Análise da associação bactéria-macroalgas em ambiente marinho e do seu potencial uso na avaliação ambiental.
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Data
2003-06-25Autor
Maurat, Maria Cristina da Silva
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In the last decades the increase in the amount of nutrients, particularly nitrogen and
phosphorus, introduced into the sea, has brought an accelerated eutrophication of the
coastal marine ecosystems, and great changes in water, sediment and biotic communities.
Nutrient enrichment is usually associated to other pollutants, as the heavy metals. The use
of macroalgae and heterotrophic bacteria has been considered an efficient tool in
environmental diagnosis when focusing these two types of pollution. The aim of the present
study was to compare the biomass of bacteria in the water column, attached to the
macroalgae and in the sediment of Praia da Baleia (Angra dos Reis/RJ), a region used as
control and of Praia de Boa Viagem (Niterói/RJ), a region where the main impact is from
domestic sewage effluents evaluating the effect of the eutrophication associated to different
concentrations of zinc on Champia parvula and accompanying microorganisms by using
laboratory experimentation. Methods involved filtration of samples on nuclepore filters,
detachment of bacteria by mechanical shaking and ultrasounding, then cell enumeration by
epifluorescence and the use of conversion factors to calculate biomass as organic carbon.
The highest bacteria biomass in the water, sediment and macroalgae was obtained for in
Praia de Boa Viagem. The evaluation of bacteria biomass in different substrates has shown
a direct correlation with the trophic state of the environment, with mean values of 0,198
µgC.cm-3 in the water; of 1,29 µgC.cm-3 in sediment and 0,038 µgC.cm-3 in the
macroalgae at the area impacted, values higher than those found in the control area.
Chronic and semi-estatic toxicity tests were also performed along 15 days in order to
determine growth rates, mortality, and morphological changes in the fronds of the
macroalgae Champia parvula, grown on different combinations of nutrients levels, zinc
concentrations and presence or absence of bacteria. Laboratory experiments evidenced that
zinc and nutrient concentrations interfere with growth, mortality and morphology of C.
parvula and also that macronutrients and bacteria probably influenced the accumulation of
zinc by the macroalgae, thus influencing its growth.