Circulating microbiome DNA in Southern Ocean seabirds: A novel tool for disease surveillance in polar ecosystems

Abstract

Marine ecosystems, particularly in polar regions, are undergoing rapid transformations due to climate change, influencing host-pathogen dynamics in wildlife populations. Seabirds, which form spatially structured social networks, serve as potential sentinels for pathogen surveillance, yet the composition and variability of their blood microbiome remain largely unexplored. The concept of a circulating blood microbiome is relatively new and debated as blood has traditionally been considered sterile. However, emerging evidence suggests that circulating microbial DNA (cmDNA) represents a transient microbial signature, potentially offering insights into host health, dysbiosis, and disease risks. In this study, we aimed to evaluate the feasibility and relevance of circulating microbial DNA (cmDNA) as a tool for pathogen surveillance in wild seabird populations. We identified inter-annual variability, sex-related, and age-related variability in blood microbiome composition, with core microbial signatures differing across sites and time periods. We also observed sex-biased microbial prevalence and age-related microbiome maturation, with dynamic shifts in diversity across chick developmental stages. Finally, we detected several potential pathogens, providing new insights into their distribution, prevalence, and potential implications for seabird health. These findings highlight the value of cmDNA analysis as an effective approach for wildlife disease surveillance and pathogen monitoring in polar ecosystems, contributing to broader efforts in marine conservation and biosecurity in the face of climate change-driven environmental shifts.