Expedited loss of soil biodiversity in blue carbon ecosystems caused by rising sea levels

Abstract

Global climate change poses a significant threat to soil biodiversity globally. Coastal wetlands are among the Earth's most extensive reservoirs of biodiversity that are susceptible to accelerating sea levels. However, in these vulnerable areas, the understanding of the responses of soil biodiversity to sea level rise remains elusive. In this study, we established an in-situ marsh organ and subjected it to a continuous inundation scenario by simulating the impact of sea level rise. Within this simulated environment, we planted monocultures of native mangrove species Kandelia obovata, alongside invasive species Spartina alterniflora. After a year and a half of incubation, we conducted comprehensive analyses of the soil microbiome, encompassing archaea, bacteria, and fungi. Our findings revealed that the soil microbiome's response to prolonged inundation is characterized by non-linear dynamics, with moderate inundation levels proving advantageous for sustaining soil biodiversity. Except for fungal richness, the decline in biodiversity was markedly more pronounced in soils hosting S. alterniflora than those hosting K. obovata. This suggests that plant invasion may exacerbate soil biodiversity loss under increasing sea levels. While prolonged inundation enhanced biotic homogenization and community stability (measured by the average variation degree) of prokaryotic communities, this phenomenon did not extend to fungal communities. Additionally, soils subjected to moderate inundation levels exhibited heightened network complexity. Structural equation modeling analyses demonstrated that the duration of inundation primarily impacted soil biodiversity by modulating community stability and network complexity. Our results emphasize the intricate, non-linear nature of soil biodiversity responses to inundation gradients within coastal wetlands. This study provides empirical evidence that rising sea levels directly contribute to the loss of soil biodiversity within blue-carbon ecosystems. These findings hold significant implications for predicting the future shifts in soil biodiversity within these critical habitats, as sea levels continue to rise due to the ongoing effects of climate change.