Understanding eutrophication: Flora and bacterial communities of an urban watershed

Background/Question/Methods
The greatest cause of degradation to major waterways, such as New Jersey’s Barnegat Bay, is eutrophication.  Our research is focused on the riparian zone of the Toms River in New Jersey, with the goal of investigating the role of plant and bacterial communities in filtering excess nitrogen.  To accomplish this, we have measured plant and soil microbial community composition at four different sites along the Toms River.  At each of the four sites, we surveyed three transects that were parallel, perpendicular and upland from the river.  Soil samples were returned to the lab for microbial DNA fingerprinting (terminal restriction fragment length polymorphism- TRFLP). Water and soil chemistry samples were also taken at all four sites.  

Results/Conclusions
Plant diversity varied greatly between sites, however, one of the most common families seen at all sites was Ericaceae.  The plant communities within the downstream sites were very different, ranging from Chamaecyparis thyoides almost entirely dominating a wetland to a Quercus/Acer dominated community.  Perpendicular and upland transects for all sites were dominated by Gaylussacia and Vaccinium species; however, the species of Gaylussacia changed predominantly from G. frondosa in the perpendicular sites to G. baccata and G. dumosa in the upland transects.  Bacterial taxa diversity based on TRFLP was markedly different between the downstream, perpendicular and upland sites.  Between the downstream sites and the upland sites there was a 63% increase in bacteria diversity.  This is in contrast to the flora, where there was more homogeneity between upland sites and more heterogeneity at downstream sites.  The results of this research will provide a better understanding of the unique interactions between plant and bacterial communities, and inform management plans for riparian communities to better mitigate the flow of excess nitrogen.