VariaÃÃo espacial e temporal da comunidade microfitoplÃnctÃnica em ecossistemas costeiros localizados no litoral sul de Pernambuco, Nordeste do Brasil




The coastal marine environment shows a strong ocean- continent-atmosphere interaction and for that reason is considered extremely complex from the biological point of view due to the influence of many systems, so it can be characterized as one of the most fertile and dynamic of the hydrosphere. The estuarine complex (Ilhetas and Mamucaba rivers) and the Tamandarà Bay are located 110km south from Recife (Pernambuco State â Northeastern Brazil), being included in the Corals Environmental Protected Area (Ãrea de ProteÃÃo Ambiental â APA â dos Corais). These ecosystems were studied to make an inventory of the microphytoplankton communities through the evaluation of space-time dynamics and the main environment variables that interfere on its composition. Phytoplankton and hydrological parameter samples were collected to February/98 from January/99 at 4 fixed stations comprehending two tidal cycles (low and high tides) on two different seasonal periods (dry and rainy). Data on the abiotic variables were gauged in situ: local depth, water temperature and transparency, and water samples were concomitantly collected with Nansen bottles for further analysis of other descriptors. The phytoplankton samples were collected on a 3-minute superficial horizontal tow using plankton net (64μm mesh) and then fixed with neutralized 4% formaldehyde solution. Temperature, salinity, phosphate and silicate levels were higher during the dry period. Dissolved oxygen, pH, saturation and BOD levels showed no great seasonal variation. While the higher nitrite, nitrate and suspended solids levels were recorded during the rainy period. Regarding the tides, the higher low tide levels were water temperature, BOD, silicate and suspended solids. During high tides, they were water salinity, dissolved oxygen and nitrate. An inventory was carried out with 203 taxa distributed among diatoms, dinoflagellates, blue-green algae, green algae and euglenoids, sequenced in order of taxonomic richness and abundance, with some species standing out as dominants and/or very frequents: Aulacodiscus kittoni Arnott, Cerataulus turgidus Ehrenberg, Chaetoceros lorenzianus Grunow, Coscinodiscus centralis Ehrenberg, Nitzschia sp. and Synechococcus elongatus (NÃgeli) NÃgeli. Microphytoplankton richness and density were higher during the dry period, when there was greater incidence of solar radiation and higher transparency levels along the water column. The specific diversity was considered high, which demonstrates a homogeneous distribution of populations and a heterogeneity strongly influenced by physical and chemical gradients resulting from the limnetic and marine fluxes. The presence of marine euryhaline species (83%) was very significant, with a much higher percentage than what is considered to be truly estuarine (7%) and oligohaline (10%). With the Principal Component Analysis (PCA), it was possible to testify that some factors, such as pluviometric precipitation, tidal cycles and salinity, contributed to the environmental complexity of the studied area, being the main regulators of both the hydrological parameters and the distribution of microphytoplanktonic composition. The data obtained from the variables that indicate the environment quality (dissolved oxygen and BOD) and the planktonic flora allowed classifying the studied coastal ecosystems as free from environmental stress, demonstrating them to be very preserved and with high complexity levels


ilhetas river tamandarà bay coastal ecosystems fitoplÃncton ecossistemas costeiros rio mamucaba pernambuco nordeste do brasil mamucaba river baÃa de tamandarà phytoplankton rios ilhetas pernambuco state oceanografia northeastern brazil

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