Limnological and ecological methods: approaches, and sampling strategies for middle Xingu River in the area of influence of future Belo Monte Power Plant.

In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units.

Spatial patterns of water quality in Xingu River Basin (Amazonia) prior to the Belo Monte dam impoundment.

The Xingu River, one of the most important of the Amazon Basin, is characterized by clear and transparent waters that drain a 509.685 km2 watershed with distinct hydrological and ecological conditions and anthropogenic pressures along its course. As in other basins of the Amazon system, studies in the Xingu are scarce. Furthermore, the eminent construction of the Belo Monte for hydropower production, which will alter the environmental conditions in the basin in its lower middle portion, denotes high importance of studies that generate relevant information that may subsidize a more balanced and equitable development in the Amazon region. Thus, the aim of this study was to analyze the water quality in the Xingu River and its tributaries focusing on spatial patterns by the use of multivariate statistical techniques, identifying which water quality parameters were more important for the environmental changes in the watershed. Data sampling were carried out during two complete hydrological cycles in twenty-five sampling stations. The data of twenty seven variables were analyzed by Spearman's correlation coefficients, cluster analysis (CA), and principal component analysis (PCA). The results showed a high auto-correlation between variables (> 0.7). These variables were removed from multivariate analyzes because they provided redundant information about the environment. The CA resulted in the formation of six clusters, which were clearly observed in the PCA and were characterized by different water quality. The statistical results allowed to identify a high spatial variation in the water quality, which were related to specific features of the environment, different uses, influences of anthropogenic activities and geochemical characteristics of the drained basins. It was also demonstrated that most of the sampling stations in the Xingu River basin showed good water quality, due to the absence of local impacts and high power of depuration of the river itself.

Limnological and ecological methods: approaches, and sampling strategies for middle Xingu River in the area of influence of future Belo Monte Power Plant / Estudo limnológico e da biota aquática no Rio Xingu na área de influência de UHE Belo Monte: metodologia e abordagens

Abstract In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units.

Resumo Neste trabalho os autores descrevem as abordagens limnológicas e a metodologia e estratégia de amostragem adotadas no estudo do Rio Xingu, na área de influência da futura Usina da Belo Monte (UHE Belo Monte). O ecossistema de rios é caracterizado por velocidade unidirecional de correntes, muitas flutuações de fluxos dependendo do clima do padrão de drenagem e do ciclo hidrológico. Mistura vertical permanente e turbulências ocorrem constantemente devido a correntes predominantes. Todos estes mecanismos gerais e específicos característicos do Rio Xingu, foram levados em consideração no plano de estudos limnológicos e amostragens desenvolvidas na área de influência de UHE Belo Monte a montante e a jusante do futuro empreendimento.

Limnological and ecological methods: approaches, and sampling strategies for middle Xingu River in the area of influence of future Belo Monte Power Plant

Abstract In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units.

Resumo Neste trabalho os autores descrevem as abordagens limnológicas e a metodologia e estratégia de amostragem adotadas no estudo do Rio Xingu, na área de influência da futura Usina da Belo Monte (UHE Belo Monte). O ecossistema de rios é caracterizado por velocidade unidirecional de correntes, muitas flutuações de fluxos dependendo do clima do padrão de drenagem e do ciclo hidrológico. Mistura vertical permanente e turbulências ocorrem constantemente devido a correntes predominantes. Todos estes mecanismos gerais e específicos característicos do Rio Xingu, foram levados em consideração no plano de estudos limnológicos e amostragens desenvolvidas na área de influência de UHE Belo Monte a montante e a jusante do futuro empreendimento.

Limnological and ecological methods: approaches, and sampling strategies for middle Xingu River in the area of influence of future Belo Monte Power Plant / Estudo limnológico e da biota aquática no Rio Xingu na área de influência de UHE Belo Monte: metodologia e abordagens

In this paper the authors describe the limnological approaches, the sampling methodology, and strategy adopted in the study of the Xingu River in the area of influence of future Belo Monte Power Plant. The river ecosystems are characterized by unidirectional current, highly variable in time depending on the climatic situation the drainage pattern an hydrological cycle. Continuous vertical mixing with currents and turbulence, are characteristic of these ecosystems. All these basic mechanisms were taken into consideration in the sampling strategy and field work carried out in the Xingu River Basin, upstream and downstream the future Belo Monte Power Plant Units.

Neste trabalho os autores descrevem as abordagens limnológicas e a metodologia e estratégia de amostragem adotadas no estudo do Rio Xingu, na área de influência da futura Usina da Belo Monte (UHE Belo Monte). O ecossistema de rios é caracterizado por velocidade unidirecional de correntes, muitas flutuações de fluxos dependendo do clima do padrão de drenagem e do ciclo hidrológico. Mistura vertical permanente e turbulências ocorrem constantemente devido a correntes predominantes. Todos estes mecanismos gerais e específicos característicos do Rio Xingu, foram levados em consideração no plano de estudos limnológicos e amostragens desenvolvidas na área de influência de UHE Belo Monte a montante e a jusante do futuro empreendimento.

Spatial patterns of water quality in Xingu River Basin (Amazonia) prior to the Belo Monte dam impoundment / Padrões espaciais de qualidade de água na Bacia do Rio Xingu (Amazônia) anteriores a barragem de Belo Monte

The Xingu River, one of the most important of the Amazon Basin, is characterized by clear and transparent waters that drain a 509.685 km2 watershed with distinct hydrological and ecological conditions and anthropogenic pressures along its course. As in other basins of the Amazon system, studies in the Xingu are scarce. Furthermore, the eminent construction of the Belo Monte for hydropower production, which will alter the environmental conditions in the basin in its lower middle portion, denotes high importance of studies that generate relevant information that may subsidize a more balanced and equitable development in the Amazon region. Thus, the aim of this study was to analyze the water quality in the Xingu River and its tributaries focusing on spatial patterns by the use of multivariate statistical techniques, identifying which water quality parameters were more important for the environmental changes in the watershed. Data sampling were carried out during two complete hydrological cycles in twenty-five sampling stations. The data of twenty seven variables were analyzed by Spearman's correlation coefficients, cluster analysis (CA), and principal component analysis (PCA). The results showed a high auto-correlation between variables (> 0.7). These variables were removed from multivariate analyzes because they provided redundant information about the environment. The CA resulted in the formation of six clusters, which were clearly observed in the PCA and were characterized by different water quality. The statistical results allowed to identify a high spatial variation in the water quality, which were related to specific features of the environment, different uses, influences of anthropogenic activities and geochemical characteristics of the drained basins. It was also demonstrated that most of the sampling stations in the Xingu River basin showed good water quality, due to the absence of local impacts and high power of depuration of the river itself.

O rio Xingu, um dos mais importantes rios que constituem a bacia amazônica, é caracterizado por águas claras e transparentes que drenam uma bacia hidrográfica de 509,685 km2 com distintas condições hidrológicas, ecológicas e pressões antrópicas ao longo de seu percurso. Assim como nas demais bacias hidrográficas da Amazônia, os estudos no Xingu são raros. A eminente construção da Usina hidrelétrica de Belo Monte, a qual alterará as condições ambientais na bacia, demanda também a realização de estudos que gerem informações relevantes e que forneçam subsídios para um desenvolvimento mais equilibrado e igualitário região amazônica. Desta maneira, o objetivo deste trabalho foi analisar a qualidade de água no rio Xingu e em seus tributários focando em padrões espaciais na área de estudo pelo uso de técnicas de estatística multivariada, identificando quais parâmetros são mais relevantes nas condições de qualidade de água na bacia hidrográfica. As coletas de dados ocorreram durante dois ciclos hidrológicos completos em vinte e cinco estações de amostragem. Os dados de vinte e sete variáveis foram analisados pelos coeficientes de correlação de Spearman, análise Cluster (CA), e análise de componentes principais (PCA). Os resultados apontaram para um elevado contingente de variáveis com elevada correlação entre si (>0,7), sendo que estas altas variáveis foram retiradas das análises multivariadas por fornecerem informações ecológicas redundantes sobre o ambiente estudado. A CA resultou na formação de 6 agrupamentos, os quais foram observados por possuírem qualidade de água consideravelmente distintas pela PCA. Os resultados estatísticos permitiram identificar uma alta variação espacial da qualidade de água superficial na bacia estudada, sendo estas ocasionadas por especificidades do entorno, diferentes usos da água locais, influências de atividades antrópicas e características geoquímicas das bacias drenadas. Pode-se também evidenciar que em grande parte das estações de coleta na bacia do rio Xingu a qualidade de água superficial foi elevada, decorrente da ausência de impactos locais e do alto poder de depuração do rio.

Alterations in land uses based on amendments to the Brazilian Forest Law and their influences on water quality of a watershed.

The amendments to the Forest Law proposed by the Brazilian government that allow partial substitution of forested areas by agricultural activities raised deep concern about the integrity of aquatic ecosystems. To assess the impacts of this alteration in land uses on the watershed, diffuse loads of total nitrogen (Nt) and total phosphorus (Pt) were estimated in Lobo Stream watershed, southeastern Brazil, based on export coefficients of the Model of Correlation between Land Use and Water Quality (MQUAL). Three scenarios were generated: scenario 1 (present scenario), with 30-meter-wide permanent preservation areas along the shore of water bodies and 50-meter-radius in springs; scenario 2, conservative, with 100-meter-wide permanent preservation areas along water bodies; and scenario 3, with the substitution of 20% of natural forest by agricultural activities. Results indicate that a suppression of 20% of forest cover would cause an increase in nutrient loads as well as in the trophic state of aquatic ecosystems of the watershed. This could result in losses of ecosystem services and compromise the quality of water and its supply for the basin. This study underlines the importance of forest cover for the maintenance of water quality in Lobo Stream watershed.

Occurrence of Ceratium furcoides (Levander) Langhans 1925 bloom at the Billings Reservoir, São Paulo State, Brazil.

An unusual bloom of Ceratium furcoides is reported for a station of the Taquacetuba compartment of the Billings Reservoir. The appearance of this bloom is attributed to the mixing and turbulence of the water column that removed Ceratium cysts from the surface of the sediment and promoted conditions for the growth of this species in the region of mixing. Cold fronts approaching the Billings Reservoir are probably the cause of the mixing and bloom. Also turbulence induced by wind increased phosphorus concentration in the water column. Ceratium furcoides was the dominant species at station 1 where the nutrient concentrations of nitrogen and phosphorus were high. Ceratium spp. blooms may be a problem for water treatment and massive mortality can affect the dissolved oxygen of the water producing fish kill.

A new species of Notodiaptomus Kiefer (Crustacea, Copepoda, Calanoida, Diaptomidae) from Brazil.

Description of a new species of Diaptomidae (Crustacea, Copepoda, Calanoida) Notodiaptomus oliveirai is given from the material obtained at a reservoir at Barra Bonita, SP in 1992. The new species is very similar to Notodiaptomus henseni Dahl 1894 although both species can be found in the same locality, constituting two distinct populations. Notodiaptomus oliveirai seems to be endowed with great adaptability to changes in environmental conditions, extending its distribution to all the hydrographic basins in the state of São Paulo.

Computerized electrocardiogram diagnosis: fuzzy approach.

This paper investigates the computerized analysis of electrocardiographic signals. The biological variability, the lack of standards in the definition of measurements and of diagnostic criteria make the classification problem a complex task. Two basic methods of the diagnostic process are described: the statistical model and the deterministic approach. In particular, a model for ECG classification will be illustrated where the imprecise knowledge of the state of cardiac system and the vague definition of the pathological classes are taken care of by means of the fuzzy set formalism.

A standard communications protocol for computerized electrocardiography.

In an international collaborative project aimed at producing common standards for quantitative electrocardiography, a standard communications protocol (SCP-ECG) was developed for computerized electrocardiography. The protocol consisted of standards for the interchange, encoding, and storage of digital ECG data. The work was performed in three distinct, but closely related, work-packages and in close collaboration with representatives from 13 manufacturers of computerized electrocardiographs from all over the world. The objectives and results of SCP-ECG are briefly described in this paper.

The diagnostic performance of computer programs for the interpretation of electrocardiograms.

BACKGROUND: Computer programs for the interpretation of electrocardiograms (ECGs) are now widely used. However, a systematic assessment of various computer programs for the interpretation of ECGs has not been performed. METHODS: We undertook a large international study to compare the performance of nine electrocardiographic computer programs with that of eight cardiologists in interpreting ECGs in 1220 clinically validated cases of various cardiac disorders. ECGs from the following groups were included in the sample: control patients (n = 382); patients with left ventricular hypertrophy (n = 183), right ventricular hypertrophy (n = 55), or biventricular hypertrophy (n = 53); patients with anterior myocardial infarction (n = 170), inferior myocardial infarction (n = 273), or combined myocardial infarction (n = 73); and patients with combined infarction and hypertrophy (n = 31). The interpretations of the computer programs and the cardiologists were compared with the clinical diagnoses made independently of the ECGs, and the computer interpretations were compared with those of the cardiologists. RESULTS: The percentage of ECGs correctly classified by the computer programs (median, 91.3 percent) was lower than that of the cardiologists (median, 96.0 percent; P less than 0.01). The median sensitivity of the computer programs was also significantly lower than that of the cardiologists in diagnosing left ventricular hypertrophy (56.6 percent vs. 63.9 percent, P less than 0.02), right ventricular hypertrophy (31.8 percent vs. 46.6 percent, P less than 0.01), anterior myocardial infarction (77.1 percent vs. 84.9 percent, P less than 0.001), and inferior myocardial infarction (58.8 percent vs. 71.7 percent, P less than 0.0001). The median total accuracy level (the percentage of correct classifications) was 6.6 percent lower for the computer programs (69.7 percent) than for the cardiologists (76.3 percent; P less than 0.001). However, the performance of the best programs nearly matched that of the most accurate cardiologists. CONCLUSIONS: Our study shows that some but not all computer programs for the interpretation of ECGs perform almost as well as cardiologists in identifying seven major cardiac disorders.

Common standards for quantitative electrocardiography: goals and main results. CSE Working Party.

Computer processing of electrocardiograms (ECGs) has over the last 15 years increased rapidly. Still, there are at present no standards for computer ECG interpretation. Different techniques are used not only for measurement and interpretation, but also for transmission and storage of data. In order to fill these gaps, a large international project, sponsored by the European Commission, was launched in 1980 to develop "Common Standards for Quantitative Electrocardiography (CSE)". The main objective of the first CSE study was to reduce the wide variation in wave measurements currently obtained by ECG computer programs. The second study was started in 1985 and aimed at the assessment and improvement of diagnostic classification of ECG interpretation programs. To this end reference libraries of well documented ECGs have been developed and comprehensive reviewing schemes devised for the visual and computer analysis of ECGs. This task was performed by a board of cardiologists in a Delphi review process, and by 9 VCG and 10 standard 12-lead programs developed by university research groups and by industry. A third action was started in June 1989 to harmonize acquisition, encoding, interchange and storing of digital ECG data. The action thus performed have become internationally recognized milestones for the standardization of quantitative electrocardiography.

Evaluation of ECG interpretation systems: signal analysis.

Performance analysis of biosignal processing systems which provide diagnostic statements requires particular care. Besides general accuracy requirements, psychological and legal implications for patient and physician have to be considered on both the development and the user sites. Cybernetics and control engineering have provided the basic methodology for performance analysis of systems: in technical systems often mathematically defined functions and signals can be fed into the system to be tested and its response and output provide the necessary performance characteristics after adequate mathematical analysis. For systems which process biosignals, as for example ECG analysis systems, instead of analytically given signals learning and test sets of data derived from patients have to be applied. The performance analysis is done on a statistical basis. In this paper construction and composition of learning and test data sets as well as methods for performance evaluation of the signal processing part of ECG programs are described. Specific reference is made to the European project Common Standards for Quantitative Electrocardiography (CSE) where ten ECG- and nine VCG-programs have been tested. The results of these tests provide reference data and standards for further program development as well as for independent system performance evaluation.

Methodology of ECG interpretation in the Padova program.

The main lines of the program designed for the interpretation of ECGs, developed in Padova by LADSEB-CNR with the cooperation of the Medical School of the University of Padova are described. In particular, the strategies used for (i) morphology recognition, (ii) measurement evaluation, and (iii) linguistic decision making are illustrated. The main aspect which discerns this program in comparison with other approaches to computerized electrocardiography is its ability of managing the imprecision in both the measurements and the medical knowledge through the use of fuzzy-set methodologies. So-called possibility distributions are used to represent ill-defined parameters as well as threshold limits for diagnostic criteria. In this way, smooth conclusions are derived when the evidence does not support a crisp decision. The influence of the CSE project on the evolution of the Padova program is illustrated.

Stability of computer ECG amplitude measurements in the presence of noise. The CSE Working Party.

An important feature of an ECG analysis program is its ability to provide reliable measurements under various operating conditions, e.g., on noise-free and noisy ECGs. Therefore, within the European cooperative project "Common Standards For Quantitative Electrocardiography" (CSE), the accuracy and stability of ECG measurements obtained by several computer programs has been compared. To investigate the stability of measurements two sets of 10 ECGs with and without seven different high- and low-frequency types of noise--altogether 160 electrocardiograms and 160 vectorcardiograms--have been analyzed by eight electrocardiographic and five vectorcardiographic computer programs. The stability of measurement was tested with respect to results obtained for the noise-free recordings. In a previous paper, the influence of noise on wave boundary recognition has been reported. In the present paper, the effect of noise on amplitude measurements and on problems of waveform definitions within the QRS complex are described. The results indicate that programs analyzing an averaged beat exhibit less variability than programs which measure every complex or a selected beat. Comparability and stability of measurements could be improved if a standardized procedure for amplitude references were to be introduced. In addition, the stability of QRS waveform labelling could be improved if waveforms' minimum amplitude and duration were to be validated against the noise level which itself should be determined by a standardized procedure.

Effect of combining electrocardiographic interpretation results on diagnostic accuracy.

In order to test the diagnostic performance of various ECG computer programs a reference library of ECGs is being established and evaluation methods are being developed in an international co-operative project. A pilot study was undertaken in which 250 validated electrocardiograms (ECG) and vectorcardiograms (VCG) comprising seven diagnostic groups i.e., normal, left, right and bi-ventricular hypertrophy, anterior, inferior and combined infarction have been analysed independently by 11 different computer programs as well as by six cardiologists. A coding scheme was applied to assign individual diagnostic statements to a common set and to obtain combined program and cardiologist interpretation results. Preliminary results indicate that the accuracy of classification by different programs varies widely. Total accuracy varied between 57.2% and 75.8% (median 69.4%). The cardiologists had a higher accuracy (median 74.3%) than the majority of programs, at least when using the standard ECG. As it is considered premature to stress individual program results, in view of the current sample size, the enhancement in diagnostic accuracy obtained by combining interpretation results is highlighted. Indeed combined cardiologist and program results demonstrated the highest accuracy i.e., respectively 78.7% and 76.1%, higher than the result of any individual reader or program. The combined result of the five most accurate programs was 78.4%, that of the six least accurate was 71.5%, which is again higher than the respective individual components. These findings demonstrate that the combination of expert knowledge of computer programs can, similar to panel review and group analysis in clinical practice, enhance diagnostic accuracy.

A reference data base for multilead electrocardiographic computer measurement programs.

In an effort to standardize and evaluate the performance of electrocardiographic computer measurement programs, a 15 lead reference library has been developed based on simultaneously recorded standard 12 lead and orthogonal XYZ lead data. A set of 250 electrocardiograms (ECGs) with selected abnormalities was analyzed by a group of five referee cardiologists and 11 different 12 lead and 6 XYZ computer programs. Attention was focused on the exact determination of the onsets and offsets of P, QRS and T waves. The referees performed their task on highly amplified, selected complexes from the library in a two round process. Median results of the referees coincided best with the median derived from all programs. An analysis of stability proved that the combined program median was a robust reference. However, some individual program results were widely divergent. Paired t tests demonstrated earlier onset for P and QRS (p less than 0.001), as well as later offset for P and T waves in the median 12 lead than in the XYZ results. Significant differences also existed among results obtained by programs analyzing all standard ECG leads at one time, the so-called multilead programs, and those obtained by the conventional standard three lead analysis programs. As a consequence, the derived P, PR, QRS and QT interval measurements varied quite widely among the various programs. Significant differences were also observed among measurements of Q, R and S duration. Some programs showed Q waves that were on the average 6 ms (p less than 0.001) longer than those of others. This may significantly influence diagnostic performance.(ABSTRACT TRUNCATED AT 250 WORDS)