Algae and cyanobacteria in the rhizosphere of lead accumulator plants

Abstract

Algae and Cyanobacteria species that grow in contaminated sites can accumulate high concentrations of heavy metals. In this work it was proposed to a) characterize the community of algae and Cyanobacteria and b) evaluate the effect of lead (Pb) on the composition of algae present in the rhizosphere of plants capable to accumulate Pb in Córdoba province. M&M: Soil samples were taken from the rhizosphere of Sorghum halepense, Bidens pilosa and Tagetes minuta at sites with different levels of Pb. In the laboratory, the soil was sown in capsules with sterilized Watanabe medium. The cultures grew 9 weeks. The algae and Cyanobacteria were identified over the time and the final relative frequency analyzed. Results: In contaminated soils, 24 species of Cyanobacteria, Chloroplastida and Xanthophyceae were identified. The heterocytous cyanobacteria Cylindrospermum muscicola, Nostoc commune and Calothrix clavata registered a relative mean frequency (between 21 and 60%). Trebouxia parmeliae (Chloroplastida) and Vaucheria sp. (Xanthophyceae) were present in soils with the highest level of Pb. Most of the species were concentrated in the lowest levels of Pb. Conclusions: A negative effect of Pb on the species richness of algae and Cyanobacteria was observed in the rhizosphere of the evaluated plants. Based on the composition of the community of algae and Cyanobacteria in the soil, two groups are determined and could be considered tolerant and non-tolerant communities of Pb contamination.