Growth and metal removal potential of a Phormidium bigranulatum-dominated mat following long-term exposure to elevated levels of copper |
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Authors: | Dhananjay Kumar J P Gaur |
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Institution: | 1. Department of Botany, School of Life Sciences, H.N.B. Garhwal University, Srinagar, Garhwal, 246 174, India 2. Laboratory of Algal Biology, Department of Botany, Banaras Hindu University, Varanasi, 221 005, India
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Abstract: | The present study explores the tolerance and metal removal response of a well-developed 2-week-old Phormidium mat after long-term exposure to Cu2+-enriched medium. Cu2+ enrichment inhibited increase in mat biomass in a concentration-dependent manner. Mat area and the number of entrapped air bubbles decreased as Cu2+ concentration increased in the medium. Decrease in number of air bubbles obviously reflects the adverse effect of Cu2+ on photosynthetic performance of the mat. Metal enrichment did not substantially alter the amount of pigments, such as chlorophyll a, chlorophyll b, carotenoids, and phycocyanin, in the mat. Enhancement of Cu2+ concentration in the medium led to changes in species composition of the test mat; however, Phormidium bigranulatum always remained the dominant organism. Relative share of green algae and some cyanobacterial taxa, namely, Lyngbya sp. and Oscillatoria tenuis, in the mat were increased by Cu2+ enrichment. The mat successfully removed 80 to 94 % Cu2+ from the growth medium containing 10 to 100 μM Cu2+. Extracellular polysaccharides, whose share increased in the mat community after metal addition, seem to have contributed substantially to metal binding by the mat biomass. |
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