Understanding Microbial Host-Symbiont Interactions in Coastal Ecosystems amid Climate Change

Coastal ecosystems, including seagrass meadows and salt marshes, are vital blue carbon sinks and biodiversity hotspots. However, these ecosystems are increasingly threatened by climate change, habitat destruction, and invasive species. This presentation highlights the research of our group on microbial host-symbiont interactions, focusing on sulfur-oxidizing bacteria and their association with key coastal ecosystem components: Lucinid clams, seagrass, and the salt marsh plant Spartina. These interactions are explored through the lens of climate change, addressing two core objectives.

The first objective examines the role of microbial symbiosis in supporting ecosystem health and functioning, particularly in seagrass meadows. Seagrasses, recognized for their carbon sequestration capacity, face challenges from sulfide toxicity around their roots, exacerbated by warming oceans. Sulfur-oxidizing bacteria detoxify their environment by using these ‘toxic’ sulfide compounds for their metabolism. They transform these components into nutrients that they share with their bivalve and possibly also plant hosts. Therefore they play a critical role in mitigating toxic sulfide build-up often found in coastal ecosystems. In collaboration with Lucinid clams, sulfur-oxidizing bacteria from the group Candidatus Thiodiazotropha contribute to maintaining seagrass health and productivity. We aim to understand how microbial interactions underpin the resilience of seagrass ecosystems, emphasizing their significance as natural carbon sinks.

The second objective focuses on the ecological disruptions caused by Spartina, a genus of salt marsh grasses. Native to the eastern United States, species such as Spartina alterniflora have become invasive in Europe, and elsewhere, displacing native flora and altering coastal habitats. We aim to test the hypothesis that Spartina’s success in colonizing harsh environments is partly due to its association with sulfur-oxidizing bacteria like Candidatus Thiodiazotropha. Our group will investigate to see if these microbes could enable Spartina to thrive in saline, sulfide-rich conditions by detoxifying the environment and potentially providing nitrogen. Invasive Spartina poses a dual threat by damaging native ecosystems and amplifying vulnerabilities to climate change.

Through these two lenses, our work underscores the intricate relationships between microbial symbionts and their hosts, revealing how these interactions influence ecosystem stability and resilience. We highlight how global changes, including warming climates and altered species distributions via trade and dispersal, could shift microbial functions and distributions, with profound implications for coastal ecosystem health and carbon dynamics. Understanding these processes is essential to inform conservation and management strategies for endangered coastal habitats. By communicating this research in an educational framework, we aim to bridge scientific discovery and public awareness. We invite interdisciplinary dialogue to advance our understanding of microbial symbiosis in coastal ecosystems and explore strategies for mitigating climate change impacts on these critical environments.