Consumo e influência de exopolissacarideos de Anabaena spiroides (Cyanophyceae) sobre a toxicidade e captura do cobre por Ceriodaphnia cornuta (Cladocera, Daphnidae).
Abstract
Human specie can alter deeply and very fast the enviroment in which it is in. Because of the
industrial development, the water, air and soil contamination have become cause of
concern, chiefly in big cities with great populations. Among the contaminants figure the
heavy metals, which levels at aquatic and terrestrial ecossistems are growin up every year.
These elements are able to bioaccumulate in the organisms and biomagnified on the food
webs. The bioavailability of metals can be influencied by several factors like the
complexation with dissolved organic matter, e.g. algal exudates, that generally decreases
the toxicity of this elements. The scope of this work was evaluate the potencial use of
exopolysccharides of Anabaena spiroides (Cyanophyceae) as food source of Ceriodaphnia
cornuta (Cladocera, Daphnidae), and to establish the influence of this organic matter on
copper toxicity and uptake to this cladoceran.
Initially, it was estabilished the C. cornuta length-weigth relation. After this, it was
investigated ingestion of exopolysccharide and its influence in life history parameters of C.
cornuta. Results showed that A. spiroides exopolysccharide is able to sustain a population
of this zooplanktonic specie. Individuals fed with this compound exhibited rate of
population growth very significant to this specie (r = 0,263). The copper acute toxicity and
uptake by C. cornuta assay revealed that addition of 30mg L-1 of A. spiroides
exopolysccharide increased about 4 times copper EC/50 (calculated by Trimmed
Spearman-Karber method) to C. Cornuta (from 8,11x10-8M ±9,80x10-9M without
exopolysccharide to 3,25x10-7M ±5,30x10-8M with addition of exopolysccharide).
Copper concentration in the organisms after 24 hours exposure to several metal
concentration was determined by DPASV using a polarograph and showed little variation
among concentrations and treatments with and without exopolysccharide. It suggests that
organisms of this study were able to regulate copper body contents.