THE METAL-TOLERANT ALGAE Hormidium fluitans (GAY) HEERING FROM ACID MINE DRAINAGE WATERS IN NORTHERN AUSTRALIA AND PAPUA-NEW GUINEA

Abstract

The filamentous green alga Hormidium fluitans (Gay) Heering grows extremely luxuriantly in turbulent outflows of mine drainage waters in Northern Territory, Australia, and on Bougainville Island, Papua-New Guinea. The drainage waters contain between 30 and 700 p.p.m. copper and have a pH range 3.2 - 5.3. The metal-concentrating ability of the naturally-occurring alga has been examined in respect of 25 elements; high concentration ratios have been noted for the elements, Ag, Al, Fe, Mo, Ti and V. In the case of copper, histochemical examination shows a possible binding of the metal in a cell-wall layer. An alkali-soluble fraction of the dried cells prepared from field samples of the alga, had a very high affinity for copper (11.8% of dry weight). This fraction made up about 1.5% of the cell polymers. The alga has been artificially cultivated in a number of modes, but grows best in vigorously sparged submerged culture on artificial mine water, in the presence of ore lumps. Under most laboratory conditions, motile and unicellular forms of the algae occur. It has been shown recently that culture filtrate from the algal growth stimulates the rate of iron oxidation and of growth of some Thiobacillus ferrooxidans strains, and enhances the rate of copper release from chalcopyrite ores.