Comparative Physiological characterization of cyanobacterial micro flora in oil polluted and non-polluted areas

Oil pollutions as a consequence of increasing consumption of petroleum، have a tremendous effect on water and soil ecosystems and their microflora. In this study the diversity in physiological parameters، including growth rate، photosynthesis، chlorophyll-a and phycobiliproteins content، between cyanobacterial strains flora isolated from oil-polluted and non-polluted areas، were assessed. To this end، strains were isolated and purified. The experiments were carried out on logarithmic phase cultures of the isolates in suitable liquid media. The chlorophyll and phycobiliproteins contents were determined using a colorimetric method. Photosynthesis was measured by Oxyview apparatus. Growth rates were calculated based on dry weights. Under laboratory conditions، the photosynthesis activity and the chlorophyll content of isolates from oil-polluted sites were significantly lower than non-polluted isolates. On the other hand، the growth rate average of strains from oil-polluted sites was significantly higher than non-polluted strains. Also despite the higher phycobiliproteins content in non-polluted isolates، there was no significant difference in any of these pigments between the two groups. Altogether the results showed that in response to petroleum stress، the cyanobacteria restore the decrease in their chlorophyll content and photosynthesis activity by increasing their biomass. In fact the response is the reflects of restructuring cyanobacterial flora from sensitive autotrophic species to oil-pollution resistant mixotrophic species in the polluted ecosystems that in addition to photosynthesis are able to use crude oil as an energy source for their growth requirements، hence overcome the energy loss due to reduction of photosynthesis and even increase growth rate than non-oil-pollution isolates.