Note Tolerance and accumulation of hexavalent chromium by two seaweed associated aspergilli Anjana K. Vala, Nisha Anand, Purva N. Bhatt, H.V. Joshi * Marine Algae and Marine Environment Discipline, Central Salt and Marine Chemicals Research Institute, Gijubhai Badheka Marg., Bhavnagar 364002, India Abstract Marine seaweed (Eucheuma sp.) associated strains of Aspergillus flavus and Aspergillus niger were tested for their Cr(VI) tol- erance. Both the isolates showed luxuriant growth in different concentrations of Cr(VI), i.e., 25, 50 and 100 ppm. There was no marked variation in the dry weight of control and test isolates, which indicated that both the isolates can tolerate a wide range of hexavalent chromium and their application for bioremediation purpose can be envisaged as XRF data revealed both the isolates accumulated more than 25% of the chromium supplied. A. flavus invariably exhibited higher accumulation potential. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction Industrial and metallurgical processes release a wide range of toxic metal pollutants as their waste products. Chromium is one of the metals of most immediate concern according to the World Health Organization (1984). Chromium may be present in effluent in various chemical forms. Hexavalent chromium compounds tend to be more mobile and toxic than trivalent chromium compounds (Calder, 1988) while Cr(VI) may be detri- mental to human beings and animals and have pro- nounced adverse effects on plants and aquatic life. Reduction in concentration of such toxic compounds in the effluent is essential to meet ever increasing legislative standards. Most of the current methods of chromium removal are expensive and inconsistent, and may gen- erate toxic sludge that requires careful disposal (Wild, 1987). Bioremediation using various microorganisms can be a more promising alternative than chemical treatment of such toxicants. Microbes (both prokaryotes and eukaryotes) have the ability to bind metal ions in the external environment at the cell surface, or to transport them into the cell. Some may form metabolic products such as acids or ligands that dissolve base metals dissolved in mineral or anions such as sulfide or carbonate that precipitate dissolved metal ion (Ehrlich, 1997). Microbes often have other genetically determined defences against harmful metals when they cannot detoxify them. Fungi can be screened as potential bio- remediation agents due to their greater growth capacity and reach by virtue of mycelial branching, a greater potential to produce a number of enzymes, and they are good accumulators of various metals. Exploration of various habitats may lead to fungal strains with diverse potentials. The aim of the study was to examine the potential of fungal strains associated with marine seaweed (a less explored habitat for fungi) to tolerate and accumulate hexavalent chromium, one of the most hazardous heavy metals, its effect on fungal biomass production and thus, to examine their application as bioremediation agents for chromium contaminated sites. 2. Materials and methods Two fungal strains Aspergillus flavus and Aspergillus niger, associated with marine seaweed (Eucheuma sp.) were selected for the study. 1 ml inoculum (spore sus- pension 10 8 /ml) was inoculated in 500 ml Potato Dex- trose medium (prepared in 75% ‘aged’ seawater) (Anonymous, 1968) containing different concentrations of Cr(VI) i.e., 25, 50 and 100 ppm, as potassium * Corresponding author. Tel.: +91-278-2561354; fax: +91-278- 2566970/2567562. E-mail address: salt@csir.res.in (H.V. Joshi). 0025-326X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2004.02.025 www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 48 (2004) 983–985