The biogeography of Mid-Atlantic CEAP wetlands

Background/Question/Methods

The national U.S.D.A. Conservation Effects Assessment Project (CEAP) is a multi-agency effort to quantify the environmental benefits of conservation practices. The goal of CEAP is to determine the effectiveness of wetland conservation practices and programs, including improved water quality, reduction of flooding, improved availability of fresh water, and enhanced habitat for waterfowl and other animals. The Mid-Atlantic CEAP study is one of five regional studies underway as part of the national CEAP effort. This study collected information at sites in the DelMarVa and North Carolina Coastal Plain regions, and were equally divided between three sets of wetland management systems: hydrologically restored wetlands; prior converted wetlands; and natural wetlands. All sites were selected to include one of each wetland management type, with samples collected for multi-year analysis.

A variety of methods were used to analyze the wetland areas presented in this study. To examine nitrous oxide emission/production, photoacoustic gas analysis (PAGA) and denitrification enzyme activity (DEA) were utilized respectively. Microbial community structure was analyzed by a mix of terminal restriction fragment length polymorphism (T-RFLP) and second generation DNA sequencing, while wetland nitrogen cycling potentials were analyzed by gene specific analysis using quantitative Real-Time PCR (qPCR).

Results/Conclusions

While PAGA proved unreliable for in-field measurements, DEA revealed that natural wetlands produced the largest percentage of nitrous oxide from denitrification (> 50%), while prior converted wetlands produced the least (< 30%). Results from qPCR revealed that the type of wetland management had different effects on the genes involved in nitrogen cycling. Overall bacterial abundances, using the 16S rDNA gene as measured by qPCR, were greatest in restored and prior converted wetlands. Gene abundances to examine wetland nitrogen cycling potential were likewise also measured by qPCR:  nifH, the gene responsible for nitrogen fixation, was greatest in restored and natural wetlands; nirS, a gene which encodes one of two forms of bacterial nitrite reductase, was greatest in restored and prior converted wetlands. Second generation DNA sequencing, produced over a half million reads and revealed three major phyla predominant across all three wetland management types: Bacteroidetes (12%), Proteobacteria (21%), and Firmicutes (52%).