still a challenge in ecology. In this study, we assessed the predictive ...power of lake morphometry, physical and chemical conditions of the water, and zooplankton density in relation to phytoplankton taxonomic and functional diversity in Amazonian floodplain lakes during low- and high-water periods. We also examined to what extent taxonomic and functional indexes were coupled. Taxonomic diversity was evaluated by species richness and Shannon index, and functional diversity by functional richness (FRic) and community-weighted mean trait value (CWM). The relative importance of predictive factors was evaluated by model selection, multi-model inference and correlations. We found that phytoplankton taxonomic and functional diversity indexes were mostly related to the same factors within the low- and high-water periods. Total phosphorus was the main driving factor in the low water, while euphotic zone depth and zooplankton density were the main driving factors in the high water. Taxonomic and functional diversity indexes were weakly coupled in the low water, but strongly coupled in the high water. Our results highlight that phytoplankton taxonomic and functional diversity can differ between periods, but respond similarly to environmental driving factors.
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