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How environmental conditions influence microalgae and coral communities
The tree rings of the sea: An international research team led by marine biologist Prof. Dr. Maren Ziegler from Justus Liebig University Giessen (JU) has developed an innovative method for reconstructing the past of corals and their symbiosis with algae by drilling into coral skeletons. The results, published in Global Change Biology, offer new insights into changes in symbiotic single-celled algae species that are crucial to the survival of coral reefs.
Symbiodiniaceae and coral reefs
Coral reefs are among the most species-rich and ecologically important ecosystems in the world. Their health depends on the symbiosis between stony corals and single-celled algae species known as Symbiodiniaceae. This symbiosis enables the calcification processes that build the reef structure. However, this symbiosis is also susceptible to heat stress, which can lead to coral bleaching. In this phenomenon, the coral loses its symbionts, jeopardising its food supply and growth.
New method for reconstructing historical Symbiodiniaceae communities
The researchers used drill cores from coral skeletons in Palau and Papua New Guinea to reconstruct the dynamics of Symbiodiniaceae communities over the last 110 years. ‘Our method allows us to analyse Symbiodiniaceae communities in coral skeletons, providing unique insights into the history of this symbiotic partnership,’ explains study leader Prof. Ziegler. The drill cores were collected during the international Tara Pacific Expedition to the coral reefs in the Pacific and subsequently analysed.
The study shows that the reconstructed Symbiodiniaceae communities vary significantly between different species and locations. Particularly striking are the dynamics in the samples from Palau, where historical heat stress events are associated with changes in the algal communities. ‘Our results suggest that coral skeleton reconstructions not only provide clues about past environmental conditions, but can also reveal how Symbiodiniaceae adapt over time,’ says Prof. Ziegler.
Significance for future research
The new method opens up numerous possibilities for researching the history and dynamics of coral reefs – similar to tree rings on land. ‘By combining the data, we can see clear correlations between changes in Symbiodiniaceaen and past environmental conditions,’ explains the researcher.
The information can improve predictions about the condition and health of coral reefs – for example, under climate change conditions. The team will continue to conduct research in this area in the future.
Prof. Dr. Maren Ziegler Marine, Marine Holobiomics Lab
Telephone: 0641 99-35727
Email: Maren.Ziegler@bio.uni-giessen.de
Jose F. Grillo, Vanessa Tirpitz, Jessica Reichert, Marine Canesi, Stéphanie Reynaud, Eric Douville, Maren Ziegler: Coral Skeletal Cores as Windows Into Past Symbiodiniaceae Community Dynamics, Global Change Biology, 07 November 2025
https://doi.org/10.1111/gcb.70575
https://fondationtaraocean.org/en/expedition/tara-pacific/ - Information about the Tara Pacific Expedition
Insights into the past of the coral reef: The brown-coloured tissue is visible at the tip of the cor ...
Source: Jessica Reichert
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