Impact of polycyclic aromatic hydrocarbons on photosynthetic and biochemical functions and its bioremediation by Chlorella vulgaris

Abstract

Among several pollutants found in the aquatic environment, polycyclic aromatic hydrocarbons (PAHs) can interfere with the normal functioning of the aquatic organisms. The aim of this study was to investigate the application of Chlorella vulgaris for bioremediation of different type of PAHs [2-ring Naphthalene (NAP), 3-ring Anthracene (ANT), and 4-ring Pyrene (PYR)] and their impact on photosynthesis and growth of C. vulgaris. After 7 days of exposure of PAHs, growth of C. vulgaris was affected in the order PYR > ANT > NAP. With regard to biomolecules, all PAHs treatments showed a significant decrease in lipid content, but the toxic effect of PYR was more pronounced. Chl a fluorescence study of algal samples indicated that photosystem II (PSII) performance was unaffected by NAP and ANT toxicity, however, severe disruption of PSII activity by PYR was noted. Interestingly, C. vulgaris was able to remove all three PAHs from the media (~90–92 % NAP, ~90–94 % ANT and ~76 % PYR) within 7 days. After 3 days of cultivation, activity of dehydrogenase was increased in NAP and ANT inoculated culture, reflecting metabolization of these compounds which reduced after 7 days. As compared to control culture (no PAHs) a sharp decline in dehydrogenase activity was noted in PYR treated culture (after 3 and 7 days). Based on the results obtained, C. vulgaris could absorb NAP and ANT (linear PAHs) more efficiently than PYR (angular PAH). These results imply that ability of C. vulgaris to degrade PAHs depends in part on the configuration of the ring structure.