Growth, composition and metal removal potential of a Phormidium bigranulatum-dominated mat at elevated levels of cadmium.
Aquat Toxicol
; 116-117: 24-33, 2012 Jul 15.
Article
em En
| MEDLINE
| ID: mdl-22459410
ABSTRACT
Prompted by the fact that interaction of metals with cyanobacterial mats has been little studied, the present study evaluates the response of a cyanobacterial mat, dominated by Phormidium bigranulatum, to elevated concentrations of Cd²âº in the medium. The mat failed to grow at 7 µM of Cd²âº when the metal as also the mat inoculum were simultaneously added to the medium right in the beginning of the experiment due to marked sensitivity of P. bigranulatum, the main constituent of the mat, to high concentrations of Cd²âº. However, the mat previously grown in Cd²âº-free medium for a time period of 1-4 weeks grew successfully when exposed to media containing very high concentrations of Cd²âº. Four-week-old mat could grow at 250 µM of Cd²âº, which has been found toxic to many cyanobacteria and algae by previous researchers. Greater tolerance of older mats to Cd²âº may be due to greater proportion of exopolysaccharides, which are well known to sequester metal ions extracellularly, in them. Whereas the relative proportion of P. bigranulatum declined at high concentrations of the test metal that of green algae increased due most likely to their tolerance to Cd²âº. Air bubbles were seen entrapped in the mat due obviously to photosynthetic activity. Elevated concentrations of Cd²âº reduced the number of air bubbles in the mat. Decline in number of air bubbles at high concentrations of metal ions was more prominent in the case of younger mat than in the older one. The present study also evaluated changes in species composition of mats of different age that were subsequently grown in Cd²âº enriched culture medium. Younger mats showed change in species composition at very low concentrations of Cd²âº, but older mats showed little changes even at very high concentrations of the test metal. Hence older mats more strongly resisted to changes in its species composition than the younger ones upon exposure to high concentrations of Cd²âº. The growing mat successfully removed Cd²âº from the medium, which was greater at lower concentrations of Cd²âº in the external environment.
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Base de dados:
MEDLINE
Assunto principal:
Cádmio
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Cianobactérias
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Metais
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article