Fire increases the productivity of sugarcane, but it also generates ashes that negatively affect native fish species in aquatic systems

Water pollution caused by ash from grassland fires alters the molecular, biochemical, and morphological biomarkers of non-biting midge larvae

The frequency and intensity of wildfires have been increasing in many parts of the world, which may result in biodiversity loss. Wildfires can devastate plant communities, generating toxic ash that pollutes watercourses through runoff. However, our understanding of the effects of ash exposure on aquatic biodiversity is still limited. Here, Chironomus sancticaroli larvae were exposed to various concentrations of grassland ash (ranging from 0.01 to 100 g/L) in acute and subchronic assays. The tested ash concentrations are environmentally relevant, as similar levels have been observed in nature after moderate runoff in post-fire conditions. We experimentally tested whether ash-contaminated waters increase mortality, induce molecular and biochemical biomarker changes, and reduce body size in chironomid larvae. Results showed that grassland ash contains micro and nanoparticles with high solubility and is rich in metals and polycyclic aromatic hydrocarbons. Adding ash to the water increased pH, conductivity, and total solids while decreasing dissolved oxygen levels. The lethal concentration (LC50) of grassland ash for C. sancticaroli was estimated at 31.43 g/L after acute exposure. However, exposure to sublethal ash concentrations led to higher metallothionein and hemoglobin gene expression related to metal sequestration and adaptation to lower oxygen levels. At the biochemical level, ash exposure increased the activity of enzymes associated with detoxification capacity, such as alpha and beta esterases. It also led to oxidative stress and damage to cell membranes, as indicated by the increased enzymatic activity of superoxide dismutase, glutathione S-transferase, and lipid peroxidation. Finally, larvae exposed to ash reduced body size by up to 55 % at exposure to higher concentrations. As wildland fires produce ashes that are later moved to the aquatic ecosystem when lixiviated, impacting the resident aquatic biota, environmental managers should adopt measures to reduce the likelihood of wildfires and the ash load to watercourses.

Tranquilizing and hepatoprotective effects of red-eye tetra (Moenkhausia Forestii) diet fed with Erythrina crista-galli

This study aimed to assess the leaf aqueous extract composition of Erythrina crista-galli and the effects of its inclusion on the diet of red-eye tetra (Moenkhausia forestii), concerning enzyme content of digestive, hepatic, and oxidation metabolism and pigmentation. Fish (1.78 ± 0.54 g) were divided into groups: fasting (without feeding), control (commercial feed), and treatment (commercial feed with leaf aqueous extract of E. crista-galli) and feeding apparent satiety for 21 days, in the extracted analysis by mass spectrometry, phenolic compost, and flavonoids. The agitation degree and number of dashes, in all supplemented treatments, were lower than those in the control diet when fed for 7 or 15 days. In the digestive enzymatic activity did not differ (p > 0.05). The hepatoprotective treatment group showed lower alanine aminotransferase (ALT) and higher levels of antioxidant catalase (CAT). The results indicated that the aqueous leaf extract of Erythrina crista-galli assists in function maintenance of the liver; and stimulates CAT in red-eye tetra, suggesting that the identified compounds act on the liver and skin, showing hepatoprotective effects and stimulating tranquility.

Rice straw ash and amphibian health: A deep dive into microbiota changes and potential ecological consequences

Rice straw is burned as a result of agricultural practices and technical limitations, generating significant volumes of ash that might have environmental and ecological consequences; however, the effects on organisms have not been researched. Amphibians depend on their gut and skin microbiomes. Ash exposure may cause inflammation and changes in microbial diversity and function in frogs' skin and gut microbiota due to its chemical composition and physical presence, but the implications remain unclear. Rana dybowskii were exposed to five aqueous extracts of ashes (AEA) concentrations for 30 days to study survival, metal concentrations, and microbial diversity, analyzing the microbiota of the cutaneous and gut microbiota using Illumina sequencing. Dominant elements in ash: K > Ca > Mg > Na > Al > Fe. In AEA, K > Na > Ca > Mg > As > Cu. Increased AEA concentrations significantly reduced frog survival. Skin microbiota alpha diversity varied significantly among all treatment groups, but not gut microbiota. Skin microbiota differed significantly across treatments via Bray-Curtis and weighted UniFrac; gut microbiota was only affected by Bray-Curtis. Skin microbiota varied significantly with AEA levels in Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes, while the gut microbiota's dominant phyla, Firmicutes, Bacteroidetes, and Proteobacteria, remained consistent across all groups. Lastly, the functional prediction showed that the skin microbiota had big differences in how it worked and looked, which were linked to different health and environmental adaptation pathways. The gut microbiota, on the other hand, had smaller differences. In conclusion, AEA exposure affects R. dybowskii survival and skin microbiota diversity, indicating potential health and ecological impacts, with less effect on gut microbiota.

Health burden of sugarcane burning on agricultural workers and nearby communities

Sugarcane is the most widely cultivated crop in the world, with equatorial developing nations performing most of this agriculture. Burning sugarcane is a common practice to facilitate harvest, producing extremely high volumes of respirable particulate matter in the process. These emissions are known to have deleterious effects on agricultural workers and nearby communities, but the extent of this exposure and potential toxicity remain poorly characterized. As the epidemicof chronic kidney disease of an unknown etiology (CKDu) and its associated mortality continue to increase along with respiratory distress, there is an urgent need to investigate the causes, determine viable interventions to mitigate disease andimprove outcomes for groups experiencing disproportionate impact. The goal of this review is to establish the state of available literature, summarize what is known in terms of human health risk, and provide recommendations for what areas should be prioritized in research.

Methane concentrations and fluxes in agricultural and preserved tropical headwater streams

Tropical streams have been intensively impacted by agricultural activities. Among the most important agricultural activities in Brazil, sugarcane production represents a large impact for economic development and for environmental conditions. Permeating sugarcane fields, several headwater streams can be affected by sugarcane cultivation, in special, aquatic biogeochemical cycles because of the deforestation, fertilization, crop residues and higher temperatures in the tropics. In this study, we analyzed the effects of sugarcane cultivation on methane fluxes and concentrations, assuming that carbon cycles are influenced by agricultural activities in headwater streams. Our study aimed to (1) measure methane fluxes and concentrations in tropical streams located in Southeastern Brazil, (2) Analyze whether seasonal cycles influence methane fluxes and concentrations, (3) Evaluate the influence of sugarcane cultivation on methane fluxes and (4) Analyze the association between water chemistry in the methane concentrations in tropical streams. We found mean fluxes of CH₄ of 0.280 mmol m^-2 d^-1, with higher fluxes during the summer and in streams draining preserved catchments. The average CH₄ concentrations were 0.695 μmol L^-1, with higher values during the summer and in streams draining preserved catchments. Methane concentrations in the studied streams was influenced by dissolved oxygen (negatively), dissolved organic carbon (negatively), water velocity (positively) and conductivity (negatively). Methane concentrations were significantly higher than concentrations found in Temperate Grasslands, Savannas & Shrublands and similar to concentrations found in other tropical biomes (excluding Tropical & Subtropical Moist Broadleaf Forests which receives large amounts of organic inputs). We conclude that sugarcane influence methane concentrations and fluxes in tropical streams by reducing the organic matter availability provided by the native vegetation in soil and water.

Fire and rain: A systematic review of the impacts of wildfire and associated runoff on aquatic fauna

Climate and land-use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events. However, the responses of aquatic fauna to wildfire disturbances are poorly understood. Here we provide a systematic review of available evidence on how aquatic animals respond to and recover from wildfire disturbance. Two databases (Web of Science and Scopus) were used to identify key literature. A total of 83 studies from across 11 countries were identified to have assessed the risk of wildfires on aquatic animals. We provide a summary of the main ecosystem-level changes associated with wildfires and the main responses of aquatic fauna to such disturbances. We pay special focus to physiological tools and biomarkers used to assess how wildfires impact aquatic animals. We conclude by providing an overview of how physiological biomarkers can further our understanding of wildfire-related impacts on aquatic fauna, and how different physiological tools can be incorporated into management and conservation plans and serve as early warning signs of wildfire disturbances.

In vivo genotoxic effects of commercial grade cypermethrin on fish peripheral erythrocytes

The study explicates the genotoxic effects of commercial grade cypermethrin on peripheral erythrocytes of Catla catla, chronically exposed to two environmentally relevant concentrations. The fish was treated with sub-lethal concentrations 0.12 μg/L and 0.41 μg/L (1/10th and /1/3rd of 96 h LC₅₀ ) of cypermethrin for 45 days. DNA damage in the exposed fish was assessed using alkaline comet assay, presence of micronuclei (MN), erythrocyte nuclear and cytoplasmic abnormalities. Exposure to cypermethrin induced a dose-dependent increase in percent DNA damage, micronucleus frequency and erythrocyte abnormalities. Nuclear anomalies such as notched nuclei, lobed nuclei, bridged nuclei, and deformed nuclei; and cytoplasmic anomalies like anisochromasia, vacuolated cytoplasm, lobed cells, and echinocytes were observed. The findings revealed the genotoxic potential of commercial formulations pyrethroid cypermethrin at concentrations found in the environment and their potential deleterious effects on nontarget aquatic organisms.

Early structural and functional changes in Baikal Sculpin gills exposed to suspended soot microparticles in experiment

The toxic influence of soot microparticles on terrestrial organisms has been well studied, although there is scarce data on how microparticles could affect hydrobionts. We performed a first-ever study of the short-term (5 days) impact of furnace soot (0.005 g/L) on the structural and functional features of gill cells in the Baikal Sculpin species Paracottus knerii, Dybowski, 1874. The soot samples used in the experiment were composed of small (10-100 nm) particles and larger (up to 20 μm) aggregates. The dominant fractions of the polycyclic aromatic hydrocarbons of these microparticles were phenanthrene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzofluoranthenes, benzopyrenes, indeno[1,2,3-c,d]pyrenes, and benzo[ghi]perylene. Trace element analysis of the soot detected the presence of C, S, Si, Al, Ca, K, Mg, P, and Fe. The gill condition was assessed with electron scanning, transmission, and laser confocal microscopy. Soot induces degenerative changes in the macrostructure and surface of secondary lamellae and increases mucus production in fish gills. A decrease in mitochondrial activity, an increase in reactive oxygen species production, and an increase in the frequency of programmed cell death in gill epithelium were observed under the influence of soot. In chloride cells, an induction of macroautophagy was detected. In general, the changes in fish gills after the short-term influence of soot microparticles indicate the stress of respiratory and osmotic regulation systems in fish. The data obtained are important for forming a coherent picture of the impact of soot on hydrobionts and for developing bioindication methods for evaluating the risks of their influence on aquatic ecosystems.

Short-Term Effects of Wildfire Ash on Water Quality Parameters: A Laboratory Approach

Climate change coupled with inappropriate burning practices has increased large-scale wildfires in Brazilian tropical savannahs (Cerrado). Considering that the effects of ash from wildfires on water parameters are scarcely known in tropical savannahs, this study investigated the chemical changes caused by ash in the soft water, commonly used for bioassays. To this end, ash samples were collected immediately following a fire in a Cerrado area (Federal District, Brazil) and put into water (1:10 ash:soft-water m/v) to check physical parameters under laboratory conditions. Major water-extractable elements (K⁺, SO₄^2-, Ca²⁺_, PO₄^3-, Na⁺, Mg²⁺) from ash strongly altered water quality parameters: elevated total dissolved solids and conductivity levels as well as an increase in pH and decrease in dissolved oxygen concentration were reported over the course of the experiment (15 days) compared to control conditions. Our results point out relevant solubilized compounds from ashes which may potentially impact water quality in post-fire scenarios.

A Fish-Based Index of Biotic Integrity for Neotropical Rainforest Sandy Soil Streams—Southern Brazil

Multimetric indices are considered a low-cost and rapid means of assessing ecological integrity in streams. This study aimed to develop a fish-based Index of Biotic Integrity (N3S-IBI) in an agricultural region within the domains of the Atlantic rainforest in Brazil. We sampled 23 first-order streams and used large-scale land use and a local physical condition index to choose reference sites and to classify sites according to the disturbance level. N3S-IBI resulted in six metrics (Simpson’s dominance; the numbers of Characiformes and non-native individuals (Poecilia reticulata); and the percentages of Characidae species, intolerant insectivorous individuals, and tolerant species), contemplating tolerance, composition, abundance, richness, trophic habits, and origin. The low number of metrics contributes to a quick and easy biomonitoring process. N3S-IBI showed an excellent performance to separate least and most disturbed sites in our study area and can provide additional knowledge about anthropogenic effects within this impacted region. In fact, this tool could be utilized by managers to direct restoration actions for the most disturbed sites and to strengthen the preservation of the least disturbed sites.

Short-term effects of wildfire ash exposure on behaviour and hepatosomatic condition of a potamodromous cyprinid fish, the Iberian barbel Luciobarbus bocagei (Steindachner, 1864)

Wildfires are a common phenomenon in Mediterranean regions that is becoming increasingly frequent and severe, causing several environmental concerns, of which ash runoff represents an important source of disturbance for aquatic organisms, in particular for fishes. Studies on the behavioural response of fishes to wildfire ash runoff are scarce and seldom include cyprinid species. The goal of this study was to investigate in a 3-artificial flume channel mesocosm, the behavioural and hepatosomatic condition responses of a native widespread potamodromous fish, the Iberian barbel (Luciobarbus bocagei), previously exposed for 24 h to different concentrations of wildfire ashes: 0.0 g/L (the control, no ash), 1.0 g/L (low concentration) and 2.0 g/L (high concentration). Behavioural parameters included i) routine activity, ii) boldness and iii) shoaling cohesion. The hepatosomatic index (HSI) was further determined to assess the health condition of fish. Significant differences on fish behaviour parameters were detected between the control and the high concentration of ash. Accordingly, i) an increasing proportion of fish were found on resting activity (56.2% vs 30.6% in the control), whereas the proportion of fish on searching behaviour (58.4% in the control) decreased (41.5%); ii) the proportion of bolder individuals was found to decrease (42.5% in the control vs. 29.4%) and iii) the same trend was detected for shoaling cohesion (61.3% in the control to 33.8%, of all fish within a body length of each other). Such differences were paralleled by an increase in the HSI from 1.62% (control) to 2.40% (high concentration). The present study shows that even short duration exposure to ash-loaded runoff can alter fish behaviour and hepatosomatic condition and highlights the need to maintain an unfragmented river network, or, when this is not possible, to prioritize the removal or retrofitting of barriers to increase movement dispersal and provide conditions for species recovery from fire-disturbances.