Fernando Antônio do Nascimento Feitosa

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.

Spatial and temporal distribution of the phytoplanktonic biomass and environmental variables in the Maranhense Gulf, Brazil

Este trabalho foi desenvolvido com o objetivo de caracterizar alguns estuarios do Golfao Maranhense, atraves da analise da biomassa fitoplanctonica e das variaveis ambientais. As amostras bimestrais foram coletadas em quatro pontos fixos, na superficie, em mare de sizigia, durante a vazante, no periodo de maio/2002 a marco/2003. A pluviometria anual durante o periodo amostrado foi de 1.898,5 mm; a salinidade variou entre 6 e 35; transparencia de 18 a 61 cm; oxigenio dissolvido de 2,1 a 6,3 ml.L-1; taxa de saturacao do oxigenio de 45 a 126%; amonia de 0,02 a 26,45 μM; nitrito de 0,01 a 0,25 μM; nitrato de 0,24 a 3,53 μM e fosfato de 0,13 a 0,58 μM. A concentracao da clorofila a variou de 1,92 a 72,23 mg.m-3 caracterizando esta regiao como de alta produtividade e a fracao <20 μm (nano e picofitoplâncton) foi considerada a mais representativa. AAnalise dos Componentes Principais (ACP) evidenciou que a clorofila a relacionou-se positivamente com a salinidade, transparencia da agua, velocidade do vento, fosfato e nitrato e inversamente com a pluviosidade, oxigenio dissolvido, taxa de saturacao do oxigenio, temperatura e amonia. No Golfao Maranhense forcantes fisicas como vento, macromare e a alta turbidez sao as principais causas da reducao da zona eufotica e consequentemente da biomassa fitoplanctonica.

Eutrophication and water quality in a tropical Brazilian estuary

ABSTRACT Nascimento-Filho, G.A.; Montes, M. de J.F.; Gaspar, F.L.; Paulo, J.G.; Feitosa, F.A. Eutrophication and water quality in a tropical estuary. The use of indexes and trophic state models are gaining importance in evaluating the degree of anthropogenic influence on estuarine eutrophication and the impact on coastal and adjacent areas. A TRIX index and an ASSETS model were used to evaluate the level of eutrophication in the estuary of Suape Industrial Port Complex. The values for the TRIX trophic state multivariate index revealed the increase towards the upper estuary, going from 2.26 at high tide at station 1 (low estuary), demonstrating a medium trophic state and good water quality, to 6.43 at low tide at station 3 (upper estuary), showing an elevated trophic state and poor water quality, where continental drainage is accelerating the eutrophication process in the environment. In the evaluation generated by the ASSETS eutrophication model, the estuary eutrophication level was considered to be moderate, with Overall Human Influence considered Low, General Eutrophication Conditions also considered Low. Finally, the Determination of Future Outlook showed an unchanged expression and perspectives for slow degradation. The comparison between the index and model showed some similarities, in general, TRIX quantified the Massangana river estuary at a level medium of eutrophication and ASSETS qualified it as moderate.

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.

Hydrology, plankton, and corals of the Maracajaú reefs (Northeastern Brazil): an ecosystem under severe thermal stress

This study provides baseline information on the hydrological conditions and on the coral and plankton communities at the Maracajau reef ecosystem (Northeastern Brazil). Studies were performed from February to June 2000, covering the transition from dry to rainy season. In this area, there is an offshore coral reef formation, where corals were observed in loco; the water samples were collected to obtain the hydrological and plankton data. Six scleractinian species were identified. Stable isotope analysis on the carbonate fraction of Favia gravida fragments showed that these corals were under severe thermal stress. Chlorophyll-a varied from 1.1 to 9.3 mg m-3, with higher values during the rainy season. Average zooplankton wet weight biomass were 117.0 (microzooplankton) and 15.7 mg m -3(mesozooplankton). A total of 136 Phytoplankton and 61 zooplankton taxa were identified. Seasonal forcing determined the phyto-micro-and mesozooplankton community structure, rather than the coastal-offshore gradient.

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.

A Synoptic Assessment of the Amazon River-Ocean Continuum during Boreal Autumn: From Physics to Plankton Communities and Carbon Flux

The Amazon generates the worlds largest offshore river plume, which covers extensive areas of the tropical Atlantic. The data and samples in this study were obtained during the oceanographic cruise Camadas Finas III in October 2012 along the Amazon River-Ocean Continuum (AROC). The cruise occurred during boreal autumn, when the river plume reaches its maximum eastward extent. In this study, we examine the links between physics, biogeochemistry and plankton community structure along the AROC. Hydrographic results showed very different conditions, ranging from shallow well-mixed coastal waters to offshore areas, where low salinity Amazonian waters mix with open ocean waters. Nutrients, mainly NO3− and SiO2−, were highly depleted in coastal regions, and the magnitude of primary production was greater than that of respiration (negative apparent oxygen utilization). In terms of phytoplankton groups, diatoms dominated the region from the river mouth to the edge of the area affected by the North Brazil Current (NBC) retroflection (with chlorophyll a concentrations ranging from 0.02 to 0.94 mg m−3). The North Equatorial Counter Current (NECC) region, east of retroflection, is fully oligotrophic and the most representative groups are Cyanobacteria and dinoflagellates. Additionally, in this region, blooms of cyanophyte species were associated with diatoms and Mesozooplankton (copepods). A total of 178 zooplankton taxa were observed in this area, with Copepoda being the most diverse and abundant group. Two different zooplankton communities were identified: a low-diversity, high-abundance coastal community and a high-diversity, low-abundance oceanic community offshore. The CO2 fugacity (fCO2sw), calculated from total alkalinity (1,450 < TA < 2,394 μmol kg−1) and dissolved inorganic carbon (1,303 < DIC < 2,062 μmol kg−1) measurements, confirms that the Amazon River plume is a sink of atmospheric CO2 in areas with salinities <35 psu, whereas, in regions with salinities >35 and higher-intensity winds, the CO2 flux is reversed. Lower fCO2sw values were observed in the NECC area. The ΔfCO2 in this region was less than 5 μatm (−0.3 mmol m−2 d−1), while the ΔfCO2 in the coastal region was approximately 50 μatm (+3.7 mmol m−2 d−1). During the cruise, heterotrophic and autotrophic processes were observed and are indicative of the influences of terrestrial material and biological activity, respectively.

Dynamics of Chlorophyll a and Oceanographic Parameters in the Coastal Zone: Barra das Jangadas-Pernambuco, Brazil

ABSTRACT Otsuka, A.Y.; Feitosa, F.A.N.; Flores-Montes, M.J., and Silva, A., 2016. Dynamics of chlorophyll a and oceanographic parameters in the coastal zone: Barra das Jangadas-Pernambuco, Brazil. The Pernambuco shelf, inserted into the NE-E continental margin of Brazil, is about 187 km long and is characterized by reduced width, shallow depth, gentle slope, relatively warm water, and high salinity. It is influenced to some extent by translittoral rivers, the Jaboatão River being among these. This study aimed to analyze the dynamics of chlorophyll a and hydrological parameters on the Pernambuco inner continental shelf under the influence of the Jaboatão River plume. Bimonthly samplings were carried out during the rainy and dry seasons at one point in the estuarine area and four points along the adjacent inner continental shelf. The parameters evaluated were chlorophyll a, temperature, salinity, transparency, dissolved oxygen, suspended particulate matter, pH, depth, and inorganic nutrients. Most parameters had significant seasonal variation. In the dry period, chlorophyll-a ranged from 2.89 to 34.71 mg m−3 in the estuary and varied from 0.21 to 9.67 mg m−3 on the shelf. In the rainy period, it varied from 0.79 to 12.46 mg m−3 in the estuary and from 0.26 to 4.59 mg m−3 on the shelf. According to a principal components analysis, chlorophyll a showed a direct relationship with oxygen saturation rate and temperature and an inverse relationship with pH, salinity, and water transparency. Two points on the shelf (points 3 and 4) were most influenced by river outflow. The limiting factor for phytoplankton biomass was water turbidity due to the higher values reached in the dry period. The estuarine zone was in a stage of high eutrophication, thus sometimes affecting the waters of the inner shelf. RESUMO A plataforma de Pernambuco está inserida na margem continental nordeste-leste do Brasil, possui cerca de 187 Km de extensão e se caracteriza por ter uma reduzida largura, pouca profundidade, declive suave, águas relativamente quentes, elevada salinidade. Recebe influência de alguns rios translitorâneos, dentre eles, o rio Jaboatão. O presente trabalho apresentou como objetivo analisar a dinâmica da clorofila a e parâmetros hidrológicos na plataforma continental de Pernambuco sob o efeito da pluma do rio Jaboatão. Foram realizadas coletas bimestrais, no período chuvoso e estiagem, em um ponto na zona estuarina e quatro ao longo plataforma continental adjacente. Os parâmetros avaliados foram: clorofila a, salinidade, oxigênio dissolvido, material particulado em suspensão e nutrientes inorgânicos dissolvidos. A maioria dos parâmetros apresentou variação sazonal significativa. A clorofila a no estuário variou de 2,89 à 34,71 mg.m−3 e na plataforma continental de 0,21 à 9,67 mg.m−3 no período de estiagem e, no período chuvoso, apresentou uma variação no estuário de 0,79 à 12,46 mg.m−3 e na plataforma de 0,26 à 4,59 mg.m−3. De acordo com ACP, a clorofila a apresentou uma relação direta com a temperatura e taxa de saturação do oxigênio e inversa com pH, salinidade e transparência da água. Os pontos da plataforma que mais sofreram influência do deságüe fluvial foram os pontos centrais P3 e P4. O fator limitante para a biomassa fitoplanctônica foi a turbidez da água e os maiores teores foram observados no período de estiagem. A zona estuarina encontra-se em um elevado processo de eutrofização antrópica e, desta forma, vem interferindo na qualidade das águas da plataforma continental.

Phytoplankton Productivity and Hydrology of Porto de Galinhas Reef Ecosystem (Pernambuco, Brazil)

ABSTRACT Machado, R.C.A.; Feitosa, F.A.N.; Koening, M.L.; Flores Montes, M.J.; Bastos, R.B., and Jales, M.C., 2014. Phytoplankton productivity and hydrology of Porto de Galinhas reef ecosystem (Pernambuco, Brazil). Porto de Galinhas beach is located on the south coast of Pernambuco, Brazil, around 50 km from Recife, has sandstone fringing reefs, and has intense tourist activity. To contribute to the environmental water quality, the phytoplankton biomass and productivity were analyzed, as well as some hydrological parameters at three fixed collection points. Water samples were collected in 3 months of both dry and rainy seasons, from the water column surface, at three fixed points between the reef and the beach, at high and low tides and diurnal spring tides. Temperature ranged from 26°C to 31°C, salinity ranged from 33 to 37, the saturation index of dissolved oxygen ranged from 97.16% to 174.54%. Nitrite and phosphate were lower than 1 μmol L−1, nitrate was <2.5 μmol L−1, and silicate ranged from 5.01 to 37.12 μmol L−1. Chlorophyll a ranged between 1.17 and 3.23 mg m−3, productivity ranged between 1.36 and 23.90 mg C m−3 h−1, and the assimilation rate was between 0.93 and 8.62 mg C mg Chl a −1 h−1. The environmental parameters oscillated more in relation to seasonality than regarding the different tide stages and spatiality. According to the principal component analysis, rainfall was the most important physical forcing mechanism for the studied system, presenting direct correlation with suspended particulate material and nitrite and inverse correlation with the saturation index of dissolved oxygen, temperature, and transparency. The reef ecosystem is still free from the anthropogenic eutrophication process. It ranged from oligotrophic (dry season) to eutrophic (rainy season), and in the rainy season, the Maracaípe River plume can change the environmental conditions in the system. Although the reef area is under strong anthropogenic pressure due to intense local tourist activity, this impact has not been perceptible in the pelagic environment.

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.