A utilizaÃÃo da microalga skeletonema costatum (greville) cleve (bacillariophyceae) na avaliaÃÃo da qualidade ambiental de Ãreas estuarinas de Pernambuco

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Coastal environments are characterized by the high complexity and biological diversity, where the variety overcomes others ecosystems. The estuaries represent one of the most productive ecosystems of the world, due to the great contribution of inorganic dissolved nutritients, coming from the continent. It has been changing in the last years, as a result of arbitrary manage. In this context, be present the Ipojuca River Estuary, located 40km south of Recifeâs city, and Pina Basin Estuary, right inside the mentioned city, both in the Recife Metropolitan Area. These ecosystems were studied aim to identify the diatom Skeletonema costatum (Greville) Cleve occurrence, analyzing the quantitative and morphometric variations and the most important environmental variables influencing its development. Samples were collected in June, July and August (dry season) and October, November and December (rainy season) in 1986, at the Ipojuca River, and 1990, at the Pina Basin, in low and high tide. It was also register in situ air and water temperature and transparency. Water samples were collected with Nansen bottle for others hydrologic parameters analysis. Phytoplankton hauls were made, for the duration of 3 minutes on board a ship, using a plankton net (64μm mesh size) and the material was fixed in 4% neutral formaldehyde. The temperature, water transparency and salinity, in both environments, show highest values in the dry season; phosphate was high just in the Pina Basin and silicate in the Ipojuca River. The pH did not register a season variation. The highest values of dissolved oxygen, nitrite and nitrate were registered in the rainy season. In relation to tides, the highest values during low tides were temperature and nitrate (Ipojuca River) and nitrite (Pina Basin), phosphate and silicate, in both. In the high tides, larger water transparency values were register, and also salinity, pH, dissolved oxygen, nitrite (Ipojuca River), temperature and nitrate (Pina Basin). The species show different characteristics. In Ipojuca River Estuary cells were robust, larger and visible, big colonies, with evident processes. In Pina Basin Estuary the frÃstulas were fragile, whitish and almost imperceptible, with short processes and small colonies. The height values, cellular processes and cell/colony number presented small seasonal variation, in the cycles of tides and between the environments, being insignificant for the âTâ test. Cellular diameter demonstrated strong variation between the environments, being higher in the Ipojuca River Estuary, representing the most significant parameter. The cell density, in Ipojuca River, obtained high values during the rainy season, when occur low salinity and high silicate concentrations. In Pina Basin, the largest values occur in the dry season. The cell biovolume was higher in Ipojuca River Estuary and total biovolume values were equivalent in both. The Principal Components Analysis (PCA) evidenced that in the Ipojuca River the dissolved oxygen, pH, nitrite, nitrate and phosphate have had contributed positively to the species development. However, in Pina Basin, the precipitation, nutritients and water transparency were decisive for the species development. The data analyzed classify the Pina Basin Estuary as a eutrophic ecosystem with strong environmental stress. The Ipojuca River Esturay still is preserved, in a certain point. The study show that the species Skeletonema costatum enhance grows rates in non eutrophic environments, thus, it is an excellent indicative species for environmental quality

ASSUNTO(S)

skeletonema costatum rio ipojuca skeletonema costatum bioindicaÃÃo brazilâs northeast ipojuca river pernambuco pernambuco estuary bioindicator pina basin estuÃrio nordeste do brasil bacia do pina administracao municipal e urbana

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