A recent article in the journal Nature reports that "Coral Sea heat extremes in 2024, 2017 and 2020 (in order of descending mean SST anomalies) were the warmest in 400 years..," causing "mass coral bleachings." These extreme temperatures pose an "existential threat" to the Great Barrier Reef. The findings are based on a reconstruction of temperatures back to 1618.
The article poses the following long term implications of increasing ocean temperatures:
Coral reefs of the future, if they can persist, are likely to have a different community structure to those in the recent past, probably one with much less diversity in coral species. This is because mass bleaching events have a differential impact on different coral species. For example, fast-growing branching and tabulate corals are affected more than slower-growing massive species because they have different thermal tolerance. The simplification of reef structures will have adverse impacts on the many thousands of species that rely on the complex three-dimensional structure of reefs. Therefore, even with an ambitious long-term international mitigation goal, the ecological function of the GBR is likely to deteriorate further before it stabilizes.
Reference
Henley, B. J., McGregor, H. V., King, A. D., Hoegh-Guldberg, O., Arzey, A. K., Karoly, D. J., ... & Linsley, B. K. (2024). Highest ocean heat in four centuries places Great Barrier Reef in danger. Nature, 632(8024), 320-326.