Paulo Ricardo Petter Medeiros

Assessment of the trophic status of four coastal lagoons and one estuarine delta, eastern Brazil

Anthropogenic eutrophication of aquatic ecosystems continues to be one of the major environmental issues worldwide and also of Brazil. Over the last five decades, several approaches have been proposed to discern the trophic state and the natural and cultural processes involved in eutrophication, including the multi-parameter Assessment of Estuarine Trophic Status (ASSETS) index model. This study applies ASSETS to four Brazilian lagoons (Mundaú, Manguaba, Guarapina, and Piratininga) and one estuarine delta (Paraíba do Sul River), set along the eastern Brazilian coast. The model combines three indices based on the pressure–state–response (PSR) approach to rank the trophic status and forecast the potential eutrophication of a system, to which a final ASSETS grade is established. The lagoons were classified as being eutrophic and highly susceptible to eutrophication, due primarily to their longer residence times but also their high nutrient input index. ASSETS classified the estuary of the Paraíba do Sul river with a low to moderate trophic state (e.g., largely mesotrophic) and low susceptibility to eutrophication. Its nutrient input index was high, but the natural high dilution and flushing potential driven by river flow mitigated the susceptibility to eutrophication. Eutrophication forecasting provided more favorable trends for the Mundaú and Manguaba lagoons and the Paraíba do Sul estuary, in view of the larger investments in wastewater treatment and remediation plans. The final ASSETS ranking system established the lagoons of Mundaú as “moderate,” Manguaba as “bad,” Guarapina as “poor,” and Piratininga as “bad,” whereas the Paraíba do Sul River Estuary was “good.”

Changes in nutrient loads (N, P and Si) in the São Francisco estuary after the construction of dams

The aim of this study was to investigate the post-d am conditions of the loads and yields of dissolved inorganic nitrogen (DIN), orthophosphate (DIP, silicate (DSi) and total phosphorous (TP) in the Lower Sao Franci sco riverestuary (NE-Brazil) after the river was regulated t o a constant flow by the dams. Loads and yields of monthly measurements performed from November 2000 to March 2002 at a gauging station downstream of the dams (8 0 km from the coast) showed 4.1 x 10 3 t/yr and 0.006 t/km 2 /yr of DIN, 0.2 x 10 3 t/yr and 0.002 t/km 2 /yr of DIP, and 448 x 10 3 t/yr and 0.71 t/km 2 /yr of DSi, respectively. Over the last 15 years, D IN loads reduced by 94 % and DSi by 31%. The river turned into an oligotrophic system with p rimary production limited by nitrogen and nutrient yields being among the lowest of Brazilian coastal rivers.

A satellite view of riverine turbidity plumes on the NE-E Brazilian coastal zone

Turbidity plumes of Sao 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 Sao 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 Paraiba 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 Sao Francisco and Doce river plumes tend to disperse obliquely to the coast and transport materials further offshore, while the Caravelas and Paraiba do Sul plumes tend to disperse mainly parallel to the coast, enhancing TSS retention nearshore.

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.

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

Aim This study characterized the water quality in the lower Sao Francisco River (NE-Brazil).This research represents the first work to be carried out in the lower sector of the Sao 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 Sao 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 Sao Francisco River.

Circulation and salt balance in the São Francisco river Estuary (NE/Brazil)

Para avaliar como a descarga do rio e as correntes de mare influenciam a circulacao e o transporte de sal no estuario do rio Sao Francisco, foram realizadas duas campanhas de 25 horas, alem de perfis ao longo do canal principal do estuario (18/19 e 25/26 de fevereiro de 2014). A velocidade das correntes mostraram uma maior assimetria entre as correntes de enchente (v 0) durante a sizigia (-0,6 e 1,1 m/s), em comparacao com a mare de quadratura (-0,4 e 1,0 m/s). Tal resultado foi atribuido a forte energia de empuxo intensificado pela maior forca da descarga fluvial na sizigia. Em geral, a salinidade apresentou forte estratificacao vertical variando da superficie ao fundo entre 0,0 <S <36,6 e 0,5 <S <36,1, durante a sizigia e quadratura, respectivamente. Apesar de a descarga do rio ter reduzido entre a mare da sizigia e quadratura, as condicoes de parcialmente misturado e altamente estratificado (tipo 2b) permaneceram para ambos os periodos, com adveccao e difusao turbulenta contribuindo com 34% e 66% para o transporte de sal estuario acima na sizigia, respectivamente, e 56% e 44% durante a quadratura. Tal resultado foi atribuido ao equilibrio entre as forcantes da mare e baroclinico, alem da descarga do rio. O transporte de sal advectivo predominantemente na direcao estuario abaixo para os ciclos das mares de sizigia (12,5 kg m-1s-1) e quadratura (15,2 kg m-1s-1) sugere que ha pouca acumulacao de sal dentro do estuario do Sao Francisco.

Dams Impacts upon the fluxes of biogenic matter

Dams impacts are usually associated with the formation of artificial lakes, population displacements and loss of continental habitats. However, but not less significant, are the impacts upon the fluxes of water and materials to the coastal zone with severe quantitative and qualitative alterations which may cause saline water intrusion and coastal erosion, loss of estuarine and coastal zone fertility and the alterations of regional and global biogeochemical cycles. The present article, presents a brief review on the theme by incorporating Brazilian examples addressed by the work group from the Instituto Nacional de Ciência e Tecnologia de Transferência de Materiais Continente-Oceano (INCT-TMCOcean).