Diatom Blooms and Planktonic Grazers: Paradigm or Paradox?

硅藻华和浮游食草动物：范式还是悖论？

• 批准号: 0118044
• 负责人: Bruce Frost
• 金额: $ 47.03万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-10-01 至 2005-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0118044&HistoricalAwards=false
• 关键词: Diatom; Blooms; Planktonic; Grazers; Paradigm

Phytoplankton blooms are major events in the pelagic environment of temperate to subpolar coastal seas. Because blooms are large and relatively reliable seasonal pulses of food resources, the life histories of many pelagic consumer populations, both planktonic grazers and higher trophic level types such as fish, appear synchronized with them. Yet there is an apparent paradox. Results from numerous recent laboratory studies indicate that some species of diatoms, including species that may be biomass dominants during phytoplankton blooms, can inhibit egg production and/or embryonic and postembryonic development of several species of planktonic suspension-feeding copepods. The specific mechanism underlying the inhibition is currently under debate. Diatoms may be nutritionally deficient, but they also contain toxic substances that induce deleterious effects in copepods. However, the general relevance of these laboratory studies for natural populations of copepods is uncertain, as field investigations of the effects of diatom blooms have yielded contradictory results.The goal of this research project is to test in the sea the hypothesis that diatom-dominated phytoplankton blooms have inhibitory effects on egg production rate and/or postembryonic development of natural populations of the planktonic suspension-feeding copepods Calanus pacificus and Pseudocalanus newmani. The study will be done in Dabob Bay (Washington State) where intense, diatom-dominated phytoplankton blooms occur reliably in March. During these blooms, diatom concentrations reach or exceed levels known from laboratory studies to have deleterious effects on copepods. Previous field studies elsewhere of effects of diatom blooms on copepods have not met this condition. To test the hypothesis a combination of approaches is proposed: (1) observations on the distribution and abundance of copepods, diatoms, and other potential prey; (2) analysis of fecal pellets of adult copepods to verify that they are ingesting diatoms in situ; (3) experiments providing adequate control and replication to determine feeding rates of adult copepods on diatoms and other prey; (4) incubations to estimate in situ egg production rate and hatching success of both copepod species; (5) experiments to test for the direct effects of diatoms on egg production rate and hatching success and postembryonic development of the two copepod species. The possibility that diatoms may impact metazoan grazers such as copepods is of enormous basic and applied scientific interest. At a basic level, the problem is central to understanding the structure and function of marine planktonic systems. Any process by which phytoplankton inhibit reproduction or development of grazing zooplankton could markedly affect the pelagic food web well beyond the level of primary consumers. That is, a process affecting the population response of grazers would ramify through the food web, directly impacting other consumer species whose reproduction and growth depend on occurrence and abundance of eggs and immature stages of grazers. Thus, it is crucial to know whether diatoms are deleterious to natural populations of copepods and, if so, the specific nature of the effect, how frequently it occurs, and what the implications are for higher trophic levels.On a practical level, the magnitude of sustainable harvest of fish from the ocean is ultimately dependent not just on the level of primary production, but how that production is (or is not) transferred through the food web to higher (harvestable) trophic levels. An unambiguous test of the effects of diatom blooms on natural populations of planktonic grazers could therefore represent a major advance in understanding for pelagic biological oceanography.

浮游植物盛开是温带到沿海海洋的层状环境中的重大事件。由于花朵是大型且相对可靠的食物资源季节性脉冲，因此许多上层消费者种群的生活史，包括浮游生物的放牧者和较高的营养水平类型（如鱼类），似乎与它们同步。然而，有一个明显的悖论。最近的许多实验室研究的结果表明，某些种类的硅藻，包括在浮游植物盛开期间可能是生物量主导物的物种，可以抑制几种浮游生物悬浮液的copepods的几种浮游生物悬浮液的产生和/或胚胎后的胚胎发育。抑制作用的基本机制目前正在争论中。硅藻在营养上可能缺乏，但它们还含有在copepods中诱导有害作用的有毒物质。 However, the general relevance of these laboratory studies for natural populations of copepods is uncertain, as field investigations of the effects of diatom blooms have yielded contradictory results.The goal of this research project is to test in the sea the hypothesis that diatom-dominated phytoplankton blooms have inhibitory effects on egg production rate and/or postembryonic development of natural populations of the planktonic suspension-feeding copepods Calanus pacificus和伪newmani。这项研究将在华盛顿州的达博布湾（华盛顿州）进行，在三月份可靠地发生了强烈的，以硅藻为主导的浮游植物。在这些花朵期间，硅藻浓度从实验室研究中得出或超过对copepods产生有害影响的水平。先前在其他地方研究硅藻花对copepods的影响尚未满足这种情况。为了检验该假设，提出了一种方法的组合：（1）观察Copepods，硅藻和其他潜在猎物的分布和丰度； （2）分析成年copepods的粪便颗粒，以验证它们正在原位摄入硅藻； （3）提供足够的控制和复制的实验，以确定硅藻和其他猎物对成年copods的喂养率； （4）孵育以估计两种copepod物种的原位卵产量和孵化成功； （5）测试硅藻对鸡蛋产量和孵化成功的直接影响的实验以及两种copepod物种的胚胎后发育。硅藻可能会影响诸如CopePods之类的后生动物放牧者的可能性具有巨大的基本和应用科学兴趣。在基本层面上，问题对于理解海洋浮游系统的结构和功能至关重要。浮游植物抑制繁殖或开发放牧浮游动物的任何过程都可能显着影响远离主要消费者水平的上层食品网。也就是说，影响放牧者人口反应的过程将通过食物网络对待，直接影响其他消费者物种，其生殖和生长取决于鸡蛋的发生和丰度以及放牧者的未成熟阶段。因此，重要的是要知道硅藻是否对copepods的自然人群有害，如果是的，效果的特定本质，发生的频率以及对更高营养水平的影响是什么。实际上，从海洋中获得鱼类的可持续收获的幅度最终不仅取决于较高的生产水平，而不是该级别的级别（或不适合该级别）（或不适合该级别）（或不适合该级别）（或不适合该级别）（或者）（或收获）（或收获）（或者）（或者）（均不再是）（或者）（或者）（均不在范围内）（或者）（或者）（均未获得）。因此，对硅藻植物对浮游植物植物天然种群的影响的明确检验可能代表了理解脊柱生物海洋学的重大进步。