Coral Larvae Adapt to Acidic and Warmer Seas

Jenn Hoskins
11th March, 2024

Coral Larvae Adapt to Acidic and Warmer Seas

Image Source: Natural Science News, 2024

Key Findings

  • Study in China shows how coral larvae genes react to warmer, more acidic oceans
  • Coral larvae exposed to stress changed gene expression, hinting at survival strategies
  • Findings help predict coral resilience to climate change, aiding conservation efforts
Coral reefs are among the most biodiverse and ecologically important ecosystems on our planet. They are built by reef-building corals that have a special relationship, known as endosymbiosis, with tiny algae called Symbiodiniaceae. These algae live inside the coral's cells and provide them with energy through photosynthesis, while the coral provides a protected environment and access to sunlight. However, this delicate partnership is under threat from rising ocean temperatures and acidification due to climate change. Understanding how these stressors affect corals at different life stages is crucial for predicting the future of coral reefs. While much research has focused on adult coral colonies, the early life stages, such as larvae, have been less studied. Larvae are responsible for dispersing and establishing new coral populations, making their survival and health critical for reef resilience and recovery. In a recent study by the Chinese Academy of Sciences[1], scientists have taken a significant step towards understanding how coral larvae respond to the double threat of ocean acidification and elevated temperatures. They created a gene expression dataset from larvae of the coral Pocillopora damicornis, a common reef-building species, exposed to various stress conditions. The study reveals how these stressors affect the larvae at the genetic level, which can lead to a better understanding of the potential impacts on coral symbiosis and survival. The research involved exposing coral larvae to four different treatments: a control group with current ocean conditions, a group with increased levels of carbon dioxide (high pCO2), a group with higher temperatures, and a group with both high pCO2 and elevated temperatures. After five days, the researchers analyzed changes in gene expression across 16 samples, each containing 30 larvae. This study builds on previous research that has shown how adult corals manage their symbiotic algae. For instance, a study[2] found that cnidarians, the animal group that includes corals, control their algae population through a carbon-nitrogen feedback loop. When corals take in more carbon from their algae, they can assimilate more nitrogen waste, which in turn regulates the algae's growth. Moreover, the larvae's response to warming and acidification has been previously explored[3]. Heat stress was found to cause bleaching and reduce the larvae's ability to settle and form new colonies, while high pCO2 seemed to stimulate photosynthesis in the algae. This suggests that the larvae's ability to find and adapt to suitable habitats could be compromised under future ocean conditions. Another study[4] indicated that heat stress could lead to a breakdown in nutrient cycling between the coral and its algae. This disruption could eventually lead to the coral expelling its symbiotic algae, a process known as bleaching, which is often fatal for the coral. The gene expression dataset from the Chinese Academy of Sciences adds to this body of knowledge by providing a detailed look at how coral larvae genes react to stress before bleaching occurs. By comparing the larvae's gene expression under normal and stress conditions, researchers can identify which genes are involved in maintaining the symbiosis and which are responsive to environmental changes. Such transcriptomic resources are invaluable for future research, as they can help scientists unravel the complex genetic networks that control coral-algal symbiosis. They can also identify potential genetic markers of stress tolerance, which could be used to predict and perhaps enhance the resilience of coral populations. The findings from this study and previous research[2][3][4] collectively suggest that the future of coral reefs hinges on understanding and mitigating the impacts of climate change on every stage of coral life. By continuing to study how corals and their symbiotic algae interact at the genetic level, scientists are piecing together the puzzle of how these organisms can survive in a rapidly changing ocean. This knowledge is essential for developing strategies to conserve and restore coral reefs, which are vital to the health of our oceans and the planet.

EnvironmentGeneticsMarine Biology

References

Main Study

1) Gene expression of Pocillopora damicornis coral larvae in response to acidification and ocean warming.

Published 8th March, 2024

https://doi.org/10.1186/s12863-024-01211-3

Related Studies

2) A carbon-nitrogen negative feedback loop underlies the repeated evolution of cnidarian-Symbiodiniaceae symbioses.

https://doi.org/10.1038/s41467-023-42582-y

3) Ocean acidification elicits differential bleaching and gene expression patterns in larval reef coral Pocillopora damicornis under heat stress.

https://doi.org/10.1016/j.scitotenv.2022.156851

4) Heat stress destabilizes symbiotic nutrient cycling in corals.

https://doi.org/10.1073/pnas.2022653118


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