Phytoplankton Composition, Growth Rates and Oil Production Potential of Fast Growing Species from Lake Naivasha and Water Reservoirs at Embu University College

Abstract

The demand for non-renewable fossil fuel has greatly increased in the last few years from 84 million barrels of fossil fuel per day in 1980’s to over 100 million barrels per day in 1990. To supplement this demand, research on alternative sources has been going on since 1960’s in different parts of the world. Among the alternative sources, the phytoplanktons have shown great promise due to their high oil yield in comparison to energy crops. In Kenya, despite the occurrence of highly productive eutrophic lakes, no research has been carried out to assess the potential of phytoplankton species in oil production. This study therefore aimed at identifying and assessing the oil production potential of fast growing phytoplankton species in a species rich natural freshwater lake (Lake Naivasha) and man-made reservoirs at Embu University College. Data was collected from December 2014 to May 2015. During each sampling trip, selected physico-chemical parameters were measured and water samples collected for analysis of nutrients as well as species identification, composition, isolation and culturing in the laboratory. The samples were inoculated in phytoplankton growth media and cultured under 14:10 light: dark photoperiod. The fast growing species were identified through screening the biomass accumulated. These species were then cultured for lipid extraction. Results on physico-chemical characteristics revealed that, inflows during the wet months (December 2014 and April 2015) resulted in low Secchi depth, conductivity and total alkalinity. Highest values were recorded during the dry month of February 2015. High values of pH (8.6 both in lake Naivasha and EUC dams were recorded). High total nitrogen (TN range =0.18-0.271 mg L-1 in Lake Naivasha and 0.091-0.097 in EUC dams) and total phosphorous (TP range =0.069-0.093 mg L-1 in Lake Naivasha and 0.004-0.073 in EUC dams) ranges were recorded during the wet months. Results showed that phytoplankton species composition consisted of a total of 134 species in Lake Naivasha and 122 species in EUC reservoirs. Species diversities ranged from 1.29 to 1.68 with Lake Naivasha registering a mean of 1.5 which was not significantly different (p < 0.158) from the mean of 1.44 in EUC Dams. The fastest growing phytoplankton species in both Lake Naivasha and EUC reservoirs included; Closteriopsis acicularis (0.64 mg L-1 d-1), Chlorella saccharophilla (0.53 mg L-1 d-1), Chlorella vulgaris (0.49 mg L-1 d-1), Cosmarium contractum (0.42 mg L-1 d-1) and Scenedesmus ellipticus (0.37 mg L-1 d-1). Oil production potential recorded by Nannochloropsis sp, Chlorella saccharophilla, Chlorella vulgaris and Scenedesmus ellipticus was 30%, 10.8%, 8.7% and 5.4% respectively. The results also showed that mean oil produced by phytoplankton isolates from Lake Naivasha and EUC reservoirs did not differ significantly(p< 0.05). The findings of phytoplankton species from Lake Naivasha and EUC reservoirs having oil production potential opens an opportunity for discussion and further research on how to incoporate recent technology in phytoplankton biofuel production to offer a solution to the experienced energy crisis.