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Articles 61 - 90 of 117
Full-Text Articles in Oceanography
Biological Hot Spots And The Accumulation Of Marine Dissolved Organic Matter In A Highly Productive Ocean Margin, Yuan Shen, Cédric G. Fichot, Sheng-Kang Liang, Ronald Benner
Biological Hot Spots And The Accumulation Of Marine Dissolved Organic Matter In A Highly Productive Ocean Margin, Yuan Shen, Cédric G. Fichot, Sheng-Kang Liang, Ronald Benner
Faculty Publications
Concentrations of dissolved organic carbon (DOC) and major biochemicals (amino acids and carbohydrates) were measured during five cruises (2009–2010) to the Louisiana margin in the northern Gulf of Mexico. Concentrations of amino acids and carbohydrates were elevated at mid-salinities and were indicative of plankton production of dissolved organic matter (DOM) in surface waters. Hot spots of two compositionally distinct types of labile DOM were identified based on the relative abundances of amino acids and carbohydrates. Amino acid-rich hot spots occurred sporadically in regions of high phytoplankton biomass and were mostly observed between dusk and dawn, reflecting a grazing source. In …
Influence Of The Mississippi River On Pseudo-Nitzschia Spp. Abundance And Toxicity In Louisiana Coastal Waters, Sibel Bargu, Melissa M. Baustian, Nancy N. Rabalais, Ross Del Rio, Benjamin Von Korff, R. Eugene Turner
Influence Of The Mississippi River On Pseudo-Nitzschia Spp. Abundance And Toxicity In Louisiana Coastal Waters, Sibel Bargu, Melissa M. Baustian, Nancy N. Rabalais, Ross Del Rio, Benjamin Von Korff, R. Eugene Turner
Faculty Publications
The presence of domoic acid (DA) toxin from multiple species of Pseudo-nitzschia is a concern in the highly productive food webs of the northern 1,* 2,3 2 1 1,4 1 1 2 3 4 Gulf of Mexico. We documented the Pseudo-nitzschia presence, abundance, blooms, and toxicity over 3 years along a transect ∼100 km west of the Mississippi River Delta on the continental shelf. Pseudo-nitzschia were present throughout the year and occurred in high abundances (>10 cells l ) in the early spring months during high Mississippi River (MSR) flow (∼20,000 m s ) but were most abundant ( …
Size-Dependent Top-Down Control On Phytoplankton Growth By Microzooplankton In Eutrophic Lakes, Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner
Size-Dependent Top-Down Control On Phytoplankton Growth By Microzooplankton In Eutrophic Lakes, Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner
Faculty Publications
We hypothesized that the grazing on phytoplankton by the microzooplankton community is size-dependent and, therefore, the top-down control on phytoplankton by microzooplankton community could be one possible mechanism explaining why small phytoplankton become less abundant than large phytoplankton in eutrophic waters. We tested this hypothesis using the dilution method to measure microzooplankton grazing rates and phytoplankton growth rates in the eutrophic waters of the Barataria estuary, southeastern Louisiana. Microzooplankton grazing rates on the slower growing, small phytoplankton (\5 lm) were higher than on the large phytoplankton ([20 lm) which had relatively faster growth rates. The proportional loss of the small, …
Effects Of Oil-Contaminated Sediments On Submerged Vegetation: An Experimental Assessment Of Ruppia Maritima, Charles W. Martin, Lauris O. Hollis, R. Eugene Turner
Effects Of Oil-Contaminated Sediments On Submerged Vegetation: An Experimental Assessment Of Ruppia Maritima, Charles W. Martin, Lauris O. Hollis, R. Eugene Turner
Faculty Publications
Oil spills threaten the productivity of ecosystems through the degradation of coastal flora and the ecosystem services these plants provide. While lab and field investigations have quantified the response of numerous species of emergent vegetation to oil, the effects on submerged vegetation remain uncertain. Here, we discuss the implications of oil exposure for Ruppia maritima, one of the most common species of submerged vegetation found in the region affected by the recent Deepwater Horizon oil spill. We grew R. maritima in a range of manipulated sediment oil concentrations: 0, 0.26, 0.53, and 1.05 mL oil /L tank volume, and tracked …
Dissolved Fe And Al In The Upper 1000 M Of The Eastern Indian Ocean: A High‐Resolution Transect Along 95°E From The Antarctic Margin To The Bay Of Bengal, Maxime Grand, Christopher Measures, Mariko Hatta, William Hiscock, William Landing, Peter Morton, Clifton Buck, Pamela Barrett, Joseph Resing
Dissolved Fe And Al In The Upper 1000 M Of The Eastern Indian Ocean: A High‐Resolution Transect Along 95°E From The Antarctic Margin To The Bay Of Bengal, Maxime Grand, Christopher Measures, Mariko Hatta, William Hiscock, William Landing, Peter Morton, Clifton Buck, Pamela Barrett, Joseph Resing
Faculty Publications
A high‐resolution section of dissolved iron (dFe) and aluminum (dAl) was obtained along ~95°E in the upper 1000 m of the eastern Indian Ocean from the Antarctic margin (66°S) to the Bay of Bengal (18°N) during the U.S. Climate Variability and Predictability (CLIVAR) CO2 Repeat Hydrography I08S and I09N sections (February–April 2007). In the Southern Ocean, low concentrations of dAl (<1 n M) reflect the negligible dust inputs impacting the water masses subducted in the circumpolar domain. The low dAl concentrations characterizing the Southern Ocean terminate near 45°S, probably because of the advection of subtropical water masses that received dust and sedimentary inputs in their formation region. Our subsurface dFe data near the southern Kerguelen Plateau were significantly higher than historical observations in other Indian sectors of the Southern Ocean. We surmise that the offshore advection of dFe‐rich waters along the western flank of the southern Kerguelen plateau and enhanced vertical mixing could contribute to this elevated subsurface dFe inventory. Elevated subsurface particulate and dFe levels downstream of the northern Kerguelen Plateau may reflect long‐range lateral transport from the plateau's sediments and/or remineralization inputs. At the northern edge of the south Indian subtropical gyre, the deposition of Australian dust, possibly combined with the advection of dAl‐enriched waters from the Indonesian Throughflow, creates a region of elevated dAl in the upper 400 m but without a corresponding enrichment in dFe. In the northern Indian Ocean, the South Equatorial Current constitutes a remarkable biogeochemical front separating the oxygen‐rich and dFe‐poor subtropical gyre waters from the dFe‐rich and oxygen‐depleted waters of the northern Indian Ocean. By tracing the accumulation of macronutrients and dFe along the advective pathway of Indian Central Water, we show that the central waters of the northern Indian Ocean receive excess dFe in addition to that produced by remineralization inputs. The resuspension of shelf sediments and release of pore waters probably contribute to the elevated dFe and dAl levels observed below the highly stratified upper layers of the Bay of Bengal.
Dust Deposition In The Eastern Indian Ocean: The Ocean Perspective From Antarctica To The Bay Of Bengal, Maxime Grand, Christopher Measures, Mariko Hatta, William Hiscock, Clifton Buck, William Landing
Dust Deposition In The Eastern Indian Ocean: The Ocean Perspective From Antarctica To The Bay Of Bengal, Maxime Grand, Christopher Measures, Mariko Hatta, William Hiscock, Clifton Buck, William Landing
Faculty Publications
Atmospheric deposition is an important but still poorly constrained source of trace micronutrients to the open ocean because of the dearth of in situ measurements of total deposition (i.e., wet + dry deposition) in remote regions. In this work, we discuss the upper ocean distribution of dissolved Fe and Al in the eastern Indian Ocean along a 95°E meridional transect spanning the Antarctic margin to the Bay of Bengal. We use the mixed layer concentration of dissolved Al in conjunction with empirical data in a simple steady state model to produce 75 estimates of total dust deposition that we compare …
Quantifying The Impact Of Atmospheric Deposition On The Biogeochemistry Of Fe And Al In The Upper Ocean: A Decade Of Collaboration With The Us Clivar-Co2 Repeat Hydrography Program, Maxime Grand, Clifton Buck, William Landing, Christopher Measures, Mariko Hatta, William Hiscock, Matthew Brown, Joseph Resing
Quantifying The Impact Of Atmospheric Deposition On The Biogeochemistry Of Fe And Al In The Upper Ocean: A Decade Of Collaboration With The Us Clivar-Co2 Repeat Hydrography Program, Maxime Grand, Clifton Buck, William Landing, Christopher Measures, Mariko Hatta, William Hiscock, Matthew Brown, Joseph Resing
Faculty Publications
The aerosol deposition of continental material and its partial dissolution in the surface ocean exerts an important control on the distribution of iron and other potentially limiting trace metal (TM) micronutrients in the open ocean. This dust deposition has implications for the regulation of global climate through the coupling of biolimiting TM cycles, marine productivity, and the global carbon cycle. Thus, it is important to determine the locations of dust deposition in the open ocean and to quantify the magnitude and subsequent dissolution of the dust. At present, there are too few dust deposition estimates and solubility measurements in the …
The Global Sustainability Transition: It Is More Than Changing Light Bulbs, Michael P. Weinstein, R. Eugene Turner, Carles Ibanez
The Global Sustainability Transition: It Is More Than Changing Light Bulbs, Michael P. Weinstein, R. Eugene Turner, Carles Ibanez
Faculty Publications
Current policies and norms to reconcile human demands for resources with the Earth’s ability to supply them have resulted in practices that mainly treat the symptoms of unsustainability rather than their underlying causes. Moreover, the increase in our knowledge about humankind’s role in ecosystems is not keeping pace with our understanding of the consequences of our actions, resulting in a deepening inability to address sustainability issues. The extreme complexity and intricate workings of the world require the expansion of our mental models in a systems-thinking framework if we are to realize a sustainable place for humans in it. The challenge …
Isotopic (Δ13c, Δ14c) Analysis Of Organic Acids In Marine Samples Using Wet Chemical Oxidation, Susan Q. Lang, G. L. Früh-Green, S. M. Bernasconi, L. Wacker
Isotopic (Δ13c, Δ14c) Analysis Of Organic Acids In Marine Samples Using Wet Chemical Oxidation, Susan Q. Lang, G. L. Früh-Green, S. M. Bernasconi, L. Wacker
Faculty Publications
We present a method for the isolation and off-line isotope analysis of formate and acetate in marine samples. Organic acids are separated by high performance liquid chromatography and collected in glass Exetainer® screw-capped vials that have been prespiked with an oxidant and flushed with helium. The vials are subsequently heated to convert the organic compounds to CO2 for radiocarbon and δ13C analysis. Small aliquots are sampled for measurement of δ13C by isotope ratio mass spectrometry, whereas the majority of the CO2 is saved for radiocarbon analysis by accelerator mass spectrometry using a gas ion …
Bioactive Trace Metal Distributions And Biogeochemical Controls In The Southern Ocean, Christopher Measures, Mariko Hatta, Maxime Grand
Bioactive Trace Metal Distributions And Biogeochemical Controls In The Southern Ocean, Christopher Measures, Mariko Hatta, Maxime Grand
Faculty Publications
Extensive sampling in many regions of the Southern Ocean has demonstrated that surface water concentrations of dissolved Fe are low enough to limit phytoplankton growth. In contrast, there is currently no evidence that other bioactive elements (e.g., Mn, Zn, Co) are similarly limiting. Although atmospheric input of dissolved Fe to Southern Ocean surface waters appears to be low, resuspension of sediments from shallow regions around islands and the Antarctic coastline can inject significant amounts of Fe into the surrounding waters, stimulating primary production and providing a natural laboratory for studying the response of biological systems to natural Fe fertilization processes. …
Carbon Sequestration And Sediment Accretion In San Francisco Bay Tidal Wetlands, John C. Callaway, Evyan L. Borgnis, R. Eugene Turner, Charles S. Milan
Carbon Sequestration And Sediment Accretion In San Francisco Bay Tidal Wetlands, John C. Callaway, Evyan L. Borgnis, R. Eugene Turner, Charles S. Milan
Faculty Publications
Tidal wetlands play an important role with respect to climate change because of both their sensitivity to sea-level rise and their ability to sequester carbon dioxide from the atmosphere. Policy-based interest in carbon sequestration has increased recently, and wetland restoration projects have potential for carbon credits through soil carbon sequestration. We measured sediment accretion, mineral and organic matter accumulation, and carbon sequestration rates using 137Cs and 210Pb downcore distributions at six natural tidal wetlands in the San Francisco Bay Estuary. The accretion rates were, in general, 0.2–0.5 cm year−1, indicating that local wetlands are keeping pace with recent rates of …
Sustainability: More About The Toolmaker Than The Tools, R. Eugene Turner
Sustainability: More About The Toolmaker Than The Tools, R. Eugene Turner
Faculty Publications
A sustainable system is not necessarily a high-quality one, but it could be. We could, for example, “survive” on the desperate edge, as the remnants in a self-fouled and deteriorating environment. Why won’t a future sustainable system be just another industrial model of mass efficiency and throughput? Perhaps the incompatible outcomes are a choice between the sometimes nearly invisible civilizing aspects of culture nurturing respect, equality, and cooperation on one hand, and the greed and self-indulgences undermining social tolerance, empathy, and cooperation that ends up promoting violence and dehumanization. The human heritage is subtle, indestructible, and worth nurturing if we …
A Once And Future Gulf Of Mexico Ecosystem: Restoration Recommendations Of An Expert Working Group, Charles H. Peterson, Felicia C. Coleman, Jeremy B. C. Jackson, R. Eugene Turner, Gilbert T. Rowe, Richard T. Barber, Karen A. Bjorndal, Robert S. Carney, Robert K. Cowen, Jonathan M. Hoekstra, James T. Hollibaugh, Shirley B. Laska, Richard A. Luettich, Jr., Craig W. Osenberg, Stephen E. Roady, Stanley Senner, John M. Teal, Ping Wong
A Once And Future Gulf Of Mexico Ecosystem: Restoration Recommendations Of An Expert Working Group, Charles H. Peterson, Felicia C. Coleman, Jeremy B. C. Jackson, R. Eugene Turner, Gilbert T. Rowe, Richard T. Barber, Karen A. Bjorndal, Robert S. Carney, Robert K. Cowen, Jonathan M. Hoekstra, James T. Hollibaugh, Shirley B. Laska, Richard A. Luettich, Jr., Craig W. Osenberg, Stephen E. Roady, Stanley Senner, John M. Teal, Ping Wong
Faculty Publications
The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants—liquid and gaseous petroleum compounds plus chemical dispersants—poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these …
Beneath The Salt Marsh Canopy: Loss Of Soil Strength With Increasing Nutrient Loads, R. Eugene Turner
Beneath The Salt Marsh Canopy: Loss Of Soil Strength With Increasing Nutrient Loads, R. Eugene Turner
Faculty Publications
Although the broadly observed increase in nutrient loading rates to coastal waters in the last 100 years may increase aboveground biomass, it also tends to increase soil metabolism and lower root and rhizome biomass—responses that can compromise soil strength. Fourteen different multiyear field combinations of nutrient amendments to salt marshes were made to determine the relationship between soil strength and various nitrogen, phosphorus, and nitrogen+phosphorus loadings. There was a proportional decline in soil strength that reached 35% in the 60- to 100-cm soil layer at the highest loadings and did not level off. These loading rates are equivalent to those …
Abundance And Ecological Significance Of The Clam Rangia Cuneata (Sowerby, 1831) In The Upper Barataria Estuary (Louisiana, Usa), Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner
Abundance And Ecological Significance Of The Clam Rangia Cuneata (Sowerby, 1831) In The Upper Barataria Estuary (Louisiana, Usa), Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner
Faculty Publications
We proposed that Rangia cuneata (Sowerby, 1831) is an important estuarine bivalve with ecological significance in three coastal lakes in Barataria Bay, Gulf of Mexico—Lake Cataouatche, Lake Salvador and Lac des Allemands. Our goals were to determine the abundance and distribution of Rangia in these lakes and to measure clearance times to elucidate its potential impacts on phytoplankton communities. The estimated average densities of R. cuneata in Lake Cataouatche, Lake Salvador, and Lac des Allemands were 63, 157, and 107 individuals m−2, respectively, which is 30% lower than that observed in nearby Lake Pontchartrain. The size of clams in Lake …
Doubt And The Values Of An Ignorance-Based World View For Restoration: Coastal Louisiana Wetlands, R. Eugene Turner
Doubt And The Values Of An Ignorance-Based World View For Restoration: Coastal Louisiana Wetlands, R. Eugene Turner
Faculty Publications
Embracing doubt, a signature strength of science, is an essential core component of an ignorance-based-world view (IBWV) that assumes the areas of certainty are small relative to the large field of ignorance. The contrasting knowledge-based world view (KBWV) assumes that small and mostly insignificant knowledge gaps exist. When the KBWV is combined with a sense of urgency to “do something,” then the intellectual landscape is flattened, the introduction of new ideas is impeded, monitoring and adaptive management is marginalized, risky behaviors continue, and social learning is restricted. The history of three coastal Louisiana land-uses (agricultural impoundment, marsh management, and dredging) …
Nutrient Limitation On Phytoplankton Growth In The Upper Barataria Basin, Louisiana: Microcosm Bioassays, Ling Ren, Nancy N. Rabalais, R. Eugene Turner, Wendy Morrison, Warren Mendenhall
Nutrient Limitation On Phytoplankton Growth In The Upper Barataria Basin, Louisiana: Microcosm Bioassays, Ling Ren, Nancy N. Rabalais, R. Eugene Turner, Wendy Morrison, Warren Mendenhall
Faculty Publications
The Davis Pond Diversion (DPD) was constructed to divert Mississippi River (MR) water into the Barataria Basin to reduce the salinity in support of wetland restoration on the Louisiana coast. To assess the phytoplankton nutrient limitation in adjacent water systems and potential impacts of DPD, 12 seasonal nutrient-phytoplankton bioassay experiments were conducted from October 2003 to July 2004 using the natural phytoplankton assemblages from freshwater and brackish-water lakes, Cataouatche and Salvador, LA (USA), which receive Mississippi River water from the DPD, and from a nearby freshwater lake, Lac des Allemands, that does not. Dissolved inorganic nitrogen (N), phosphorus (P), and …
Nutrient Enrichment Drives Gulf Of Mexico Hypoxia, Donald F. Boesch, Walter R. Boyton, Larry B. Crowder, Robert J. Diaz, Robert W. Howarth, Laurence D. Mee, Scott W. Nixon, Nancy N. Rabalais, Rutger Rosenberg, James G. Sanders, Donald Scavia, R. Eugene Turner
Nutrient Enrichment Drives Gulf Of Mexico Hypoxia, Donald F. Boesch, Walter R. Boyton, Larry B. Crowder, Robert J. Diaz, Robert W. Howarth, Laurence D. Mee, Scott W. Nixon, Nancy N. Rabalais, Rutger Rosenberg, James G. Sanders, Donald Scavia, R. Eugene Turner
Faculty Publications
No abstract provided.
Comments On Buzan Et Al. “Positive Relationships Between Freshwater Inflow And Oyster Abundance In Galveston Bay, Texas”, R. Eugene Turner
Comments On Buzan Et Al. “Positive Relationships Between Freshwater Inflow And Oyster Abundance In Galveston Bay, Texas”, R. Eugene Turner
Faculty Publications
Buzan et al. critique Turner’s (Estuaries and Coasts 29:345–352, 2006) analysis of the relationship between freshwater inflow and oyster productivity in the Gulf of Mexico, using 16 years of fisheries-independent data for Galveston Bay. They conclude that the catch-per-unit effort (CPUE; number h−1) of marketable oysters increase 1 to 2 years after years with increased freshwater inflows, and they express concerns that water supply managers may mis-apply the results of Turner (Estuaries and Coasts 29:345–352, 2006) to justify a reduced freshwater inflow to Galveston Bay. I find no relationship between the CPUE of oyster spat or marketable oyster density and …
Hierarchical Modeling: Biogeochemical Processes And Mechanisms That Drive Clay Nano-And Microfabric Development, Kenneth J. Curry, Richard H. Bennett, Paula J. Smithka, Matthew H. Hulbert
Hierarchical Modeling: Biogeochemical Processes And Mechanisms That Drive Clay Nano-And Microfabric Development, Kenneth J. Curry, Richard H. Bennett, Paula J. Smithka, Matthew H. Hulbert
Faculty Publications
Conceptual scientific models of clay and clay fabric development can be constructed profitably by considering chemical and physical systems in terms of an ordered hierarchy. We develop here a hierarchical model of early stages of marine sediment development identifying processes and focusing on mechanisms. While the focus of our model is on mechanisms, the physical aspects of the hierarchy are cast in terms of the nanometer (nanofabric) level of organization of sediment fabric. This level is nested below the micrometer (microfabric) level that includes aggregates of clay signatures and is nested above the molecular level that includes edges and faces …
Restoration Of Dredged Canals In Wetlands: A Comparison Of Methods, Joseph Baustian, R. Eugene Turner, Nancy F. Walters, David P. Muth
Restoration Of Dredged Canals In Wetlands: A Comparison Of Methods, Joseph Baustian, R. Eugene Turner, Nancy F. Walters, David P. Muth
Faculty Publications
A comparison of two methods for restoring dredged canals to wetlands was examined at the Jean Lafitte National Historical Park and Preserve’s Barataria Preserve Unit near New Orleans, LA. Both northern and southern canals had the remnant dredged spoil material returned to the canal, but the southern canal had additional sediment pumped in from a nearby lake. The water depth in the southern canal shallowed significantly from 1.2 to 0.4 m following backfilling and sediment addition, while the depth of the northern canal (which received no additional sediment) remained unchanged following backfilling. Neither site had complete soil restoration, but the …
Below- And Aboveground Biomass Of Spartina Alterniflora: Response To Nutrient Addition In A Louisiana Salt Marsh, Faith A. Darby, R. Eugene Turner
Below- And Aboveground Biomass Of Spartina Alterniflora: Response To Nutrient Addition In A Louisiana Salt Marsh, Faith A. Darby, R. Eugene Turner
Faculty Publications
The responses of Spartina alterniflora above- and belowground biomass to various combinations of N, P, and Fe were documented in a 1-year field experiment in a Louisiana salt marsh. Five levels of N additions to 0.25 m2 plots resulted in 18% to 138% more live aboveground biomass compared to the control plots and higher stem densities, but had no effect on the amount of live belowground biomass (roots and rhizomes; R&R). There was no change in the aboveground biomass when P or Fe was added as part of a factorial experiment of +P, +N, and +Fe additions, but there was …
Hypoxia In The Northern Gulf Of Mexico: Does The Science Support The Plan To Reduce, Mitigate, And Control Hypoxia?, Nancy N. Rabalais, R. Eugene Turner, B.K. Sen Gupta, D. F. Boesch, P. Chapman, M. C. Murrell
Hypoxia In The Northern Gulf Of Mexico: Does The Science Support The Plan To Reduce, Mitigate, And Control Hypoxia?, Nancy N. Rabalais, R. Eugene Turner, B.K. Sen Gupta, D. F. Boesch, P. Chapman, M. C. Murrell
Faculty Publications
We update and reevaluate the scientific information on the distribution, history, and causes of continental shelf hypoxia that supports the 2001 Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force 2001), incorporating data, publications, and research results produced since the 1999 integrated assessment. The metric of mid-summer hypoxic area on the Louisiana-Texas shelf is an adequate and suitable measure for continued efforts to reduce nutrients loads from the Mississippi River and hypoxia in the northern Gulf of Mexico as outlined in the Action Plan. More frequent measurements …
Will Lowering Estuarine Salinity Increase Gulf Of Mexico Oyster Landings?, R. Eugene Turner
Will Lowering Estuarine Salinity Increase Gulf Of Mexico Oyster Landings?, R. Eugene Turner
Faculty Publications
Previous studies provide conflicting opinions on whether lower than average salinities in Gulf of Mexico (GOM) estuaries are likely to increase or decrease oyster harvests (Crassostrea virginica), which represented 69% and 54% of the United States oyster landings by weight, and dockside value, respectively, in 2003. The present study examined a 54-yr record (1950–2003) of oyster harvests and river discharge in five major estuaries in GOM states (Florida, Alabama, Mississippi, Louisiana, and Texas). Oyster landings were inversely related to freshwater inflow. Peaks in landings, 21 of 23 in West Florida, Alabama, Mississippi, and Texas combined, were coincidental with …
Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner
Oxygen Depletion In The Gulf Of Mexico Adjacent To The Mississippi River, Nancy N. Rabalais, R. Eugene Turner
Faculty Publications
The seasonal formation of a bottom water layer severely depleted in dissolved oxygen has become a perennial occurrence on the Louisiana continental shelf adjacent to the Mississippi River system. Dramatic changes have occurred in this coastal ecosystem in the last half of the 20th century as the loads of dissolved inorganic nitrogen tripled. There are increases in primary production, shifts in phytoplankton community composition, changes in trophic interactions, and worsening severity of hypoxia. The hypoxic conditions (dissolved oxygen less than 2 mg l-1) cover up to 22,000 km2 of the seabed in mid-summer. Dissolved oxygen concentrations seldom decrease to anoxia, …
Monsoon-Driven Biogeochemical Processes In The Arabian Sea, Jerry D. Wiggert, Raleigh Hood, Karl Banse, John Kindle
Monsoon-Driven Biogeochemical Processes In The Arabian Sea, Jerry D. Wiggert, Raleigh Hood, Karl Banse, John Kindle
Faculty Publications
Although it is nominally a tropical locale, the semiannual wind reversals associated with the Monsoon system of the Arabian Sea result annually in two distinct periods of elevated biological activity. While in both cases monsoonal forcing drives surface layer nutrient enrichment that supports increased rates of primary productivity, fundamentally different entrainment mechanisms are operating in summer (Southwest) and winter (Northeast) Monsoons. Moreover, the intervening intermonsoon periods, during which the region relaxes toward oligotrophic conditions more typical of tropical environments, provide a stark contrast to the dynamic biogeochemical activity of the monsoons. The resulting spatial and temporal variability is great and …
A Physiochemically Constrained Seawater Culturing System For Production Of Benthic Foraminifera, Christopher J. Hintz, G. Thomas Chandler, Jay M. Bernhardt, Daniel C. Mccorkle, Suzanne M. Havach, Jessica K. Blanks, Timothy J. Shaw
A Physiochemically Constrained Seawater Culturing System For Production Of Benthic Foraminifera, Christopher J. Hintz, G. Thomas Chandler, Jay M. Bernhardt, Daniel C. Mccorkle, Suzanne M. Havach, Jessica K. Blanks, Timothy J. Shaw
Faculty Publications
No abstract provided.
Coastal Wetland Subsidence Arising From Local Hydrologic Manipulations, R. Eugene Turner
Coastal Wetland Subsidence Arising From Local Hydrologic Manipulations, R. Eugene Turner
Faculty Publications
Twenty-three estimates of soil subsidence rates arising under the influence of local hydrologic changes from flap-gates, weirs, dikes, and culverts in tidal wetlands were compared to 75 examples of subsidence in drained agricultural wetlands. The induced subsidence rates from these hydrologic modifications in tidal wetlands can continue for more than 100 years, and range between 1.67 to 0.10 cm yr−1 within 1 to 155 years after the hydrologic modifications commence. These subsidence rates are lower than in freshwater wetlands drained for agricultural purposes, decline with age, and are significant in comparison to the rates of global sea level rise or …
Inorganic Nitrogen Transformations At High Loading Rates In An Oligohaline Estuary, R. Eugene Turner, Q. Dortch, Nancy N. Rabalais
Inorganic Nitrogen Transformations At High Loading Rates In An Oligohaline Estuary, R. Eugene Turner, Q. Dortch, Nancy N. Rabalais
Faculty Publications
A well-defined nitrogen retention and turnover budget was estimated for a shallow oligohaline lake (Lake Pontchartrain, Louisiana, USA). In 1997 a month-long diversion of the Mississippi River filled the Lake with highly concentrated river water (80 µM nitrate) and lowered the salinity to 0 psu within 2 weeks. After the spillway was closed the Lake mixed with estuarine tidal waters and came to equilibrium over 4 months with the riverine, atmospheric and offshore water nitrogen sources. A flushing rate of 1.78% d−1 was estimated by analyzing a plot of ln salinity versus time for the first 120 days after the …
Suspended Sediment, C, N, P, And Si Yields From The Mississippi River Basin, R. Eugene Turner, Nancy N. Rabalais
Suspended Sediment, C, N, P, And Si Yields From The Mississippi River Basin, R. Eugene Turner, Nancy N. Rabalais
Faculty Publications
The annual loads of C,N,P, silicate, total suspended sediment (mass) and their yields (mass area−1) were estimated for six watersheds of the Mississippi River Basin (MRB) using water quality and water discharge records for 1973 to 1994. The highest load of suspended sediments is from the Missouri watershed (58 mt km2 yr−1), which is also the largest among the six major sub-basins. The Ohio watershed delivers the largest load of water (38%). The Upper Mississippi has the largest total nitrogen load (32%) and yield (1120 kg TN km2 yr−1). The loading of organic carbon, total phosphorus and silicate from the …