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1. Paleo reefs provide clues for contemporary climate-change refugia

   https://doi.org/10.1016/j.crsus.2024.100289  

   van_Woesik, Robert (February 2025, Cell Reports Sustainability)

   Plail, Melissa (Ed.)

   Marine heatwaves are increasing in intensity and frequency, causing worldwide coral bleaching, reductions in coral cover, and shifts in species composition. Recent studies have found, however, that inshore turbid reefs are more resistant to heat stress than offshore clear-water reefs. Inshore turbid reefs, therefore, may play a critical role as climate-change refuges for contemporary coral reefs subjected to marine heatwaves. This perspective explores the importance of inshore reefs in the past, present, and future. Paleo records show that inshore reefs were also crucial as refuges during historically warm periods. Yet, contemporary inshore reefs are especially vulnerable to pollution and land-use-change runoff, which were absent in paleo times. Therefore, inshore reefs need strategic management and protection to maintain their role as climate-change refugia as the oceans continue to warm. 

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2. A global database on coral recovery following marine heatwaves

   https://doi.org/10.1038/s41597-024-03221-3  

   van Woesik, Robert; Kratochwill, Chelsey (April 2024, Scientific Data)

   Abstract Coral reefs support the world’s most diverse marine ecosystem and provide invaluable goods and services for millions of people worldwide. They are however experiencing frequent and intensive marine heatwaves that are causing coral bleaching and mortality. Coarse-grained climate models predict that few coral reefs will survive the 3 °C sea-surface temperature rise in the coming century. Yet, field studies show localized pockets of coral survival and recovery even under high-temperature conditions. Quantifying recovery from marine heatwaves is central to making accurate predictions of coral-reef trajectories into the near future. Here we introduce the world’s most comprehensive database on coral recovery following marine heatwaves and other disturbances, called Heatwaves and Coral-Recovery Database (HeatCRD) encompassing 29,205 data records spanning 44 years from 12,266 sites, 83 countries, and 160 data sources. These data provide essential information to coral-reef scientists and managers to best guide coral-reef conservation efforts at both local and regional scales. 

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3. Early life stage bottleneck determines rates of coral recovery following severe disturbance

   https://doi.org/10.1002/ecy.4510  

   Speare, Kelly E; Enright, Lauren N; Aplin, Allison; Adam, Thomas C; Edmunds, Peter J; Burkepile, Deron E (January 2025, Ecology)

   Abstract Understanding how foundation species recover from disturbances is key for predicting the future of ecosystems in the Anthropocene. Coral reefs are dynamic ecosystems that can undergo rapid declines in coral abundance following disturbances. Understanding why some reefs recover quickly from these disturbances whereas others recover slowly (or not at all) gives insight into the drivers of community resilience. From 2006 to 2010 coral reefs on the fore reef of Moorea, French Polynesia, experienced severe disturbances that reduced coral cover from ~46% in 2005 to <1% in 2010. Following these disturbances, coral cover increased from 2010 to 2018. Although there was a rapid and widespread recovery of corals, reefs at 17 m depth recovered more slowly than reefs at 10 m depth. We investigated the drivers of different rates of coral recovery between depths from 2010 to 2018 using a combination of time‐series data on coral recruitment, density, growth, and mortality in addition to field experiments testing for the effects of predation. Propagule abundance did not influence recovery, as the density of coral recruits (spat <6 months old) did not differ between depths. However, mortality of juvenile corals (≤5 cm diameter) was higher at 17 m, leading to densities of juvenile corals 3.5 times higher at 10 m than at 17 m depth. Yet, there were no differences in the growth of corals between depths. These results point to an early life stage bottleneck after settlement, resulting in greater mortality at 17 m than at 10 m as the likely driver of differential coral recovery between depths. We used experiments and time‐series data to test mechanisms that could drive different rates of juvenile coral mortality across depths, including differences in predation, competition, and the availability of suitable substratum. The results of these experiments suggested that increased coral mortality at 17 m may have been influenced by higher intensity of fish predation, and higher mortality of corals attached to unfavorable substratum. In contrast, the abundance of macroalgae, a coral competitor, did not explain differences in coral survival. Our work suggests that top‐down processes and substratum quality can create bottlenecks in corals that can drive rates of coral recovery after disturbance. 

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4. Geographical patterns of intraspecific genetic diversity reflect the adaptive potential of the coral Pocillopora damicornis species complex

   https://doi.org/10.1371/journal.pone.0316380  

   Carr, M; Kratochwill, C; Daly-Engel, T; Crombie, T; van_Woesik, R (January 2025, PLOS ONE)

   Tavakoli-Kolour, Parviz (Ed.)

   Marine heatwaves are increasing in intensity and frequency however, responses and survival of reef corals vary geographically. Geographical differences in thermal tolerance may be in part a consequence of intraspecific diversity, where high-diversity localities are more likely to support heat-tolerant alleles that promote survival through thermal stress. Here, we assessed geographical patterns of intraspecific genetic diversity in the ubiquitous coralPocillopora damicornisspecies complex using 428 sequences of the Internal Transcribed Spacer 2 (ITS2) region across 44 sites in the Pacific and Indian Oceans. We focused on detecting genetic diversity hotspots, wherein some individuals are likely to possess gene variants that tolerate marine heatwaves. A deep-learning, multi-layer neural-network model showed that geographical location played a major role in intraspecific diversity, with mean sea-surface temperature and oceanic regions being the most influential predictor variables differentiating diversity. The highest estimate of intraspecific variation was recorded in French Polynesia and Southeast Asia. The corals on these reefs are more likely than corals elsewhere to harbor alleles with adaptive potential to survive climate change, so managers should prioritize high-diversity regions when forming conservation goals. 

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5. Coral reef resilience to thermal stress in the Eastern Tropical Pacific

   https://doi.org/10.1111/gcb.15126  

   Romero‐Torres, Mauricio; Acosta, Alberto; Palacio‐Castro, Ana M; Treml, Eric A; Zapata, Fernando A; Paz‐García, David A; Porter, James W (July 2020, Global Change Biology)

   Abstract Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios. 

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