Coral reef resilience to climate change [electronic resource] : insights from field measurements and models
Keywords: Environmental Earth System Science.

Coral reefs are simultaneously the most biodiverse, arguably most valuable, and most vulnerable to climate change type of marine ecosystem. Reefs provide many ecosystem services, such as food, income, protection from storm surge and sea level rise, and yet coral reefs are at high risk of negative impacts due to climate change. In order to understand climate change vulnerability in reef ecosystems and the factors which could confer or preclude resilience, we need to examine and have a thorough grasp of reef environmental variability on different time scales when it comes to temperature and carbon chemistry specifically, and particularly the biological and physical drivers of such variability. This dissertation addresses both aspects of climate change threats to coral reefs: rise in sea surface temperatures (SSTs) as well as the dynamics of declining pH associated with changes to the carbon system with continued ocean acidification (OA). The former is examined through a methodological paper on improved projections of coral bleaching for reef globally based on global climate models, and the latter is addressed via three thorough field studies of carbon budgets and reef metabolism on three different reefs spanning the Western Pacific, Central Equatorial Pacific, and a high-latitude Great Barrier Reef. This dissertation offers valuable information towards the following advances: 1) progress in instrumentation which can accurately and autonomously produce high-resolution datasets of environmental variability in different reef habitat types; 2) refinement of methodologies for computing reef metabolism as well as reef sensitivity to temperature and pH stress; and 3) an improved mechanistic understanding of physical, biological, and ecological drivers of coastal carbon dynamics and their implications for conditioning reefs for the future. Specifically, this dissertation demonstrates our ability to improve future projections for thermal stress on reefs and threats from bleaching significantly depend on using global climate model output of high spatial resolution and applying a refined methodology aimed at incorporating internal temperature variability as part of the exposure to thermal stress metric. The spatial patterns in bleaching probabilities presented here and in other subsequent studies on the topic may provide insights into conservation priorities of particularly thermally resilient reef locations. In addition, perhaps the most important lesson learned from field measurements and interdisciplinary studies on reef carbon budgets presented in this dissertation is that there is rarely a one-size-fits-all type of approach that could yield robust and accurate reef metabolism estimates. Reef systems are more complex than we have previously considered, and their conditioning to environmental variability is actually based on complex feedbacks between ecological community composition and various physiological processes, which leave their mark on the overlying ambient seawater. Environmental variability and thus conditioning and the potential to resist or be resilient to future ocean acidification are all characteristics strongly modulated by the interactions between reef metabolism and hydrodynamic regimes and highlight the need to continued field monitoring aimed at high-resolution characterization of both carbon chemistry and hydrodynamics. This dissertation contributes a detailed understanding of the challenges involved in investigating reef biogeochemistry and water circulation in reef habitats in relation to reef net community calcification (NCC) and net community production (NCP) (collectively referred to as reef metabolism).