Biotic and Abiotic Factors Affecting the Population Dynamics of Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi

The present research was conducted to assess the impact of abiotic and biotic factors on the growth of freshwater dinoflagellates such as Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi, which reduce the quality of drinking water in the Zayandeh Rud Reservoir. To this end, 152 algal and zoological samples were collected from the reservoir located in the Central part of Iran in January, April, July, and October 2011. Abiotic factors such as pH, temperature, conductivity, transparency, dissolved oxygen, and nutrient concentration of the water were measured in all study stations. The results showed that the population dynamics of dinoflagellates in the Zayandeh Rud Reservoir was different depending on season, station, and depth. The findings proved that C. hirundinella was one of the dominant autumn planktons in the highest biovolume in the Zayandeh Rud Reservoir. While P. elpatiewskyi was present in the reservoir throughout a year with biovolume peak in summer. Accompanying bloom of P. elpatiewskyi and C. hirundinella, P. cinctum also grew in well-heated summer and autumn waters. It was further found that Ceratium density was positively correlated with sulfate ion concentrations, while the growth of P. cinctum and P. elpatiewskyi were associated, first and foremost, with NO2− and Mn

Effect of nutrients on total lipid content and fatty acids profile of Scenedesmus obliquus

ABSTRACT The effect of nutrients on the total lipid content and fatty acid profile of Scenedesmus obliquus isolated from the south coast of the Caspian Sea was evaluated. The nutritional compositions of the media impacted the growth rate and biomass of S. obliquus that ranged from 0.175 day-1 to 0.209 day-1and 0.92 gr·l-1 to 1.79 gr·l-1, respectively. The alga grew better in the medium which was characterized by higher levels of sodium and trace elements such as Fe, Mn, Mo, and Co and poor in N and P as compared with the other media. The highest level of the total lipid (32%) and the highest values of saturated fatty acids, in particular palmitic acid also were positively correlated with these nutrients. Peaks in polyunsaturated fatty acids (43.7 %), especially α-linolenic acid (28.4%) were related to N and P, but its correlation with K and Mg was more evident. The most important factors correlated with high amount of monounsaturated fatty acids were also N and P, followed by K and Mg to a lesser extent. This study demonstrated that the same algal strain may be a source of different amount of fatty acids, depending on the composition of the culture medium