中文摘要：

采用实验室一次性培养的方法,研究了尿素对中国近海3种赤潮藻---球形棕囊藻（Phaeocystis globosa）、锥状斯氏藻（Scrippsiellatrochoidea）和中肋骨条藻（Skeletonema costatum）生长的影响.结果表明,这3种赤潮藻均能利用有机氮源尿素生长,且表现出明显的浓度效应：当尿素浓度介于0-8.82μmol.L^-1（以N计,下同）时,3种赤潮藻的比生长速率均较低,细胞密度也较低,与对照组相比无显著差异;当尿素浓度大于8.82μmol·L-1时,这3种赤潮藻表现出明显的生长效应.然而,3种赤潮藻适宜生长的尿素浓度并不一致,当尿素浓度分别为882、8820和8820μmol·L^-1时,球形棕囊藻、锥状斯氏藻和中肋骨条藻分别达到最大比生长率0.76、0.54和0.66d^-1.将3种赤潮藻在不同尿素浓度下的最大比生长速率用Monod方程拟合,得出球形棕囊藻、锥状斯氏藻和中肋骨条藻在以尿素为唯一氮源条件下的最大比生长速率和半饱和常数分别为0.73、0.47、0.63d^-1和12.36、21.83和20.34μmo·lL^-1.由此可见,这3种藻能够利用有机氮源尿素,无疑扩展了其氮营养来源,在无机氮源缺乏时,具有竞争优势.相比较而言,球形棕囊藻对尿素的亲和力最高,在低浓度尿素条件下,球形棕囊藻具有较高的竞争力.

英文摘要：

Three bloom-forming microalgae isolated from the coastal waters of China,Phaeocystis globosa,Scrippsiella trochoidea,and Skeletonema costatum,and their growth characteristics were studied in the laboratory with urea provided as the sole nitrogen source.All three species were able to utilize urea as sole nitrogen source and their growth rates were dependent on the concentrations of urea in a dose-response manner.When urea concentrations ranged from 0 to 8.82 μmol·L^-1（by nitrogen,similarly hereinafter）,the specific growth rates and final cell densities for P.globosa,S.costatum and S.trochoidea were not significant different from their respective controls,while above 8.82μmol·L^-1,the three species exhibited significantly higher growth.The optimal urea concentrations were different among the three algae.The specific growth rates of P.globosa,S.costatum and S.trochoidea reached 0.76,0.66 and 0.54 d^-1 when the concentrations of urea were 882,8820 and 8820μmol·L-1,respectively.The correlation between specific growth rate and urea concentration could be described with the Monod equation for all species,where the maximal specific growth rates and half saturation constants were 0.73,0.47 and 0.63 d^-1 and 12.36,21.83 and 20.34μmol·L^-1 for P.globosa,S.costatum and S.trochoidea,respectively.Comparatively,the affinity of P.globosa for urea was higher than that of S.costatum and S.trochoidea,which suggests P.globosa may possess an advantage in competition over the other two at low concentrations of urea.The ability to utilize urea as the sole nitrogen source may enhance the competition potential for these bloom-forming species at lower availability of inorganic nitrogen.