IMPLICAÇÕES SOCIOAMBIENTAIS DO PROCESSO DE APROPRIAÇÃO E USO DO RIO PARAÍBA DO MEIO EM VIÇOSA (AL) / Social and environmental implications of the process of appropriation and use of the River Paraíba do meio in Viçosa (AL)

O homem ao longo de sua história evolutiva tem aperfeiçoado, por meio do trabalho, seus instrumentos e técnicas, usando-os para se relacionar com a natureza e transformá-la. O artigo traz o processo de apropriação e uso dos recursos naturais no município de Viçosa – AL, destacando o rio Paraíba do Meio, evidenciando como a população foi transformando a paisagem. Para identificar tal situação realizaram-se estudos de campo (geológicos, geomorfológicos, etc.) e coletas de amostras nas águas do rio para analisar a qualidade da água, mensurando in situ, com a utilização de sonda multiparamétrica YSI 6600, alguns elementos, tais como: oxigênio dissolvido (mg/l), clorofila a (µg/l) e pH. Ao longo da pesquisa foram detectados desmatamento da mata ciliar, dragagem do leito, moradias e atividades econômicas sem controle nas vertentes do rio; identificou-se ainda, concentrações inicias de fósforo, de nitrogênio, dentre outros. Dessa forma, a população do município ao longo de sua história degradou variados recursos da área de drenagem do rio, mediante ações sem gestão e planejamento, tornando o mesmo, atualmente, inapropriado para algumas atividades socioeconômicas

Inter-annual variability on the water quality in the Lower São Francisco River (NE-Brazil)

Abstract: Aim This study characterized the water quality in the lower São Francisco River (NE-Brazil).This research represents the first work to be carried out in the lower sector of the São Francisco river aiming to quantify and compare limnological variables, during three different years (2001, 2004 and 2007). Methods Water samples were collected in a transversal section of the river at monthly intervals period on surface layer. Temperature, conductivity, pH, and dissolved oxygen were obtained using a multiparameter probe YSI-6600. The dissolved inorganic nutrients (ammonium, nitrite, nitrate, dissolved phosphorus and silicates), chlorophyll-a and total suspended sediment (TSS) were also determined. Results The three hydrological years showed differences in precipitation rates and discharge conditions. The year 2001 had precipitation rates below the historical series of rainfall. The mean annual water temperature showed negligible differences among the three years. Dissolved inorganic nutrient concentrations were highest in 2004, with ammonia and nitrate differing statistically between the years (p<0.05); the later showed the largest concentration of dissolved inorganic nitrogen. Chlorophyll-a showed a slight difference among years. Conclusions Precipitation intensity has a direct impact on the São Francisco River discharge, but the geographical distribution of the precipitation is also a determinant factor for alterations of the chemical and physical characteristics of the water that reaches the lower sector of the São Francisco River

EXCESSO HÍDRICO SOBRE OS COMPONENTES do RENDIMENTO da CULTURA da SOJA

O cultivo da soja em solos hidromórficos do Estado do Rio Grande do Sul vem sendo utilizado como opção em rotação com arroz e pastagens. O presente trabalho teve como objetivos determinar o comportamento dos componentes do rendimento de quatro cultivares de soja, para as condições dos solos hidromórficos, e verificar as variações de comportamento em função do estádio de desenvolvimento em que ocorre o estresse por excesso hídrico. O experimento foi conduzido em uma estrutura com cobertura plástica, em vasos de PVC, no ano agrícola de 1995/96, no Departamento de Fitotecnia da UFSM, em Santa Maria, RS. O solo utilizado foi um planossolo pertencente à unidade de mapeamento Vacacaí. O delineamento experimental utilizado foi o de blocos ao acaso, fatorial (4 x 5) com três repetições. As cultivares Ocepar 14, FT Saray, IAS 5 e CEP 16 foram submetidas a tratamentos de saturação hídrica do solo por um período de 15 dias a partir dos estádios de desenvolvimento V2 e V6; e por um período de 10 dias a partir dos estádios R2, R3 e R4. Os resultados indicaram que as quatro cultivares de soja utilizadas apresentaram boa tolerância à saturação hídrica no solo e que, em termos de duração desse estresse, a tolerância à saturação hídrica no solo é maior no subperíodo vegetativo do que no subperíodo reprodutivo.Soybean cultivars in rotation with rice and pastures in hydromorphic soils in Rio Grande do Sul, has been used as an agricultural option. The present report had as main objective to determine the performance on the yield component of soybeans cultivars under hydromorphic soil conditions, and in the verification of the crop responses to excess of water in the soil at different stages of growth. The study was conducted during the crop year of 1995/96, bellow extructure covered, at the Plant Sciences Departament of the Federal University of Santa Maria, RS, Brazil (29º 41' S latitude, 58º 48' W longitude, 95 m above the sea level). PVC pots were filled with planossolo soil. The experimental design randomized blocks, bifactorial with three replications. Cultivars Ocepar 14, FT Saray, IAS 5 and CEP 16 were submitted to hydrical saturation in the V2, V6, R2, R3 and R4 plant development stages. The results indicated that the used cultivar soybeans, they showed a good tolerance to the hydrical saturation in the soil, and this tolerance to hydrical saturation in the soil is higher in the vegetative stage than in the reproductive stage

Aporte de sedimentos em suspensão no baixo Rio São Francisco (SE/AL), em diferentes condições hidrológicas

The São Francisco River estuary has since the Seventies been subject to the impact of a dam cascade constructed along its middle-lower semi-arid river course. Suspended matter and water fluxes were reduced both in their magnitude and natural seasonal pulsation. However, today´s regulated fluxes are still prone to sporadic short-term perturbations induced by extreme climatic events in the drainage basin. This study addresses suspended matter fluxes of three anomalous events, one corresponding to the drought of 2001 and the other to the floods of 2004 and 2007. The drought event extended over the whole basin leading to low suspended matter concentrations of < 5 mg/L and fluxes of 0,2 x 10^6 t/y due to low discharges and efficient material retention by the dam reservoirs. In contrast, the flood of 2004 was generated by high precipitation in the middle-lower semi-arid basin and yielded higher concentrations of suspended matter with a pulse of up to 490 mg/L and fluxes of 7,7 x 10^6 t/y. The flood of 2007 produced lower suspended matter concentrations of up to 25 mg/L and fluxes of 1,1 x 10^6 t/y, as it was induced by precipitation in the upper basin and materials were retained by the dams. The results exemplify that spatial differences of precipitation in the basin in relation to the location of the dam cascade generate different water run-off and material yields to the coast

Microphytoplankton biomass and trophic state of the Estuarine Region of São Francisco River (northeastern Brazil)

One of the most serious problems that affect estuaries is the excessive enrichment of nutrients, especially nitrogen and phosphorus compounds that result in increased productivity. Studies to evaluate the trophic conditions of the São Francisco River estuary were conducted at four stations in the rainy (July/ 2006 ) and dry (January/2007) season in neap and spring tides, during high tide and low tide. Microphytoplankton was collected using plankton nets with mesh size of 45mm and the samples for analysis of nutrients and Phytoplankton biomass (chlorophyll a) were obtained from the sub-surface layer with wide-mouthed plastic bottles. The waters of this ecosystem showed salinities ranging from an oligohaline to a limnetic regime, alkaline pH and water clarity ranging between 1.00m and 2.60m. The concentrations of dissolved nutrients varied considerably, being highest during the dry season period. The Microphytoplankton was composed of 176 taxa, mainly distributed among the Chlorophyta, Charophyta and Bacillariophyta. Phytoplankton biomass (chlorophyll a) showed no significant differences between seasons, tides and tidal regimes, however the density (Cel.L-1) was significantly higher in the dry season. Values of a TSI showed oligotrophic conditions in the four stations and in the two periods analyzed. In the dry season there was a higher cell density and increased levels of dissolved nutrients with the exception of nitrate that was considered higher in the rainy season. The Microphytoplankton species are characteristic of waters of low to moderate trophic level and the TSI indicated a predominance of oligotrophic conditions in the two seasons in the study area.Keywords: chlorophyll a, estuary,  hydrology, phytoplankton, seasonality 

Distribution of prokaryotic organisms in a tropical estuary influenced by sugar cane agriculture in northeast Brazil

In a joint Brazilian-German case study, distribution patterns of microorganisms were compared with environmental variables in the tropical coastal Manguaba lagoon in northeast Brazil, which is situated downstream of several sugar cane processing plants . 16S rDNA and 16S rRNA single strand conformation polymorphism (SSCP) gene fingerprinting were used to follow the composition and distribution of microorganisms throughout the salinity gradient of the lagoon. Potentially abundant microorganisms were identified by sequencing representative SSCP bands. It could be demonstrated that the distribution of microbes was in close relation to the physico-chemical environmental settings and followed a common scheme. In the in- and outlet areas of the lagoon rather transient microbial communities were found, whereas in the central part a stable, diverse community was encountered, that due to the long residence time of the water, had ample time for development and adaptation

Phytoplankton community structure of the São Francisco river estuary (Piaçabuçu-Alagoas-Brazil): a study of its diversity

Studies aimed at determining phytoplankton composition, biomass, ecology and some physical-chemical characteristics of the São Francisco estuary were conducted at 7 sampling stations located in Piaçabuçu-Alagoas (10º25’-10°30’S and 36º23’-36º27W) during the rainy and dry seasons. The samples were obtained from the subsurface layer at neap and spring tides, during high and low tides, using a plankton net with 45 um mesh size. The waters from this estuary are characterized by low salinity, high temperatures, pH between alkaline and slightly acid, transparency greater than 1 meter. The phytoplankton was composed of 205 taxa, mainly distributed between the divisions Chlorophyta and Bacillariophyta, considered the most representative. The diatom Aulacoseira ambigua was considered dominant. Most of the species identified were planktonic and of freshwater origin. Specific diversity and equitability were considered average and high, indicating conditions of environmental equilibrium in the studied area. The analysis of variance in taxonomic richness revealed higher averages for the dry season and for high tides. Chlorophyll a content ranged between 0.4ug/L and 24,4ug/L. The annual variation of phytoplankton and physical-chemical parameters was related to rainfall.Studies aimed at determining phytoplankton composition, biomass, ecology and some physical-chemical characteristics of the São Francisco estuary were conducted at 7 sampling stations located in Piaçabuçu-Alagoas (10º25’-10°30’S and 36º23’-36º27W) during the rainy and dry seasons. The samples were obtained from the subsurface layer at neap and spring tides, during high and low tides, using a plankton net with 45 um mesh size. The waters from this estuary are characterized by low salinity, high temperatures, pH between alkaline and slightly acid, transparency greater than 1 meter. The phytoplankton was composed of 205 taxa, mainly distributed between the divisions Chlorophyta and Bacillariophyta, considered the most representative. The diatom Aulacoseira ambigua was considered dominant. Most of the species identified were planktonic and of freshwater origin. Specific diversity and equitability were considered average and high, indicating conditions of environmental equilibrium in the studied area. The analysis of variance in taxonomic richness revealed higher averages for the dry season and for high tides. Chlorophyll a content ranged between 0.4ug/L and 24,4ug/L. The annual variation of phytoplankton and physical-chemical parameters was related to rainfall