Intensifying climate stressors are expected to alter biodiversity and ecosystem function around the globe. In marine climate change studies, however, "scaling up" from species- to ecosystem-level responses remains a difficult challenge. Here, we utilized CO2 vents as a natural laboratory to examine how ocean acidification, an emerging stressor in marine realms, modifies functioning of marine detrital food webs central to the nutrient cycling within seagrass ecosystems. In CO2 vents near Ischia island (Italy), we experimentally deployed litters produced by seagrass Posidonia oceanica along a natural acidification gradient (pH 7.4-8.0) and replicated the experiment across different vent sites.
Results/Conclusions
Overall, we found a significantly faster decomposition (~15%) of seagrass litters in lower pH zones than in ambient pH zones, which appears to be driven by changes in functional composition of decomposer community. Unexpectedly higher abundance of key detritivores and stronger detritivory (~130%) were observed under acidification. Decomposition may have been further influenced by pH-driven changes in microbial function, as evidenced by a stronger increase in litter nitrogen contents over time within lower pH zones. These results suggest that marine stressors such as ocean acidification have a major potential to alter ecological communities and their functioning.