REU: Phytoplankton Population Dynamics at the Hawaii Ocean Time Series Station

浮游植物在生物地球化学循环中起着核心作用。仅仅测量生物量和生产量是不够的；需要对群落结构进行详细评估，以阐明种群动态、年度变异性和对短期物理事件的反应。该项目的目标是：(1)确定全球海洋观测系统夏威夷海洋时间序列站浮游植物群落的组成，(2)估计不同藻类种群对总生物量的贡献，(3)了解深度分布和时间模式，并阐明年度变化。为了描述和量化浮游植物群落的不同细胞种群，将采用一些不同的技术。流式细胞术将允许快速区分不同的类群，如真核微微浮游生物、聚球藻-蓝藻和新发现的原绿藻。它将提供一种有效和定量的方法来测量细胞浓度，并在单细胞的基础上定量测定色素荧光和散射特征。免疫荧光技术，使用专门针对原核生物(聚球藻)和真核生物(如苔藓植物、食球藻类)的抗体和色素分析(通过高效液相色谱和荧光光谱)，将使群落的分类组成得到进一步完善。后者将特别有助于较小的真核生物和原叶绿素成分，它具有独特的二乙烯基叶绿素特征，被认为在贫营养水域非常重要。该项目将首次提供关于中太平洋环流浮游植物群落结构的详细时间序列数据。结果将补充在Aloha站所做的核心测量，增加对初级生产者群体的定量分析，这将作为未来现实建模工作的基础。将我们的发现与S.W.Chisholm和R.J.Olson(麻省理工学院/WHOI)将在GOFS百慕大站点进行的平行项目(浮游植物表现出明显的季节性变化)进行对比，将加强两项研究的价值。

Phytoplankton play a central role in biogeochemical cycles. Simply measuring biomass and production is not sufficient; a detailed assessment of the community structure is necessary to elucidate the population dynamics, annual variability and responses to short-term physical events. The objectives of this project are: (1) to determine the composition of the phytoplankton community at the GOFS Hawaii Ocean Time-series station, (2) to estimate the contribution of the different algal populations to the total biomass, and (3) to understand depth distribution and temporal patterns and to elucidate annual variability. In order to characterize and quantify the different populations of cells of the phytoplankton community a number of different techniques will be employed. Flow cytometry will allow rapid discrimination of different groups such as eukaryotic picoplankton, Synechococcus - cyanobacteria, and the newly discovered prochlorophytes. It will provide an efficient and quantitative way to measure cell concentration and to quantitate pigment fluorescence and scatter signature on a single-cell basis. Immunofluorescence techniques, using antibodies specifically targeted at prokaryotic (Synechococcus) and eukaryotic (e.g. prasinophytes, coccolithophorids) groups and pigment analyses (by HPLC and spectrofluorometry) will permit further refinement of the taxonomic composition of the community. The latter will be specifically helpful for the smaller eukaryotes and for the prochlorophyte component which has a unique divinyl-chlorophyll signature and which is believed to be very important in oligotrophic waters. This project will provide the first detailed time-series data on the structure of the phytoplankton community in the central Pacific gyre. The results will complement the core measurements made at station ALOHA by adding a quantitative analysis of the primary producer community, which will serve as a basis for future realistic modeling efforts. Contrasting our findings with a parallel project to be conducted by S.W. Chisholm and R.J. Olson (MIT/WHOI) at the GOFS Bermuda site, where phytoplankton exhibits pronounced seasonal variability, will reinforce the value of both studies.