About This Project

Coral reefs are under threat from ocean warming. High temperatures cause coral bleaching, the expulsion of the colorful symbiotic algae from the coral host, which can lead to coral mortality. Currently, the main bleaching forecast tool applies a single heat-stress threshold for all corals globally, even though observational and experimental studies point to species- and genus-level variations. Here, we will compile existing bleaching data globally to refine forecast models to taxonomic levels.

Ask the Scientists

What is the context of this research?

While large-scale patterns of coral bleaching can be matched to large-scale climate patterns such as El Nino, smaller scale processes also drive bleaching variability within reef systems (DeCarlo et al., 2017), due in large part to differential bleaching susceptibility among coral taxa (e.g. species- and genus-level differences). Currently, most coral reef scientists and practitioners rely heavily on the Coral Reef Watch (CRW) product for historical and near-future coral bleaching predictions globally. However, CRW applies a single bleaching sensitivity to heat stress for all corals. We have known for decades, though, that different coral taxa have different susceptibility to heat stress, resulting in bleaching occurring at various levels of heat stress per species or genus (Marshall and Baird, 2000). With several decades of coral bleaching observations now available, it should be possible to improve bleaching forecasts to consider biological variation.

What is the significance of this project?

Bleaching forecasts produced by CRW are highly valuable and play key roles in coral reef management and conservation. However, limitations clearly exist due to the "one size fits all" model that applies a single sensitivity to all reefs and all species globally, leading to relatively large rates of incorrect predictions (DeCarlo, 2020). We have already made progress on capturing regional variations, leading to substantial improvement in prediction skill (Whitaker and DeCarlo, 2024). However, biological variation remains un-assessed. This is particularly important because management or conservation decisions may depend on genus-level susceptibilities. For example, a reef dominated by relatively resistant massive Porites may fare well even when heat stress reaches bleaching-inducing levels per CRW. Conversely, restoration projects out-planting relatively susceptibly Acropora may need to take action at lower heat stress than CRW predicts will induce bleaching.

What are the goals of the project?

The goal of this project is to collate all existing coral bleaching observations that include taxonomic level into bleaching forecast models. The bleaching data compilation will be achieved by using the data in Whitaker and DeCarlo (2024) as a starting point and then conducting systematic literature searches for data that became available subsequently, such as from Eakin et al. (2026). Forecast models will fit remotely sensed sea surface temperature data to the bleaching observations, with genus included as a modulating factor. The final product will be statistically optimized thresholds for bleaching at the genus level that can be "plugged in" to heat stress forecasts to output taxon-level bleaching forecasts. In other words, we aim to change the existing model from "X reef is expected to bleaching next month" to "Y genus, but not Z genus, is expected to bleach on X reef next month". We expect to capture most common genera, though rare genera may need to be grouped as "other".