Nutrient Enrichment Increases Blue Carbon Potential of Subtropical Seagrass Beds.

Seagrass beds have potential as nature-based solutions to climate change because their high rates of primary production can bury large amounts of carbon. Yet, realizing their potential necessitates improved understanding of the mechanisms contributing to carbon burial, especially in the context of nutrient enrichment, a ubiquitous threat to seagrass beds globally. Leveraging a nine-year nutrient enrichment experiment, we tested how different nutrient sources, supply rates, and ratios altered mechanisms underpinning carbon burial. Nutrient enrichment increased aboveground and decreased belowground biomass but increased carbon production and turnover, particularly belowground. To inform conservation efforts, we showed that blade height and shoot density effectively predict belowground carbon turnover and therefore provide a simple measure to assess potential belowground carbon inputs to sediment. By identifying the mechanisms that promote carbon burial in the face of nutrient enrichment, our study advances understanding of how to prioritize protection of nature-based solutions amidst this ubiquitous stressor.