CoralChem - The Mechanics of Coral Calcification Revealed by a Novel Electrochemical Tool Kit

热带珊瑚礁是一个非常重要的海洋生态系统，每年在全球范围内贡献300亿美元的生态系统服务。它们是多样性热点，提供海岸保护，并维持重要的经济活动，如渔业和旅游业。尽管是地球上最大的生物结构之一，但支撑它们生态系统功能的3D框架是由石珊瑚构建的，空间约为人类头发宽度的十分之一，夹在活珊瑚和现有的碳酸钙骨架之间。珊瑚礁面临各种规模的人为威胁，从当地污染和过度捕捞到全球变暖和海洋酸化。面对持续的人为变化，为了更好地预测这些重要生态系统的命运，并确保采取最有效的当地缓解努力来保护它们，我们需要更好地了解它们是如何构建骨架的。通过对珊瑚进行模拟未来(例如，水温升高或pH降低，或两者兼而有之)的实验室研究，我们有很好的证据表明，在我们未来温暖、酸性的海洋中，珊瑚的钙化将大大减少。然而，我们的未来到底是什么是不确定的，它们将面临的环境变化是多方面的、多因素的和协同的，涉及水温、酸度、营养水平、海平面、光照水平和食物供应等的同时变化。因此，在简单的实验室实验中，每次改变一个变量来预测珊瑚礁未来的样子，这样的推断充满了不确定性。取而代之的是需要一种机械的理解，以便将骨骼构建过程中涉及的过程及其对环境的敏感性编码到数值模型中，以便更准确地预测这一重要生态系统的命运。要做到这一点，需要新的方法来感知夹在珊瑚动物和现有骨骼之间的微小空间中发生的过程。尽管可以将小探测器插入这个空间，但它们经常会破裂，这使得这种研究变得困难、令人沮丧和昂贵，而且很难计算出你在珊瑚动物体内的确切位置--特别是因为珊瑚是居住在流动液体(海水)中的活有机体。因此，这样的测量远远不是常规的，只有少数出版物报道了这一点。因此，我们目前的理解不足以预测珊瑚将如何应对人为压力。在这项提议中，我们将制造一种坚固、低成本的固态微电极，它比目前商业上可用的微电极更可靠地感知pH值，并且更容易抵抗破坏。通过使用新型的自定位系统控制电极，我们将确切知道骨架与电极尖端的距离有多近，并且我们将能够保持其位置，从而使我们能够首次对钙化液中的pH变化进行长期和可靠的测量。这一进展利用了扫描电化学显微镜领域的发展，并使用像雷达一样的传感尖端来确定其与骨骼(以及珊瑚细胞结构中的其他层)的距离。这一建议是朝着能够可靠地测量珊瑚钙化空间中的碳酸盐系统从而更好地识别钙化机制迈出的重要的第一步。在钙化珊瑚洞穴内进行测量将带来挑战，但我们建议的探测器具有很好的商业化潜力，可用于本项目范围之外的广泛应用，特别是在环境科学中常见但对现有技术构成重大挑战的野外地点(例如，在考察船、野外空间站或海洋生物实验室)。

Tropical coral reefs are a very important marine ecosystem contributing $30billion in ecosystem services each year worldwide. They are diversity hotspots, offer coastal protection and sustain important economic activities like fisheries and tourism. Despite being some of the largest bioconstructions on the planet, the 3D framework which underpins their ecosystem function is constructed by stony corals in a space about 1/10th of the width of a human hair sandwiched between the living coral and the existing calcium carbonate skeleton. Coral reefs face a multitude of anthropogenic threats on a range of scales from local pollution and over fishing to global warming and ocean acidification. In order to best predict the fate of these important ecosystems in the face of continued anthropogenic change and to ensure the most effective local mitigation efforts are carried out to conserve them, we need to better understand how they build their skeletons. Through laboratory studies where corals are subjected to simulations of the future (e.g. water temperature is increased, or pH lowered, or both) we have good evidence that coral calcification will be much reduced in the warm, acidic oceans of our future. However, exactly what our future holds is uncertain and the environmental change they will face is, and will be, multifaceted, multifactorial and synergistic involving simultaneous changes in water temperature, acidity, nutrient levels, sea level, light levels and food supply, amongst others. So much so, extrapolating the simple laboratory experiments where one variable is changed at time to predict what coral reefs will be like in the future is fraught with uncertainty. Instead a mechanistic understanding is required such that the processes involved in skeletal construction, and their environmental sensitivities, can be encoded in a numerical model to more accurately predict the fate of this important ecosystem. What is needed to achieve this are new ways to sense the processes occurring in the tiny space sandwiched between the coral animal and existing skeleton. Although small probes can be inserted into this space they frequently break which makes such research difficult, frustrating and expensive, and it is hard to work out exactly where you are within the coral animal - especially since the coral is a living organism inhabiting a moving fluid (seawater). As a result, such measurements are far from routine and are reported in only a handful of publications. Consequently, our current understanding is insufficient to predict how corals will respond to anthropogenic stressors.In this proposal we will make a robust, low cost, solid-state microelectrode that senses pH more reliably than those currently commercially available and one that will resist breakage more easily. By controlling this electrode with a novel self-positioning system we will know exactly how close the skeleton is from the electrode tip and we will be able to maintain its position allowing us to make prolonged and reliable measurements of the evolution of pH in the calcifying fluid for the first time. This advance draws on developments in the field of scanning electrochemical microscopy and uses the sensing tip like a radar to determine its distance from the skeleton (and other layers in the coral cellular structure). This proposal is an important first step towards being able to reliably measure the carbonate system in the calcifying space of corals so as to better identify the mechanics of calcification. Performing measurements within the calcifying coral cavity will present challenges but the probe we propose has good potential for commercialisation for a wide range of applications beyond the scope of this project, especially in field locations (e.g. on a research ship, in a field station, or marine biology lab) that are common in the environmental sciences but present a significant challenge to existing technology.