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1 Polish Journal of Ecology

1 2008

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Metal resistance of soil algae (Chlorophyta) occurring in post-flotation Zn/Pb and Cu-tailing ponds

Kalinowska R., Pawlik-Skowrońska B.

Polish Journal of Ecology

2008

Vol. 56, nr 3

415-430

Algae as pioneer organisms are important in extreme environments. We isolated several green algae (Chlorophyta) from Zn/Pb- and Cu-enriched ground samples of post-flotation tailing ponds, containing 17200-18400 mg Zn kg[^-1], 3017-6566 mg Pb kg[^-1] or 1420 mg Cu kg[^-1]. The algae with different morphologies belonged to following classes: Chlorophyceae and Trebouxiophyceae. Their Zn-, Pb- and Cu- resistance in comparison with soil green algae (Chlorophyceae) isolated from the unpolluted control soil was evaluated under laboratory conditions on the basis of 96h-EC[50] (effective metal concentration which causes 50% inhibition of algal growth after 96 h exposure). Among isolated algae Dictyococcus cf. varians Gerneck em. Starr from the Zn/Pb-tailing pond was highly resistant both to lead (EC[50] 48 [my]M) and zinc (EC[50] 126 [my]M), but sensitive to copper (EC[50] 2 [my]M). Stichococcus minor Nageli and Chlamydomonas boldii Ettl from the Cu-tailing pond were resistant to copper (EC[50] 17.8 [my]M and 10 [my]M, respectively). Simultaneously, S. minor revealed co-resistance to Zn (EC[50] 251 [my]M), while C. boldii to Pb (EC[50] 38.9 [my]M). Geminella terricola J.B. Petersen (Chlorophyceae), isolated from the unpolluted control soil, revealed high sensitivity to the three metals (Zn-EC[50] 44.6 [my]M; Pb-EC[50] 10.2 [my]M and Cu-EC[50] 6.4 [my]M). Simultaneously, G. terricola accumulated intracellularly higher amounts of Zn (7.1 amol [my]m[^-3]) and Cu (5.5 amol [my]m[^-3]) than all the algae from the polluted ground samples (Zn: 1.2-6.4 amol [my]m[^-3] and Cu: 0.4-2.7 amol [my]m[^-3]). It also accumulated high amounts of Pb (6.0 amol [my]m[^-3]), but two-fold lower than D. cf. varians. Using cytochemical staining of metals dark pink Pb-rhodizonate complexes were detected in thick cell walls of the Pb/Zn-resistant D. cf. varians and in thick mucilage layers of the Cu/Pb-resistant C. boldii. However, in the Pb-sensitive S. minor Pb-complexes were detected inside deformed cells. Pink-orange Zn-dithizone complexes were mainly distributed inside the cells of the Zn-resistant D. cf. varians. The results obtained suggest that thick cell walls or envelopes may be partly responsible for the higher Pb-resistance of some studied algae. However, in the case of micro-nutrients like Zn or Cu other resistance mechanisms (biochemical / physiological) may be involved. It seems that algal species or ecotypes living in the grounds of metal post-flotation tailing ponds have been adapted to heavy metals present in their habitats and may be useful for remediation of such degraded environments.