Role of dimethyl sulphide (DMS) in pelagic tritrophic interactions

二甲硫醚（DMS）在中上层三营养相互作用中的作用

基本信息

批准号：
NE/H008535/1
负责人：
Stephen Archer
金额：
$ 12.62万
依托单位：
Plymouth Marine Laboratory
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH008535%2F1
关键词：
Role dimethyl sulphide DMS pelagic

项目摘要

The oceans contain only about 1.5% of terrestrial biomass. However, they provide a similar amount of total annual production to that on land and the turnover time for organic matter is 1000-times faster in marine in comparison to terrestrial ecosystems. This highlights that grazing by zooplankton is disproportionally important and competition among grazers is high. It is not surprising that phytoplankton have evolved mechanisms to protect themselves from grazers. These include morphological defences such as grazing-resistant shells, for example in 'armoured' dinoflagellates, and chemical defences such as sophisticated chemical deterrence that influence the selectivity of grazers. Over the years we have accumulated a good understanding of the role of chemical defences in the bitrophic interactions between predators and their prey. However, it is also well known that land plants use another cunning defence strategy that involves the production of volatile signalling compounds (so called infochemicals) that attract the enemy of their predators. This in turn reduces the number of herbivores and releases the plants from excessive grazing pressure. Surprisingly, such infochemical-mediated tritrophic interactions have not been documented for oceanic plankton and our proposed research will rectify this shortcoming. We will focus our activities on one particular marine volatile: dimethyl sulphide (DMS). This compound is probably the best-studied of all marine trace gases, because much interest in DMS research concerns its role in regulating climate. We are starting to appreciate that DMS also has ecological importance and find that many organisms can use plumes of DMS as directional cue for their orientation. For example, some sea birds use DMS to locate areas of high food density. Recently, we also found that zooplankton copepods react to DMS gradients. Copepods are dominant consumers of microzooplankton protists (unicellular ciliates and flagellates) that are important grazers of many small phytoplankton species. In biogeochemical terms ciliates account for, on average, 30 % of the carbon consumed by copepods, representing approximately 5 % of total oceanic primary production and 100 fold the annual fisheries catch (~ 100 Mt yr-1 live weight) in carbon terms. However, these estimates may be considerably higher if other components of the microzooplankton, in particular dinoflagellates, are included. Interestingly, grazing by microzooplankton can result in a dramatic increase of DMS production and this is dependent on the ability of the phytoplankton to make this gas. Hence, phytoplankton may actively influence the 'smelliness' of their predators and this likely makes their enemies more susceptible to copepod attack. It is then not surprising that many of the DMS-producing phytoplankton species are competing successfully and can produce algal blooms that are large enough to be seen from space (for example the coccolithophore Emiliania huxleyi) or can be harmful to other organisms (for example toxic dinoflagellates). Our project will use laboratory experiments where we will quantify grazing of microzooplankton and copepods in relationship to the ability of phytoplankton to make DMS. These data will enable a first assessment of grazing-induced production of DMS in a tritrophic framework. We will also conduct field experiments with freshly collected plankton to verify our laboratory results with data from coccolithophore-dominated waters off Plymouth and in the North-East Atlantic. Our data will inform modelling efforts that aim to predict the effect of differential production of DMS on the susceptibility of microzooplankton to copepod grazing and the fecundity of copepods. This part of our project will be realised through a tied PhD studentship.

海洋仅含有约1.5%的陆地生物量。然而，它们提供的年总产量与陆地相似，而且海洋生态系统的有机物周转时间比陆地生态系统快 1000 倍。这凸显出浮游动物的放牧极其重要，而且食草动物之间的竞争也很激烈。浮游植物进化出了保护自己免受食草动物侵害的机制，这并不奇怪。这些包括形态防御，例如抗放牧的外壳，例如“装甲”甲藻，以及化学防御，例如影响食草动物选择性的复杂化学威慑。多年来，我们对化学防御在捕食者与其猎物之间双营养相互作用中的作用有了很好的了解。然而，众所周知，陆地植物使用另一种狡猾的防御策略，涉及产生挥发性信号化合物（所谓的信息化学物质）来吸引捕食者的敌人。这反过来又减少了食草动物的数量，并使植物免受过度放牧的压力。令人惊讶的是，这种信息化学介导的三营养相互作用尚未在海洋浮游生物中得到记录，我们提出的研究将纠正这一缺陷。我们的活动重点是一种特定的海洋挥发物：二甲硫醚 (DMS)。这种化合物可能是所有海洋微量气体中研究得最好的，因为人们对 DMS 研究的兴趣主要集中在它在调节气候方面的作用。我们开始认识到 DMS 也具有生态重要性，并发现许多生物体可以使用 DMS 羽流作为其方向的方向提示。例如，一些海鸟使用 DMS 来定位食物密度高的区域。最近，我们还发现浮游动物桡足类对 DMS 梯度有反应。桡足类是微型浮游动物原生生物（单细胞纤毛虫和鞭毛虫）的主要消费者，而微型浮游动物原生生物是许多小型浮游植物的重要食草动物。从生物地球化学角度来看，纤毛虫平均占桡足类消耗碳的 30%，按碳计算，约占海洋初级生产力总量的 5%，是年度渔业捕捞量（约 100 Mt yr-1 活重）的 100 倍。然而，如果包括微型浮游动物的其他成分，特别是甲藻，这些估计值可能会高得多。有趣的是，微型浮游动物的放牧可以导致 DMS 产量的急剧增加，这取决于浮游植物产生这种气体的能力。因此，浮游植物可能会积极影响其捕食者的“臭味”，这可能使它们的敌人更容易受到桡足类的攻击。因此，毫不奇怪的是，许多产生 DMS 的浮游植物物种在竞争中取得了成功，并且可以产生足够大的藻华，从太空中都可以看到（例如颗石藻 Emiliania Huxleyi），或者可能对其他生物体有害（例如有毒的藻类）。甲藻）。我们的项目将使用实验室实验，量化微型浮游动物和桡足类的放牧与浮游植物制造 DMS 的能力之间的关系。这些数据将能够对三营养框架中放牧引起的 DMS 生产进行首次评估。我们还将用新鲜收集的浮游生物进行实地实验，以利用普利茅斯附近和东北大西洋以颗石藻为主的水域的数据来验证我们的实验室结果。我们的数据将为建模工作提供信息，旨在预测 DMS 差异生产对微型浮游动物对桡足类放牧的敏感性和桡足类繁殖力的影响。我们项目的这一部分将通过固定的博士生奖学金来实现。