A recent study reveals that coral larvae lower their metabolic rate and enhance nitrogen absorption to cope with bleaching at elevated temperatures. This research, led by Ariana S. Huffmyer from the University of Washington and published on November 12 in the open-access journal PLOS Biology, sheds light on this vital process.
Coral bleaching, triggered by rising ocean temperatures, disrupts the essential relationship between corals and their symbiotic algae. As global temperatures continue to rise, the threat of bleaching has become more pressing, yet there is limited research focusing on how high temperatures affect corals in their early life stages.
In the study, Huffmyer and her team exposed coral larvae to elevated temperatures at the Hawai’i Institute of Marine Biology. For three days during their initial development week, the larvae and their algal partners were subjected to temperatures 2.5 degrees Celsius higher than the normal seawater temperature, mimicking anticipated climate-related changes. Remarkably, the coral larvae did not exhibit any signs of bleaching in these warmer conditions. They successfully maintained photosynthesis in the algae and continued receiving carbon-based nutrients from them. Nevertheless, there was a notable 19% drop in the coral’s metabolic rate alongside an increased intake and storage of nitrogen, suggesting strategies aimed at enhancing their survival.
The lowered metabolic activity allows the corals to save energy and resources, a phenomenon also observed in adult corals during bleaching events. This shift in nitrogen cycling likely functions as an adaptation, whereby the coral limits nitrogen availability to the algae, helping to prevent their overgrowth and the consequent destabilization of the symbiotic relationship.
However, it is still uncertain how effective these strategies will be under more extreme temperatures and prolonged exposure. Ongoing research into how corals respond to high temperatures is essential for understanding and safeguarding coral reefs as global warming persists.
The authors conclude, “This study highlights the necessity for coral larvae to invest in their nutritional relationship with algae to endure stress, providing valuable insights into ways to prevent bleaching during the crucial early stages of coral development.”
