Geomicrobiology of an Anthropogenically Altered Subterranean Estuary

Karen Casciotti, Marine Chemistry and Geochemistry


Project Funded 2007:

Human activities have undoubtedly altered the ecology of coastal waters. Much of the alteration is due to the addition of excess nutrients, primarily nitrogen. Thirty years of effort aimed at stemming this problem (eg. The Clean Water Act) has been unable to sufficiently reduce the anthropogenic flux of nitrogen to coastal waters resulting in the deterioration of coastal waters.  Having been unable to adequately reduce the supply of nitrogen, we must now also strive to better understand the natural processes that remove nitrogen from affected systems. Groundwater is one of the significant transport pathways of nitrogen to the coastal water and may harbor much different chemical conditions than traditional riverine inputs. Many of the processes that transform nitrogen in this groundwater system are microbially-mediated. We propose to carefully examine the potential of natural populations of microorganisms to attenuate the flux of nitrogen from groundwater to the coastal waters. We will combine the use of microbiological, molecular and chemical techniques to examine the biogeochemical cycling of nitrogen in a groundwater estuary. We will strive to understand (i) which populations are active, and under what condition are they active, (ii) what community function is served by archaea in the system, (iii) at what rate is nitrogen removed from the system by different populations. This work will address all three themes of the Coastal Ocean Institute. First, this work will provide insight into the fate of an anthropogenic pollutant on the micron to centimeter scale by describing which organisms are important in the groundwater nitrogen cycle as well as the organism’s activity, distribution and abundance. Second, we propose to examine the biogeochemical processes within the groundwater that control speciation and transport of nitrogen to the coastal waters. Finally, we propose to implement new tools by combining molecular methods, including the first metagenomic study of a groundwater system, and stable isotope techniques to elucidate the dominant biochemical processes controlling the nitrogen cycle in the groundwater estuary.