Potential use of environmental cyanobacterial species in bioremediation of lindane-contaminated effluents

This study investigated the potential degradation of lindane [γ-hexachlorocyclohexane (γ-HCH)], resulting from agricultural runoff, by environmental species of cyanobacteria. Cyanobacterial species isolated from the Egyptian Lakes Qaroun and Mariut were exposed, either individually or as mixtures, to 5 and 10 ppm lindane for 7 days. Growth inhibition or stimulation percentage, as well as the percentage of lindane removal efficiency (RE), were calculated, and factors controlling both were discussed. Lindane exhibited different degrees of toxicity or stimulation for the selected cyanobacteria. Stimulation of growth ranged between 0.0- and 13.16-fold higher than controls, while inhibition ranged between 0.0% and 100%. Results also proved that Mariut species were more resistant to lindane toxicity than were Qaroun species. Resistance to lindane among Qaroun spp. was in the order Oscillatoria sp. 12>Oscillatoria sp. 13>Synechococcus sp.>Nodularia sp.>Nostoc sp.>Cyanothece sp.>Synechococcus sp. Among Mariut spp., it was Microcystis aeruginosa MA1>Anabaena cylindrica>Microcystis aeruginosa MA15>A. spiroides>A. flos-aquae. Mixed cultures showed varying sensitivity. Lindane was removed by all the species, either as individuals or mixtures, at both concentrations. The lindane RE percentage of Qaroun species ranged between 71.6% and 99.6% with a maximum of 98.0–99.6% at 5 ppm, 83.9% and 99.7% at 10 ppm, and maximum between 95.5% and 99.7%. Mariut species showed an RE percentage of 45.23–100.0% with maximum between 99.23% and 100.0% at 5 ppm and 43.15% and 100.0% at 10 ppm with maximal RE percentage between 99.67% and 100.0%. Mixed culture RE percentages ranged between 91.6% and 100% at 5 ppm with a maximum range of 99.3–100%, while at 10 ppm, the RE percentage ranged between 90.4% and 100%, with a maximum range of 96.0–100%. Results indicate the potential of natural resources as efficient agents for pollution control.