Active Fluorescence Assays of Phytoplankton Physiological State: Population and Individual Cell Measurements

浮游植物生理状态的主动荧光测定：种群和个体细胞测量

• 批准号: 9819206
• 负责人: Robert Olson
• 金额: $ 43.59万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-01 至 2005-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9819206&HistoricalAwards=false
• 关键词: Active; Fluorescence; Assays; Phytoplankton; Physiological

Olson9819206Active fluorescence techniques such as Fast Repetition Rate (FRR) fluorometry are becoming commonly used to monitor phytoplankton condition in the sea, but many questions remain about the relationships between these measurements of photosynthetic potential and ecologically relevant phytoplankton properties such as growth rate. Photosynthetic parameters such as the fraction of functional reaction centers, the functional absorption cross section of photosystem 2 (PS2), and the rate of electron transfer between PS2 and PSI appear to be valuable diagnostic indicators of specific suboptimal conditions, but it is not clear how quantitatively we can interpret these indicators, or how important a role heterogeneity among phytoplankton species and individuals might play in such interpretation. Olson and Sosik therefore will conduct a series of studies designed to investigate the effects of environmental conditions on phytoplankton growth and active fluorescence parameters, and to determine the extent of variability in active fluorescence responses among phytoplankton species and individual cells in natural populations. Specifically, Olson and Sosik will investigate relationships between nitrogen-, iron-, and light-limitation on phytoplankton growth and photosynthetic parameters as measured by active fluorescence techniques. Observations of wide areas of ocean in which active fluorescence indicates suboptimal phytoplankton condition, and experiments in which growth rate appears to be uncoupled from active fluorescence parameters raise questions about these relationships. Batch and continuous cultures of phytoplankton will be used to study transient and steady-state limitation (including supraoptimal light intensities) of cell growth and the accompanying effects on photochemical energy conversion efficiency of PS2 (i.e., the fraction of functional photosynthetic reaction centers), the functional absorption cross section of PS2, and the rate of electron transfer from PS2 to PS 1. Fluorescence responses of natural populations of phytoplankton to changing environmental conditions will be assessed through observations of local waters, transects between Woods Hole and the Sargasso Sea in spring and summer, and through bottle incubation experiments. The approach the investigators will use focuses on examining inter- and intra-species heterogeneity in active fluorescence parameters, and in active fluorescence responses to environmental conditions. Olson and Sosik will analyze the samples described above by both FRR fluorometry (a bulk method) and individual cell "pump-during-probe" (PDP) techniques. A PDP flow cytometer will be used to measure pico- and nanophytoplankton populations and individual larger cells, and a PDP microfluorometer will be used to analyze individual cells of selected species larger than 5 gm. The distribution of active fluorescence parameters both within and between species will thus be assessed in pure cultures under different growth conditions, including transient and steady state situations. Application of both bulk and individual cell techniques to natural samples will allow the investigators to determine the influence of various phytoplankton groups on the bulk measurements, and analysis of the distribution of properties among individual cells may enable them to deduce the recent nutrient history of the phytoplankton.The combination of bulk and individual-cell measurements of active fluorescence will provide new insights into the regulation and growth of marine phytoplankton, including a new way to evaluate the dynamics of nutrient availability.

Olson9819206 快速重复率 (FRR) 荧光测定等主动荧光技术正在普遍用于监测海洋中的浮游植物状况，但关于这些光合潜力测量与生态相关的浮游植物特性（例如生长速率）之间的关系仍然存在许多问题。光合参数，如功能反应中心的比例、光系统 2 (PS2) 的功能吸收截面以及 PS2 和 PSI 之间的电子转移速率似乎是特定次优条件的有价值的诊断指标，但尚不清楚我们如何定量地解释这些指标，也不清楚浮游植物物种和个体之间的异质性在这种解释中可能发挥的重要作用。因此，奥尔森和索西克将进行一系列研究，旨在调查环境条件对浮游植物生长和活性荧光参数的影响，并确定浮游植物物种和自然种群中单个细胞之间活性荧光响应的变异程度。具体来说，奥尔森和索西克将研究浮游植物生长的氮、铁和光限制与通过主动荧光技术测量的光合参数之间的关系。对大片海洋区域的观察（其中活性荧光表明浮游植物状况不佳）以及生长速率似乎与活性荧光参数脱钩的实验提出了关于这些关系的问题。浮游植物的批量和连续培养将用于研究细胞生长的瞬时和稳态限制（包括超优光强度）以及对 PS2 光化学能量转换效率（即功能性光合反应中心的分数）、PS2 功能吸收截面以及从 PS2 到 PS 1 的电子转移速率的伴随影响。天然的荧光响应 将通过对当地水域、春季和夏季伍兹霍尔和马尾藻海之间的横断面的观察以及瓶子孵化实验来评估浮游植物种群对环境条件变化的影响。研究人员将使用的方法侧重于检查活性荧光参数以及对环境条件的活性荧光响应的种间和种内异质性。 Olson 和 Sosik 将通过 FRR 荧光测定法（批量方法）和单个细胞“探测期间泵浦”(PDP) 技术来分析上述样品。 PDP 流式细胞仪将用于测量微微和纳米浮游植物种群以及个体较大的细胞，PDP 微荧光计将用于分析大于 5 克的选定物种的个体细胞。因此，将在不同生长条件（包括瞬态和稳态情况）下的纯培养物中评估物种内部和物种之间的活性荧光参数的分布。将批量和单个细胞技术应用于自然样品将使研究人员能够确定各种浮游植物群对批量测量的影响，并且分析单个细胞之间的特性分布可能使他们能够推断出浮游植物最近的营养历史。活性荧光的批量和单个细胞测量的结合将为海洋浮游植物的调节和生长提供新的见解，包括 评估养分有效性动态的新方法。