The effect of different photoperiods: 24 h illumination and a 12:12-h light/dark (12L:12D) cycle on the growth rate and biomass productivity was studied in five algal species: Neochloris conjuncta, Neochloris terrestris, Neochloris texensis, Botryococcus braunii and Scenedesmus obliquus. The green microalgae examined differ in the reproduction mode. Continuous illumination stimulated the growth of B. braunii and S. obliquus more effectively than the growth of the microalgal species from the genus Neochloris. However, under shorter duration of light of the same intensity (12L:12D cycle), the growth of all the three species of Neochloris was stimulated. Under continuous illumination, the specific growth rate in the first phase of B. braunii and S. obliquus cultures was higher than the growth rate of Neochloris, whereas under the 12L:12D cycle, the specific growth rate of all the three Neochloris species was generally higher than that in B. braunii and S. obliquus. As a result, the light regime influenced algal biomass productivity differently. The maximum biomass productivity was obtained in B. braunii and S. obliquus cultures carried out at continuous illumination. All the Neochloris species produced biomass more efficiently at the 12L:12D cycle, which was two–threefold higher than that of B. braunii and S. obliquus. The unicellular species of the green microalgae from the genus Neochloris, examined for the first time in this study, are promising prospective objects for algal biotechnology.

Algal communities inhabiting four calamine mine spoils differing in time since cessation of exploitation and loaded with high concentrations of zinc (20,284-61,599 μg g −1 soil DW), lead (2,620-3,885 μg g −1 DW) and cadmium (104-232 μg g −1 DW) were studied. In dump soils of slightly alkaline pH (7.28-7.52) and low nutrient (P À PO 3À 4 , N À NH þ 4 , N À NO À 3 ) concentrations, chlorophyll a content ranged from 0.41 to 2.27 μg g −1 soil DW. In total, 23 algal species were recorded. Chlorophyta were the dominant taxonomic group (42-55% of all identified species) followed by Cyanobacteria (28-36%) and Heterokontophyta (13-21%). The highest species richness (18) was observed in the oldest dump (120 years old) with natural succession, while in younger dumps it was lower (11-15). Total algal abundance ranged between 5.5 and 19.1×10 2 ind. g −1 soil DW, and values of Margalef's diversity indices (1.59-2.25) were low. These results may suggest that both high concentrations of heavy metals and low nutrient content influenced the algal communities in all the dumps studied. The differences in algal microflora observed between tailing dumps may indicate that habitat quality improved with time and that algae isolated from Zn/Pb-loaded soils may be Zn/Pbresistant ecotypes of ubiquitous species.

Knowledge on species diversity and distribution of eustigmatophycean algae (Stramenopiles) in the environment is currently very limited. Some of them are considered promising organisms for industrial application. Phylogenetic analysis of two strains (E120, E5) of a coccoid microalga isolated from highly Zn-and Pb-polluted calamine mine spoils revealed that they belong to the genus Eustigmatos. Cells of both strains were morphologically identical. Some features of their vegetative cells and zoospores differed from other described nominal Eustigmatos species. 18S rDNA sequences of E120 and E5 were identical but also differed in two or three nucleotide substitutions from the other Eustigmatos species (E. vischeri, E. magnus, E. polyphem). Only 1 -3 nucleotide substitutions in 18S rDNA sequence were found among all the examined Eustigmatos species. ITS1-5.8S rDNA-ITS2 region was more variable (15 -22 differences) than 18S rDNA, except for E120 and E5 strains which differed in only one nucleotide substitution (in 5.8S rDNA). Genetic differences found between the isolated strains (E120, E5) and the other Eustigmatos species were comparable to those observed among all nominal Eustigmatos species studied. This suggests that the isolates represent a new species. The name Eustigmatos calaminaris sp. nov. (referred to the locality) has been proposed. The E120 strain from the mine spoil with higher heavy metal contents was more Zn-and Pb-resistant than E5 from the less polluted ground. Their high, though varied resistance to Zn/Pb stress, together with the very slight genetic divergence between them, indicate that they represent two ecotypes of the same new species.

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