Discontinuous Grazing Pressure by Microzooflagellates on Marine Synechococcus

小型浮游植物在海洋初级生产中发挥着重要作用。单细胞蓝藻聚球藻是这个群落中一个重要的重要成员，它的细胞密度可以达到每升10万个细胞以上，实现每天3倍的就地生长速度，因此可能贡献温带和热带海洋总初级生产力的5%至25%。到目前为止的研究表明，聚球藻的捕食速度与其生长速度相当，微鞭毛虫是负责转移聚球藻生物量的主要群体。聚球藻在自然界和培养物中都有一种典型的不连续生长模式，可以通过直接和间接方法进行监测。在马尾藻海测量聚球藻的生长和捕食率的实验结果导致了一种假设，即微鞭毛虫对聚球藻的捕食可能是周期性的，主要发生在夜间。为了验证这一假设，沃特伯里博士将分离和鉴定导致聚球藻周转的微鞭毛虫，并记录它们对聚球藻丰度的时间模式的影响。该项目将在近岸和远洋水域进行，并将试验性地采用养殖技术、使用直接细胞计数直接和间接测量就地生长和放牧率以及掺入C-14碳酸氢盐。这项研究的意义不仅仅是加深了我们对海洋聚球藻生态的理解。这种单细胞光合作用细菌是海洋微生物食物网的重要组成部分。关于聚球藻捕食者的身份和对聚球藻的放牧模式和比率的见解可以作为“微生物环”的模型，并为其工作提供重要的见解。

Small phytoplankton play a major role in the primary production of the oceans. The unicellular cyanobacterium Synechococcus is a prominent and important member of this community that can reach cell densities of more than 100 thousands cells per liter, achieve in situ growth rates of 3 doubling per day and as a result may contribute between 5 and 25% of the total primary productivity in the temperate and tropical oceans. Studies to date indicate that Synechococcus is grazed at rates comparable to its growth rate and that microflagellates are the major group responsible for turning over Synechococcus biomass. Synechococcus has a characteristic discontinuous pattern of diel growth both in nature and in culture that can be monitored by direct and indirect methods. Results of experiments measuring both growth and grazing rates of Synechococcus in the Sargasso Sea led to the hypothesis that grazing of Synechococcus by microflagellates can be periodic, occurring primarily at night. To test this hypothesis, Dr. Waterbury will isolate and characterize the microflagellates responsible for Synechococcus turnover and document their impact on the temporal patterns of Synechococcus abundance. The project will be conducted in both inshore and open-ocean waters and will experimentally employ culture techniques, direct and indirect measurements of in situ growth and grazing rates using direct cell counts, and C-14 bicarbonate incorporation. The significance of this study extends beyond simply furthering our understanding of the ecology of marine Synechococcus spp. This unicellular photosynthetic bacterium is an important component of the marine microbial food web. Insights concerning the identity of Synechococcus grazers and patterns and rates of grazing on Synechococcus can act as a model for and provide important insights into the workings of the "microbial loop".//