Thermal stress and bleaching in reefs: Are giant clams more resilient than corals to a warming ocean?
Giant clams (Tridacninae) and corals both rely on a symbiotic relationship with zooxanthellae—photosynthetic algae that provide essential nutrients. However, rising sea temperatures pose significant challenges to these relationships, leading to a phenomenon known as bleaching. While both giant clams and corals experience bleaching under thermal stress, recent studies suggest that the zooxanthellae within giant clams may exhibit a degree of resilience to higher temperatures, offering insights into reef survival in a warming world.
Image Credits: https://www.iflscience.com/to-make-a-better-solar-cell-consult-a-giant-clam-74921
Thermal stress and bleaching in corals
Giant clams also maintain symbiotic relationships with zooxanthellae and are susceptible to bleaching under thermal stress. However, some research indicates that the zooxanthellae in giant clams might possess a higher tolerance to temperature increases compared to those in corals (Brahmi et al., 2021). This resilience could be attributed to differences in the species of zooxanthellae hosted or variations in the microenvironments within the host organisms. The IMARCS Foundation is currently conducting research into the differing zooxanthellae attributes of giant clams and corals to see if there could be opportunities to reduce thermal stress and improve overall reef health.
Implications for reef ecosystems:
The potential thermal resilience of giant clam zooxanthellae has significant implications for reef ecosystems facing climate change. Giant clams already contribute to reef health by filtering water, providing habitat structures, and participating in nutrient cycling, and their ability to maintain symbiosis under elevated temperatures may help sustain these essential functions even as other reef organisms suffer from bleaching (Hong, 2015). Furthermore, giant clams may provide clues as to what allows for better resilience to bleaching for corals in warming reef environments.
Image Credits: https://newatlas.com/giant-clams-color-displays-solar-cells/41394/
Future research directions
While both giant clams and corals are vulnerable to the adverse effects of rising sea temperatures, the zooxanthellae within giant clams may offer a glimmer of hope. Their potential resilience to thermal stress underscores the importance of protecting giant clams as vital components of reef ecosystems and as subjects of study in the quest to understand and mitigate the impacts of climate change on marine life.
Understanding the mechanisms behind the thermal tolerance of giant clam zooxanthellae is crucial. Further studies are needed to explore the genetic and physiological factors contributing to this resilience. Such insights could inform conservation strategies and potentially lead to interventions that enhance the thermal tolerance of other reef organisms, thereby bolstering reef resilience in a warming world. This is why the IMARCS Foundation is focusing on these issues - and in the process has already become a world leader in pioneering novel research into improving reef health, reef biodiversity, and carbon sequestration in reef environments.
If you are interested in supporting the IMARCS Foundation's mission please reach out to us at relationships@imarcs.org
References
Featured Image Credits: https://www.iflscience.com/to-make-a-better-solar-cell-consult-a-giant-clam-74921
Berkelmans, R., & van Oppen, M. J. H. (2006). The role of zooxanthellae in the thermal tolerance of corals: A ‘nugget of hope’ for coral reefs in an era of climate change. Proceedings of the Royal Society B: Biological Sciences, 273(1599), 2305–2312. https://doi.org/10.1098/rspb.2006.3567
Brahmi, C., Chapron, L., Le Moullac, G., Soyez, C., Beliaeff, B., Lazareth, C. E., Gaertner-Mazouni, N., & Vidal-Dupiol, J. (2021). Effects of elevated temperature and pCO2 on the respiration, biomineralization and photophysiology of the giant clam Tridacna maxima. Conservation Physiology, 9(1), coab041. https://doi.org/10.1093/conphys/coab041
Hoey, A. S., Howells, E., Johansen, J. L., Hobbs, J. P. A., Messmer, V., McCowan, D. M., Wilson, S. K., & Pratchett, M. S. (2016). Recent advances in understanding the effects of climate change on coral reefs. Diversity, 8(2), Article 12. https://doi.org/10.3390/d8020012
Hong, J. (2015). Giant clam = giant impact: Study compiles how mega-clams impact seas. Mongabay. Retrieved from https://news.mongabay.com
Featured Image Credits: https://www.iflscience.com/to-make-a-better-solar-cell-consult-a-giant-clam-74921
Berkelmans, R., & van Oppen, M. J. H. (2006). The role of zooxanthellae in the thermal tolerance of corals: A ‘nugget of hope’ for coral reefs in an era of climate change. Proceedings of the Royal Society B: Biological Sciences, 273(1599), 2305–2312. https://doi.org/10.1098/rspb.2006.3567
Brahmi, C., Chapron, L., Le Moullac, G., Soyez, C., Beliaeff, B., Lazareth, C. E., Gaertner-Mazouni, N., & Vidal-Dupiol, J. (2021). Effects of elevated temperature and pCO2 on the respiration, biomineralization and photophysiology of the giant clam Tridacna maxima. Conservation Physiology, 9(1), coab041. https://doi.org/10.1093/conphys/coab041
Hoey, A. S., Howells, E., Johansen, J. L., Hobbs, J. P. A., Messmer, V., McCowan, D. M., Wilson, S. K., & Pratchett, M. S. (2016). Recent advances in understanding the effects of climate change on coral reefs. Diversity, 8(2), Article 12. https://doi.org/10.3390/d8020012
Hong, J. (2015). Giant clam = giant impact: Study compiles how mega-clams impact seas. Mongabay. Retrieved from https://news.mongabay.com