Chemical communication in epiphytic communities under ocean acidification

海洋酸化通过吸收大气中额外的二氧化碳进入海洋水域，被认为是对海洋生态系统的严重威胁。然而，关于OA对底栖无脊椎动物化学交流的潜在影响，特别是与食物和栖息地线索的利用有关的潜在影响，人们知之甚少。这里提出的项目旨在在全球相关的开放式获取的背景下，扩展我们在底栖无脊椎动物群落中的化学交流方面的知识。在伊斯基亚附近，火山二氧化碳喷口沿海岸线造成了pH梯度，自然海洋酸化对底栖生物群落的生态系统影响。我们将利用这一自然梯度来研究OA对海草林中初级生产者和大型脊椎动物种间化学通讯的影响。我们将重点关注pH值为8.1(未酸化)和pH 7.7(酸化)的海草林，以涵盖预计将持续到本世纪末的挥发性有机化合物(VOC)的范围。在早期的工作中，我们已经表明，挥发性有机化合物(VOC)是海草林中初级生产者和大型植物群落中重要的信号分子。在这里，我们将研究OA如何影响VOC介导的信号转导。据推测，对信号的影响将在无脊椎动物的信号接收器分类群中有所不同。将测试OA对大型无脊椎动物对VOCs敏感性的影响是否类似于(I)在系统发育上更接近的无脊椎动物群体，(Ii)起源于正常或酸化栖息地的类群，或(Iii)具有相同营养偏好的类群。我们将从附生群落和从这些群落分离的藻类菌株中提取VOC花束，通过GC-MS进行分析比较，并将它们与从海草相关群落收集的大型无脊椎动物进行行为分析。在海草上的自然群落中，当幼体以微小球藻为食时，相当丰富的软体对虾Hippolte inermis的性别由雄性恢复为雌性。我们将通过在生物测定过程中通过不同pH值的硅藻培养过程中不同的pH值来研究OA对这一独特信号的影响，并将使用代谢组学方法来鉴定诱导化合物，目的是了解OA对化合物水平的影响。我们假设，在目前的pH条件下，OA将干扰这种由食物介导的性别变化，而性别变化是确保这种对虾自然种群稳定的基础。总之，这个项目将揭示迄今为止被忽视的OA在海洋底栖群落中由化学信号介导的重要生物相互作用中的作用。

Ocean acidification (OA) through the uptake of additional CO2 from the atmosphere into marine waters is considered a serious threat to marine ecosystems. However, there is only very little known on potential effects of OA on chemical communication of benthic invertebrates, in particular in connection to utilization of food and habitat cues. The project proposed here aims to extend our knowledge on chemical communication in benthic invertebrate communities in the globally relevant context of OA. Close to Ischia, volcanic CO2 vents have caused a gradient of pH along the coastline with ecosystem effects of natural ocean acidification on benthic communities. We will use this natural gradient to investigate effects of OA on interspecific chemical communication of primary producers and macro¬in-verte¬brates in seagrass stands. We will focus on seagrass stands at pH 8.1 (non-acidified) and pH 7.7 (acidified) to cover the range of OA that is predicted to occur until the end of the century.In earlier work we have shown that volatile organic compounds (VOCs) are important signalling molecules among primary producers and macro¬in¬verte¬brates in communities found in seagrass stands. Here we will investigate how OA affects this VOC-mediated signalling. It is hypothesized that effects on signaling will differ between invertebrate signal receiver taxa. It will be tested whether the effects of OA on the sensitivity of macroinvertebrates to VOCs are similar for (i) phylogenetically more closely related invertebrate groups, (ii) taxa that originate from the normal or the acidified habitat or (iii) taxa that share the same trophic preference. We will extract VOC bouquets from epiphytic communities and from algal strains isolated from these communities, compare them analytically via GC-MS and subject them to behavioural assays with macroinvertebrates collected from seagrass-associated communities. In the natural community on seagrass, the sex of the fairly abundant shrimp Hippolyte inermis is reverted from male to female, when young individuals feed on the diatom Coccconeis scutellum parva. We will investigate effects of OA on this unique signalling by crossing different pH-values during culturing of the diatom with different pH-values during the bioassay, and we will use a metabolomics approach to identify the inducing chemical compound, with the objective to understand the effects of OA on the level of the chemical compound. We hypothesize that OA will interfere with this diet-mediated change in sex, which at the current pH is fundamental to assure stability of natural populations of this shrimp.Overall this project will shed light on the so far neglected role of OA for important biotic interactions in marine benthic communities mediated by chemical signals.