An official website of the United States government
Abstract Coral reefs are increasingly exposed to elevated temperatures that can cause coral bleaching and high levels of mortality of corals and associated organisms. The temperature threshold for coral bleaching depends on the acclimation and adaptation of corals to the local maximum temperature regime. However, because of larval dispersal, coral populations can receive larvae from corals that are adapted to very different temperature regimes. We combine an offline particle tracking routine with output from a high‐resolution physical oceanographic model to investigate whether connectivity of coral larvae between reefs of different thermal regimes could alter the thermal stress threshold of corals. Our results suggest that larval transport between reefs of widely varying temperatures is likely in the Coral Triangle and that accounting for this connectivity may be important in bleaching predictions. This has important implications in conservation planning, because connectivity may allow some reefs to have an inherited heat tolerance that is higher or lower than predicted based on local conditions alone.
more »
« less
Predicting coral metapopulation decline in a changing thermal environment
Abstract Thermal stress is expected to compromise the persistence of tropical corals throughout their biogeographic ranges, making many reefs inhospitable to corals by the end of the century. We integrated models of local predictions of thermal stress throughout the coming century, coral larval dispersal, and the persistence of a coral’s metapopulation(s) in the Caribbean to investigate broad trends in metapopulation fragmentation and decline. As coral reef patches become inhospitable throughout the next century, the metapopulation of Orbicella annularis is predicted to fragment, with sub-networks centered around highly connected patches and thermal refuges. Some of these are predicted to include the reefs of Colombia, Panama, Honduras, Guatemala, Belize, Southern and Northern Cuba, Haiti, and the Bahamas. Unknown coral population demographic parameters, such as lifetime egg production and stock-recruitment rates, limit the model’s predictions; however, a sensitivity analysis demonstrates that broadscale patterns of fragmentation and metapopulation collapse before the end of the century are consistent across a range of potential parameterizations. Despite dire predictions, the model highlights the potential value in protecting and restoring coral populations at strategic locations that are highly connected and/or influential to persistence. Coordinated conservation activities that support local resilience at low coral cover have the potential to stave off metapopulation collapse for decades, buying valuable time. Thermal refuges are linchpins of metapopulation persistence during moderate thermal stress, and targeted conservation or restoration that supports connectivity between these refuges by enhancing local population growth or sexual propagation may be critically important to species conservation on coral reefs.
more »
« less
- Award ID(s):
- 1946412
- PAR ID:
- 10327494
- Date Published:
- Journal Name:
- Coral Reefs
- ISSN:
- 0722-4028
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The potential of reef‐building corals to adapt to increasing sea‐surface temperatures is often debated but has rarely been comprehensively modeled on a region‐wide scale. We used individual‐based simulations to model adaptation to warming in a coral metapopulation comprising 680 reefs and representing the whole of the Central Indo‐West Pacific. Encouragingly, some reefs—most notably Vietnam, Japan, Taiwan, New Caledonia and the southern half of the Great Barrier Reef—exhibited high capacity for adaptation and, in our model, maintained coral cover even under a rapid “business‐as‐usual” warming scenario throughout the modeled period (200 years). Higher resilience of these reefs was observed under all tested parameter settings except the models prohibiting selection and/or migration during warming. At the same time, the majority of reefs in the region tended to collapse within the first 100 years of warming. The adaptive potential (odds of maintaining high coral cover) of a given reef could be predicted based on two metrics: the reef's present‐day temperature, and the proportion of recruits immigrating from warmer locations. The latter metric explains the most variation in adaptive potential, and significantly correlates with actual coral cover changes observed throughout the region between the 1970s and the early 2000s. These findings will help prioritize coral conservation efforts and plan assisted gene flow interventions to boost the adaptive potential of specific coral populations.more » « less
-
Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014–2017 global coral bleach- ing event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse.more » « less
-
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.more » « less
-
Abstract Consumers can play critical roles in ecosystem resilience by modifying community resistance and recovery rates. In coral reefs, grazers can increase reef resilience by controlling algae and maintaining open space for coral recruitment, but can also erode the reef framework critical for coral recovery. Here we examine the context‐dependent effects of herbivores on reef persistence in Caribbean Panamá. Using a series of lab and field experiments, we found that the erosional effects of the herbivorous reef urchin (Echinometra viridis) were 2 orders of magnitude greater on dead corals than live corals, and surveys across multiple similarly overfished reefs revealed a positive relationship between urchin densities and percent cover of bare dead coral with urchin densities exceeding 150 m−2in some reefs. However, we observed that a mat‐forming zoanthid (Zoanthus pulchellus), found exclusively on dead corals, had an inverse spatial relationship with urchins. Through a series of field experiments, we found that zoanthid overgrowth repelled urchins, increased dead coral persistence, and decreased erosion of dead corals making up the reef framework by more than 50% over a 22‐month period. Our findings reveal that zoanthids can provide associational refuge to dead corals by enhancing their persistence under high urchin grazing pressure. We suggest that secondary space‐holders, such as zoanthids, may play increasingly important functional roles in degraded reef systems by shielding coral skeletons from external bioeroders. Moreover, the Stress Gradient Hypothesis, which predicts that the importance of positive interactions such as associational refuges increases with consumer pressure, extends to dead foundation species such as coral skeletons crucial for ecosystem recovery.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s00338-022-02252-9
