Waterloo Pereira Filho

Seasonal changes in chlorophyll distributions in Amazon floodplain lakes derived from MODIS images

To assess seasonal changes in phytoplanktonic chlorophyll distributions in Amazon floodplain lakes, a linear mixing model was applied to Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data acquired at four river stages: rising (April), high (June), decreasing (September), and low (November). The study area is located in a floodplain reach from Parintins (Amazonas) to near Almeirim (Pará). A three-end-member mixing model designed to uncouple three fractions [high suspended inorganic matter (ip), low inorganic suspended matter (w), and high chlorophyll a (Chl)] was tested in Lake Curuaí (1.5°S 55.43°W) based on field sampling done almost concurrently with satellite overpasses. During high water, phytoplankton patches are confined to lakes closer to terra firme under the influence of clear water inflow, whereas during the low and decreasing water stages, the patches are more evenly distributed over the floodplain.

Freshwater temperature in the state of Rio Grande do Sul, Southern Brazil, and its implication for fish culture

In this study we verified data of water temperatures collected by CORSAN-RS from 1996 to 2004 in several cities of the state of Rio Grande do Sul, southern Brazil, and analyzed the possibility of raising the most cultivated fish species in Brazil. The water temperature from 1996 to 2004 was 16 to 28oC in summer, 17 to 23oC in fall, 14 to 17oC (down to 9oC in the coldest months) in winter and 14 to 21oC in spring. Native species of this state, such as silver catfish (Rhamdia quelen), traira (Hoplias malabaricus), dorado (Salminus brasiliensis), pintado (Pimelodus maculatus), as well as carps (family Cyprinidae), are resistant to the low winter temperatures. These species have a lower growth rate in coldest months (winter/spring) but a good development in warmer months (summer/fall), reaching a satisfactory performance throughout the year. In the periods of more intense cold, mortality of some introduced species, such as surubim from Amazon Basin (Pseudoplatystoma sp.), pirapitinga (Piaractus brachypomus), pirarucu (Arapaimas gigas), pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropomum) and Nile tilapia (Oreochromis niloticus) may occur. In addition, as most tropical species have a thermal range for growth and reproduction between 20 to 28oC, some species may have poor development even in fall. Therefore, water temperature in this state should be considered in the choice of fish species to be cultivated.

Geospatial analysis of spatiotemporal patterns of pH, total suspended sediment and chlorophyll-a on the Amazon floodplain

We applied spatial data analysis and geostatistical procedures to pH, total suspended sediment and chlorophyll-a concentration data gathered on an Amazon floodplain lake. Variographic analysis and ordinary kriging interpolation were used to identify and describe spatiotemporal patterns of variability in these parameters, which are relevant to understand the dynamics of water circulation on the floodplain lake. In spite of the complexity of the processes underlying the spatiotemporal patterns, this approach demonstrated that the heterogeneity in the seasonal water composition is forced not only by the Amazon River flood pulse, but also by the lake bottom topography and the wind intensity.

Análise derivativa de dados hiperespectrais medidos em nível de campo e orbital para caracterizar a composição de águas opticamente complexas na Amazônia

Derivative analysis of spectral data was used as a technique to study the variation of optically active constituents (OACs) of water, using field data and hyperspectral imagery of EO-1 Hyperion orbital sensor. The Hyperion image used in this study was acquired on June 23, 2005, at the end of the high water period for the Amazon River. A field campaign was carried out between June 23 and 29, 2005 to collect spectral and limnological in situ data. The image was pre-processed to remove stripes of abnormal pixels and converted from radiance to surface reflectance values, thus, correcting the effects of atmospheric absorption and scattering. A correlation analysis was carried out to examine the association of the spectral reflectance and its first derivative to the concentrations of OACs. Better results were obtained after spectra differentiation, which helped to reduce the influence of undesirable effects, coming from different sources of radiance, on the measurements of water surface reflectance taken at both data acquisition levels. Through empirical regression fits, considering the Hyperion dataset, the first spectral derivative at 711 nm explained 86% of the variation of suspended inorganic sediment concentration (µg.l-1), and the first derivative at 691 nm explained 73% of the variation of chlorophyll-a concentration (µg.l-1). The regression relations were nonlinear because, generally, the water masses that mix in the Amazon floodplain become optically complex. The hyperspectral derivative analysis demonstrated potential for mapping the composition of these waters.

Assessing the Long-Term Variability of TSS and Chlorophyll in Subtropical Reservoirs Using MODIS Data

The remote sensing assessment of the long-term variability in optically active constituents of the waters is very important to understand the dynamics of the reservoirs at temporal and spatial scales. We evaluated variations over time (2000-2015) in total suspended solids (TSS) and chlorophyll-a concentrations in the Passo Real reservoir, located in south Brazil. For this purpose, we tested two MODIS composite products: MOD09A1 and MCD43A4. Regression relationships of the red (TSS) and green (chlorophyll-a) reflectance of these products with limnological data of 12 field campaigns were obtained and compared to estimate these constituents on a per-pixel basis. Three major sections of the reservoir (upper, middle, and lower sections) were selected in the analysis. The results showed that the MODIS MCD43A4 (corrected for bidirectional effects) produced better estimates of TSS and chlorophyll-a than the MOD09A1 product. The highest concentrations of TSS were observed from September to October with the concomitant increase in precipitation and the predominance of exposed soils. The peak of TSS concentration between these two months was closely followed by another peak of chlorophyll-a content. It occurs probably because of the higher nutrient availability with sediment loading, the intensive land use with crop development, and the increase in water temperatures. Differences over time between the peaks of TSS and chlorophyll-a varied from the upper (two-month shift) to the lower (one-month shift) sections of the reservoir. They were associated with the different stream inflows and the residence time of the waters.

AVALIAÇÃO DA REFLECTÂNCIA ESPECTRAL DE CORPOS D’ÁGUA EM SANTA MARIA-RS POR MEIO DE ESPECTRORRADIOMETRIA DE CAMPO

POLLINATOR FORAGING STRATEGY IN Galactia peduncularis (BENTH.) TAUB. (LEGUMINOSAE: PAPILIONOIDEA) IN THE PARQUE ESTADUAL DA SERRA DE CALDAS NOVAS BRAZIL The way the animals look for food is an important characteristic of their behavior. The optimal foraging theory is based on the existence of a balance between costs and benefits of these behavioral decisions. The present study aimed to evaluate the behavior of the pollinator in response to increased availability of floral resources. The experiment was conducted in a recently burned Cerrado area (Campo rupestre) in the State Park of Serra de Caldas Novas , located in the municipalities of Caldas Novas and Rio Quente Brazil. The species chosen to test our hypothesis was Galactia peduncularis (Benth.) Taub. (Leguminosae: Papilionoidea). 17 pairs of specimens were selected with a number of flowers, and the individuals of each pair were spaced by about 2m. In these pairs, one of them was considered the focal, and the other, the isolated. To test possible differences in pollination between isolated plants and focus, we performed two randomization tests: a test binary (TB), where all pairs were analyzed and verified the number of times where the focus on the individual floral visits were higher than the number of visits in isolated. According to the data analyzed, floral visitors preferred to use plants that could provide a greater amount of floral resources so that the number of visitors varied positively with the increment of flowers. Plants with many flowers can provide a greater amount of food in one location so that visitors do not need to flower around for long distances in search of meeting their energy needs.

ANÁLISE DO USO E COBERTURA DA TERRA DE TRÊS SUB-BACIAS HIDROGRÁFICAS - RIO GRANDE DO SUL/BRASIL

O artigo teve como objetivo realizar o levantamento do uso e ocupacao da terra, por meio de classificacao de imagens orbitais CBERS CCD 2, das sub-bacias do arroio Cadena e rios Vacacai-Mirim e Ibicui-Mirim, localizadas na mesorregiao Centro Ocidental Rio-Grandense. As imagens foram processadas com o uso do software IDRISI 32, por classificacao supervisionada que permitiu a identificacao e quantificacao das diferentes areas de uso da terra (Area Urbana, Agricultura, Pastagens, Campos e Vegetacao de pequeno porte, Corpos d’agua e Florestamento). A metodologia adotada foi satisfatoria, e os resultados encontrados forneceram dados de qualidade para o trabalho. Destacamos a importância das tecnicas de geoprocessamento e sensoriamento remoto, para trabalhos em areas urbanas, rurais e outras areas afins.

Dynamics of limnological parameters in reservoirs: A case study in South Brazil using remote sensing and meteorological data

Reservoirs are important in Brazil for the production of hydroelectric power and human water consumption. The objective was to evaluate the variability of total suspended solids (TSS) and chlorophyll-a as well as the rainfall/temperature and land use impacts on these optically active constituents (OAC). The study area is the Passo Real reservoir in south Brazil. The methodology was divided in four steps. First, we used wavelet to detect anomalous periods of rainfall and temperature (2002-2014). Second, we carried out 12 field campaigns to obtain in situ measurements for limnological characterization (2009-2010). The third step was the analysis of Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra and Aqua satellites data corrected and non-corrected for bidirectional effects. Finally, we evaluated potential drivers of OAC changes over time using cross-correlation analysis. The results showed a decrease in the TSS and chlorophyll-a concentrations from the upper to the lower streams of the reservoir. The exponential regression between the MODIS red reflectance and TSS had an adjusted r2 of 0.63. It decreased to 0.53 for the relationship between the green reflectance and chlorophyll-a. MODIS data corrected for bidirectional effects provided better OAC estimates than non-corrected data. The validation of MODIS TSS and chlorophyll-a estimates using a separate set of measurements showed a RMSE of 2.98mg/l and 2.33μg/l, respectively. MODIS estimates indicated a gradual transition in OAC from the upper to the lower streams in agreement with the patterns observed using field limnological data. The analysis of land use (greenness) showed two well-defined crop cycles per year. The highest seasonal concentrations of TSS and chlorophyll-a were observed in December and the lowest concentrations in April. Despite the interrelationships between both factors, our cross-correlation analysis indicated that the great concentrations of TSS and chlorophyll-a were primarily controlled by rainfall and secondarily by land use.

EVALUATION OF TRANSPARENCY AND PH OF ERNESTINA POWER PLANT WATERSHED – RIO GRANDE DO SUL

The anthropic activities, such as the usage of land for agriculture, have been modifying the natural processes, mainly on aquatic environments. Following this statement, this work aimed at characterizing and analyzing the transparency and pH of the Ernestina power plant watershed (UHE) located on the state of Rio Grande do Sul, Brazil. The methodology consisted on the collection of water samples in six points of the watershed and laboratorial analysis of the limnological variables pH and Transparency. The results of the sample points show high values for transparency and basic pH levels associated to the absence of rainfall on the day before the field study. The analysis of the compiled results compared to previous researches shows that a seasonal eutrophication process that may be related to the inadequate usage of land on the microbasins that constitute the watershed in the face of intense rainfall.

Limnological Alterations on Lentic Environments Related to the conditions of the Watershed – Jacuí-Mirim river – RS

On limnological studies, the influence of terrestrial environments and the meteorological conditions have been altering the natural characteristics of the optically active elements of water. Facing this problem, the following study proposes to identify, analyze and gather evidences supporting the variation on TSS concentration, pH and CE on the watershed of the Jacui-Mirim River, RS, Brazil. The limnological collections were performed in October 2009, on three sample stations located on the site of study. The data collected on site and in the laboratory were interpreted and complemented with information of other works done on the same field of study. It was observed that the alterations of the natural characteristics caused on the aquatic environment evolve due to a variety of on influences, mainly on predominantly rural areas. Such finding was evident because of expressive values found for TSS concentration (maximum of 14 mg/L). It is believed the highest value of pH (7.5) is due to the influence of sediments deriving from farmable soils that use limestone for correction. The CE presented good conditions (maximum of 26.9 μS /cm). However, it is needed to constantly verify pH, CE and other parameters of analysis in order to achieve a more precise conclusion.