Regulation of isoprene production by coastal benthic communities

异戊二烯（2-甲基-1,3-丁二烯）是由微生物产生的几种挥发性有机化合物之一，但它是最具活性的碳氢化合物之一，可以改变我们的气候，因此特别令人感兴趣。异戊二烯在释放到大气中时迅速氧化，这反过来又延长了导致“温室”效应的气体的停留时间，并诱导臭氧（在一氧化氮存在的情况下）和云凝结核的形成。迄今为止，国际上对全球异戊二烯通量的关注主要集中在陆地系统，而水生系统在很大程度上被忽视了。据认为，海洋系统的全球异戊二烯排放量的估计值大大低于陆地系统。然而，这些对海洋系统的估计是基于很少的基于实验室的微藻研究。最近在实地进行的研究表明，海水的异戊二烯排放量可能高于以前的估计，特别是在微藻繁殖期间。然而，以往对海洋系统异戊二烯排放的有限研究的重点忽视了可能决定其全球重要性的两个关键因素：(1)高产沿海海洋群落的生产；(2)异戊二烯合成和降解背后的动力学。异戊二烯是由植物、藻类和细菌合成的，这些植物、藻类和细菌在沿海水域的边缘和永久水下栖息地都很丰富。沿海海洋系统只占地球表面相对较小的一部分，但生产力很高（占所有水产产量的25%）。同时，这些系统使其居民处于持续（通常是极端）波动的环境条件下，例如光线和温度；已知这种高度可变的生长环境会导致陆地系统中异戊二烯合成升高。热带和温带海洋海岸系统的特点是类似的官能团可能合成大量的异戊二烯，例如盐沼、大藻和微藻（温带）和红树林、珊瑚和海草（热带）。然而，并不是所有合成的异戊二烯都会进入大气。土壤中异养细菌对异戊二烯的降解也被确定为陆地系统中异戊二烯净排放的一个重要组成部分。最近在埃塞克斯大学进行的微观实验表明，沿河口梯度有大量异戊二烯降解，因此出现了异戊二烯总产量的海洋汇。在这里，我们提出了一项好奇心驱动但概念验证的调查，以解决沿海海洋系统中异戊二烯合成和降解的未知重要性。这里收集的数据将直接构成未来全面提案的基础，该提案将审查海洋系统净异戊二烯生产和排放的机制和生物相互作用。在本研究的背景下，我们建议购买一种可用于现场操作的商用快速异戊二烯传感器（FIS, Hill Scientific， USA），并首次使用该仪器在实验室和现场环境中分析海洋群落。因此，该提案还将确定FIS分析水生生物和产生快速现场测量的能力。本文描述了对温带和热带沿海海洋系统中常见的各种水生生物进行短期和长期孵化实验的实验。

Isporene (2-methyl-1,3-butadiene) is one of several volatile organic compounds produced by micro-organisms but is of particular interest since it is one of the most highly reactive hydrocarbons emitted that can alter the our climate. Isoprene rapidly oxidises when released to the atmosphere, which in turn lengthens the residence times of gases that contribute to the 'greenhouse' affect, and induces formation of ozone (in presence of nitric oxides) and cloud-condensing nuclei. To date, international attention of global isoprene fluxes has focused primarily on terrestrial systems whilst aquatic systems have been largely ignored. Estimates for global isoprene emissions from marine systems are thought to be substantially lower than those from terrestrial systems. However, these estimates from marine systems have been constructed from few laboratory-based studies upon microalgae. Recent research conducted in the field suggests that isoprene emissions from marine waters may be higher than previously estimated, in particular during microalgal blooms. Nevertheless, the focus of the limited previous research investigating isoprene emissions from marine systems has neglected two key factors that likely determine its global importance: (1) production by highly productive coastal marine communities and (2) the dynamics underlying both isoprene synthesis and degradation. Isoprene is synthesised by plants, algae and bacteria, all of which are abundant across the fringing, and permanently submerged habitats of coastal waters. Coastal marine systems cover a relatively small fraction of the earth's surface yet are highly productive (accounting 25% of all aquatic production). Simultaneously, these systems subject their inhabitants to continuously (and often extreme) fluctuating environmental conditions, such as light and temperature; such a highly variable growth environment is known to induce elevated isoprene synthesis in terrestrial systems. Both tropical and temperate marine coastal systems are characterised by analogous functional groups that likely synthesis substantial concentrations of isoprene, for example saltmarshes, macroalgae and microalgae (temperate) and mangroves, corals and seagrasses (tropical). However, not all isoprene that is synthesised is thought to reach the atmosphere. Degradation of isoprene by heterotrophic bacteria in soils has also been identified as an important component contributing to net isoprene emissions from terrestrial systems. Recent microcosm experiments at the University of Essex have demonstrated substantial isoprene degradation along an estuarine gradient and thus the occurrence of a marine sink for gross isoprene production. Here, we propose a curiosity-driven but proof-of-concept investigation to address this unknown importance of isoprene synthesis and degradation within coastal marine systems. Data collected here will directly form the basis of a future full proposal that will examine the mechanistics and biological interactions if net isoprene production and emission by marine systems. Within the context of this study, we have proposed the purchase of a commercially available field-operable Fast Isoprene Sensor (FIS, Hill Scientific, USA) and use this instrument for the first time for assaying marine communities in both laboratory and field settings. Therefore, this proposal will also determine the capabilities of the FIS for assaying aquatic organisms and for generating rapid field-based measurements. Experiments are described that will employ short- and long- term incubation experiments for a wide range of aquatic organisms that are commonly found within temperate and tropical coastal marine systems.