Climate change is accelerating sea‐level rise and saltwater intrusion in coastal regions world‐wide and interacting with large‐scale changes in species composition in coastal wetlands. Quantifying macrophyte litter breakdown along freshwater‐to‐marine coastal gradients is needed to predict how carbon stores will respond to shifts in both macrophyte communities and water chemistry under changing environmental conditions. To test the interactive drivers of changing species identity and water chemistry, we performed a reciprocal transplant of four macrophyte litter species in seven sites along freshwater‐to‐marine gradients in the Florida Coastal Everglades. We measured surface water chemistry (dissolved organic carbon, total nitrogen and total phosphorus), litter chemistry (% nitrogen, % phosphorus, change in N:P molar ratio, % cellulose and % lignin as proxies for recalcitrance) and litter breakdown rates ( Direct effects of salinity and surface water nutrients were the strongest drivers of
This content will become publicly available on October 1, 2025
Leaf litter in coastal wetlands lays the foundation for carbon storage, and the creation of coastal wetland soils. As climate change alters the biogeochemical conditions and macrophyte composition of coastal wetlands, a better understanding of the interactions between microbial communities, changing chemistry, and leaf litter is required to understand the dynamics of coastal litter breakdown in changing wetlands. Coastal wetlands are dynamic systems with shifting biogeochemical conditions, with both tidal and seasonal redox fluctuations, and marine subsidies to inland habitats. Here, we investigated gene expression associated with various microbial redox pathways to understand how changing conditions are affecting the benthic microbial communities responsible for litter breakdown in coastal wetlands. We performed a reciprocal transplant of leaf litter from four distinct plant species along freshwater‐to‐marine gradients in the Florida Coastal Everglades, tracking changes in environmental and litter biogeochemistry, as well as benthic microbial gene expression associated with varying redox conditions, carbon degradation, and phosphorus acquisition. Early litter breakdown varied primarily by species, with highest breakdown in coastal species, regardless of the site they were at during breakdown, while microbial gene expression showed a strong seasonal relationship between sulfate cycling and salinity, and was not correlated with breakdown rates. The effect of salinity is likely a combination of direct effects, and indirect effects from associated marine subsidies. We found a positive correlation between sulfate uptake and salinity during January with higher freshwater inputs to coastal areas. However, we found a peak of dissimilatory sulfate reduction at intermediate salinity during April when freshwater inputs to coastal sites are lower. The combination of these two results suggests that sulfate acquisition is limiting to microbes when freshwater inputs are high, but that when marine influence increases and sulfate becomes more available, dissimilatory sulfate reduction becomes a key microbial process. As marine influence in coastal wetlands increases with climate change, our study suggests that sulfate dynamics will become increasingly important to microbial communities colonizing decomposing leaf litter.
more » « less- PAR ID:
- 10549349
- Publisher / Repository:
- Wiley Periodicals LLC
- Date Published:
- Journal Name:
- Ecology
- ISSN:
- 0012-9658
- Page Range / eLocation ID:
- e4427
- Subject(s) / Keyword(s):
- benthic carbon decomposition phosphorus sea-level rise sulfate transcriptome
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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