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Environmental reference conditions (RC) and historical trends are crucial for assessing the degree of freshwater impact and formulating restoration measures. This is particularly relevant for freshwater systems used as potable water sources. Using sediments from the Carlos Maggiolo reservoir (Minas, Uruguay), located in a watershed with a mining history, this study aimed to (1) establish metal (As, Cr, Cu, Ni, Pb, and Zn) RC using a predicted interval (PI) chemometric technique; (2) evaluate metal enrichment and toxicity over time and space; and (3) assess environmental changes examining geochemical proxies. Surface sediments from 29 stations were used to establish RC and a core from the dam area was sampled to infer past conditions. The sediments were submitted to partial digestion and analyzed by inductively coupled plasma optical emission spectrometry- ICP-OES. Enrichment factor (EF) calculated using both PI and bottom core values did not show significant differences over time. Over space and time, most metals primarily originated from natural sources (EF < 2). The PI in mg/kg was Cr: 23.74-37.32; Cu: 25.75-48.99; Ni: 16.29-25.55; Pb: 7.63-13.75; and Zn: 94.34-174.80. A stratigraphically constrained cluster analysis corroborated by a permutational multivariate analysis of variance categorized the reservoir into two zones: Zone I, before reservoir operation to ~ 1996, and Zone II from ~ 1997 to 2017. The average concentrations of the main metals of toxicological interest in zones I and II, respectively, were as follows: Cr 37.60 ± 1.59, 34.54 ± 1.49 mg/kg; Cu 49.76 ± 2.84, 44.55 ± 2.70 mg/kg; Ni 24.11 ± 0.67, 22.53 ± 1.22 mg/kg; Pb 12.40 ± 0.63, 13.52 ± 0.82 mg/kg; Zn 99.25 ± 3.12, 93.86 ± 4.42 mg/kg; Mn 1160.56 ± 68.88, 1441.61 ± 83.55 mg/kg; and P 1243.21 ± 271.56, 1128.42 ± 183.10 mg/kg. According to a principal component analysis, the period preceding reservoir operation until ~ 1985 was linked to mining activities and application of Cu2SO4, and the period from 1985s to 2000 was influenced by C and P concentrations due to increasing agricultural and afforestation activities in the watershed that consume P fertilizers. The most recent period, from 2000 to ~ 2017, was characterized by an increase in sedimentation rates mainly associated with erosion, particularly in the agricultural areas. This subsequent soil loss in the watershed could compromise the reservoir's useful life. This study contributes to a better understanding of metal geochemistry in subtropical reservoirs and aids in formulating effective recovery and restoration measures.

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The existing literature provides limited insights into the dynamics of phytoplankton communities and the spatial heterogeneity of physicochemical parameters in multisystem cascade reservoirs (interconnected reservoirs derived from different rivers). The existing studies are concentrated on cascade reservoirs (interconnected reservoirs derived from the same river). To address this knowledge gap, the aims of the present study were as follows: (1) investigate the spatial heterogeneity, within and between reservoirs, of geochemical parameters associated with the eutrophication process, considering total phosphorus, chlorophyll-a, pheophytin, and metals (chromium, copper, nickel, lead, zinc, iron, and manganese); (2) evaluate sediment quality at the designated locations; (3) assess differences in the richness and concentration of sedimentary photopigments between the reservoirs. Application of principal component analysis revealed discernible gradients for the abiotic variables, although the differences were not statistically significant (one-way PERMANOVA test, p > 0.05). The observations suggested a tendency towards spatial homogeneity within and between the reservoirs. The metal concentrations were consistent with regional reference values, while phosphorus levels in the sediment approached the threshold for classification as pollution (~ 2000 mg/kg). Analysis of pigments indicated low dissimilarity among the reservoirs, which could be mainly attributed to the eutrophication process and high connectivity of the sampled areas. To counteract ongoing biotic homogenization, it is essential to reduce nutrient inputs and invest in ecological protection and restoration programs. The analysis of sedimentary photopigments provides an efficient and cost-effective alternative way to assess phytoplankton communities.

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Studies on functional traits of aquatic communities are useful for understanding the ecosystem dynamics as well as the diversity of ecological niches. Here, we characterize zooplankton functional groups and which limnological factors are responsible to changes in traits. Water samples were collected to evaluate limnological parameters and vertical hauls with plankton net (68 µm) were performed to characterize the community in seven reservoirs (Itupararanga, Atibainha, Salto Grande, Rio Grande, Igaratá, Barra Bonita, and Broa, São Paulo state, Brazil). Each species identified was classified according to a trophic group, reproduction mode, body length, habitat, and feeding habitats. Our results showed a predominance of pelagic suspensory herbivores with cilia (31%) followed by pelagic herbivore suspension filter feeders (17%) and raptorial omnivores (15.38%). The other individuals were categorized as pelagic herbivore suspension with oral device (12.3%), littoral herbivores suspensive with cilia (12.3%), pelagic-sucking herbivores (9.2%), and littoral grazing herbivores (3%). The dominance of herbivores may be influenced by the availability of nutrients, influencing their food sources. The abundance of omnivores engaged in predatory behavior can be attributed to disponible prey, thereby exerting significant repercussions on the organization of biological communities.

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The historical impacts of eutrophication processes were investigated in six subtropical reservoirs (São Paulo, Brazil) using a paleolimnological approach. We questioned whether the levels of pigment indicators of algal biomass could provide information about trophic increase and whether carotenoid pigments could offer additional insights. The following proxies were employed: organic matter, total phosphorus, total nitrogen, photosynthetic pigments (by high-performance liquid chromatography), sedimentation rates, and geochronology (by 210 Pb technique). Principal component analysis indicated a gradient of eutrophication. In eutrophic reservoirs (e.g., Rio Grande and Salto Grande), levels of lutein and zeaxanthin increased over time, suggesting growth of Chlorophyta and Cyanobacteria. These pigments were significantly associated with algal biomass, reflecting their participation in phytoplankton composition. In mesotrophic reservoirs, Broa and Itupararanga, increases and significative linear correlations (r > 0.70) between pigments and nutrients are mainly linked to agricultural and urban activities. In the oligotrophic reservoir Igaratá, lower pigment and nutrient levels reflected lesser human impact and good water quality. This study underscores eutrophication's complexity across subtropical reservoirs. Photosynthetic pigments associated with specific algal groups were informative, especially when correlated with nutrient data. The trophic increase, notably in the 1990s, may have been influenced by neoliberal policies. Integrated pigment and geochemical analysis offers a more precise understanding of eutrophication changes and their ties to human factors. Such research can aid environmental monitoring and sustainable policy development.

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Spatial distribution linked to geostatistical techniques contributes to sum up information into an easier-to-comprehend knowledge. This study compares copper spatial distribution in surface sediments and subsequent categorization according to its toxicological potential in two reservoirs, Rio Grande (RG) and Itupararanga (ITU) (São Paulo-Brazil), where copper sulfate is applied and not applied, respectively. Sediments from 47 sites in RG and 52 sites in ITU were collected, and then, copper concentrations were interpolated using geostatistical techniques (kriging). The resulting sediment distributions were classified in categories based on sediment quality guides: threshold effect level and probable effect level; regional reference values (RRVs) and enrichment factor (EF). Copper presented a heterogenic distribution and higher concentrations in RG (2283.00 ± 1308.75 mg/kg) especially on the upstream downstream, associated with algicide application as well as the sediment grain size, contrary to ITU (21.81 ± 8.28 mg/kg) where a no-clear pattern of distribution was observed. Sediments in RG are predominantly categorized as "Very Bad", whereas sediments in ITU are mainly categorized as "Good", showing values higher than RRV. The classification is supported by the EF categorization, which in RG is primarily categorized as "Very High" contrasting to ITU classified as "Absent/Very Low". Copper total stock in superficial sediment estimated for RG is 4515.35 Ton of Cu and for ITU is 27.45 Ton of Cu.

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Sediment cores were used to establish past environmental impacts associated with eutrophication, erosion and metal contamination in the subtropical Atibainha reservoir (São Paulo State, Brazil). We hypothesize that: (1) the levels of nutrients, determined by a spectrophotometric method, reflect the contributions of these elements over time and (2) changes in sedimentation rates, determined by 210Pb geochronology, and metal flows, determined by ICP-AEOS, are related to anthropic activities. Stratigraphic changes in the analysed variables were used to divide the sediment cores into three intervals, according to PCA and cluster analysis (Euclidian distances, Ward's method). Interval I, composed by the period prior to operation of the reservoir, was influenced by organic matter levels. Interval II, between 1967 and 1993 (PC2: 14.94% of the total variability), a period of minor impacts, was mainly influenced by Mn (eigenvalue of 0.71) and Zn (0.74). Interval III, which included sediment deposited between 1993 and 2015 (PC1: 60.28% of the total variability), was influenced by the highest levels of the pigments lutein (0.86), zeaxanthin (0.90) and fucoxanthin (0.65), together with total nitrogen (0.78) and sedimentation rate (0.91), suggesting changes in the phytoplankton community composition probably associated to the intensification of eutrophication and erosion processes. Despite the limitations of applying paleolimnological techniques in reservoirs and the use of pigments as proxies in regions with higher temperatures, it was observed that the anoxic conditions and the aphotic environment in the hypolimnion acted to preserve pigments associated with the groups Chlorophyta (lutein), Cyanobacteria (zeaxanthin) and Bacillariophyta (fucoxanthin). The isolated analysis of nutrients was not sufficient to make conclusive inferences regarding the eutrophication history, since the levels of TP tended to decrease over time, in contrast to an increase in the levels of TN. Despite intensification of eutrophication and erosion, associated to anthropic activities, no signs of metal contamination were recorded.

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Toxic cyanobacteria blooms are a frequent problem in subtropical reservoirs and freshwater systems. The purpose of this study was to investigate the occurrence of potentially toxic cyanobacteria and the environmental conditions associated with the presence of cyanotoxins in a Brazilian subtropical reservoir. Five collections were carried out at seven sampling locations in the reservoir, during the rainy and dry seasons, between the years 2016 and 2017. There was permanent occurrence of Raphidiopsis raciborskii (Woloszynska) Aguilera, Berrendero Gómez, Kastovsky, Echenique & Salerno (Phycologia 57(2):130-146, 2018), ranging between dominant and abundant, with an average biomass of 38.8 ± 29.9 mg L-1. Also abundant were Dolichospermum solitarium, D. planctonicum, Planktothrix isothrix, and Aphanizomenon gracile. Saxitoxin (STX) was detected in all the collected samples (0.11 ± 0.05 µg L-1). Microcystin (MC) was also detected, but at lower concentrations (0.01 ± 0.0 µg L-1). Low availability of NO3- and phosphorus limitation had significant effects on the R. raciborskii biomass and the levels of STX and MC. It was observed that R. raciborskii was sensitive to thermal stratification, at the same time that STX levels were higher. This suggested that STX was produced under conditions that restricted the growth of R. raciborskii. These are important findings, because they add information about the permanent occurrence of STX and R. raciborskii in an aquatic ecosystem limited by phosphorus, vulnerable to climatic variations, and polluted by domestic effluents.

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Satellite images were used to assess surface water quality based on the concentration of chlorophyll a (chla), light penetration measured by the Secchi disk method (SD), and the Cyanobacteria cells number per mL (cyano). For this case study, six reservoirs interconnected were evaluated, comprising the Cantareira System (CS) in São Paulo State (Brazil). The work employed Sentinel-2 images from 2015 to 2018, SNAP image processing software, and the native products conc_chl and kd_z90max, treated using Case 2 Regional Coast Color (C2RCC) atmospheric correction. The database was obtained from CETESB, the agency legally responsible for operation of the Inland Water Quality Monitoring Network in São Paulo State. The results demonstrated robustness in the estimates of chla (RMSE = 3.73; NRMSE% = 19%) and SD (RMSE = 2,26; NRMSE% = 14%). Due to the strong relationship between cyano and chla (r2 = 0.84, p < 0.01, n = 90), both obtained from field measurements, there was also robustness in cyano estimates based on the estimates of chla from the satellite images. The data revealed a clear pattern, with the upstream reservoirs being more eutrophic, compared to those downstream. There were evident concerns, about water quality, particularly due to the high numbers of Cyanobacteria cells, especially in the upstream reservoirs.

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The establishment of reference conditions and typology are two important steps in water resources management. The reference conditions enable the determination of how impacted an ecosystem is, while the typology facilitates the implementation of management procedures. A study of subtropical reservoirs in São Paulo State (Brazil) was performed to obtain (1) an abiotic typology, using principal component analysis (PCA) and cluster analysis (Ward's method with Euclidean distances), and (2) reference conditions for total phosphorus (TP), total nitrogen (TN), and chlorophyll-a (Chl-a) in the dry and rainy seasons for one of the established typologies. Two main statistical techniques were used: the lake population distribution approach and the trisection method. PCA identified an environmental gradient in the east-west direction, with reservoirs at higher latitudes and with larger dimensions in the west, and smaller reservoirs in eastern areas with higher altitude and higher average annual rainfall. The PCA and cluster analysis indicated that there were four main types of reservoirs. The nutrient criteria techniques, obtained for 13 type I rainy-east reservoirs, were not significantly different (t test, p < 0.05). Although the methods resulted in similar reference conditions, one-way ANOVA indicated significant differences between the seasons for Chl-a, which levels were slightly higher in the rainy season. As far as we know, this is the first study to simultaneously provide an abiotic typology and reference conditions for chlorophyll-a and nutrients in different seasons, considering subtropical reservoirs in South America. This investigation makes an important contribution to the monitoring and management of subtropical reservoirs, and the promotion of dialog between the scientific community and managers, aiming at ensuring the sustainability of water bodies.

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Benthic macroinvertebrates are organisms that are recognized as water quality bio-indicators. A wide variety of indices and metrics have been shown to respond to a variety of anthropogenic impacts, usually under a general condition of environmental impairment. The absence of a clear distinction in the relations between specific pollutants and biotic variables is very common and can lead to biased interpretation of biomonitoring. The aims of this research were to test taxonomic and non-taxonomic responses to specific environmental conditions instead to general conditions. For this purpose, we estimated the theoretical toxicity by comparing toxicity values published by EPA with metal concentrations in water and sediments. Then we tested the responses of biological variables to toxicity and other environmental conditions using the linear mixed effects models approach. We generated 32 models considering 24 different biological metrics and indices that were grouped in five levels. Taxonomic and abundance metrics were best predictor than functional or tolerance-based indexes. The strongest model was that which considered subfamily taxonomic resolution responding to Al_w and Cr_s.

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The impacts of anthropic activities have had profound effects on the nitrogen (N) and phosphorus (P) cycles in many aquatic ecosystems. We investigated the spatial and temporal distributions of carbon (C), N, and P in the sediments of a tropical Paiva Castro Reservoir (São Paulo, Brazil), as well as their release and retention in the system. In 2010, surface sediments were collected at nine sites in the reservoir, and a core was obtained in the limnetic zone, in 2010. The core was dated using the 210Pb technique. The organic C content was estimated from organic matter concentration, which was measured by the loss-on-ignition method, and the concentrations of P and N were determined by spectrophotometry. Marked spatial heterogeneity in the Paiva Castro sediments associated with both natural variations in the water body and variations induced by human impacts was observed. Heterogeneity was evidenced by a decrease in the allochthonous contribution of organic matter (C/N) in the upstream-downstream direction and increases of N and P, mainly associated with water flows in the different compartments of the reservoir. In the core, C and N concentrations display significant positive correlations with increases in population and agricultural activities in the drainage basin through time. The C/P molar ratios in surface sediments are indicative of human impacts in the region, as C:P ratios in the sediment are low (7.8:1) compared to the Redfield ratio (C:P = 108:1). Predominance of oxic conditions at the sediment surface and particles sizes < 63 µm provided favorable conditions for P retention in the sediments, which helps prevent eutrophication. Approaches used in this research should be extended to other locations, especially in mesotrophic and oligotrophic reservoirs, to provide information on historical impacts in such aquatic ecosystems.

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Depending on the environmental conditions, surface sediments can retain all the contaminants present and provide a record of the anthropic activities affecting the aquatic environment. In order to analyze the impacts on reservoirs, surface sediments were collected in three characteristic regions (riverine, transitional, and limnetic zones) of seven reservoirs in São Paulo State, Brazil. Analyses were made of grain size, organic matter (OM), total phosphorus (TP), and total nitrogen (TN). Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) was used to determine pseudo-total and bioavailable metals (Cu, Cd, Cr, Ni, Pb, Zn, Mn, Fe, and Al). A Horiba probe was used to measure dissolved oxygen (DO), pH, redox potential (ORP), and temperature (Temp) in the bottom water. The data were analyzed using multivariate statistics. Enrichment factors (EF), pollution load index values (PLI), and background values (BG) were also determined in order to evaluate the potential toxicity. Intra-reservoir and inter-reservoir spatial heterogeneity (p < 0.05) were observed using two-way analysis of similarities. Principal component analysis indicated greater influence of metals in the Barra Bonita, Salto Grande, and Rio Grande reservoirs, corroborating the PLI, EF, and BG data. Bioavailable Cu was found in the Rio Grande reservoir, possibly associated with copper sulfate used to control algal blooms, while bioavailable Ni in the Barra Bonita reservoir was attributed to the presence of industrial wastes and natural geology. The bottom water conditions indicated that the metals remained in insoluble forms.

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Zooplanktonic communities are important components in trophic chain considering primary producers and other levels. In addition, some species are sensitive or tolerant to organic pollution. Here we test the hypothesis that species composition varies according to the eutrophication gradient. We sought to establish which environmental factors are responsible for the variation of the species distribution. This study aimed to characterize zooplankton community and to establish a link between water quality in São Paulo State reservoirs. Samples were collected through vertical hauls with plankton net (68 (m) in seven water bodies. All specimens were identified with specific literature and counted in Sedgwick rafter chamber. Abiotic and biotic data were analyzed by a canonical correspondence analysis. A total of 67 taxa was identified, being Rotifera predominant. The reservoirs exhibited eutrophic conditions mainly Salto Grande, Barra Bonita and Broa. The results point out the rotifers Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. and Keratella tropica (Apstein, 1907) followed eutrophication gradient. Additionally, microcrustaceans such as Notodiaptomus, Mesocyclops, Metacyclops and Diaphanossoma occurred in eutrophic reservoirs. On other hand, the cladocerans Ceriodaphnia cornuta (Sars, 1886) and Bosminopsis deitersi Richard, 1895 were considered indicators of better water quality due to relationship with transparency. The results point out that some indicator species are effective in environmental monitoring without reject physico-chemical and biological analysis.

As comunidades zooplanctônicas são importantes componentes na cadeia alimentar considerando os produtores primários e os demais níveis. Além disso, algumas espécies são sensíveis ou tolerantes à poluição orgânica. Aqui testamos a hipótese de que a composição de espécies varia conforme o gradiente de eutrofização. Buscou-se estabelecer os possíveis fatores ambientais responsáveis pela variação na distribuição das espécies. Esse estudo teve como objetivo caracterizar a comunidade zooplanctônica e relacionar os dados com a qualidade da água em reservatórios do Estado de São Paulo. Amostras foram coletadas através de arrasto vertical por meio de rede de plâncton (68 (m) em sete corpos dágua. Todos os espécimes foram identificados através de literatura específica e contados em camâra de Sedgwick rafter. Os dados bióticos e abióticos foram analisados através da análise de correspondência canônica. Um total de 67 táxons foram encontrados, sendo Rotifera o predominante. No geral, os reservatórios apresentaram condições eutróficas, principalmente Salto Grande, Barra Bonita e Broa. Os resultados apontaram que os rotíferos Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. e Keratella tropica (Apstein, 1907) seguiram o gradiente de eutrofização. Além desses, microcrustáceos como Notodiaptomus, Mesocyclops, Metacyclops e Diaphanossoma ocorreram em reservatórios eutróficos. Por outro lado, os cládoceros Ceriodaphnia cornuta (Sars, 1886) e Bosminopsis deitersi Richard, 1895 foram considerados indicadores de melhor qualidade devido à relação com águas mais transparentes. Os resultados apontam que algumas espécies do zooplâncton são efetivas para o monitoramento ambiental sem descartar as análises físico-químicas e biológicas.

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ABSTRACT: Zooplanktonic communities are important components in trophic chain considering primary producers and other levels. In addition, some species are sensitive or tolerant to organic pollution. Here we test the hypothesis that species composition varies according to the eutrophication gradient. We sought to establish which environmental factors are responsible for the variation of the species distribution. This study aimed to characterize zooplankton community and to establish a link between water quality in São Paulo State reservoirs. Samples were collected through vertical hauls with plankton net (68 (m) in seven water bodies. All specimens were identified with specific literature and counted in Sedgwick rafter chamber. Abiotic and biotic data were analyzed by a canonical correspondence analysis. A total of 67 taxa was identified, being Rotifera predominant. The reservoirs exhibited eutrophic conditions mainly Salto Grande, Barra Bonita and Broa. The results point out the rotifers Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. and Keratella tropica (Apstein, 1907) followed eutrophication gradient. Additionally, microcrustaceans such as Notodiaptomus, Mesocyclops, Metacyclops and Diaphanossoma occurred in eutrophic reservoirs. On other hand, the cladocerans Ceriodaphnia cornuta (Sars, 1886) and Bosminopsis deitersi Richard, 1895 were considered indicators of better water quality due to relationship with transparency. The results point out that some indicator species are effective in environmental monitoring without reject physico-chemical and biological analysis.

RESUMO: As comunidades zooplanctônicas são importantes componentes na cadeia alimentar considerando os produtores primários e os demais níveis. Além disso, algumas espécies são sensíveis ou tolerantes à poluição orgânica. Aqui testamos a hipótese de que a composição de espécies varia conforme o gradiente de eutrofização. Buscou-se estabelecer os possíveis fatores ambientais responsáveis pela variação na distribuição das espécies. Esse estudo teve como objetivo caracterizar a comunidade zooplanctônica e relacionar os dados com a qualidade da água em reservatórios do Estado de São Paulo. Amostras foram coletadas através de arrasto vertical por meio de rede de plâncton (68 (m) em sete corpos dágua. Todos os espécimes foram identificados através de literatura específica e contados em camâra de Sedgwick rafter. Os dados bióticos e abióticos foram analisados através da análise de correspondência canônica. Um total de 67 táxons foram encontrados, sendo Rotifera o predominante. No geral, os reservatórios apresentaram condições eutróficas, principalmente Salto Grande, Barra Bonita e Broa. Os resultados apontaram que os rotíferos Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. e Keratella tropica (Apstein, 1907) seguiram o gradiente de eutrofização. Além desses, microcrustáceos como Notodiaptomus, Mesocyclops, Metacyclops e Diaphanossoma ocorreram em reservatórios eutróficos. Por outro lado, os cládoceros Ceriodaphnia cornuta (Sars, 1886) e Bosminopsis deitersi Richard, 1895 foram considerados indicadores de melhor qualidade devido à relação com águas mais transparentes. Os resultados apontam que algumas espécies do zooplâncton são efetivas para o monitoramento ambiental sem descartar as análises físico-químicas e biológicas.

RESUMEN

Zooplanktonic communities are important components in trophic chain considering primary producers and other levels. In addition, some species are sensitive or tolerant to organic pollution. Here we test the hypothesis that species composition varies according to the eutrophication gradient. We sought to establish which environmental factors are responsible for the variation of the species distribution. This study aimed to characterize zooplankton community and to establish a link between water quality in São Paulo State reservoirs. Samples were collected through vertical hauls with plankton net (68 (m) in seven water bodies. All specimens were identified with specific literature and counted in Sedgwick rafter chamber. Abiotic and biotic data were analyzed by a canonical correspondence analysis. A total of 67 taxa was identified, being Rotifera predominant. The reservoirs exhibited eutrophic conditions mainly Salto Grande, Barra Bonita and Broa. The results point out the rotifers Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. and Keratella tropica (Apstein, 1907) followed eutrophication gradient. Additionally, microcrustaceans such as Notodiaptomus, Mesocyclops, Metacyclops and Diaphanossoma occurred in eutrophic reservoirs. On other hand, the cladocerans Ceriodaphnia cornuta (Sars, 1886) and Bosminopsis deitersi Richard, 1895 were considered indicators of better water quality due to relationship with transparency. The results point out that some indicator species are effective in environmental monitoring without reject physico-chemical and biological analysis.(AU)

As comunidades zooplanctônicas são importantes componentes na cadeia alimentar considerando os produtores primários e os demais níveis. Além disso, algumas espécies são sensíveis ou tolerantes à poluição orgânica. Aqui testamos a hipótese de que a composição de espécies varia conforme o gradiente de eutrofização. Buscou-se estabelecer os possíveis fatores ambientais responsáveis pela variação na distribuição das espécies. Esse estudo teve como objetivo caracterizar a comunidade zooplanctônica e relacionar os dados com a qualidade da água em reservatórios do Estado de São Paulo. Amostras foram coletadas através de arrasto vertical por meio de rede de plâncton (68 (m) em sete corpos dágua. Todos os espécimes foram identificados através de literatura específica e contados em camâra de Sedgwick rafter. Os dados bióticos e abióticos foram analisados através da análise de correspondência canônica. Um total de 67 táxons foram encontrados, sendo Rotifera o predominante. No geral, os reservatórios apresentaram condições eutróficas, principalmente Salto Grande, Barra Bonita e Broa. Os resultados apontaram que os rotíferos Trichocerca longiseta (Schrank, 1802), Hexarthra sp., Brachiounus spp. e Keratella tropica (Apstein, 1907) seguiram o gradiente de eutrofização. Além desses, microcrustáceos como Notodiaptomus, Mesocyclops, Metacyclops e Diaphanossoma ocorreram em reservatórios eutróficos. Por outro lado, os cládoceros Ceriodaphnia cornuta (Sars, 1886) e Bosminopsis deitersi Richard, 1895 foram considerados indicadores de melhor qualidade devido à relação com águas mais transparentes. Os resultados apontam que algumas espécies do zooplâncton são efetivas para o monitoramento ambiental sem descartar as análises físico-químicas e biológicas.(AU)

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Reservoirs in urban areas are used for different purposes and are liable to different types of pressures that can cause the loss of chemical and biological quality, hence diminishing their ecological, economic, and cultural benefits. Here, a study of surface water heterogeneity was undertaken at the Guarapiranga urban reservoir (São Paulo, Brazil) in order to improve understanding of the structure and functioning of these ecosystems. Sampling was performed during the dry and rainy seasons at 33 sites. Limnological variables and total contents of the metals cadmium, nickel, lead, and zinc were analyzed. The risks associated with the metals were evaluated based on the toxicity unit approach. A principal component analysis enabled differentiation of the reservoir into six different areas. Some of the most powerful discriminatory variables (nutrients and metals) showed the existence of anthropogenic impacts on the system. The most strongly affected compartments were located in the following: (1) upstream area, under the influence of the Parelheiros stream, with the highest total phosphorus levels (318 mg L-1) and (2) dam area, with high values for total nitrogen, suspended organic matter, total solids, and pH. The results for the dam compartment were a consequence of substantial urbanization and a longer residence time. Despite high levels of cadmium during the rainy season, no significant potential risk for zooplankton was observed. The data indicated the need to control unauthorized land occupation and to implement adequate sanitation in the Guarapiranga watershed. This research provides information that should assist water resource agencies in the sustainable management of urban reservoirs.

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Reservoirs located in urban areas suffer specific pressures related to human activities. Their monitoring, management, and protection requirements differ from reservoirs situated in non-urbanized areas. The objectives of this study were: (a) to determine the concentrations of select pesticides and emerging pollutants (EPs) present in an urban reservoir; (b) to describe their possible spatial distributions; and (c) to quantify the risks for aquatic life and safeguard drinking water supplies. For this purpose, the Guarapiranga reservoir was studied as an example of a multi-stressed urban reservoir in a tropical region. A total of 31 organic compounds (including pesticides, illicit drugs, pharmaceuticals, and endocrine disruptors) were analyzed twice over a period of one year, together with classical indicators of water quality. The physical and chemical data were treated using principal component analysis (PCA) to identify possible temporal or spatial patterns. Risk assessment was performed for biota and drinking water use, comparing maximum environmental concentrations (MECs) with the predicted no-effect concentrations (PNECs) or drinking water quality criteria (DWC), respectively. The results demonstrated the presence of pesticides and EPs, as well as pollution by high levels of nutrients and Chlorophyll a (Chl. a), during the study period. The nutrients and Trophic State Index (TSI) showed gradients in the reservoir and regional distributions, while the pesticides and EPs only clearly showed this pattern in the dry season. The concentrations and distributions of the pesticides and EPs therefore showed seasonality. These findings suggested that the two groups of pollutants (EPs+pesticides and nutrients) possessed different sources and behavior and were not always correlated in the reservoir studied. In the studied period, no risk was observed in raw water for drinking water use, but carbendazim, imidacloprid, and BPA showed risks for the biota in the reservoir.

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Sediments may be a repository of contaminants in freshwater ecosystems. One way to assess the quality of this compartment, in terms of potentially bioavailable metals, is by the analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM). In order to investigate the bioavailability, toxicity, and compartmentalization of different metals (Cd, Cr, Cu, Ni, Pb, Zn), sampling of surface sediments was performed at nine stations along the Paiva Castro reservoir (São Paulo, Brazil). The metals were analyzed using atomic absorption spectroscopy. Sediment organic matter (OM), organic carbon (OC), and grain size were also measured. The parameters pH, EH, temperature, and dissolved oxygen were determined at the sediment-water interface. Chronic and acute toxicological tests were performed with sediments from the area where water was extracted for the public water supply. Low levels of OM, associated with loss of stratification in the water column, explained the relatively low AVS values. The molar ratio ∑[SEM]-[AVS]/fOC was less than 130 mmol/kg(-1) for all the sampling stations, indicating that the metals were not bioavailable. With the exception of Cd, metal levels were in accordance with background concentrations and the threshold effect level (TEL) established by the Canadian Council of Ministers of the Environment. The ecotoxicological tests confirmed the absence of toxic effects to biota. Application of principal component analysis indicated the presence of four compartments along the reservoir: (1) a riverine zone, potentially threatened by contamination with Cd; (2) an intermediate zone; (3) a limnic area; and (4) the area where water was taken for the public water supply.

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The Metropolitan Region of São Paulo (MRSP) is located in the Brazilian State of São Paulo and reservoirs in this region are vital for water supply and energy production. Changes in economic, social, and demographic trends produced pollution of water bodies, decreasing water quality for human uses and affecting freshwater populations. The presence of emerging pollutants, classical priority substances, nutrient excess and the interaction with tropical-climate conditions require periodic reviews of water policies and monitoring programs in order to detect and manage these threats in a global change scenario. The objective of this work is to determine whether the monitoring program of the São Paulo's Environmental Agency, is sufficient to explain the toxicological and biological responses observed in organisms in reservoirs of the MRSP, and whether it can identify the possible agents causing these responses. For that, we used publicly available data on water quality compiled by this agency in their routine monitoring program. A general overview of these data and a chemometric approach to analyze the responses of biotic indexes and toxicological bioassays, as a function of the physical and chemical parameters monitored, were performed. Data compiled showed temporal and geographical information gaps on variables measured. Toxicological responses have been observed in the reservoirs of the MRSP, together with a high incidence of impairments of the zooplankton community. This demonstrates the presence of stressors that affect the viability of organisms and populations. The statistical approach showed that the data compiled by the environmental agency are insufficient to identify and explain the factors causing the observed ecotoxicological responses and impairments in the zooplankton community, and are therefore insufficient to identify clear cause-effect relationships. Stressors different from those analyzed could be responsible for the observed responses.

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Billings reservoir, the biggest reservoir in the Metropolitan Region of São Paulo (SP), due its strategic importance and the deterioration in its water quality over time, was and remains, subject of many studies in several areas. In order to assess the water quality of this source, several limnological features were investigated throughout 20 surface points. Were analysed: temperature, pH, electrical conductivity, water body transparency, dissolved oxygen, total solids, total nitrogen, nitrate, nitrite, ammonium, orthophosphate, orthosilicate, chlorophyll a and phaeophytin. In general, Billings Complex has signs of water quality degration, with high levels of chlorophyll a. Principal Component Analysis provided a clear separation of the Complex Billings arms. Were observed seven compartments: 1) Pedreira region, influenced by Pinheiros river, presented high levels of nutrients and chlorophyll-a; 2) Corpo Central and Bororé regions, influenced by Pedreiras waters, with high levels of total solids; 3) Taquacetuba region; 4) Summit Control, Riacho Grande and parts of Taquacetuba and Capivari, influenced by the variable ammonium; 5) Capivari and 6) Rio Pequeno, both areas had the lowest levels of chlorophyll a and nutrients; 7) Rio Grande, with constant applications of algaecides, isolated from the other Billings reservoir regions. The separation was probably due to the dendritic conformation of the reservoir associated with the operating system and human activities such as illegal occupation in the vicinity of the dam. Therefore, actions must be taken in order to reduce nutrient loading that continually enters this ecosystem, through urban settlements control in the region and appropriate sanitation.

A Represa Billings, maior reservatório de água da Região Metropolitana de São Paulo, devido à sua importância estratégica e à degradação na qualidade de suas águas, foi e continua sendo alvo de muitos estudos. A fim de avaliar de maneira integral a qualidade das águas superficiais desse manancial, investigaram-se diversas variáveis limnológicas ao longo de 20 pontos. Analisaram-se as variáveis: temperatura, pH, condutividade elétrica, transparência da água, oxigênio dissolvido, sólidos totais, nitrogênio total, nitrato, nitrito, amônio, ortofosfato, ortosilicato, clorofila a e feofitina. De maneira geral, a represa apresenta sinais de degradação da qualidade da água, com elevados teores de clorofila a. Análise de Componentes Principais forneceu nítida separação dos braços formadores da Represa Billings. Observaram-se sete compartimentos: 1) região de Pedreira, sob influência das águas do rio Pinheiros, apresentou elevados teores de nutrientes e clorofila a; 2) região do Corpo Central e Bororé, sob influência das águas provenientes de Pedreira, apresentou elevados teores de sólidos totais; 3) região do Taquacetuba; 4) região do Summit Control, Riacho Grande, partes do Taquacetuba e Capivari, sob influência da variável amônio; 5) Braços Capivari e 6) Rio Pequeno apresentaram os menores teores de clorofila a e nutrientes; 7) Braço Rio Grande, constantemente submetido à aplicação de algicidas, isolado do restante da Represa Billings. A compartimentação da Represa Billings deve-se principalmente à sua conformação dendrítica, associada às atividades antrópicas, como a ocupação do seu entorno. Portanto, é crucial reduzir a carga de nutrientes que penetram nesse ecossistema, o que pode ser obtido por meio do controle dos assentamentos urbanos e medidas de saneamento básico.

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