三角褐指藻是一类海洋单细胞硅藻,富含多不饱和脂肪酸,可以作为鱼、虾、贝等理想的饵料.而近年该藻曾多次在我国沿海海域发生暴发性增殖,给当地生态环境带来了一定的影响.为了探讨不同氮浓度对三角褐指藻生长特性和化学组成的影响,设置了低氮(44 μ mol.L-1)、中氮(880 μmol.L-1)和高氮(4400 μmol.L-1)浓度三种处理,着重测定三角褐指藻的细胞密度、比生长率、生物量、可溶性糖、蛋白质含量和叶绿素含量等指标.结果表明,高氮浓度明显地促进了藻细胞的生长繁殖.高氮浓度下的藻细胞密度、比生长率和生物量分别比低氮浓度下的提高了5.38倍、0.81倍和2.86倍.藻生长前期,高氮浓度和中氮浓度下的生长曲线相似,呈现一个"S"型的曲线.另外,高氮浓度下的藻细胞可溶性糖、蛋白质和叶绿素a含量分别是低氮浓度下的2.5倍、1.5倍和15倍,说明高氮浓度促进了藻细胞化学组成的转化和积累.结果揭示,氮浓度可能是导致三角褐指藻近年在我国沿海海域发生暴发性增殖的重要因素.%The marine diatom Phaeodactylum tricornutum is a phytoplankton species that contains a high content of bioactive compounds and thus it can be served as an important food source and feed additive in the successful rearing of aquatic animals like shrimp and fish.While its overproliferation along the coastal areas of China in recent years has brought about many negatively environmental and economic consequences around.In order to investigate the effects of different nitrogen concentrations on the growth characteristics and chemical compositions in Phaeodactylum tricornutum, algal cell density, specific growth rate, biomass, and the contents of soluble sugar, protein and chlorophyll a have been examined in laboratory cultures by employing low nitrogen (LN, 44 μmol·L-1 NaNO3), medium nitrogen (MN, 880 μmol·L-1 NaNO3) and high nitrogen (HN, 4400 μmol·L-1 NaNO3) concentrations.Our results indicated that the growth curve, specific growth rate and cell biomass of Phaeodactylum tricornutum were significantly affected by nitrogen concentrations.They were 149.50×104 cells·mL-1, 0.37 d-1, and 209.33 μg·mL-1 under LN condition, whereas they were 951.67×104 cells·mL-1, 0.67 d-1, and 806.00 μg·mL-1 under HN condition at the 10th day during the stationary phase.Although HN treatment significantly enhanced the algal cell number and cell yield in the stationary phase, it did not show remarkable differences in the growth curve and specific growth rate in the early stages as compared with MN treatment.Besides, the contents of soluble sugar, protein and chlorophyll a were obviously increased with the increasing of nitrogen concentrations, which were approximately 2.5, 1.5 and 15 times higher in HN treatment than those in LN treatment, respectively.It can be concluded from the present investigation that higher nitrogen concentrations can accelerate the growth and division as well as biosynthesis of some chemical compositions of Phaeodactylum tricornutum, and therefore this should be taken into account for the prevalence of red tides dominated by this marine microalga in recent years.
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