Corals in Fluctuating Coastal Bays Exhibit Enhanced Climate Resilience

Corals inhabiting coastal bays with significant fluctuations in temperature and environmental conditions exhibit enhanced resilience to heat stress compared to their counterparts in more stable reef environments. This finding emerges from research conducted by marine biologist Sarah Solomon, who will defend her PhD thesis at the University of Amsterdam on February 19.

Coral reefs, covering less than 0.1% of the ocean's surface, provide habitat for approximately 32% of all known marine species. Despite their ecological importance, these reefs are experiencing rapid decline due to climate change and local human activities, such as pollution and nutrient runoff. Solomon notes that increasing ocean temperatures and more frequent marine heatwaves are leading to widespread coral bleaching and mass mortality events.

To investigate coral adaptation to stressful conditions, Solomon studied corals in Curaçao's coastal bays, characterized by warmer waters and greater daily fluctuations in temperature, pH, and oxygen levels, compared to adjacent stable fringing reefs. She observed that corals in these extreme environments have developed flexible nutritional strategies, often associating with heat-tolerant algae and hosting microbial communities that may enhance their stress resistance. These corals adjust their feeding methods in response to changing conditions, such as seasonal variations.

Solomon's experiments involved transplanting corals between bays and reefs and exposing them to heat stress. She found that reef-originating corals could acclimate to harsher bay conditions, maintaining survival and growth, albeit with increased energy expenditure and a decline in overall health. Conversely, bay-native corals, specialized for their environment, exhibited reduced growth when moved to more stable reef settings. Additionally, bay corals demonstrated natural heat resistance, while some reef species increased their heat tolerance after exposure to extreme bay conditions. Solomon notes that certain species can enhance their heat tolerance within a year, though this capacity varies among species and has clear limitations.

Solomon concludes that extreme environments offer valuable insights into coral resilience and adaptive capacity. She suggests that naturally climate-change-resistant corals could support restoration initiatives aimed at bolstering reef resilience. Furthermore, certain coastal bays might serve as nurseries where corals are conditioned to withstand higher temperatures before being used in the restoration of degraded reefs. However, she emphasizes that even the most stress-resistant corals have their limits, and without addressing climate change and pollution, they too will eventually decline.