<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Joye, Samantha B.</style></author><author><style face="normal" font="default" size="100%">Moore, Willard S.</style></author><author><style face="normal" font="default" size="100%">Tuncay, Kagan</style></author><author><style face="normal" font="default" size="100%">Meile, Christof</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Field measurements and modeling of groundwater flow and biogeochemistry at Moses Hammock, a backbarrier island on the Georgia coast</style></title><secondary-title><style face="normal" font="default" size="100%">Biogeochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/content/t18x02358tt6x123/</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">104</style></volume><pages><style face="normal" font="default" size="100%">69-90</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A combination of field measurements, laboratory experiments and model simulations were used to characterize the groundwater biogeochemical dynamics along a shallow monitoring well transect on a coastal hammock. A switch in the redox status of the dissolved inorganic nitrogen (DIN) pool in the well at the upland/saltmarsh interface occurred over the spring-neap tidal transition: the DIN pool was dominated by nitrate during spring tide and by ammonium during neap tide. A density-dependent reaction-transport model was used to investigate the relative importance of individual processes to the observed N redox-switch. The observed N redox-switch was evaluated with regard to the roles of nitrification, denitrification, dissimilatory nitrate reduction to ammonium (DNRA), ammonium adsorption, and variations in inflowing water geochemistry between spring and neap tides.Transport was driven by measured pressure heads and process parameterizations were derived from field observations, targeted laboratory experiments, and the literature. Modeling results suggest that the variation in inflow water chemistry was the dominant driver of DIN dynamics and highlight the importance of spring-neap tide variations in the high marsh, which influences groundwater biogeochemistry at the marsh-upland transition.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2011-93253</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Weston, Nathaniel B.</style></author><author><style face="normal" font="default" size="100%">Joye, Samantha B.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Benthic metabolism and the fate of dissolved inorganic nitrogen in intertidal sediments</style></title><secondary-title><style face="normal" font="default" size="100%">Estuarine Coastal and Shelf Science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://dx.doi.org/10.1016/j.ecss.2009.04.012</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">83</style></volume><pages><style face="normal" font="default" size="100%">392-402</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We determined patterns of benthic metabolism and examined the relative importance of denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) as sinks for nitrate (NO3&amp;#8722;) in intertidal sediments in the presence and absence of benthic microalgal (BMA) activity. By influencing the activity of BMA, light regulated the metabolic status of the sediments, and, in turn, exerted strong control on sediment nitrogen dynamics and the fate of inorganic nitrogen. A pulsed addition of 15N-labeled NO3&amp;#8722; tracked the effect and fate of dissolved inorganic nitrogen (DIN) in the system. Under illuminated conditions, BMA communities influenced benthic fluxes directly, via DIN uptake, and indirectly, by altering the oxygen penetration depth. Under dark hypoxic and anoxic conditions, the fate of water column NO3&amp;#8722; was determined largely by three competing dissimilatory reductive processes; DNF, DNRA, and, on one occasion, anaerobic ammonium oxidation (anammox). Mass balance of the added 15N tracer illustrated that DNF accounted for a maximum of 48.2% of the 15NO3&amp;#8722; reduced while DNRA (a minimum of 11.4%) and anammox (a minimum of 2.2%) accounted for much less. A slurry experiment was employed to further examine the partitioning between DNF and DNRA. High sulfide concentrations negatively impacted rates of both processes, while high DOC:NO3&amp;#8722; ratios favored DNRA over DNF.</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.2009-93322</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Meile, Christof</style></author><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Walker, Randall L.</style></author><author><style face="normal" font="default" size="100%">Payne, Karen</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Natural Attenuation Of Nitrogen Loading From Septic Effluents: Spatial And Environmental Controls</style></title><secondary-title><style face="normal" font="default" size="100%">Water Research</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><volume><style face="normal" font="default" size="100%">44</style></volume><pages><style face="normal" font="default" size="100%">1399-1408</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We assess the role of septic systems as potential nitrogen (N) sources to coastal open water bodies. To quantify the potential role of septic tanks, we document the distribution pattern and functionality of septic tanks in McIntosh County in Georgia, USA, and examine factors governing the mitigation of septic N loading in coastal groundwater. Employing a field calibrated 2D variable-density reaction-transport model, we focus on the role of setback distance of a leaky septic source from the receiving surface waters, on transport and biogeochemical characteristics of the subsurface environment, and on leachate composition and reactivity. We conclude that the removal of bioavailable nitrogen  via denitrification may be increased by increasing the septic system setback distance, in particular in brackish and saline coastal settings where sulfide produced in sulfate reduction can limit N2 production.</style></abstract><issue><style face="normal" font="default" size="100%">5</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.2009-93316</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>32</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biogeochemical dynamics in coastal sediments and shallow aquifers</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://gce-lter.marsci.uga.edu/public/files/pubs/Porubsky_William_P_200812_PhD.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">University of Georgia</style></publisher><pub-location><style face="normal" font="default" size="100%">Athens, Georgia</style></pub-location><pages><style face="normal" font="default" size="100%">222</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Patterns of benthic metabolism and the relative importance of assimilatory and dissimilatory processes as sinks for nitrate (NO3-) in intertidal sediments were examined. Under illuminated, nitrogen (N)-replete conditions, sequential nutrient limitation of benthic microalgae (BMA) was observed, with N limitation preceding silicate limitation; and biological assimilation dominated nitrate uptake. Conversely, under dark hypoxic and anoxic conditions, water column NO3- uptake was dominated largely by three competing dissimilatory reductive processes; denitrification (DNF), dissimilatory nitrate reduction to ammonium (DNRA), and, on one occasion, anaerobic ammonium oxidation (anammox). High sulfide concentrations negatively impacted DNF and DNRA rates, while high dissolved organic carbon (DOC):NO3- ratios favored DNRA over DNF. Under baseline conditions sediments exhibited tight coupling between photosynthesis and respiration. Nitrogen addition shifted the metabolic status of the sediments from a balance between autotrophy and heterotrophy to net autotrophy, and the sediments became a source of DOC. The role of groundwater as a source of nutrients and organics to the coastal ocean was evaluated using a combination of radium isotopes and geochemical characterization. Geochemical data indicated significant spatial variations in groundwater chemical composition and radium activity ratios indicated geographically distinct hydrological regimes. Spatial variations in microbially mediated processes, DOC distribution, and/or groundwater residence time contributed to this pattern. Radium based geochemical loading rates illustrated a substantial groundwater contribution of organics, DIC, nutrients, methane and nitrous oxide to the Okatee estuary. The groundwater biogeochemical dynamics along a shallow monitoring well transect on a coastal hammock were evaluated by density-dependent reaction transport model. A switch in the redox status of the DIN pool occurred during the spring-neap tidal transition (spring high NO3- low NH4+; neap low NO3- high NH4+). The observed N redox-switch was evaluated with regard to the relative roles of nitrification, DNF, DNRA, ammonium adsorption, and variations in inflowing water geochemistry between spring and neap tides. The latter was found to most significantly affect the observed pattern in DIN dynamics. Additionally, the fate of DOC and DIN originating from a septic system was studied. Simulation results indicated that while DNF increased ~15 fold, higher N removal rates could not keep pace with the increase in DIN loading, resulting in higher export of DIN to coastal waters.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2008-93358</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Velasquez, Liliana E.</style></author><author><style face="normal" font="default" size="100%">Joye, Samantha B.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Nutrient replete benthic microalgae as a source of labile dissolved organic carbon to coastal waters</style></title><secondary-title><style face="normal" font="default" size="100%">Estuaries and Coasts</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/content/j6531n2472m364u4/?p=4887a9488d8a46098b68a028eafc3b71&amp;pi=0</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">31</style></volume><pages><style face="normal" font="default" size="100%">860-876</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Dissolved organic carbon (DOC) flux dynamics were examined in the context of other biogeochemical cycles in intertidal sediments inhabited by benthic microalgae. In August 2003, gross oxygenic photosynthetic (GOP) rates, oxygen penetration depths, and benthic flux rates were quantified at seven sites along the Duplin River, GA, USA. Sediments contained abundant benthic microalgal (BMA) biomass with a maximum chlorophyll a concentration of 201 mg chl a m-2. Oxygen microelectrodes were used to determine GOP rates and O2 penetration depth, which were tightly correlated with light intensity. Baseline and 15N-nitrate amended benthic flux core incubations were employed to quantify benthic fluxes and to investigate the impact of BMA on sediment water exchange under nitrogen (N)-limited and N-replete conditions. Unamended sediments exhibited tight coupling between GOP and respiration and served as a sink for water column dissolved inorganic nitrogen (DIN) and a source of silicate and dissolved inorganic carbon (DIC). The BMA response to the N addition indicated sequential nutrient limitation, with N limitation followed by silicate limitation. In diel (light</style></abstract><issue><style face="normal" font="default" size="100%">5</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.2008-93359</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Weston, Nathaniel B.</style></author><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Samarkin, Vladimir</style></author><author><style face="normal" font="default" size="100%">MacAvoy, Steven E.</style></author><author><style face="normal" font="default" size="100%">Erickson, Matthew</style></author><author><style face="normal" font="default" size="100%">Joye, Samantha B.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pore water stoichiometry of terminal metabolic products, sulfate, and dissolved organic carbon and nitrogen in intertidal creek-bank sediments</style></title><secondary-title><style face="normal" font="default" size="100%">Biogeochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><volume><style face="normal" font="default" size="100%">77</style></volume><pages><style face="normal" font="default" size="100%">375-408</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Porewater equilibration samplers were used to obtain porewater inventories of inorganic nutrients (NH4 +, NOx, PO4 3-), dissolved organic carbon (DOC) and nitrogen (DON), sulfate (SO4 2-), dissolved inorganic carbon (DIC), hydrogen sulfide (H2S), chloride (Cl-), methane (CH4) and reduced iron (Fe2+) in intertidal creek-bank sediments at eight sites in three estuarine systems over a range of salinities and seasons. Sulfate reduction (SR) rates and sediment particulate organic carbon (POC) and nitrogen (PON) were also determined at several of the sites. Four sites in the Okatee River estuary in South Carolina, two sites on Sapelo Island, Georgia and one site in White Oak Creek, Georgia appeared to be relatively pristine. The eighth site in Umbrella Creek, Georgia was directly adjacent to a small residential development employing septic systems to handle household waste. The large data set (&gt;700 porewater profiles) offers an opportunity to assess system-scale patterns of porewater biogeochemical dynamics with an emphasis on DOC and DON distributions. SO4 2- depletion (SO4 2-)Dep was used as a proxy for SR, and (SO4 2-)Dep patterns agreed with measured (35S) patterns of SR. There were significant system-scale correlations between the inorganic products of terminal metabolism (DIC, NH4 + and PO4 3-) and (SO4 2-)Dep, and SR appeared to be the dominant terminal carbon oxidation pathway in these sediments. Porewater inventories of DIC and (SO4 2-)Dep indicate a 2:1 stoichiometry across sites, and the C:N ratio of the organic matter undergoing mineralization was between 7.5 and 10. The data suggest that septic-derived dissolved organic matter with a C:N ratio below 6 fueled microbial metabolism and SR at a site with development in the upland. Seasonality was observed in the porewater inventories, but temperature alone did not adequately describe the patterns of (SO4 2-)Dep, terminal metabolic products (DIC, NH4 +, PO4 3-), DOC and DON, and SR observed in this study. It appears that production and consumption of labile DOC are tightly coupled in these sediments, and that bulk DOC is likely a recalcitrant pool. Preferential hydrolysis of PON relative to POC when overall organic matter mineralization rates were high appears to drive the observed patterns in POC:PON, DOC:DON and DIC:DIN ratios. These data, along with the weak seasonal patterns of SR and organic and inorganic porewater inventories, suggest that the rate of hydrolysis limits organic matter mineralization in these intertidal creek-bank sediments.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2006-93398</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Joye, Samantha B.</style></author><author><style face="normal" font="default" size="100%">Porubsky, William P.</style></author><author><style face="normal" font="default" size="100%">Weston, Nathaniel B.</style></author><author><style face="normal" font="default" size="100%">Lee, Rosalynn Y.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Rullk</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Benthic microalgal production and nutrient dynamics in intertidal sediments</style></title><secondary-title><style face="normal" font="default" size="100%">BioGeoChemistry of Tidal Flats</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">GCE</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><publisher><style face="normal" font="default" size="100%">Forschungszentrum Terramare Berichte Nr. 12, Proceedings of a Workshop held at the Hanse Institute of Advanced Study</style></publisher><pub-location><style face="normal" font="default" size="100%">Delmenhorst, Germany</style></pub-location><pages><style face="normal" font="default" size="100%">67-70</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.2003-93454</style></accession-num></record></records></xml>