RESUMO

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.

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RESUMO

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.

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RESUMO

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.

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