Hydropower Plants as Dispersal Barriers in Freshwater Species Distribution Models: Using Restrictions through Asymmetrical Dispersal Predictors.

Hydropower plants represent one of the greatest threats for freshwater fish by fragmenting the habitat and avoiding the species dispersal. This type of dispersal barrier is often disregarded when predicting freshwater species distribution due to the complexity in inserting the species dispersal routes, and thus the barriers, into the models. Here, we evaluate the impact of including hydroelectric dams into species distribution models through asymmetrical dispersal predictors on the predicted geographic distribution of freshwater fish species. For this, we used asymmetrical dispersal (i.e., AEM) as predictors for modeling the distribution of 29 native fish species of Tocantins-Araguaia River basin. After that, we included the hydropower power plant (HPP) location into the asymmetrical binary matrix for the AEM construction by removing the connections where the HPP is located, representing the downstream disconnection a dam causes in the fish species dispersal route. Besides having higher predicted accuracy, the models using the HPP information generated more realistic predictions, avoiding overpredictions to areas suitable but limited to the species dispersal due to an anthropic barrier. Furthermore, the predictions including HPPs showed higher loss of species richness and nestedness (i.e., loss of species instead of replacement), especially for the southeastern area which concentrates most planned and built HPPs. Therefore, using dispersal constraints in species distribution models increases the reliability of the predictions by avoiding overpredictions based on premise of complete access by the species to any area that is climatically suitable regardless of dispersal barriers or capacity. In conclusion, in this study, we use a novel method of including dispersal constraints into distribution models through a priori insertion of their location within the asymmetrical dispersal predictors, avoiding a posteriori adjustment of the predicted distribution.

Combining ecological niche models with experimental seed germination to estimate the effect of climate change on the distribution of endangered plant species in the Brazilian Cerrado.

Predicting the geographic distribution of plants that provide ecosystem services is essential to understand the adaptation of communities and conserve that group toward climate change. Predictions can be more accurate if changes in physiological characteristics of species due to those changes are included. Thus, we aimed to evaluate the impacts of climate change on the different hierarchical levels of Apuleia leiocarpa (Vogel) J. F. Macbr. (Fabaceae). Therefore, we experimentally evaluate the effect of different temperatures on the initial development (vigor) and estimate the impact of climate change on the potential geographic distribution of the species, using ecological niche approaches. For the experiment, we used 11 temperature intervals of 2 °C ranging from 21 to 41 °C. We used ecological niche modeling techniques (ENM) to predict the species' environmental suitability in future climate scenarios. The association between the experiment and niche models was obtained by testing the relationships of temperature increase on the species vigor and geographic distribution. This conceptual model to determine the direct and indirect effects of temperature was generated using the methodological framework of structural equation models. The experiment showed that the seeds had the highest growth at 31 °C. ENMs indicated that due to climate change, there is a tendency for the plant to migrate to regions with milder temperatures. However, such regions may be unsuitable for the plant since they do not have ideal temperatures to germinate, which may cause a drastic reduction in their availability in a future climate change scenario. The inclusion of seed germination through experimental research allowed us to detect an area that is less suitable for germination despite being climatically suitable for the species. Thus, research that integrates the effect of climate on the different stages of the organism's development is essential to understand the impact of climate change on biodiversity.

Large-scale Degradation of the Tocantins-Araguaia River Basin.

The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations.

The impact of global climate change on the number and replacement of provisioning ecosystem services of Brazilian Cerrado plants.

It is essential to predict areas of losses or exchanges of ecosystem services to adapt communities to the impacts caused by climate change. Particularly for provisioning ecosystem services provided by economically important plant species, understanding the association between climate change impacts and deforestation of native vegetation increases the accuracy of those predictions. Thus, we aim to (i) map the richness of provisioning ecosystem services from economically important native plants; (ii) use forecasts (present and future) of the distribution of ecosystem services to assess areas of changes in the number and type of provisioning ecosystems services. We evaluated provisioning ecosystem services from 110 Cerrado native species of economic importance for the local population. We determined the potential distribution of these plants using ecological niche modeling techniques, which were grouped according to the 21 different services provided. The forecasts for variation in richness and type of service used four future climate change scenarios (RCPs 4.5 and 8.5 in 2050 and 2070). The service losses detected in our models were associated with variables representing the progress of native vegetation deforestation in the biome due to agricultural expansion. Currently, ecosystem services can be found simultaneously in practically the entire biome. However, changes in the global climate will impact the potential geographic distribution of those plants, causing many areas in the biome to have reduced availability of potential ecosystem services. Moreover, due to the association between exposure to climate change and deforestation of native vegetation, the northern region of the biome will likely have the distribution of ecosystem services severely affected.

Uncovering the spatial variability of recent deforestation drivers in the Brazilian Cerrado.

In recent years, the Cerrado deforestation has increased considerably, reaching rates higher than in the Amazonian realm. Although the effects of deforestation are well known, the understanding of its drives at regional levels is incipient. Most studies consider that a driver influences deforestation likewise in all regions. However, deforestation has a strong spatial structure that can lead drivers to vary their influence on deforestation in different regions. Here, we evaluated the spatial variability in the relationship between the recent Cerrado deforestation and socioeconomic, environmental, and structural drivers at a regional scale. We used a geographically weighted regression (GWR) to assess the spatial variability of predictor variables. We identified regions that respond similarly to the drivers by grouping municipalities, considering their GWR coefficients through hierarchical clustering. The analyses that consider the spatial variability of predictors are more appropriated to assess the causes of recent deforestation. Remnant natural vegetation influenced the recent deforestation in all defined regions. Greater access to rural credit concession was the main driving force of deforestation in the northeast region defined here. Distance to roads increased deforestation in the northeast and north regions, while it inhibited deforestation in the central-east and southeast regions. Rainfall inhibited deforestation in the northeast, north, and southwest regions. Steep slope prevented deforestation mainly in the northeast, north, and southwest regions. Our results highlight that, to effectively reduce Cerrado deforestation, public policies should integrate strategies focusing not only at national and biome levels but also at the regional spatial level.

The Impact of Global Climate Change on the Geographic Distribution and Sustainable Harvest of Hancornia speciosa Gomes (Apocynaceae) in Brazil.

The global Climate change may affect biodiversity and the functioning of ecosystems by changing the appropriate locations for the development and establishment of the species. The Hancornia speciosa, popularly called Mangaba, is a plant species that has potential commercial value and contributes to rural economic activities in Brazil. The aim of this study was to evaluate the impact of global climate change on the potential geographic distribution, productivity, and value of production of H. speciosa in Brazil. We used MaxEnt to estimate the potential geographic distribution of the species in current and future (2050) climate scenarios. We obtained the productivity and value of production for 74 municipalities in Brazil. Moreover, to explain the variation the productivity and value of production, we constructed 15 models based on four variables: two ecological (ecological niche model and the presence of Unity of conservation) and two socio-economic (gross domestic product and human developed index). The models were selected using Akaike Information Criteria. Our results suggest that municipalities currently harvesting H. speciosa will have lower harvest rates in the future (mainly in northeastern Brazil). The best model to explain the productivity was ecological niche model; thus, municipalities with higher productivity are inserted in regions with higher environmental suitability (indicated by niche model). Thus, in the future, the municipalities harvesting H. speciosa will produce less because there will be less suitable habitat for H. speciosa, which in turn will affect the H. speciosa harvest and the local economy.

Environmental factors affecting chlorophyll-a concentration in tropical floodplain lakes, Central Brazil.

Chlorophyll-a (Chl-a) has been widely used in the assessment and monitoring of aquatic environments. Local and regional factors can influence Chl-a concentrations; moreover, the connection between terrestrial and aquatic ecosystems is a major paradigm within aquatic ecology. Here, we investigate the spatial distribution of Chl-a concentrations in a tropical savannah floodplain in Central Brazil using a broad spatial data set (a 900-km north-south transect; 30 lakes). We determine the relative importance of local environmental variables (limnological and morphometric) and regional (land use) and spatial distances (spatial eigenvector) on Chl-a concentrations using partial linear regression. We evaluate the direct and indirect effects of local and regional variables on Chl-a with a path analysis. Our results indicate spatially autocorrelated patterns wherein lakes in closer proximity showed more similar levels of Chl-a than more distant lakes. Local environmental factors explained most variance in Chl-a (R 2adj = 0.28; P = 0.02); more specifically, both lake area and total nitrogen significantly (P < 0.05) explained Chl-a concentrations (direct effects). Meanwhile, regional factors neither directly nor indirectly predicted Chl-a. Thus, internal processes, such as the resuspension of sediment (which is frequent in tropical floodplains), rather than external influences, were the main factors that explained Chl-a concentrations in this study. The importance of local variables in structuring Chl-a concentration may be used to guide the conservation of the aquatic ecosystems in these tropical floodplain lakes.

Shortcuts for biomonitoring programs of stream ecosystems: Evaluating the taxonomic, numeric, and cross-taxa congruence in phytoplankton, periphyton, zooplankton, and fish assemblages.

Different biological groups can be used for monitoring aquatic ecosystems because they can respond to variations in the environment. However, the evaluation of different bioindicators may demand multiple financial resources and time, especially when abundance quantification and species-level identification are required. In this study, we evaluated whether taxonomic, numerical resolution and cross-taxa can be used to optimize costs and time for stream biomonitoring in Central Brazil (Cerrado biome). For this, we sampled different biological groups (fish, zooplankton, phytoplankton, and periphyton) in stream stretches distributed in a gradient of land conversion dominated by agriculture and livestock. We used the Mantel and Procrustes analyses to test the association among different taxonomic levels (species to class), the association between incidence and abundance data (numerical resolution), and biological groups. We also assessed the relative effect of local environmental and spatial predictors on different groups. The taxonomic levels and numerical resolutions were strongly correlated in all taxonomic groups (r > 0.70). We found no correlations among biological groups. Different sets of environmental variables were the most important to explain the variability in species composition of distinct biological groups. Thus, we conclude that monitoring the streams in this region using bioindicators is more informative through higher taxonomic levels with occurrence data than abundance. However, different biological groups provide complementary information, reinforcing the need for a multi-taxa approach in biomonitoring.

Stream fish metacommunity organisation across a Neotropical ecoregion: The role of environment, anthropogenic impact and dispersal-based processes.

Understanding how assemblages are structured in space and the factors promoting their distributions is one of the main goals in Ecology, however, studies regarding the distribution of organisms at larger scales remain biased towards terrestrial groups. We attempt to understand if the structure of stream fish metacommunities across a Neotropical ecoregion (Upper Paraná-drainage area of 820,000 km2) are affected by environmental variables, describing natural environmental gradient, anthropogenic impacts and spatial predictors. For this, we obtained 586 sampling points of fish assemblages in the ecoregion and data on environmental and spatial predictors that potentially affect fish assemblages. We calculated the local beta diversity (Local Contribution to Beta Diversity, LCBD) and alpha diversity from the species list, to be used as response variables in the partial regression models, while the anthropogenic impacts, environmental gradient and spatial factors were used as predictors. We found a high total beta diversity for the ecoregion (0.41) where the greatest values for each site sampled were located at the edges of the ecoregion, while richer communities were found more centrally. All sets of predictors explained the LCBD and alpha diversity, but the most important was dispersal variables, followed by the natural environmental gradient and anthropogenic impact. However, we found an increase in the models' prediction power through the shared effect. Results suggest that environmental filters (i.e. environmental variables such as climate, hydrology and anthropogenic impact) and dispersal limitation together shape fish assemblages of the Upper Paraná ecoregion, showing the importance of using multiple sets of predictors to understand the processes structuring biodiversity distribution.

Modeling body size evolution in Felidae under alternative phylogenetic hypotheses.

The use of phylogenetic comparative methods in ecological research has advanced during the last twenty years, mainly due to accurate phylogenetic reconstructions based on molecular data and computational and statistical advances. We used phylogenetic correlograms and phylogenetic eigenvector regression (PVR) to model body size evolution in 35 worldwide Felidae (Mammalia, Carnivora) species using two alternative phylogenies and published body size data. The purpose was not to contrast the phylogenetic hypotheses but to evaluate how analyses of body size evolution patterns can be affected by the phylogeny used for comparative analyses (CA). Both phylogenies produced a strong phylogenetic pattern, with closely related species having similar body sizes and the similarity decreasing with increasing distances in time. The PVR explained 65% to 67% of body size variation and all Moran's I values for the PVR residuals were non-significant, indicating that both these models explained phylogenetic structures in trait variation. Even though our results did not suggest that any phylogeny can be used for CA with the same power, or that "good" phylogenies are unnecessary for the correct interpretation of the evolutionary dynamics of ecological, biogeographical, physiological or behavioral patterns, it does suggest that developments in CA can, and indeed should, proceed without waiting for perfect and fully resolved phylogenies.

A review of techniques for spatial modeling in geographical, conservation and landscape genetics.

Most evolutionary processes occur in a spatial context and several spatial analysis techniques have been employed in an exploratory context. However, the existence of autocorrelation can also perturb significance tests when data is analyzed using standard correlation and regression techniques on modeling genetic data as a function of explanatory variables. In this case, more complex models incorporating the effects of autocorrelation must be used. Here we review those models and compared their relative performances in a simple simulation, in which spatial patterns in allele frequencies were generated by a balance between random variation within populations and spatially-structured gene flow. Notwithstanding the somewhat idiosyncratic behavior of the techniques evaluated, it is clear that spatial autocorrelation affects Type I errors and that standard linear regression does not provide minimum variance estimators. Due to its flexibility, we stress that principal coordinate of neighbor matrices (PCNM) and related eigenvector mapping techniques seem to be the best approaches to spatial regression. In general, we hope that our review of commonly used spatial regression techniques in biology and ecology may aid population geneticists towards providing better explanations for population structures dealing with more complex regression problems throughout geographic space.

High school students' knowledge of endangered fauna in the Brazilian Cerrado: A cross-species and spatial analysis.

The ability of high school students to know endangered species can vary among species (e.g., large body size can influence people's interest) or among municipalities (e.g., more contact with biodiversity can influence people's interest). Thus, in the present paper, we evaluated high school students' knowledge about the endangered and non-endangered mammalian species of the Brazilian Cerrado. We tested whether the recognition of the endangered and non-endangered species varied in a cross-species analysis (twelve total species) according to species characteristics, such as body size, popularity, endangered status and the length of time of inclusion on the endangered species list. Moreover, we tested whether the recognition of the endangered mammal species varied between municipalities (spatial analysis). We interviewed 366 students in their first year of high school in 21 schools (one in each municipality). Our results indicated that the proportion of correctly identified endangered species varied according to species (cross-species). The endangered species that were most often correctly identified were Myrmecophaga tridactyla (known by its popular name, Tamanduá-bandeira, in Brazil), Priodontes maximus (Tatu canastra) and Panthera onca (onça-pintada), with more than 80% correct answers. Thus, students tended to recognize the more popular species and the endangered species more than the non-endangered species. The analysis of student knowledge according to municipality demonstrated that the students' ability to recognize endangered species followed a spatial pattern. Finally, the cross-species and spatial variation patterns detected in the present study indicated the importance of formal education in increasing high school students' knowledge about endangered species and suggested that education should also promote less well-known species, species with smaller body sizes, and other groups of vertebrates and invertebrates and consider local and regional biodiversity whenever possible.

Geographical patterns in climate and agricultural technology drive soybean productivity in Brazil.

The impacts of global climate change have been a worldwide concern for several research areas, including those dealing with resources essential to human well being, such as agriculture, which directly impact economic activities and food security. Here we evaluate the relative effect of climate (as indicated by the Ecological Niche Model-ENM) and agricultural technology on actual soybean productivity in Brazilian municipalities and estimate the future geographic distribution of soybeans using a novel statistical approach allowing the evaluation of partial coefficients in a non-stationary (Geographically Weighted Regression; GWR) model. We found that technology was more important than climate in explaining soybean productivity in Brazil. However, some municipalities are more dependent on environmental suitability (mainly in Southern Brazil). The future environmental suitability for soybean cultivation tends to decrease by up 50% in the central region of Brazil. Meanwhile, southern-most Brazil will have more favourable conditions, with an increase of ca. 25% in environmental suitability. Considering that opening new areas for cultivation can degrade environmental quality, we suggest that, in the face of climate change impacts on soybean cultivation, the Brazilian government and producers must invest in breeding programmes and more general ecosystem-based strategies for adaptation to climate change, including the development of varieties tolerant to climate stress, and strategies to increase productivity and reduce costs (social and environmental).

Correlation between genetic diversity and environmental suitability: taking uncertainty from ecological niche models into account.

The hindcast of shifts in the geographical ranges of species as estimated by ecological niche modelling (ENM) has been coupled with phylogeographical patterns, allowing the inference of past processes that drove population differentiation and genetic variability. However, more recently, some studies have suggested that maps of environmental suitability estimated by ENM may be correlated to species' abundance, raising the possibility of using environmental suitability to infer processes related to population demographic dynamics and genetic variability. In both cases, one of the main problems is that there is a wide variation in ENM development methods and climatic models. In this study, we analyse the relationship between heterozygosity (He) and environmental suitability from multiple ENMs for 25 population estimates for Dipteryx alata, a widely distributed, endemic tree species of the Cerrado region of central Brazil. We propose a new approach for generating a statistical distribution of correlations under randomly generated ENM. The confidence intervals from these distributions indicate how model selection with different properties affects the ability to detect a correlation of interest (e.g. the correlation between He and suitability). Additionally, our approach allows us to explore which particular ensemble of ENMs produces the better result for finding an association between environmental suitability and He. Caution is necessary when choosing a method or a climatic data set for modelling geographical distributions, but the new approach proposed here provides a conservative way to evaluate the ability of ensembles to detect patterns of interest.

The chick embryo chorioallantoic membrane assay as a model for the study of angiogenesis / Ensaio da membrana corioalantóide de embrião de galinha como modelo para o estudo da angiogênese

Angiogenesis is a fundamental physiological process with strong implications in tissue homeostasis. Animal models helping to identify how angiogenesis is regulated are fundamental to answer many biological questions. Chick embryo chorioallantoic membrane (CAM) assay is one of the most employed methods to study angiogenesis. In this study we applied a scientometric approach to evaluate the employment of CAM assay in published articles. Temporal trends indicated that CAM assay was the preferred method to investigate angiogenesis over time. The publications had a significant number of citations and the impact factor of journals publishing articles is relevant for the scientific community. A total of 52 different research areas have articles published using this particular technique. Oncology is the research field in which CAM assay was mostly used. Accordingly, tumor-derived cell lines were the most frequent sample tested on CAM. We also identified that 73,6% of articles published used only CAM assay to answer questions concerning angiogenesis. We concluded that although the CAM assay is a classical approach, that does not need so much infrastructure and financial support to be performed, it is a well-accepted technique by the scientific community. In addition, this methodology has gain attention in scientific community because no pain is experienced by the chick and they are minor ethical concerns to employ this method. Moreover, this data can help researchers who are unfamiliar with the CAM assay to identify if this particular method is suitable for their research.

A angiogênese é um processo fisiológico fundamental com fortes implicações na homeostase tecidual. Modelos animais que ajudam a entender como a angiogênese é regulada, são fundamentais para responder a muitas questões biológicas. O ensaio de membrana corioalantóide de embrião de galinha (CAM) é um dos métodos mais empregados para estudar a angiogênese. Neste estudo foi aplicada uma abordagem cientométrica para avaliar o emprego do ensaio CAM em artigos científicos já publicados. Tendências temporais indicaram que o ensaio CAM foi o método mais usado para investigar a angiogênese ao longo do tempo. Os artigos científicos que usaram a metodologia CAM foram publicados em periódicos com significativos números de citações e fator de impacto. No total 52 diferentes áreas de conhecimento usaram a técnica CAM, sendo a oncologia o campo o qual produziu maior número de artigos usando essa metodologia. Consequentemente o material biológico mais testado foi as linhagens celulares tumorais. Também foi identificado que 73,6% dos artigos publicados utilizaram apenas o teste CAM para responder questões relacionadas à angiogênese. Pode se concluir que embora o ensaio CAM seja uma abordagem clássica, que não necessita de muita infraestrutura e apoio financeiro para ser realizado, é uma técnica bem aceita pela comunidade científica. Além disso, esta metodologia tem ganhado atenção na comunidade científica porque os animais testados não sofrem dor e por essa razão esse modelo experimental exige mínimas preocupações éticas. Além disso, esses dados podem ajudar os pesquisadores que não estão familiarizados com o ensaio CAM a identificar se esse método específico é adequado para sua pesquisa.

Environmental constraints structuring fish assemblages in riffles: evidences from a tropical stream

ABSTRACT Riffles are unique habitats regarding to assemblage structure. However, understanding how these assemblages respond to environmental variations in small spatial extents, as within a stream, is a challenge. We assess whether the quantitative structure and the trophic composition of fish assemblages vary predictably among stream riffles. We predict that the variation of environmental conditions will explain species abundance and trophic composition, with the latter presenting higher predictive power, since species would be filtered according to their traits (e.g. diet). Moreover, we expect that the low among-riffle dispersal limitation within a stream and the strong habitat filtering would result in lower importance of spatial variables in the structure of riffle fish assemblages. We tested these predictions by studying 18 riffles of a stream in the Central Brazil. Environmental variables, but not spatial ones, were the most important in explaining the variation in assemblages structure. Environmental variables explained a greater portion of the trophic structure variation (R2=0.62) than of abundance (R2=0.37), indicating that the variation on the trophic traits at community level are more predictable. These results also indicate that these assemblages are subject to environmental control, highlighting the importance of riffle characteristics in driving ecological processes within streams.

RESUMO Corredeiras são habitats singulares no que se refere à estrutura das suas assembleias. Entretanto, a compreensão sobre como essas assembleias respondem às variações ambientais em pequenas extensões espaciais, como dentro de um riacho, ainda é um desafio. Avaliamos se a estrutura quantitativa das assembleias de peixes, assim como a sua composição trófica variam previsivelmente entre corredeiras de riachos. Predizemos que a variação nas condições ambientais explicará a abundância das espécies, assim como a sua composição trófica, entretanto, com uma maior proporção da variação explicada para a segunda, já que as espécies seriam filtradas de acordo com seus atributos (e.g. dieta). Além disso, esperamos que a pequena limitação para a dispersão entre as corredeiras de um mesmo riacho, associada à forte filtragem ambiental, resultaria em uma menor importância de variáveis espaciais na estruturação das assembleias de corredeiras. Para testar essas predições, estudamos 18 corredeiras de um rio do Brasil Central. As variáveis ambientais, e não as espaciais, foram mais importantes para explicar a variação na estrutura das assembleias. As variáveis ambientais explicaram uma maior proporção da variação da composição trófica (R2=0,62), em comparação com a abundância (R2=0,37), indicando maior previsibilidade na variação dos atributos relacionados a dieta em nível de comunidade. Esses resultados também indicam que essas assembleias são sujeitas a forte controle ambiental, destacando a importância das características desses habitats nos processos ecológicos dentro dos riachos.

An estimate of the potential number of mayfly species (Ephemeroptera, Insecta) still to be described in Brazil

ABSTRACTThis study reviewed the data on the Brazilian Ephemeroptera, based on the studies published before July, 2013, estimated the number of species still to be described, and identified which regions of the country have been the subject of least research. More than half the species are known from the description of only one developmental stage, with imagoes being described more frequently than nymphs. The Brazilian Northeast is the region with the weakest database. Body size affected description rates, with a strong tendency for the larger species to be described first. The estimated number of unknown Brazilian species was accentuated by the fact that so few species have been described so far. The steep slope of the asymptote and the considerable confidence interval of the estimate reinforce the conclusion that a large number of species are still to be described. This emphasizes the need for investments in the training of specialists in systematics and ecology for all regions of Brazil to correct these deficiencies, given the role of published papers as a primary source of information, and the fundamental importance of taxonomic knowledge for the development of effective measures for the conservation of ephemeropteran and the aquatic ecosystems they depend on.

The state of global scientific literature on chlorophyll-A / O estado da arte da literatura científica global sobre clorofila-A

Chlorophyll is a green pigment common to all photosynthetic cells of autotrophic organisms in aquatic or terrestrial environments. Techniques used to quantify this pigment include fluorescence, UV spectrophotometer, chromatography, HPLC, and remote sensing. Determination of the photosynthetic pigment chlorophyll - a (Chl-a), has been used widely in many areas of science. The present study investigated the state of the global scientific literature on Chl-a, determining the countries, approaches, and environments where Chl-a has been studied and the geographic scale used. To obtain this scientometric information, we conducted a study from the Scopus database over a 21-year period from 1990 through 2011. This period saw significant increases in the number of publications (r=0.84 and P< 0.001), different journals where publications appeared (160 journals), major papers with a multidisciplinary character, and a predominance of descriptive approaches with studies conducted in aquatic and marine habitats at a regional scale. The country with the highest number of publications was China (21.64% of total papers; location of study), and the USA had the highest number of authors (19.52% of total papers). The main determining factor for publications was socioeconomic (according to model selection criteria; AIC). This study highlight the multidisciplinary use of Chl-a, and may give some directions to new studies about this pigment.

A clorofila é um pigmento verde, comum em todas as células fotossintéticas de organismos autotróficos, de ambientes aquáticos ou terrestres. As técnicas mais utilizadas para quantificar esse pigmento são a fluorescência, a espectrofotometria de UV, a cromatografia HPLC e o uso de sensores remotos. Assim, a determinação do pigmento fotossintético chlorofila-a (Chl-a), tem sido utilizada amplamente em diversas áreas da ciência. Portanto, o objetivo deste trabalho foi investigar o estado da arte da literatura científica para o pigmento fotossintetizante clorofila-a, determinando os países de estudo, os fatores socioeconômicos- ambiental que estão ligados ao estudo de clorofila ­a, abordagens utilizadas, e ainda, os ambientes estudados, a escala geográfica e as revistas. Para obter tais informações realizou-se um estudo cienciométrico, a partir da base de dados Scopus, numa escala temporal de 21 anos (entre 1990 e 2011). Os padrões encontrados para as pesquisas com Chl-a são o aumento temporal de publicações (r=0.84 and P<0.001), a diversidade de revistas que publicaram estudos sobre o assunto (160 revistas), maior número de publicações com caráter multidisciplinar, predomínio de estudos com abordagens descritivas realizados em ambientes aquáticos e marinhos e estudos em escala geográfica regional. A China foi o país mais estudado com 21,64% do total de artigos publicados, e os estadunidenses lideraram com o maior número de publicações sobre este assunto (19,52% do total de artigos publicados). Utilizando o critério de seleção de modelos de Akaike observou-se que as publicações são impulsionadas pelo fator socioeconômico PIB. Este estudo demonstrou o uso multidisciplinar da Chl-a e pode indicar algumas direções para novos estudos com esse pigmento.