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T-2 toxin, a hazardous mycotoxin often present in cereals and products based on cereals, poses a substantial risk to humans and animals due to its high toxicity. The development of uncomplicated, quick and highly sensitive methods for detecting T-2 toxin is imperative. In this work, a portable sensing system was constructed using water column height as a readout device in combination with a controlled release system, which allows for an accurate quantitative analysis of T-2 toxin without the need for expensive instrumentation or skilled technicians. Hyaluronic acid (HA) hydrogel was constructed by double cross-linked DNA/aptamer hybrids with polyethyleneimine (PEI) and embedded with platinum nanoparticles (Pt NPs). The aptamer specifically bound to T-2 toxin in its presence, resulting in the disruption of the hydrogel and subsequent release of the Pt NPs. These Pt NPs were later mixed with a solution of H2O2 in a confined reaction flask, leading to the decomposition of H2O2 into O2. A glass capillary tube containing a column of red water had been inserted into the cap of the reaction flask, and the low solubility of O2 led to an increase in pressure within the reaction unit, causing the red water column to rise. There is a good linear correlation between the height of the capillary liquid level and the T-2 toxin concentration in the range of 20 ng/mL to 6 µg/mL. The system has been successfully used to detect T-2 toxin in samples of barley tea and corn.

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This study examines the mercury content in the marine matrices water column, surface sediment and benthic invertebrates of Coronel and Coliumo bays, central Chile, under winter and summer conditions. Coronel Bay has been subject to intense industrialization in the last three decades, while Coliumo Bay remains as a fisherman's cove and a popular summer tourism destination. Our results reveal significantly higher mercury concentrations in the three environmental matrices analyzed for Coronel Bay, while Coliumo Bay exhibits levels within the range considered natural. Moreover, the mercury levels in Coronel Bay exceed the optimal criteria for aquatic life, indicating a deterioration in environmental quality of this locality. Industrial development is identified as main factor explaining the differences observed between these two coastal water bodies. This study presents the most updated record of mercury levels in the Southeast Pacific and represents the first comprehensive evaluation of marine environmental matrices in two bays with divergent activities.

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Bacteria and archaea play a fundamental role in the biogeochemical cycles of organic matter, pollutants, and nutrients to maintain the trophic state of aquatic ecosystems. However, very little is known about the composition patterns of microbial communities in vertical distribution (water column) in freshwater lakes and their relationship with the physicochemical properties of water. "La Encantada" lake in the Lagunas de Montebello National Park (LMNP) is a site of interest due to the anthropogenic impact received and the little information about it. In this study, 3 sites were evaluated; samples were collected using 0-15 m deep water columns and analyzed using Illumina MiSeq sequencing technology based on the 16S rRNA gene. The physical parameters of pH, temperature, dissolved oxygen, electrolytic conductivity, and PO-4 were determined. The results revealed clear differences in the microbial composition of the water throughout the column; the most abundant phyla in bacterial communities were Proteobacteria (23.2%), Cyanobacteria (17.3%), and Bacteroidetes (17.2%), and for archaea were Crenarchaeota (35.9%) and Euryarchaeota (33.2%). PICRUSt metabolic inference analysis revealed that the main functional genes were related to cellular processes and biodegradation of xenobiotics, indicating an increasing trend of contaminants and residual discharges that may act as a precursor to alter microbial communities and stability of the lakes. At depths of 10 and 15 m, the microbial diversity was greater; likewise, the correlation between the physicochemical parameters and the microbial communities at the genus level showed that Chlorobaculum, Desulfomonile, and Candidatus Xiphinematobacter were favored by an increase in dissolved phosphates and by the decrease in pH and temperature. These results highlight that the microbial communities exhibit variation in their composition due to the effect of depth and physicochemical parameters, which could play a role as biological factors in the trophic states of a lake.

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Microplastics debris in the marine environment have been widely studied across the globe. Within these particles, the most abundant and prevalent type in the oceans are anthropogenic microfibers (MFs), although they have been historically overlooked mostly due to methodological constraints. MFs are currently considered omnipresent in natural environments, however, contrary to the Northern Hemisphere, data on their abundance and distribution in Southern Oceans ecosystems are still scarce, in particular for sub-Antarctic regions. Using Niskin bottles we've explored microfibers abundance and distribution in the water column (3-2450 m depth) at the Burdwood Bank (BB), a seamount located at the southern extreme of the Patagonian shelf, in the Southwestern Atlantic Ocean. The MFs detected from filtered water samples were photographed and measured using ImageJ software, to estimate length, width, and the projected surface area of each particle. Our results indicate that small pieces of fibers are widespread in the water column at the BB (mean of 17.4 ± 12.6 MFs.L-1), from which, 10.6 ± 5.3 MFs.L-1 were at the surface (3-10 m depth), 20 ± 9 MFs.L-1 in intermediate waters (41-97 m), 24.6 ± 17.3 MFs.L-1 in deeper waters (102-164 m), and 9.2 ± 5.3 MFs.L-1 within the slope break of the seamount. Approximately 76.1% of the MFs were composed of Polyethylene terephthalate, and the abundance was dominated by the size fraction from 0.1 to 0.3 mm of length. Given the high relative abundance of small and aged MFs, and the oceanographic complexity of the study area, we postulate that MFs are most likely transported to the BB via the Antarctic Circumpolar Current. Our findings imply that this sub-Antarctic protected ecosystem is highly exposed to microplastic pollution, and this threat could be spreading towards the highly productive waters, north of the study area.

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Due to the low incidence of precipitation attributed to climate change, many high-altitude Andean lakes (HAALs) and lagoons distributed along the central Andes in South America may soon disappear. This includes La Brava-La Punta, a brackish lake system located south of the Salar de Atacama within a hyper-arid and halophytic biome in the Atacama Desert. Variations in the physicochemical parameters of the water column can induce changes in microbial community composition, which we aimed to determine. Sixteen sampling points across La Brava-La Punta were studied to assess the influence of water physicochemical properties on the aquatic microbial community, determined via 16S rRNA gene analysis. Parameters such as pH and the concentrations of silica, magnesium, calcium, salinity, and dissolved oxygen showed a more homogenous pattern in La Punta samples, whereas those from La Brava had greater variability; pH and total silica were significantly different between La Brava and La Punta. The predominant phyla were Proteobacteria, Bacteroidetes, Actinobacteria, and Verrucomicrobia. The genera Psychroflexus (36.85%), Thiomicrospira (12.48%), and Pseudomonas (7.81%) were more abundant in La Brava, while Pseudospirillum (20.73%) and Roseovarius (17.20%) were more abundant in La Punta. Among the parameters, pH was the only statistically significant factor influencing the diversity within La Brava lake. These results complement the known microbial diversity and composition in the HAALs of the Atacama Desert.

RESUMO

Several areas within the Bahía Blanca estuary (BBE), with different maritime traffic intensity, were studied in order to confirm the presence and assess the distribution of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) in the water column. The organotin compounds (OTCs) were determined in the water samples-taken in summer, autumn, winter, and spring of 2014-by gas chromatography coupled to mass spectrometry after liquid-liquid extraction with hexane. The incidence of TBT throughout the whole sampling period indicated a continuous presence of this compound to the study area. However, in accordance with the butyltin degradation index (BDI), TBT was not recently introduced in the BBE. Furthermore, the average TBT levels exceeded the international guideline established by the Oslo-Paris commission (0.62 ng Sn L-1). As a result, certain biological effects could be expected to occur in sensitive species such as mussels. While DBT were below the detection limit in the 75% of the samples analyzed, MBT was detected in all the samples and no significant differences were found among the concentrations measured in the different seasons (Kruskal-Wallis test, p > 0.05). In addition, no correlations were found among the OTCs levels and the evaluated physiochemical parameters (Spearman coefficient, p > 0.05).

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This study investigated, on both metric and centimetric scales, mercury (Hg) transformations and dynamics within a water column chemocline of a tropical reservoir. Data collected included conventional measurement of Hg in water samples, diffusive gradients in thin-films (DGT) assessments, and thermodynamic speciation modeling in order to portray the biogeochemical processes that control elemental Hg (EM) and dissolved monomethylated Hg (MeHgD) production. The primary contribution of this study is demonstration that the DGT technique can be successfully implemented to examine labile Hg compound mobilization, and estimation of how local substratum facilitates Hg reduction and methylation reactions. DGT profiles with a resolution of 1cm revealed a fine sequence of prominent Hg reduction/oxidation reactions at the chemocline level. This is interpreted as a manifestation of both: i) kinetic effects capable of arising inside the diffusive layer of DGT devices, and ii) extremely localized production or consumption of reducible and methylable Hg. Another key result obtained at the metric scale is that EM and MeHgD production at a water column chemocline are intricately linked, as both are fueled by nutrients episodically released during the decomposition of falling epilimnetic organic particles or inhibited by dissolved organic matter and inorganic compounds continuously transported from the deeper monimolimnion. Finally, it is worth noting that the chemocline acts as an accumulation and recycling domain for falling MeHg-loaded organic particles, whereas the high primary productivity layer in the epilimnion represents the principal reactor with respect to Hg methylation and reduction.

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Satellite-derived bathymetry methods over coastal areas were developed to deliver basic and useful bathymetry information. However, the process is not straightforward, the main limitation being the need for field data. The Self-calibrated Spectral Supervised Shallow-water Modeler (4SM) method was tested to obtain coastal bathymetry without the use of any field data. Using Landsat-8 multispectral images from 2013 to 2016, a bathymetric time series was produced. Groundtruthed depths and an alternative method, Stumpf's Band Ratio Algorithm, were used to verify the results. Retrieved (4SM) vs groundtruthed depths scored an average r² (0.90), and a low error (RMSE = 1.47 m). 4SM also showed, over the whole time series, the same average accuracy of the control method (40%). Advantages, limitations and operability under complex atmosphere and water column conditions, and high and low-albedo bottom processing capabilities of 4SM are discussed. In conclusion, the findings suggest that 4SM is as accurate as the commonly used Stumpf's method, the only difference being the independence of 4SM from previous field data, and the potential to deliver bottom spectral characteristics for further modeling. 4SM thus represents a significant advance in coastal remote sensing potential to obtain bathymetry and optical properties of the marine bottom.

RESUMO

The relationship between the occurrence of forest fires in central Chile and the total concentration of dioxins and furans (PCDD/F) in nearby coastal waters was analyzed. The data for this analysis was obtained from a long-term environmental monitoring program (PROMNA) in the Bio-Bio Region. Quantification of PCDD/F was performed using HRGC/HRMS at the MSS laboratory in England. Between 2006 and 2014, peaks were observed in February 2007 and 2012. These concentration maxima coincided with major forest fires in the Bio-Bio Region and particularly with those in the Itata River Basin. The January 2012 fires generated an intense short-term response that was associated with atmospheric transport which increases medium toxicity furan-type congeners concentrations (TCDF, PCDF and HxCDF) and six months later a concentration increase of low toxicity dioxin-type congeners was observed (OCDD, HpCDD and HxCDD) coinciding with maximum winter river flow. These results suggest that forest fires near the coastal zone are responsible for increases in PCDD/F concentration observed in the study area.

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This study aimed to evaluate the contamination level of the Peri Lagoon, the main freshwater reservoir of Santa Catarina Island, Southern Brazil, for human adenovirus (HAdV), hepatitis A virus (HAV), rotavirus species A (RVA), and somatic coliphages (SOMCPH). Viruses were also investigated in sediments and their sensitivity against natural sunlight was analysed by studying their spatial distribution in different depths of the water column. A total of 84 water samples and 48 sediment samples were examined by qPCR or RT-qPCR. Infectivity of HAdV and SOMCPH was determined and quantified by plaque assay method. A sum of 64% and 48% of water and sediment samples were positive for HAdV, respectively. RVA was present in 33% and 18% of water and sediment samples, and 25% of water samples were positive for HAV. HAdV were infectious in 76% of water and 83% of sediment samples that were positive by qPCR. SOMCPH could be detected in 42% and 18% of water and sediment samples, respectively. The data pointed a variation of viruses' prevalence according to the different water column depths. These results demonstrated that water sources and sediments contaminated by human wastes could play an important role in the recontamination of water columns harvested for further treatment or used for recreational purposes. These data can be of great value for future risk assessment analysis.

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Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.(AU)

Corbicula fluminea é um bivalve invasor, responsável por inúmeros problemas ambientais e econômicos ao redor do mundo. Apesar de sua capacidade de invasão, a espécie sofre certas restrições devido a fenômenos naturais em ambientes lênticos, afetando significativamente sua estrutura populacional (e.g. flutuação do nível da água e a exposição à luz solar). O presente trabalho avaliou como o decréscimo temporal do nível da água de um reservatório neotropical e a exposição solar, afeta a estrutura populacional de C. fluminea. Duas amostragens foram realizadas no reservatório da Usina Hidrelétrica (UHE) de Furnas (Minas Gerais, Brasil), em 2011 e 2012. A densidade populacional, o comprimento médio e a distribuição espacial da espécie para cada ano foram estimados após amostragem em 51 quadrats (0,0625m2) dispostos em três transectos em diferentes distâncias das margens do reservatório (0, 10 e 20 m em relação a um ponto fixo). Observou-se o predomínio de C. fluminea em ambos os anos, coincidindo com o decréscimo da densidade e riqueza de espécies nativas nas áreas de amostragem. Foram registradas diferenças significativas na densidade de C. fluminea entre as distâncias da margem, sendo atribuídas principalmente à variabilidade temporal do substrato e da água desses ambientes. Registrou-se também uma tendência em aumento da densidade e agregação com o aumento da distância da margem, devido à maior estabilidade dessas áreas (>10 m). Houveram diferenças significativas no tamanho médio das conchas de C. fluminea entre às distâncias da margem e durante os anos, assim como na interação desses fatores (Distâncias vs. Anos). Tais resultados foram associados à capacidade reprodutiva e invasiva da espécie. Esse estudo revelou que eventos temporais (principalmente, a flutuação do nível da água) em ambientes lênticos neotropicais provocam alterações na densidade, tamanho médio e distribuição de C. fluminea e na composição da malacofauna nativa.(AU)

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RESUMO

Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.

Corbicula fluminea é um bivalve invasor, responsável por inúmeros problemas ambientais e econômicos ao redor do mundo. Apesar de sua capacidade de invasão, a espécie sofre certas restrições devido a fenômenos naturais em ambientes lênticos, afetando significativamente sua estrutura populacional (e.g. flutuação do nível da água e a exposição à luz solar). O presente trabalho avaliou como o decréscimo temporal do nível da água de um reservatório neotropical e a exposição solar, afeta a estrutura populacional de C. fluminea. Duas amostragens foram realizadas no reservatório da Usina Hidrelétrica (UHE) de Furnas (Minas Gerais, Brasil), em 2011 e 2012. A densidade populacional, o comprimento médio e a distribuição espacial da espécie para cada ano foram estimados após amostragem em 51 quadrats (0,0625m2) dispostos em três transectos em diferentes distâncias das margens do reservatório (0, 10 e 20 m em relação a um ponto fixo). Observou-se o predomínio de C. fluminea em ambos os anos, coincidindo com o decréscimo da densidade e riqueza de espécies nativas nas áreas de amostragem. Foram registradas diferenças significativas na densidade de C. fluminea entre as distâncias da margem, sendo atribuídas principalmente à variabilidade temporal do substrato e da água desses ambientes. Registrou-se também uma tendência em aumento da densidade e agregação com o aumento da distância da margem, devido à maior estabilidade dessas áreas (>10 m). Houveram diferenças significativas no tamanho médio das conchas de C. fluminea entre às distâncias da margem e durante os anos, assim como na interação desses fatores (Distâncias vs. Anos). Tais resultados foram associados à capacidade reprodutiva e invasiva da espécie. Esse estudo revelou que eventos temporais (principalmente, a flutuação do nível da água) em ambientes lênticos neotropicais provocam alterações na densidade, tamanho médio e distribuição de C. fluminea e na composição da malacofauna nativa.

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