Kátia Muniz

Influence of the Amazon and Para Rivers on Water Composition and Phytoplankton Biomass on the Adjacent Shelf

Abstract In the context of the REVIZEE programme, an extensive sampling cruise was carried out in the northern section of the Brazilian Exclusive Economic Zone on board O.V. Antares (Operation North III). Several parameters were surveyed along the Amazon continental shelf during this cruise, such as horizontal and vertical distributions of temperature, salinity, dissolved oxygen, pH, dissolved inorganic nutrients, and phytoplankton biomass. Water with salinity below 33 psu and high silicate content was observed throughout the shelf, indicating the influence of the Amazon River plume up to a distance of 147 km from the coast; pH always remained alkaline. Water temperature was relatively homogeneous at the surface, with an average of 28°C. A permanent thermocline was detected in oceanic regions. Coastal waters were eutrophic, well oxygenated (maximum of 6.54 mL O2 L−1), and presented high chlorophyll a (maximum of 9.8 mg chlorophyll a m−3) and nutrient concentrations (up to 9.54 μmol L−1 NO3−, 0.89 μmol L−1 PO42−, and 108.59 μmol L−1 Si044−). Oceanic waters adjacent to the Amazon shelf presented high transparency (Secchi depth up to 35 m) and chlorophyll a (mean: 0.1 mg m−3) and low nutrient concentrations (maximum of 1.58 μmol L−1 NO3−, 0.18 μmol L−1 PO42−, and 5.92 μmol L−1 Si044−). Cluster analysis performed with all data showed a clear separation between coastal and oceanic waters at the surface layer and at 1% light penetration layers. This separation into two groups of stations clearly represents areas with different degrees of influence from the discharges of the Amazon Basin. The Amazon River is very important to the nutrient budgets of the shelf.

Estrutura sazonal e espacial do microfitoplâncton no estuário tropical do rio Formoso, PE, Brasil

This work aimed to evaluate spatial and temporal variations of the microphytoplankton and environmental variables in the Formoso River estuary, southern coast of Pernambuco state. The samples were collected at three stations, in the rainy season (May to July/2002) and dry season (October to December/2002). The plankton samples were obtained through horizontal superficial hauls, with a 64im-mesh net. Temperature and transparency were recorded in situ and, at the same time, water samples were collected using a Kitahara bottle to analyze salinity, pH, dissolved oxygen, nutrients and biomass. A total of 204 taxa were identified with the diatom group (75%) ranking first; dominant species were Chaetoceros costatus Pavillard, Chaetoceros curvisetus Cleve, Chaetoceros sp., Coscinodiscus centralis Ehrenberg, followed by the dinoflagellates (10.79%), cyanophycea (6.37%), chlorophycea (3.92%), euglenophycea (3.43%) and silicoflagellates (0.49%). Oxygen concentrations evidence a high capacity of environment renewal due to sea-water input; higher concentrations of nutrients and microalgae biomass occurred during the rainy season and at low tide. The parameters rainfall and sea-water input influenced hydrology and phytoplankton community distribution to the greatest degree, contributing to species richness.

Nutrient and phytoplankton biomass in the Amazon River shelf waters

The Amazon River estuary is notable at the Amazon Continental Shelf, where the presence of the large amount of water originating from the Amazon during the rivers falling discharge period was made evident by the low salinity values and high nutrient levels. Even so, the presence of oceanic waters in the shelf area was significant. Dissolved organic nitrogen was the predominant species of the nitrogen cycle phases, followed by total particulate nitrogen, nitrate, ammonium and nitrite. The chlorophyll a data in the eutrophic area indicated that there is sufficient nitrogen in the area to withstand productivity, though dissolved inorganic nitrogen removal processes are faster than regeneration or mineralization. The anomalous amounts of inorganic dissolved nitrogen showed more removal than addition. The simulations with the bidimensional MAAC-2D model confirmed that high nutrient waters are displaced northwest-ward (two cores at 2.5 degrees N-50 degrees W and 4 degrees N-51 degrees W) by the stronger NBC during falling river discharge. During high river flow period these nutrient-rich lenses are distributed around 0.5 degrees N-48.5 degrees W as well as along the shallow Amazonian shelf (20 m-50 m depth, 1 degree N-3.5 degrees N), as a result of the spreading of Amazon freshwater outflow.

Series temporales de variables hidrobiológicas en un estuario tropical (Brasil)

Este trabajo muestra los resultados de series temporales en el estuario de Barra de Jangadas en el Noreste de Brasil. El estudio fue realizado durante siete dias consecutivos desde una marea de sicigia a una de cuadratura, en una estacion fija durante el periodo seco (enero) y lluvioso (julio), en 2001. Se analizaron parametros meteorologicos (precipitacion pluviometrica, evaporacion, intensidad de los vientos), hidrologicos (temperatura, salinidad, pH, oxigeno disuelto-OD y tasa de saturacion, DBO5, nutrientes (NH3 +NH4, NO2 -, NO3 -, PO4 -3, SiO2)), batimetria, intensidad de las corrientes y clorofila-a. El analisis de componentes principales (ACP), explico el 80% de la varianza total, mostrando una relacion inversa entre nutrientes y OD, salinidad y pH. Este analisis mostro una correlacion positiva entre la bajamar y los nutrientes, indicativo de polucion de origen antropogenica. La temperatura del agua vario poco estacionalmente, similar a la clorofila-a que caracterizo un ambiente eutrofico con valores superiores a 20 mg m-3. Mayores concentraciones de sal ocurrieron en el mes estival y sin mostrar estratificacion vertical. El oxigeno disuelto vario significativamente entre ambos periodos. Los valores totales de nitrogeno y fosforo inorganico disuelto en julio fueron en promedio 2 y 5 veces superiores a los de enero, respectivamente. Las medias de N:P variaron de 35:1 en enero a 8:1 en julio, siendo ambos, el fosfato y el nitrogeno limitantes para el crecimiento del fitoplancton. Diferencias dia/noche evidenciaron que, en enero, el amonio decrecio en mayor proporcion que el resto de los compuestos nitrogenados, indicativo de la asimilacion por los organismos autotroficos durante el dia.

Hydrological Impact of the Port Complex of Suape on the Ipojuca River (Pernambuco-Brazil)

Abstract A port complex was implanted in the coast region of Suape, PE-Brasil, in 1979–80, which altered the geomorphological and hydrodynamic conditions of the area, mainly in the estuary of the Ipojuca River. Water samples were collected from the surface and the deep layer to determine the salinity, pH, dissolved oxygen, transparency, and temperature from three fixed stations in the estuary of the Ipojuca River during the summer and winter before (1978) and after (1986–87) the ports construction, in order to evaluate the effects of the port-induced changes. The data were subjected to a principal component analysis and to individual t tests. The first principal component, the axis of maximum information, alone explained 50% of the total variance, being associated with the generalized increase of the chemical parameters after the ports construction, mainly the salinity. Despite the fact that the results of the t tests presented significant differences only for the dissolved oxygen, pH, and temperature, the increased salinity produced the greatest ecological effects in the estuary. The water flow of the Ipojuca River was diverted toward the ocean, decreasing the river-flow velocity at the mouth. This decrease in flow caused a sedimentation in the area, a decrease in the circulation and depth, and a transformation of the mouth of the river into a coastal lagoon with an increase in evaporation and salinity. A delay of more than 2 hours was observed in the dynamic tide in relation to the normal 6-hour cycles. Despite an increase in the concentration of dissolved oxygen and transparency values, effects that theoretically improve environmental conditions, a morphological transformation occurred that caused drastic changes in the estuarys circulation and in the tidal currents.

Estudo das diferentes formas de fósforo nas águas da plataforma continental do Amazonas

Hydrological samples were collected on the continental shelf of the Amazon river to determine particulate organic and inorganic matter, dissolved organic phosphorus (DOP), phosphate, total particulate phosphorus (TPP), chlorophyll a, temperature, salinity, pH, water transparency, dissolved oxygen (DO) and saturation rate. The objective was to study the forms of DOP, phosphate and TPP. In the euphotic layer, the fluvial discharge from the Amazon river favored the distribution of phosphate, TPP and DOP. In the aphotic layer, the phosphate concentration increased due to the decomposition of DOP and TPP. This increase is due to the absence of photosynthetic processes.

Status Of The Barra Das Jangadas Estuary(North-eastern Brazil): An Ecological Approach

The basic hydrological and planktonic characteristics of the Barra das Jangadas estuary were monitored to assess the water quality and the abiotic factors influencing the plankton populations. An intensive seven day sampling program was conducted at a fixed station, during the dry (January/2001) and the rainy (July/2001) seasons. Phytoplankton, zooplankton and the water physicochemical parameters were sampled in different tides, totaling 56 sampling procedures during the 168-hours-program, in each season. The dissolved oxygen was under saturation at low tide in both seasons, indicating a polluted area; and saturated during high tide due to marine influence. High overall nutrient concentrations indicated an eutrophic environment. Chlorophyll-a was high (~25 mg.m). The marine eurihaline plankton dominated the area. Phytoplankton presented 266 species, however only six were abundant and frequent; density varied from 95.10 cel.L to 7,830.10 both in the rainy season, and cyanobacterial blooms usually occurred in the estuary unbalancing the system. The zooplankton presented 87 taxa and varied from 1,300 to 18,500 ind.m. The plankton diversity was low, mostly composed of r-strategists. The main pattern observed was marine eurihaline species in the dry season during high tide and limnetic species in the rainy season, low tide. During the neap tide in both seasons the water renovation was very poor, increasing the pollution load residence time.