Four coral species were tracked across 10 different temperatures in the National Sea Simulator—a technically challenging feat. Credit: Juan Ortiz
In a study published recently in the Proceedings of the Royal Society B, scientists at the Australian Institute of Marine Science (AIMS) have found that some fast-growing coral species on the Great Barrier Reef slow down their growth rates when exposed to warm water. The study is the first to take such a deep dive into quantifying the relationship between coral growth and temperature.
The growth of four coral species from one reef on the central Great Barrier Reef were tracked over a month across 10 different temperatures between 19°C and 31°C in AIMS’ National Sea Simulator. Examined for the study Acropora hyacinthus, Acropora tenuis, Pocillopora verrucosa and Stylophora pistillata are fast growing coral species which are common on the Great Barrier Reef, providing essential shelter for other marine life. They are also some of the most susceptible to marine heat waves though, and can bleach easily or break during storms. The study shows that corals such species are likely to experience a double whammy with high mortality during acute heat stress events and significant reductions in growth due to an increasingly warming ocean.
Recent surveys for AIMS’ Long Term Monitoring Program found that increases in hard coral cover in northern and central regions were largely driven by these species. “Our results demonstrate that these fast-growing table corals, critical for reef recovery, have evolved strategies that are perfect to maximize growth in their current environment,” said Dr. Juan Ortiz, senior author of the study. “But these initial findings may indicate that they have limited potential for adaptation to future hotter conditions. Low variability in their response to temperature could make it harder for corals to naturally evolve higher thermal tolerance. This was a technically challenging and ambitious study made possible by the unique facilities and controlled environment of the National Sea Simulator. We are looking forward to expanding our initial investigations across more coral species from different parts of the Reef later this year,” continued Dr. Ortiz.
Of particular interest to reef-keepers, the study also notes optimum growth temperatures for each of the species. Acropora hyacinthus grew fastest at 27.4C while the figure for Acropora tenuis was 28.2, Pocillopora verrucosa 29.5 and Stylophora pistillata 28.5. The report also covers key aspects such as lighting, flow and feeding.
More information: Mariana Álvarez-Noriega et al, Highly conserved thermal performance strategies may limit adaptive potential in corals, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2022.1703