Wetlands are characterized by a variety of diverse biotic and abiotic factors that influence the capacity of the resident community to provide important ecosystem services, such as the alleviation of excess nutrients. In coastal wetlands, many of these factors are affected by changes in elevation; these differences in elevation are often reflected by alterations in plant community but little is known about the structure and function of the soil prokaryotic community. Using a natural elevation gradient at Weeks Bay National Estuarine Research Reserve, we measured physical and chemical features of soils from three distinct wetland regions, including organic matter (%), pH, salinity, temperature, and porewater nutrients, and examined the composition of prokaryotic communities. As we were particularly interested in the removal of urea from wetlands, urease activity was also measured within each region. Because plants and prokaryotes are known to degrade urea, examination of both communities was necessary to obtain a better understanding of this process. Measurements within the 3 regions were taken multiple times throughout the year to provide insight into the spatial and temporal stability of wetland plant and prokaryotic communities. Prokaryotic community composition was assessed via terminal restriction fragment length polymorphism (T-RFLP) analyses using universal primers and urease activity was evaluated using a soil slurry method followed by colorimetric analyses.
Results/Conclusions
Along our natural wetland elevation gradient, spatial and temporal differences in soil prokaryotic community structure and urease activity were found. Unique prokaryotic communities were identified within each of the three regions, with those in the Spartina spp. dominated marsh, the lowest elevation region, highly correlated with salinity. In contrast, prokaryotic communities in the ecotone and forest regions were most correlated with percent of organic matter and pH. The highest urease rates were found in the Spartina spp. marsh, with rates ten times higher than those from the forest site, where trees dominate the vegetation. Temporally, urease activity significantly decreased at all sites when soil temperatures were below 10° C. These results demonstrate the impact of environmental factors on the composition and function of wetland prokaryotic communities across space and time. Due to the dynamic nature of wetland ecosystems, additional interdisciplinary studies will be necessary to better understand the consequences of predicted climate changes and increasing urea-based pollution on wetland environments, particularly with regard to prokaryotic community structure and function.