4 PM – “Meet the Scientist” with Laura Lehnhoff
The event series “On Water… from the Sea” kicks off with marine biologist Laura Lehnhoff from Freie Universität Berlin as part of the popular “Meet the Scientist” format. Her research focuses on the calcium carbonate skeletons of tropical stony corals, which build vast reefs over generations and provide habitats for countless marine animals. In her presentation, she explores how these natural archives of ocean history offer insights into past environmental conditions and what they can tell us about the future of coral reefs in a changing climate.
Ahead of the event, we spoke with Laura Lehnhoff about her research, the complex relationships between corals and seawater, and the stories their skeletons tell about life in the ocean.
In Conversation with Laura Lehnhoff
I. Coral reefs are among the most biodiverse ecosystems on Earth, built by tiny coral polyps. What fascinates you personally about these organisms, and what led you to study them scientifically?
I have always been interested in everything related to water—from marine and freshwater organisms to the geology, chemistry, and physics behind it all. Alongside marine biology, I also took courses in geosciences during my studies, where I discovered a field of geochemistry that focuses on the calcium carbonate structures of shellfish, fish, and corals. Through a student research position and my thesis, I eventually found my way into the geochemistry of coral skeletons. What fascinates me is that these animals build enormous reefs while preserving traces of their lives and their environment in their skeletons.
II. What can coral skeletons reveal about a coral’s life history and the history of the seawater surrounding it? And how can scientists extract this information from the skeletons?
Coral skeletons are archives: As they form, the conditions in which the corals live leave traces in their structure and chemical composition. X-ray images reveal annual density bands, similar to the growth rings of a tree. Chemical analyses can provide insights into past water temperatures and other environmental conditions during the formation of the calcium carbonate skeleton. Together, this information can reveal when and how a coral grew and whether environmental changes affected the formation of its skeleton.
III. Corals are constantly interacting with the water around them. How do changes in water conditions affect the corals?
Changes in temperature, light, salinity, or nutrient availability can affect the metabolism and growth of corals. Prolonged heat or other forms of stress can disrupt their symbiotic relationship with tiny single-celled organisms that live in their tissues and provide them with energy. When corals lose these organisms, their white skeletons become visible through their tissues: the corals bleach. If the stress subsides, the symbiotic relationship can be restored, allowing the corals to recover. If the stress persists, the corals may die. Ocean acidification can also make it more difficult for corals to build their calcium carbonate skeletons.
IV. Rising water temperatures and ocean acidification are threatening coral reefs worldwide. What can your research tell us about their ability to adapt and their future? And what would their continued decline mean for marine ecosystems?
I investigate what traces repeated heat stress leaves in coral skeletons. By comparing bleached and unbleached corals, I aim to identify signals and clues that might explain differences in their resilience. This can help us better understand their current resilience. To assess their long-term capacity to adapt, we could also look for these signals in older and fossil corals that were exposed to heat stress. If coral reefs were lost, countless animals would lose their sources of food, shelter, and nursery habitats. For us humans, too, essential resources for fisheries, livelihoods, and coastal protection are at stake.
