Comparing the Magnitude and Mechanisms of Submarine Groundwater Discharge (SGD) and Associated Nutrient Fluxes in Estuaries and Coastal Karst Systems PDF Download
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Author: Daniel Agustin Montiel Martin
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 271
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Book Description
Submarine groundwater discharge (SGD) is an important source of natural and anthropogenic nutrients and contaminants in coastal waters. Nutrient inputs from SGD can cause or exacerbate eutrophication, hypoxia, seagrass beds degradation, and harmful algal blooms (HABs), among other ecological impacts. Coastal karst systems and estuaries are among the most complex coastal areas, where the assessment of SGD and derived nutrient fluxes is particularly challenging. Their typically heterogeneous hydrogeology combined with temporal fluctuations of marine and terrestrial forcing result in large variations of SGD in both systems. In this dissertation I evaluated the magnitude and mechanisms driving SGD and its importance as a source of water and nutrients to Maro-Cerro Gordo (a coastal karst system in southern Spain) and Mobile Bay (an estuary of the northern Gulf of Mexico). In Maro-Cerro Gordo I found that SGD accounted for an important part of the water budget of the coastal karst aquifer, the only source of freshwater for nearby population and agricultural activities. Additionally, SGD served as a vector for NO3- fertilizers contamination to the sea, putting at risk the endangered species of the coastal ecosystem. In Mobile Bay I found that 1/4 of the nutrient budget is delivered by SGD during the dry season as NH4+ (56% of the total) and DON (15% of the total), mostly on the east shore, where Jubilees occur. I demonstrated that these SGD-derived nutrient inputs, in contrast to previous hypotheses, are originated naturally from organic matter mineralization in a peat layer found only on the east shore of the bay. In comparison, groundwater discharge in Maro-Cerro Gordo was primarily controlled by the terrestrially driven hydraulic gradient of the karst aquifer, while in Mobile Bay SGD was mainly marine-driven by sea level fluctuations (tidal pumping). Furthermore, the extremely fast groundwater flow of the karst aquifer in Maro-Cerro Gordo always created oxic conditions, allowing the NO3- contamination to reach the sea. In contrast, in the shallow coastal aquifer of Mobile Bay I found that, while the main form of nitrogen in inland fresh groundwater was NO3-, the SGD-derived nitrogen inputs to the bay was almost entirely in the form of NH4+. These large fluxes of NH4+ were produced by two main processes: organic matter mineralization and dissimilatory nitrate reduction to ammonium (DNRA).
Author: Daniel Agustin Montiel Martin
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 271
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Book Description
Submarine groundwater discharge (SGD) is an important source of natural and anthropogenic nutrients and contaminants in coastal waters. Nutrient inputs from SGD can cause or exacerbate eutrophication, hypoxia, seagrass beds degradation, and harmful algal blooms (HABs), among other ecological impacts. Coastal karst systems and estuaries are among the most complex coastal areas, where the assessment of SGD and derived nutrient fluxes is particularly challenging. Their typically heterogeneous hydrogeology combined with temporal fluctuations of marine and terrestrial forcing result in large variations of SGD in both systems. In this dissertation I evaluated the magnitude and mechanisms driving SGD and its importance as a source of water and nutrients to Maro-Cerro Gordo (a coastal karst system in southern Spain) and Mobile Bay (an estuary of the northern Gulf of Mexico). In Maro-Cerro Gordo I found that SGD accounted for an important part of the water budget of the coastal karst aquifer, the only source of freshwater for nearby population and agricultural activities. Additionally, SGD served as a vector for NO3- fertilizers contamination to the sea, putting at risk the endangered species of the coastal ecosystem. In Mobile Bay I found that 1/4 of the nutrient budget is delivered by SGD during the dry season as NH4+ (56% of the total) and DON (15% of the total), mostly on the east shore, where Jubilees occur. I demonstrated that these SGD-derived nutrient inputs, in contrast to previous hypotheses, are originated naturally from organic matter mineralization in a peat layer found only on the east shore of the bay. In comparison, groundwater discharge in Maro-Cerro Gordo was primarily controlled by the terrestrially driven hydraulic gradient of the karst aquifer, while in Mobile Bay SGD was mainly marine-driven by sea level fluctuations (tidal pumping). Furthermore, the extremely fast groundwater flow of the karst aquifer in Maro-Cerro Gordo always created oxic conditions, allowing the NO3- contamination to reach the sea. In contrast, in the shallow coastal aquifer of Mobile Bay I found that, while the main form of nitrogen in inland fresh groundwater was NO3-, the SGD-derived nitrogen inputs to the bay was almost entirely in the form of NH4+. These large fluxes of NH4+ were produced by two main processes: organic matter mineralization and dissimilatory nitrate reduction to ammonium (DNRA).
Author: Mark Allen Henry
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0
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Book Description
Submarine groundwater discharge (SGD) is a demonstrated source of fresh water, nutrients, contaminants, and other materials to nearshore environments. The terrestrially derived fresh groundwater component of submarine groundwater discharge (FSGD) is of particular interest in monitoring contaminant pathways to coastal regions. Because the chemical loads of FSGD can have ecological and economic impacts on nearshore environments, it is important to have generally applicable methods to quantify FSGD along the global coastline. In this research, I pursued multivariable regression modeling as a novel method to model FSGD along any point of the global coastline. Modeling was conducted using literature-compiled FSGD flux estimates for sites around the globe and a suite of hydrogeological and precipitation data sets available on the global scale. Additionally, I used an approximation of Darcy0́9s law, where the topographic slope is used as a proxy of hydraulic gradient, as an additional method to predict FSGD fluxes. The approximation of Darcy0́9s law method used global scale saturated hydraulic conductivity and global topographic slope data. This research was guided by the following questions: (1) Can multivariable regression predict FSGD fluxes when utilizing some combination of permeability, porosity, topographic slope, saturated hydraulic conductivity, precipitation, and soil moisture? and (2) What is the level of intercomparability between FSGD estimates from different SGD publications? To address these questions, I reviewed over 500 SGD-related publications to obtain FSGD flux estimates for 44 field study sites. These FSGD flux estimates were used in regression with the aforementioned hydrogeological and precipitation data. They were also used to assess the approximation results of Darcy0́9s law. The results of these methods indicated that the multivariable regression modeling based on field estimates of FSGD is likely not feasible with the current state of the data due to a lack of standardization in the field methods used to estimate FSGD flux. I suggest that research groups that study FSGD establish a higher level of standardization in study methods to increase the comparability between FSGD flux estimates. This would facilitate modeling efforts that rely on FSGD flux estimates from multiple field sites.
Author: Makoto Taniguchi
Publisher: Frontiers Media SA
ISBN: 2889665356
Category : Science
Languages : en
Pages : 158
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Book Description
Author: Kayla D. Holleman
Publisher:
ISBN:
Category : Coastal ecology
Languages : en
Pages : 126
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Book Description
Submarine groundwater discharge (SGD) is an important land-to-ocean pathway for biogeochemically significant nutrients, such as nitrate, silicate and phosphate. Introduction of new bioavailable nutrients from SGD into coastal waters can alter a coastal system's nutrient balance, and may result in increases in phytoplankton or macroalgae growth that in turn can cause other ecological shifts in biological species' composition (Valiela et al., 1990). In order to attempt a first investigation of the possible relative impact(s) of the amount, flux, and residence times of SGD and SGD-derived nutrients on coastal phytoplankton in the oligotrophic coastal waters off Hawaii, detailed studies were completed to compare the flux and residence times of SGD and SGD-derived nutrients on biological processes at three sites on the leeward-side of the Koolau Mountains along the southern shore of Oahu (the Ala Wai Canal, Black Point, and Wailupe Beach) and at one site on the leeward-side of Hualalai, on the western side of the Big Island of Hawaii (Honokohau Harbor, Hawaii). At each site, radon and short-lived radium isotopes were used to calculate the flux of SGD and SGD-derived constituents into the coastal areas and their residence times. The rate of uptake of 13C by photoautotrophs was determined using in situ incubation experiments with addition of 13C-labeled bicarbonate at most sites and was used as a relative indicator of photosynthetic activity and its response to potential input of SGD-derived nutrients At study sites along the southern shore of Oahu, nutrient fluxes for a shoreline length of 1.18 km was 281 PO43−, 113,015 Si(OH)4, and 10,505 NO3− mol/d, respectively. Nutrient fluxes for Honokohau Harbor, estimated to have a 375-m wide seepage face, were 194 PO43−, 31,998 Si(OH)4, and 3,123 NO3− mol/d respectively. Photosynthetic carbon production rates were significantly higher for the Ala Wai Canal (1.39 [micro]gC/L/h) than for Honokohau Harbor (0.10[micro]gC/L/h). Using these carbon uptake rates and assuming a Redfield C:N:P ratio of 106:16:1, nitrogen and phosphorus uptake rates for both the Ala Wai Canal and Honokohau Harbor were less than 2% of the nutrients delivered by SGD. Variation in the N:P ratios observed in the groundwater and coastal waters could imply nutrient limitation. We found for the restricted estuarine-like embayments of the Ala Wai canal (water mass residence time 10-13 days) and Honokohau Harbor (water mass residence time 0.5 -6 days), that primary productivity is not controlled by the availability of nutrients (nutrient supply> phytoplankton demand in both settings), but is nonetheless directly linked to each water mass' residence time. As nutrients are in excess of demand in both settings, we conclude that it is the physical longevity and residence time of the phytoplankton itself that ultimately controls each basin's ultimate level of sustained primary productivity.
Author: C. Spiteri
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: J. A. Breier
Publisher:
ISBN:
Category : Groundwater disposal in rivers, lakes, etc
Languages : en
Pages : 53
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Author: Beata Szymczycha
Publisher: Springer
ISBN: 3319259601
Category : Science
Languages : en
Pages : 158
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Book Description
The book provides a review of experimental methods and presents the worldwide newest literature regarding chemical substances fluxes via submarine groundwater discharge (SGD). Thus, the book characterizes both the distribution of chemicals in groundwater impacted areas in the Baltic Sea and their fluxes via SGD to the Baltic Sea. This book presents the state of art regarding the SGD and detailed studies on SGD characterization in the Baltic Sea. The Baltic Sea is an example of a region highly influenced by a variety of human activities that affect the ecosystem. It is shown that SGD has been proven to be one of the important sources introducing dissolved substances into the Baltic Sea. The loads of chemical substances delivered to the Baltic sea with SGD have not been quantified so far.
Author: John Arthur Breier
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 0
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Book Description
Recent studies have provided evidence that submarine groundwater discharge is a signifi cant source of water and dissolved nutrients to the coastal ocean. The chemical implications of these studies are especially important because, relative to surface water, groundwater is typically enriched in many compounds including nitrogen bearing nutrients. Therefore by affecting the supply and relative proportions of essential nutrients, direct groundwater discharge has the potential to influence phytoplankton populations and estuarine ecosystems as a whole. Another potential submarine discharge that may occur in the shallow restricted waters of the Texas coast is leakage of oil-field brine. Such leakage also has important ecological implications similar in some ways to groundwater discharge. The studies in this dissertation concern improving the methods and techniques used in measuring submarine discharges. Using the Texas Coastal Bend as a study area I have: 1) conducted a detailed evaluation of submarine discharges to Nueces Bay and 2) compared indications of submarine discharge between Nueces, Baffin, and Copano Bays. These investigations use a combination of geochemical and geophysical techniques. The geochemical methods are based primarily on measurements of naturally-occurring dissolved Ra isotopes in samples of bay, river, ocean, and groundwater. The geophysical methods employ electrical resistivity profiling to look for evidence of groundwater movement within the bay bottom sediments. Results show that dissolved radium concentrations within Nueces Bay are among the highest observed in coastal estuaries. Geochemical analysis and geophysical surveys indicate that both groundwater and leakage of oil-field brine are potential submarine inputs. Samples from Nueces, Copano, and Baffin Bays show that the seasonal increase in dissolved 226Ra activity for Nueces Bay is substantially larger than that of the other two bays. This increase is not readily explained by either evaporation or riverine supply. These results clearly suggest that the Ra supply to Nueces Bay is unusually large. For Nueces Bay, the most relevant differences between the three bays that might account for this are 1) the proportionally larger salt marsh and 2) the higher density of petroleum wells and pipelines. Though submarine groundwater discharge is not to be ruled out, leakage of oil-field brine is strongly indicated.
Author:
Publisher: Academic Press
ISBN: 0080878857
Category : Science
Languages : en
Pages : 4604
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Book Description
The study of estuaries and coasts has seen enormous growth in recent years, since changes in these areas have a large effect on the food chain, as well as on the physics and chemistry of the ocean. As the coasts and river banks around the world become more densely populated, the pressure on these ecosystems intensifies, putting a new focus on environmental, socio-economic and policy issues. Written by a team of international expert scientists, under the guidance of Chief Editors Eric Wolanski and Donald McClusky, the Treatise on Estuarine and Coastal Science, Ten Volume Set examines topics in depth, and aims to provide a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Most up-to-date reference for system-based coastal and estuarine science and management, from the inland watershed to the ocean shelf Chief editors have assembled a world-class team of volume editors and contributing authors Approach focuses on the physical, biological, chemistry, ecosystem, human, ecological and economics processes, to show how to best use multidisciplinary science to ensure earth's sustainability Provides a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Features up-to-date chapters covering a full range of topics
Author: Meagan Joan Eagle Gonneea
Publisher:
ISBN:
Category : Biogeochemical cycles
Languages : en
Pages : 331
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Book Description
At the land-ocean interface, terrestrial groundwater interacts with seawater to form a subterranean estuary, which can play host to dynamic biogeochemical cycling of nutrients, trace metals and radionuclides. This chemically altered groundwater enters the ocean through submarine groundwater discharge (SGD), a process that is driven by a number of physical processes acting on aquifers and the coastal ocean. In this thesis, seasonal variability in chemical cycling and associated loading to the coastal ocean was observed in a monthly time series within the Waquoit Bay (MA, USA) subterranean estuary. The position of the aquifer mixing zone moved seaward with an increase in hydraulic gradient, resulting in low salinity conditions and reduced mixing, while a decrease in gradient led to landward movement, high salinity groundwater and enhanced mixing. At this location, seasonal variability in sea level, not groundwater level, was the dominant variable driving the hydraulic gradient and therefore SGD. Fluxes of sediment bound cations to the ocean increased coincidently with sea level rise due to desorption. There was enhanced nitrogen attenuation during winter, potentially due to longer groundwater residence times, with greater nutrient delivery to coastal waters during the spring and summer bloom. Interannual climate fluctuations that control sea level and precipitation may ultimately control the timing and magnitude of chemical and water flux via SGD. In addition to temporal variability, aquifer lithology influences chemical export. This thesis also demonstrates that SGD from karst subterranean estuaries may play a role in local and global element budgets. The potential for the chemical signature of SGD to be recorded in the coral record was tested through a combination of coral culture experiments and field and modeling studies in the Yucatan Peninsula. Coral barium was well correlated with precipitation for a twelve-year record, with coral geochemistry reflecting the passage of a hurricane in 2002. While additional complexities in deciphering coral records remain, this proxy offers the potential to extend SGD records into the past.
