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Testing For Ecological Correlations between Greenhouse Gas Fluxes and their Potential Biotic Drivers in Coastal Wetlands
Citation:
Holgate, J., R. Martin, AND Rick Mckinney. Testing For Ecological Correlations between Greenhouse Gas Fluxes and their Potential Biotic Drivers in Coastal Wetlands. New England Estuarine Research Society (NEERS) Fall Meeting, Block Island, Rhode Island, October 20 - 22, 2016.
Impact/Purpose:
This experiment measured greenhouse gas fluxes along a gradient of ribbed mussel and fiddler crab burrow densities in vegetated and unvegetated salt marsh habitats. The objective of this research was to test for relationships between biotic variables and methane and carbon dioxide fluxes in a coastal wetland.
Description:
The role of coastal wetlands in ameliorating the plight of climate change is well documented. Per unit area, coastal wetlands are among the largest natural carbon sinks, taking up abundant carbon dioxide (CO2) and emitting minimal methane (CH4). While the role of coastal marsh vegetation in mediating CO2 and CH4 flux dynamics has been well-studied, less is known about effects that other biotic drivers, including marsh invertebrates, exert on GHG fluxes. Crabs and mollusks may directly alter soil biogeochemistry and GHG fluxes by bioturbation and deposition of nutrient-rich feces, and indirectly through impacts to vegetation. The objective of this research was to survey GHG fluxes along a gradient of fiddler crab (Uca pugnax) and ribbed mussel (Geukensia demissa) densities. Surveys were performed in a Rhode Island salt marsh at randomly-chosen points in both the Spartina alterniflora-vegetated low marsh and the unvegetated creek bank. During the peak growing season, GHG (CO2 and CH4) fluxes and S. alterniflora, live and dead mussel, and crab burrow densities were measured. GHG fluxes differed substantially between the S. alterniflora marsh and creek bank, with greater CO2 uptake and CH4 emission in the S. alterniflora marsh than along the creek bank. In the S. alterniflora marsh, Spearman’s Correlation Analysis revealed a significant positive correlation between density of dead mussels and CH4 emission. However, none of the measured variables correlated with CH4 fluxes on the creek bank. Though preliminary, results of this experiment underscore both the spatial variability of coastal marsh GHG fluxes and the potential for distinct drivers to mediate fluxes across the marsh landscape.