不同碳磷比的斜生栅藻(Scenedesmus obliquus)对同型溞(Daphnia similis)生长和繁殖的影响

食物质量会影响浮游动物的生长和繁殖,表征食物质量的指标包括食物大小、元素比、生物化学组成和毒性有无等.用斜生栅藻(Scenedesmus obliquus)的碳磷比(C/P)表征食物质量,分析不同C/P斜生栅藻对同型溞(Daphnia similis)生长和繁殖的影响.研究中4个处理组斜生栅藻C/P分别为881.8、512.3、124.3和42.4.培养9 d后不同处理组同型溞的生长速率分别为0.15、0.27、0.47和0.44 d-1.C/P比为881.8的处理组同型溞在整个培养过程中没有产仔,其余3个处理组的同型溞第1成龄期的产仔量分别为1.2±1.3、9.8±2.3和9.5±2.5 ind./female.结果表明,与斜生栅藻C/P为124.3处理条件相比,斜生栅藻C/P过高(512.3和881.8)及C/P过低(42.4)处理条件下同型溞生长速率和产仔量均降低.本研究表明食物C/P的高低会影响溞的生长和繁殖,从而影响其在湖泊中的生存.

Effects of Scenedesmus obliquus with different C/P ratios on the growth and reproduction of Daphnia similis

Food quality can influence the growth and reproduction of zooplankton in freshwater systems.Food size,element ratios,biochemical composition and toxicity are indicative of food quality.The C/P ratios of Scenedesmus obliquus was used to represent the food quality in this experiment.We analyzed the effects of S.obliquus with different C/P ratios on the growth and reproduction of Daphnia similis.The C/P ratios of S.obliquus in four treatments were 881.8,512.3,124.3 and 42.4,respectively.The growth rates of D.similis in four treatments were 0.15,0.27,0.47 and 0.44 d^-1,respectively. D.similis did not release any offspring dur-ing this period of growth in treatment with C/P=881.8.The average numbers of offspring of first adult instar of D.similis in other three treatments were 1.2±1.3,9.8±2.3 and 9.5±2.5 ind./female,respectively.The results showed that the growth rate and off-spring number of D.similis decreased when the C/P ratio of S.obliquus was too high (512.3 and 881.8) or too low (42.4) com-pared with C/P=124.3.Our study indicated that different C/P ratios of food could affect the growth and reproduction of Daphnia,thus determining their survival in freshwater lakes.