Climate change impacts on host-microbe interactions in North Pacific kelp forests

Nora Salland^1,2, Colleen Kellogg^1,2, Matthew Lemay^1,3, Margot Hessing-Lewis^1,2, Laura Wegener Parfrey^1,2

¹Hakai Institute (Tula Foundation), Canada - ²University of British Columbia, Canada - ³Dalhousie University, Canada

Changing environmental conditions and extreme events, such as rising temperatures and marine heatwaves, are impacting habitat-forming kelps and their associated species. In the Northeast Pacific Ocean, the declines in kelp forests are related to anthropogenic climate change, with cascading effects on broader ecological processes and ecosystem services. Climate change influences not only seaweed growth, development, persistence, and overall health, but also impacts the associated microbial communities, including bacterial symbionts and opportunistic pathogens. To investigate the role of kelp-associated microbes in kelp resilience to climate stressors, we are combining field surveys of kelp populations along the southern B.C. coast (Salish Sea and beyond) with laboratory-based experiments. We are linking the interactions between kelp hosts and their associated microbial communities (i.e., the holobiont), with a focus on their diversity and functional roles. We predict that the kelp physiology and the kelp microbiome will change in response to climate stressors (such as temperature rise), and aim to test whether changes in the microbiome exacerbate stress or promote kelp resilience. Monitoring efforts that build a baseline understanding of the variation in the kelp microbiome coupled with experimental approaches to determine whether microbiome changes causally influence kelp responses to climate stressors are essential for identifying consequences of climate change on holobionts. These results may inform policy and management strategies aimed at protecting coastal marine habitats and guiding restoration efforts.