Monitoring seagrass meadow health using coastal bird fecal fatty acid biomarkers

Lipids have the potential to trace trophic interactions through an ecosystem, but their use has been largely limited to predator/prey-scale studies. Carnivore fecal lipids offer an unexplored way to strategically monitor the health and spatial distribution of ecosystems that are difficult to access. This hypothesis is explored here in seagrass meadows, which are a globally significant long-term carbon storage reservoir. This study tested the hypothesis that lipids can be used to passively monitor seagrass meadow health by tracing fatty acids transferred up the food chain and onto nearby beaches via coastal bird stool. By comparing the lipids produced by seagrasses and those made by diverse microbial eukaryotes, such as diatoms and dinoflagellates, our analysis could distinguish between healthy and collapsed meadows in a pilot dataset. A metabolite that is produced by the seagrass wasting disease pathogen was also recovered in our data, providing a potential diagnostic for seagrass health. The advantages to this non-invasive monitoring approach using lipids are that beaches are far more accessible than seagrass meadows, and birds spatially sample a larger area than researchers could do efficiently. Although this pilot study was limited in samples and field sites, our results provide compelling reasons to pursue carnivorous fecal dietary lipids as a source of ecosystem data.