Techniques for isolation and purification of marine microalgae from the coast of Qatar

Background Unicellular algae, at the base of aquatic food chains, are particularly sensitive to a wide range of pollutants and are therefore important in toxicity tests for hazard assessment and aquatic environment protection. EMRQ (ExxonMobil Research Qatar) in collaboration with ESC (Environmental Studies Center, Qatar) and the Ministry of Environment, Qatar, is investigating the impact of common toxicants on the performance (growth and survival) of microalgae found in the coastal regions of Qatar. The present work was undertaken to establish the techniques for the isolation and purification of four microalgal species in order to culture them under specific laboratory conditions. Objectives * To conduct laboratory experiments to determine the most appropriate method for the isolation and purification of different microalgal species found in the coastal waters of Qatar. * To establish axenic cultures of the purified unialgae at EMRQ. * To conduct chronic toxicity tests of certain toxicants commonly found in seawaters on the microalgal species isolated and cultured. Methodology Different phytoplankton species were identified and isolated from freshly collected seawater from various sites around the coast of Qatar. * Unialgal isolates were obtained by four major techniques: streaking, spraying, serial dilution, and single-cell isolations by capillary method * Purifications of the unialgal samples to obtain axenic cultures were realized by micropipette washing technique followed by streak-plating technique and using antibiotics. Results The isolation by streak-plating showed to be the most suitable method for the small non motile microalgal species (<10mm) that grow well on a substrate. The serial-dilution technique looked to be ideal for all types of microalgae, specially the small motile species. The isolation by picking-up a single cell was found to be more adequate for the large phytoplankton species. A mixture of antibiotics showed to be more effective than the use of any individual antibiotic. Conclusion and Discussion A few microalgae have been successfully isolated and purified using the techniques mentioned above. The streak-plating method seems to be the most promising technique for the species found in Qatari waters. At present we are doing experiments to determine the specific biological and physical conditions for culturing the purified microalgae species for optimum growth at EMRQ. The purpose of obtaining axenic cultures of phytoplankton is to study the impact of specific toxicants on these species by performing chronic toxicity tests.