OCE-RIG Canary on the coral reef: ecophysiology of tropical crustose coralline algae across latitudinal gradients

在该项目中，研究人员将研究温度升高和酸化对热带甲壳珊瑚藻生理学的影响-矿物学和净钙化-目的是确定哪些物种可以作为与全球气候变化有关的珊瑚礁影响的生物指标，或适应这些影响。为了实现这一结果，研究人员将在已建立的地点进行实地研究，并在广泛的地理范围内进行海洋酸化研究。扩大参与的活动包括教育和推广到太平洋岛民在偏远的实地地点，学生将从事手的研究活动。海表温度上升（SST）和海洋酸化（OA）威胁到钙化生物建造碳酸盐珊瑚礁的能力。目前对有机酸对珊瑚礁影响的认识来自主要集中于珊瑚生长的静态实验室研究。但是热带甲壳珊瑚藻（CCA）被称为“珊瑚礁上的金丝雀”，因为一些物种在这些OA“冲击”实验中溶解。确切的生理机制尚不清楚，但可能与骨骼组织中的镁含量有关，这使得方解石在酸化条件下更易溶解。原位CCA中Mg的摩尔分数受温度和盐度的影响，并与较暖的SST呈正相关。这种关系已被用于气候重建研究，但尚未被认为是在OA的背景下。如果CCA不是表型塑料镁分馏，那么变暖可能会加剧这些物种的OA的反应。本研究的总体目标是研究镁含量的生态重要性，在最近沉积的骨骼组织的共同，泛热带CCA在很宽的纬度范围内，包括自然的时空梯度碳酸盐饱和度和SST。该项目包括三个具体目标：1）描述几种常见热带CCA碳酸盐骨架中Mg含量的地理和精细尺度模式。2)探讨温度和海水碳酸盐化学与几种CCA中镁含量的关系。3)测试镁含量是否改变CCA对全球变暖和/或海洋酸化的生物反应（例如物种特定的净钙化率和群落组成）。粉末X射线衍射分析和激光烧蚀电感耦合等离子体质谱法将用于量化CCA骨骼组织方解石晶格中相对于Ca 2+的Mg 2+含量;生长增量模式将精确定位沉积时间。高频时间序列海水pH值或pCO 2，盐度和SST数据，补充离散采样的其余碳酸盐参数（从既定的OA监测计划），将解决日常，潮汐和季节性周期，并与一致的生物数据（钙化和生产率和镁含量）在原位。

In this project, the investigator will study the effects of increasing temperatures and acidification on the physiology of tropical crustose coralline algae (CCA) - mineralogy and net calcification - with the objective of identifying which species can serve as bioindicators of, or are acclimated to, reef impacts related to global climate change. To achieve this outcome, the investigator will conduct field research at established sites with on-going ocean acidification research across a broad geographic range. The broadening participation activities involve education and outreach to Pacific islanders at the remote field sites where students will engage in hands on research activities.Rising sea surface temperatures (SST) and ocean acidification (OA) threatens the ability of calcified organisms to build carbonate reefs. Current understanding of the effects of OA on coral reefs originates from static laboratory studies largely focused on growth of corals. But tropical crustose coralline algae (CCA) have been proclaimed as the "canary on the coral reef" because some species dissolve in these OA "shock" experiments. The exact physiological mechanism is unknown, but may be related to the magnesium content of the skeletal tissue, which renders the calcite more soluble in acidified conditions. The mole fraction of Mg in CCA in situ is subject to temperature and salinity and is positively correlated with warmer SST. This relationship has been exploited for climate reconstruction studies, but has not yet been considered in the context of OA. If CCA are not phenotypically plastic for Mg fractionation, then warming may exacerbate the response of these species to OA. The overall objective of this research is to examine the ecological importance of Mg content in recently deposited skeletal tissue of common, pantropical CCA across a wide latitudinal range that encompasses natural spatio-temporal gradients in carbonate saturation and SST. The project includes three specific objectives: 1) Describe the biogeographic and fine-scale patterns of Mg content in the carbonate skeleton of several species of common tropical CCA. 2) Explore the relationships of temperature and seawater carbonate chemistry with Mg content in several species of CCA. 3) Test whether Mg content alters the biological response (e.g. species-specific net calcification rates and community composition) of CCA to global warming and/or ocean acidification. Both powdered X-ray diffraction analysis and laser ablation inductively coupled plasma mass spectrometry will be used to quantify Mg2+ content relative to Ca2+ in the calcite lattice of CCA skeletal tissue; growth increment patterns will pinpoint the timing of deposition. High frequency time-series seawater pH or pCO2, salinity, and SST data, complimented by discrete sampling for the remaining carbonate parameters (from established OA monitoring programs), will resolve daily, tidal, and seasonal cycles and be related with coincident biological data (calcification and production rates and Mg content) in situ.