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。它们是生物多样性的热点，提供海岸保护，并维持着渔业和旅游业等重要的经济活动。尽管是地球上最大的生物结构，支撑其生态系统功能的3D框架是由石珊瑚在一个约为人类头发宽度1/10的空间中构建的，夹在活珊瑚和现有碳酸钙骨架之间。珊瑚礁面临着各种各样的人为威胁，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，为了最好地预测这些重要生态系统的命运，并确保采取最有效的地方缓解措施来保护它们，我们需要更好地了解它们是如何构建骨架的。通过对珊瑚进行未来模拟的实验室研究（例如水温升高，或pH值降低，或两者兼而有之），我们有充分的证据表明，在我们未来温暖、酸性的海洋中，珊瑚钙化将大大减少。然而，我们的未来究竟是什么是不确定的，他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方面的同时变化。因此，通过一次改变一个变量的简单实验室实验来推断珊瑚礁未来的样子充满了不确定性。相反，我们需要一种机械的理解，以便将骨骼构造过程及其对环境的敏感性编码为数值模型，从而更准确地预测这一重要生态系统的命运。为了实现这一目标，需要新的方法来感知在珊瑚动物和现有骨骼之间的微小空间中发生的过程。虽然小探针可以插入这个空间，但它们经常破裂，这使得研究变得困难，令人沮丧和昂贵，而且很难准确地确定你在珊瑚动物体内的位置-特别是因为珊瑚是一种生活在流动流体（海水）中的生物。因此，这样的测量远不是常规的，只有少数出版物报道过。因此，我们目前的了解不足以预测珊瑚将如何应对人为压力。在这个提议中，我们将制造一种坚固、低成本的固态微电极，它比目前市面上的微电极更可靠地感应pH值，而且更容易抵抗破损。通过用一种新颖的自定位系统控制这个电极，我们将确切地知道骨架离电极尖端有多近，我们将能够保持它的位置，使我们能够第一次对钙化液中pH值的演变进行长时间和可靠的测量。这一进展借鉴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架（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。在钙化珊瑚腔内进行测量将带来挑战，但我们提出的探针具有良好的商业化潜力，可以在本项目范围之外的广泛应用，特别是在环境科学中常见的野外位置（例如在研究船上，野外站或海洋生物实验室），但对现有技术提出了重大挑战。

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.