Microbial communities in restored and natural wetlands on the U.S. Mid-Atlantic coastal plain
An important ecosystem service wetlands provide is the removal of nitrogen, which is mediated by the microbial community (bacteria, archaea, fungi). Many existing wetlands were created or restored through mitigation efforts, and it is essential to determine how they function ecologically post-restoration when compared to established natural systems. Few studies have analyzed the inter- and intra-wetland variation of microbial biomass between restored and natural depressional wetlands, and fewer still have investigated the hydrologic effect on these microbial communities. We compared ten restored and five natural depressional freshwater wetlands on the Delmarva Peninsula (Maryland and Delaware, USA). At each wetland, soil samples were collected to a depth of 10 cm in three different hydrologic zones (emergent, transition, upland). Chloroform fumigation extraction was used to quantify microbial biomass carbon. DNA was also extracted and functional genes specific to denitrification (nirS, nirK, and nosZ) will be quantified. Additionally, denitrifying community composition will be determined by creating nosZ T-RFLP profiles.
Preliminary results show higher microbial biomass in natural wetlands than in restored systems (659.5 ± 336.0 µg C/g dry soil and 108.1 ± 71.3 µg C/g, respectively). Microbial biomass was highest in the emergent zones in both natural (1186.7 ± 245.3 µg C/g) and restored wetlands (184.3 ± 61.8 µg C/g), and lowest in the upland zones of both wetland types as well (natural = 291.2 ± 74.2 µg C/g; restored = 21.4 ± 15.9 µg C/g); natural wetland microbial biomass values in each of the three hydrologic zones are each an order of magnitude higher than the biomass values in restored wetland hydrologic zones. These initial data indicate that these restored wetlands (5-31 years old) have not yet developed the microbial biomass that natural systems contain. We are currently measuring the gene copy numbers of 16S rRNA and denitrification functional genes and plan to also present those results. In this case we hypothesize that the 16S rRNA amount will correlate to microbial biomass carbon and that emergent zones will have greater amounts of denitrification genes.