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

• 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

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。但是，与地面生态系统相比，它们提供的年度总产量与土地上的总产量相似，有机物的营业率更快。这一点凸显了浮游动物的放牧非常重要，放牧者之间的竞争很高。浮游植物已经发展出保护自己免受放牧者的机制并不奇怪。其中包括形态防御，例如放牧的壳，例如“装甲”鞭毛藻和化学防御剂，例如影响放牧者选择性的复杂化学威质。多年来，我们积累了对化学防御剂在捕食者及其猎物之间的肉眼相互作用中的作用的充分理解。但是，众所周知，陆地植物采用另一种狡猾的防御策略，涉及生产挥发性信号传导化合物（所谓的Infochemicals），这些策略吸引了捕食者的敌人。反过来，这减少了草食动物的数量，并释放了植物免于过多的放牧压力。令人惊讶的是，这种物化介导的粮食相互作用尚未记录在海洋浮游生物中，我们提出的研究将纠正这一缺点。我们将把活动集中在一种特定的海洋挥发性上：二甲基硫化物（DMS）。这种化合物可能是所有海洋痕量气体中最有研究的，因为对DMS研究的极大兴趣涉及其在调节气候中的作用。我们开始意识到DMS也具有生态意义，并发现许多生物可以将DMS羽毛用作其取向的方向提示。例如，一些海鸟使用DMS定位高食物密度的区域。最近，我们还发现浮游动物对DMS梯度反应。 CopePods是微Zooplankton生物（单细胞纤毛和鞭毛）的主要消费者，它们是许多小型浮游植物物种的重要放牧者。用生物地球化学术语，纤毛平均占Copepods消耗的碳的30％，约占总海洋初级生产的5％，每年的渔业捕获（约100吨YR-1 Live Regite）用碳含量占100倍。但是，如果包括Microzooplankton的其他组件，尤其是鞭毛鞭毛盐，这些估计值可能更高。有趣的是，通过微Zooplankton放牧会导致DMS产生的急剧增加，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掠食者的“嗅觉”，这可能会使他们的敌人更容易受到pepepod攻击的影响。毫不奇怪，许多产生DMS的浮游植物物种都在成功竞争，并且可以产生足够大的藻华，可以从太空中看到足够大的藻类（例如，埃米利安尼亚Huxleyi）或可能对其他有机体有害（例如有毒毒性果仁酸酯）。我们的项目将使用实验室实验，在其中我们将与浮游植物制造DMS的能力相关的微Zooplankton和Copepods放牧。这些数据将使在粮食框架中首次评估放牧引起的DMS的生产。我们还将使用新鲜收集的浮游生物进行现场实验，以通过来自普利茅斯和东北大西洋的Coccolithophore主导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差异产生对Microzooplankton对Copepod放牧和copepods的易感性的影响。我们项目的这一部分将通过绑定的博士学位学生实现。

项目成果

Role of infochemical mediated zooplankton grazing in a phytoplankton competition model

• DOI: 10.1016/j.ecocom.2012.10.003
• 发表时间: 2013-12
• 期刊: Ecological Complexity
• 影响因子: 3.5
• 作者: N. Lewis;M. Breckels;M. Steinke;Edward A. Codling