Unravelling the drivers of coral reproductive phenology and synchrony

珊瑚是珊瑚礁的生态系统工程师，珊瑚礁是地球上生物多样性最丰富的海洋生态系统之一。珊瑚礁是所有海洋物种的家园，通过渔业、旅游业和海岸保护支持全世界数亿人的福祉和生计。大多数珊瑚物种是广播性产卵者，依靠同步产卵活动作为种群补充和适应的基本过程。大多数珊瑚在短暂的季节性期间同步产卵，这些事件的发生时间取决于环境线索。鉴于大多数珊瑚在水柱中释放配子的时间窗口很短，受精取决于珊瑚群体根据适当的环境线索调整它们的繁殖时机。此外，它们还依赖于高度同步地释放配子，以确保异交发生在有利的环境条件下。海洋表面温度、太阳辐射、风速、月相和周期已被证明影响珊瑚的产卵，并对产卵的月份或周负责，但珊瑚将这一事件计入特定日期的机制仍不清楚。尽管珊瑚礁在维持生态系统功能和为许多沿海社区提供服务方面起着关键作用，但仍然有必要了解全球范围的人类影响是如何影响珊瑚繁殖的时间和同步的。直到最近，气候变化对珊瑚繁殖同步性的影响一直受到缺乏大规模珊瑚繁殖物候数据的限制，以及与操纵季节环境周期的实验相关的技术挑战。在此之前，环境参数的影响已经被用广泛的时空尺度(例如，月平均)来研究，因此，为珊瑚产卵同步化寻找合适的环境线索仍然是一个挑战。在我的博士论文期间，我的目标是：i)确定哪些气候驱动因素与类群和生态区域内的产卵物候和同步性更相关，ii)调查哪些过程和气候驱动因素是不同物候策略的幕后推手，例如分离产卵、高度同步或组合内的异步繁殖策略，iii)评估几个类群对所选驱动因素变化的反应，以便确定哪些科或物种可能更容易经历生殖物候的中断和产卵同步性的可能崩溃。对于这项任务，我将使用现在、过去和预测的未来气候情景来创建生态模型，iv)确定珊瑚产卵不同步的高风险区域，创建考虑物候变化的预测性物种分布模型。这样的模型将有助于绘制产卵分解风险地图，确定哪些物种更容易受到不同驱动因素的影响，这可能有助于保护珊瑚礁。我正在使用一个最近编制的关于珊瑚产卵计时(CSD)的大型数据库，其中包括对300多个珊瑚物种产卵时间或日期的6000次单独观察，以调查产卵同步性和物候的空间和时间模式。我将使用统计模型来检验精细时空尺度气候驱动因素对产卵时间的影响。此外，我还将进行野外和实验室实验，以测试温度、月亮周期和光照条件对珊瑚产卵物候同步性的影响。

Scleractinian corals are the ecosystem engineers of coral reefs, one of the most biodiverse marine ecosystems on the planet. Coral reefs are home to a quarter of all marine species and support the wellbeing and livelihoods of hundreds of millions of people worldwide through fisheries, tourism and coastal protection. Most coral species are broadcast spawners which relay on synchronous spawning events as an essential process for the replenishment and adaptation of populations. Most corals spawn synchronously during short seasonal periods and the timing of these events depends on environmental cues. Given most corals present a short time window in which they release gametes in the water column, fertilization depends on coral colonies adjusting their reproductive timing following the appropriate environmental cues. Moreover, they also depend on releasing gametes with a high degree of synchrony to ensure that outcrossing happen in beneficial environmental conditions. Sea surface temperature, solar insolation, wind speed, lunar phase and cycle have been demonstrated to influence coral spawning and be responsible for month or week of spawning but the mechanisms corals time this event to a particular day still remain unclear. Given the importance of several environmentalcuesin reproductive phenology, climate change impacts could disrupt spawning synchrony, with long-term consequences for population viability.Despite the key role thatcoral reefsplayfor maintaining ecosystem functions and the services they provide to many coastal communities,there is still a need to understand how global-scale human impacts affect coral reproductive timing and synchrony.Until recently, the described impacts of climate change on coral reproductive synchrony have been limitedby a lack of large-scale datasets on coral reproductive phenology, and technical challenges associated with experiments to manipulate seasonal environmental cycles.Previously,the effect of environmental parameters hasbeen studied using broadspatiotemporal scale(e.g., monthly averaged means)and,therefore,identifyingappropriate environmental cues for coral spawning synchrony remains a challenge. Duringmy Ph.D.I aim to i) determine which climate drivers are more relevant for spawning phenology and synchrony within taxa and ecoregions,ii) investigate which processes and climate drivers are behind different phenological strategies such as split spawning, highlysynchronousvs asynchronousreproductive strategies within assemblages,iii) Evaluate the responses of several taxa to changes in the selected drivers in order to determine which families or species could be more susceptible to experience disruptions in their reproductive phenology and possible breakdowns in spawning synchrony. For this task I will use present, past and predicted future climate scenarios to create ecological models, iv) to identify areas of higher risk to experience asynchronies in coral spawning, creating predictive species distribution models accounting for phenological changes. Such models will help to develop maps of risk of spawning breakdown identifying which species are more vulnerable to different drivers which could help to preserve coral reefs. I am working with a recently compiled, large database on coral spawning timing (CSD), including 6000 individual observations of the time or day of spawning for over 300 coral species, to investigate spatial and temporal patterns of spawning synchrony and phenology. I will use statistical models to test he effect of fine spatiotemporal scale climate drivers on spawning timing. Additionally, I will conduct field and laboratory experiments to test the effects of temperature, lunar cycle and light regime in order to disentangle their effect in coral spawning phenology synchrony.