No abstract

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.

The aim of this study was to investigate the post-dam conditions of the loads and yields of dissolved inorganic nitrogen (DIN), orthophosphate (DIP, silicate (DSi) and total phosphorous (TP) in the Lower São Francisco riverestuary (NE-Brazil) after the river was regulated to a constant flow by the dams. Loads and yields of monthly

In estuarine systems, the distribution, composition and density of phytoplanktonic populations, their seasonal and spatial variations are controlled mainly by factors such as tolerance to salinity, luminosity, nutrients and grazing (Kinne, 1970;Santelices, 1977). The geomorphologic characteristics, the anthropogenic impacts and the variations in the weather conditions are other Determination of eutrophic areas in Mundaú/Manguaba lagoons, Alagoas-Brazil, through studies of the phytoplanktonic community Melo-Magalhães, EM.*, Medeiros, PRP., Lira, MCA., Koening, ML. and AbstractMundaú and Manguaba Lagoons (9° 34' 38"-9° 45' 30" S and 35° 44' 00"-35° 58' 13" W) are considered the largest and most productive ones in the state of Alagoas and were studied with the purpose of identifying the existence of anthropic impacts. Samples were collected at 8 stations, during low tide and flooding in rainy and dry periods, using the "Van Dorn" bottle and plankton net. In total, 155 taxons were identified, with special emphasis on Bacillariophyta and Cyanophyta divisions. The most abundant species in Mundaú Lagoon was Skeletonema cf. costatum, and in the Manguaba Lagoon, Cyclotella meneghiniana, Microcystis aeruginosa and Anabaena spiroides. The diversity ranged from 0.17 bits cell/L to 4.81 bits cell/L. The predominance of freshwater species (51%), evidenced higher influence of the limnetic flow on the two environments studied. The high values related to the phytoplanktonic density characterize the lagoons as strongly impacted environments, indicating the existence of eutrophic conditions in most of the studied stations.Keywords: phytoplankton, ecology, density, Mundaú/Manguaba lagoons. Determinação de áreas eutróficas nas lagoas Mundaú e Manguaba, Alagoas-Brasil, através de estudos com a comunidade fitoplanctônica ResumoAs lagunas Mundaú e Manguaba (9° 34' 38"-9° 45' 30" S e 35° 44' 00"-35° 58' 13" W) são consideradas as maiores e mais produtivas do Estado de Alagoas e foram estudadas com o objetivo de identificar a existência de impactos antrópicos, nos períodos chuvoso e seco, com base na composição, diversidade e densidade fitoplanctônica. Coletas de material fitoplanctônico foram realizadas em 8 estações fixas, durante maré vazante e enchente nos períodos chuvoso e seco. As amostras foram coletadas com garrafa de "Van Dorn" e rede de plâncton. Foram identificados 155 táxons destacando-se as divisões Bacillariophyta e Cyanophyta. A espécie mais abundante na laguna Mundaú foi Skeletonema cf. costatum; na laguna Manguaba foram Cyclotella meneghiniana, Microcystis aeruginosa e Anabaena spiroides. A diversidade oscilou ente 0,17 bits cell/L e 4,81 bits cell/L. A predominância de espécies dulciaquícolas, (51%) evidenciou maior influência do fluxo limnético nos dois ambientes estudados. Os altos valores da densidade fitoplanctônica caracterizam as lagunas como ambientes fortemente impactados, indicando a existência de condições eutróficas na maioria das estações estudadas.Palavras-chave: fitoplâncton, ecologia, densidade, lagun...

Turbidity plumes of São Francisco, Caravelas, Doce, and Paraiba do Sul river systems, located along the NE/E Brazilian coast, are analyzed for their dispersal patterns of Total Suspended Solids (TSS) concentration using Landsat images and a logarithmic algorithm proposed by Tassan (1987) to convert satellite reflectance values to TSS. The TSS results obtained were compared to in situ collected TSS data. The analysis of the satellite image data set revealed that each river system exhibits a distinct turbidity plume dispersal pattern. The behavior, dimension and degree of turbidity of the São Francisco River plume have been greatly altered by the construction of a cascade of hydroelectric dam reservoirs in its hydrological basin. The plume has lost its typical unimodal seasonal pattern of material dispersion and its turbidity has decreased due to the regulation of river flow by the dams and TSS retainance by the reservoirs. In contrast, the Doce and Paraíba do Sul river plumes are still subject to seasonal pulsations and show more turbid conditions than the SF plume, as dams are less numerous, set in the middle river sections and the natural river flow has been maintained. The Caravelas Coastal System river plume is restricted to near shore shallow waters dominated by resuspension processes. During austral spring and summer when NE-E winds prevail, all plumes generally disperse southward. Short-term northward reversals may occur in winter with the passage of atmospheric cold fronts. The São Francisco and Doce river plumes tend to disperse obliquely to the coast and transport materials further offshore, while the Caravelas and Paraíba do Sul plumes tend to disperse mainly parallel to the coast, enhancing TSS retention nearshore.
O presente estudo analisa as plumas de turbidez dos sistemas dos rios São Francisco, Caravelas, Doce, e Paraiba do Sul localizados na costa NE/E do Brasil utilizando imagens Landsat e o algoritmo logarítmico para Total de Sólidos em Suspensão (TSS) proposto por Tassan (1987). Os resultados obtidos foram comparados com Total de Sólidos em Suspensão medidos in situ. A pluma de turbidez de cada sistema mostra padrões de dispersão distintos. O comportamento, a dimensão e o grau de turbidez da pluma do Rio São Francisco têm sido drasticamente alterados devido à cascata de barragens e seus reservatórios presentes em sua bacia de drenagem. Já as plumas dos rios Doce e Paraíba do Sul apresentam pulsações sazonais e maior turbidez, uma vez que as barragens nesses rios localizam-se no setor médio e mantiveram a pulsação sazonal da vazão. A pluma do sistema costeiro de caravelas permanece restrita às águas rasas dominadas por processos de ressuspensão. Durante a primavera e verão, quando os ventos de NE-E prevalecem, as plumas dos quatro sistemas se dispersam na direção sul. Durante o inverno, inversões do padrão de dispersão podem ocorrer com a passagem de frentes frias. As plumas dos sistemas São Francisco e Doce tendem a se dispersar obliquamente à costa, favorecendo o transporte de material para...