Cellular physiological mechanisms for coral calcification and photosynthesis: extending lab-based models to the field

珊瑚礁是世界上最具生物多样性和生产力的生态系统之一，为沿海社区提供数百万美元的生态系统服务。人们越来越担心珊瑚礁的未来和人为压力因素的影响，包括富营养化、海洋酸化、气候变暖和海平面上升。然而，缺乏对基本珊瑚细胞机制的了解限制了我们理解和预测反应以及实施适当管理决策的能力。该提案将结合实地和实验室实验，利用免疫学技术研究珊瑚细胞对环境条件的反应。该项目将重点关注与钙化、光合作用和营养吸收有关的过程，并在自然界中测试从实验室实验中获得的机制模型的相关性。本研究的结果可以为未来的生理学、生态学和跨学科研究提供生物标志物。为了最大限度地发挥这项研究的科学、社会和教育影响，一系列协调的活动将包括：(1)培养一名分子、细胞和生态研究方面的研究生。(2)通过期刊、会议和本科及研究生生理学课程传播研究成果。(3)与斯克里普斯的伯奇水族馆合作，提高公众对珊瑚礁生物学、生态学和保护问题的认识，并向公众传播研究结果。这些活动每年将吸引数十万参加Birch的儿童和成人，并通过在线资源吸引数百万观众。(4)通过斯克里普斯本科生研究奖学金暑期项目，吸引和培训来自代表性不足的少数民族的本科生。这项研究将使用最近开发的免疫学技术来定位和定量特定珊瑚细胞类型中的蛋白质，并在细胞水平上确定珊瑚对环境条件的反应。我们感兴趣的一种酶是空泡质子三磷酸腺苷酶（VHA），它最近在腹真皮细胞的共生体膜中被发现，并被认为是珊瑚共生藻类浓缩二氧化碳进行光合作用所必需的。另一种酶，钠/钾atp酶（NKA），被免疫定位到成钙质细胞，表明在钙化中起作用。此外，NKA在复杂枝的珊瑚细胞中被发现，而在强健枝的珊瑚细胞中没有发现，这表明NKA只在前者的营养吸收中起作用。在该项目中，将使用一系列实地和操作水族馆研究来确定VHA和NKA在两个珊瑚物种中的生理作用，每个物种来自一个分支。具体而言，本研究将：(1)定位和量化巴拿马Bocas del Toro泻湖和开放海洋暴露珊瑚礁中1和5米深度的鹿角Acropora cervicornis和环环环轮虫特定组织层中的VHA和NKA。(2)将VHA和NKA电位差异与不同地点和深度的光照、pH和营养水平联系起来，研究对环境条件的进化适应。(3)进行一年的反向移植，检查慢性适应情况。(4)进行一个月的反向移植，检查急性适应情况。(5)在流动的海水系统中，将珊瑚暴露于一系列与环境有关的营养、光照和pH水平，以确定是否有任何单一因素引起细胞反应的变化。除了描述从进化、慢性到急性暴露的广泛时间尺度上对环境条件的反应外，本研究还将研究稳健珊瑚和复杂珊瑚之间潜在的细胞机制差异。长期目标是生成基于特定细胞生理过程的生物标志物，以解释和预测环境压力（例如富营养化、海洋酸化和海平面上升）对珊瑚稳态反应的影响。

Coral reefs are amongst the most biodiverse and productive ecosystems in the world, providing millions of dollars of ecosystem services to coastal communities. There is growing concern about the future of coral reefs and the impact of anthropogenic stressors including eutrophication, ocean acidification, warming and sea level rise. However, the lack of knowledge of fundamental coral cellular mechanisms limits our ability to understand and predict responses and to implement appropriate management decisions. This proposal will use a combination of field and laboratory experiments to use immunological techniques to study coral cellular responses to environmental conditions. This project will focus on processes related to calcification, photosynthesis and nutrient uptake and test in nature the relevance of mechanistic models obtained from laboratory experiments. Results from this study could help generate biomarkers for future physiological, ecological and interdisciplinary studies. To maximize the scientific, societal and educational impacts of this research, a coordinated set of activities will include: (1) Training of one graduate student in molecular, cellular, and ecological research. (2) Dissemination of results through journals, conferences and undergraduate and graduate physiology courses. (3) Partnering with the Birch Aquarium at Scripps to build awareness of coral reef biology, ecology and conservation issues and disseminate the findings of this study to the general public. These activities will reach hundreds of thousands of children and adults that attend Birch annually, and millions of viewers through online resources. (4) Engage and train undergraduate students from underrepresented minorities through the Scripps Undergraduate Research Fellowship summer program. This research will use recently developed immunological techniques to localize and quantity proteins in specific coral cell types and determine coral responses to environmental conditions at the cellular level. One enzyme of interest is the vacuolar proton ATPase (VHA), which was recently found in the symbiosome membrane of gastrodermal cells and identified as essential for the coral's symbiotic algae to concentrate CO2 for photosynthesis. Another enzyme, the sodium/potassium ATPase (NKA), was immunolocalized to calicoblastic cells suggesting a role in calcification. Additionally, NKA was found in cells in corals from the Complex but not the Robust clades, suggesting a role in nutrient uptake only in the former. In the project a series of field and manipulative aquarium studies will be used to determine the physiological roles of VHA and NKA in two coral species, one from each clade. Specifically, this research will: (1) Localize and quantify VHA and NKA in specific tissue layers of Acropora cervicornis and Orbicella annularis from 1 and 5m depth at a lagoonal and an open ocean exposed reef in Bocas del Toro, Panama. (2) Correlate potential differences in VHA and NKA to light, pH, and nutrient levels at the different field sites and depths, to study evolutionary adaptation to environmental conditions. (3) Perform one-year reciprocal transplantations to examine chronic acclimatization. (4) Perform one-month reciprocal transplantations to examine acute acclimatization. (5) In a flowing seawater system expose corals to a range of environmentally relevant nutrient, light and pH levels to determine if any of the single factors are causing changes in the cellular responses. In addition to characterizing responses to environmental conditions on a broad temporal scale from evolutionary, chronic, to acute exposure, this research will examine potential cellular mechanistic differences between Robust and Complex corals. The long-term goal is to generate biomarkers based on specific cellular physiology processes to explain and predict effects of environmental stress (e.g. eutrophication, ocean acidification, and sea level rise) on coral homeostatic responses.