Oceanography Commons^™

Spatial Variations In Chlorophyll A, C, N, And P In A Louisiana Estuary From 1994 To 2016, R. Eugene Turner, Erick M. Swenson, Charles S. Milan, James M. Lee

Faculty Publications

Intense sampling of an estuary can reveal relative spatial changes that are significant irrespective of whether or not the estuary is eutrophic, micro- or meso-tidal, disturbed, or restored. This waterscape' perspective is analogous to a landscape perspective. We collected monthly water samples in the Barataria Basin watershed from 1994 to 2016 at 37 stations along a 129km transect from 1km offshore to a freshwater stream. The average Chlorophyll a (Chl) concentration from 267 trips was supported from both nitrogen-fixing cyanobacteria in a freshwater lake and partially from nutrients in seaward sources. Estuarine salinity was correlated with the discharge of the …

Spatiotemporal Variation Of Benthic Silica Fluxes In The Ngom Shelf, Byron Ebner

LSU Master's Theses

Dissolved silica (DSi), plays an important role in regulating primary productivity of silicifying organisms, such as diatoms which precipitate hard parts composed of biogenic silica (bSi) in coastal and shelf ecosystems fed by major rivers. In the Northern Gulf of Mexico (NGOM), loading of nitrogen and phosphorous have increased compared to a decline in DSi in the Mississippi River. Continued decreasing in DSi loading could lead to limited diatom growth and production or shifts in community composition, therefore, it is important understand the role of benthic fluxes in providing silica to the overlying water column as there are few regional …

Assessment And Correction Of Lidar-Derived Dems In The Coastal Marshes Of Louisiana, William M. Lauve

LSU Master's Theses

The onset of airborne light detection and ranging (lidar) has resulted in expansive, precise digital elevation models (DEMs). DEMs are essential for modeling complex systems, such as the coastal land margin of Louisiana. They are used for many applications (e.g. tide, storm surge, and ecological modeling) and by diverse groups (e.g. state and federal agencies, NGOs, and academia). However, in a marsh environment, it is difficult for airborne lidar to produce accurate bare-earth measurements and even accurate elevations are rarely verified by ground truth data. The accuracy of lidar in marshes is limited by the sensor’s resolution …

Vulnerability Of Industrial Facilities In The Lower Mississippi River Industrial Corridor To Relative Sea Level Rise And Tropical Cyclone Storm Surge, Joseph Blake Harris

LSU Doctoral Dissertations

Relative sea level rise (RSLR) and tropical cyclone-induced storm surge are major threats to the Lower Mississippi River Industrial Corridor (LMRIC) which has approximately 120 industrial complexes located within the corridor. Spatial interpolation methods were applied to the 2004 National Oceanic and Atmospheric published Technical Report #50 subsidence dataset and cross-validation techniques were used to determine the accuracy of each method. Digital elevation models (DEMs) were created for the years 2025, 2050, and 2075, based on these predictive surface of subsidence rates. Future DEMs were utilized to model RSLR and determine the extent of storm surge on the LMRIC by …

Iron Mediated Organic Preservation In A River Influenced Continental Margin, Neha Ajit Ghaisas

LSU Doctoral Dissertations

Continental margins such as the Mississippi river influenced Louisiana shelf (MIS), are important land-ocean interfaces where excessive water column productivity and rapid burial results in large amounts of organic carbon (OC) being sequestered in the sediments. The preservation of OC in sediments is controlled by a number of processes among which mineral-OC interactions are considered to be more important. Specifically, the interactions between sediment iron (Fe) species and OC have been shown to promote carbon preservation. However, the exact nature of preservation mechanism is not well understood and is based on limited global data, which specifically lacks estimates from large …

Evaluating Seasonal Nutrient Fluxes In Emerging And Eroding Wetlands Of The Louisiana Delta Plain, Kiran Upreti

LSU Doctoral Dissertations

Deltaic wetlands can ameliorate high NO₃^- loads via denitrification, a dominant NO₃^- reduction pathway in inland and coastal habitats. Dissimilatory Nitrate Reduction to Ammonia (DNRA), in contrast to denitrification, conserves N within the system and has been found to be favored over denitrification with increase in salinity and temperature. There are no studies in the Louisiana Deltaic plain with simultaneous estimation of denitrification and DNRA. Increased P availability has been shown to increase denitrification so it is essential to understand P biogeochemistry when studying N cycle. Here, we evaluated net denitrification using N₂:Ar and …

In Situ Geochemistry Of Middle Ordovician Dolomites Of The Upper Mississippi Valley, Achim D. Herrmann

Faculty Publications

The dolomitization and diagenetic history of Ordovician carbonates of southern Wisconsin is complex. Previous studies attributed dolomitization to various diagenetic factors and environments. In this study, high-resolution, in situ laser ablation inductively coupled mass spectrometry analysis of rare earth element patterns of dolomite was used to assess the diagenetic fluids responsible for dolomitization of the Ordovician Decorah Formation. Integrated geochemical data and petrographic evidence suggest that the dolostones are formed in two different diagenetic realms: shallow burial and hydrothermal. Shallow burial dolomites exhibit three distinct rare earth element patterns. Dolomite from the middle portion of the Guttenberg Member exhibits light …

Habitat Usage Patterns Of Bottlenose Dolphins (Tursiops Truncatus) In Terrebonne And Timbalier Bays, Louisiana, Mary Allison Manning

LSU Master's Theses

I coupled fine-scale environmental data with observed behavior and group composition data to examine overall distribution within the bay system and to characterize the habitat associated with foraging and the presence of calves. Semi-isolated populations of bottlenose dolphins (Tursiops truncatus) along Louisiana’s coast are undergoing increased risks from boat traffic, oil spills, land subsidence, and planned water diversions (CPRA 2017). Characterizing the habitat use of bottlenose dolphins in Terrebonne and Timbalier bays, Louisiana, is important given the likely high site fidelity, small home ranges, and low exchange of individuals with nearby coastal populations (Lane et al. 2015, McDonald …

Effects Of Shoal Margin Collapses On The Morphodynamics Of A Sandy Estuary, M. R. Hiatt

Faculty Publications

Shoal margin collapses of several million cubic meters have occurred in the Western Scheldt estuary, the Netherlands, on average five times a year over the last decades. While these collapses involve significant volumes of material, their effect on the channel-shoal morphology is unknown. We hypothesize that collapses dynamicize the channel-shoal interactions, which could impact the ecological functioning, flood safety, and navigation in the estuary. The objective is to investigate how locations, probability, type, and volume of shoal margin collapse affect the channel-shoal dynamics. We implemented an empirically validated parameterization for shoal margin collapses and tested its effect on simulated estuary …

Tidal-, Wind-, And Buoyancy-Driven Dynamics In The Barataria Estuary And Its Impact On Estuarine-Shelf Exchange Processes, Linlin Cui

LSU Doctoral Dissertations

A three-dimensional, high-resolution, Finite-Volume Coastal Ocean Model (FVCOM) was used to study the dynamics of Barataria Estuary located in the Southeastern Louisiana. Three numerical experiments with different discharge scenarios, including the actual discharge (average ~ 160 m³ s^-1) from the Davis Pond Diversion (DPD) over three months from April to June 2010, no discharge (NO), and the proposed Mid-Barataria Diversion (MBD) with a constant discharge of 850 m³ s^-1, were conducted to investigate the impacts of river diversions on salinity gradients and residence times in the estuary. The three-month average salinity indicated that surface …

Using Local Fishery Monitoring To Understand Small-Scale Coastal Fisheries In Tanzania, Matthew Robertson

LSU Master's Theses

Nearshore marine fisheries provide the main source of protein for nearly 9 million people in the coastal villages of Tanzania, yet for decades the fisheries have shown signs of overexploitation. These fisheries are small-scale and co-managed by local coastal communities in groups known as Beach Management Units (BMUs). BMUs monitor individual fishing trip data (e.g. gear, vessel, taxa); however, these data have only been analyzed in nationally aggregated statistics and to our knowledge, are not presently used in management decision making. The present thesis aimed to identify the forms of data and information that local fishery monitoring can record about …

Effects Of Natural And Anthropogenic Forcing On Marsh Channel Evolution, Jeremiah Robinson

LSU Master's Theses

Wetlands have many ecological and physical properties that are essential for coastal communities. These ecosystems sustain local economies, provide essential habitats, are a source of numerous ecological and biological services, and protect coastal populations from storms. Of the many wetland types, salt marshes are among the most vulnerable to environmental changes. Salt marshes quickly respond to natural and human-driven perturbations and their high rate of loss in the last century is cause for concern.

In this project the rate of marsh loss driven by channel widening was measured through a comparative analysis of modern high resolution images and historic aerial …

A Novel Multiproxy Approach To Reconstructing Sea Surface Temperature In The Southwestern Gulf Of Mexico, Marissa Anne Vara

LSU Master's Theses

Coral Sr/Ca is a widely-used proxy for sea surface temperature (SST); however, discrepancies in the coral Sr/Ca-SST relationship among colonies of the same species makes uncertainty in absolute temperature reconstructions larger than the climate signal yet climate variability studies are possible. Furthermore, the riverine input of terrestrial carbonate weathering products to the coastal waters can disrupt the coral Sr/Ca-SST signal by changing local seawater chemistry. This study evaluates the fidelity and reproducibly of coral SST proxies (Sr/Ca, Li/Ca, Mg/Li, Sr-U, Mg/Ca, and U/Ca) and a riverine-upwelling proxy (Ba/Ca) in four Orbicella faveolata colonies in two reefs offshore from Veracruz, Mexico …

Influence Of Black Mangrove Expansion On Salt Marsh Faunal Communities Of Eastern Coastal Louisiana, Christina Powell

LSU Master's Theses

The salt marshes along the Gulf of Mexico provide a critical habitat for many species, but their spatial distribution is changing, because Avicennia germinans (black mangroves) are expanding due to warmer winters. Currently, little is known about how A. germinans are used as habitat providing food and refuge for aquatic fauna. Therefore, the overall goal of this study was to determine how A.germinans expansion into the Spartina alterniflora (smooth cordgrass) marshes of Louisiana’s Mississippi River delta plain affects salt marsh-dependent organisms. This study analyzed three habitat types: Spartina-dominated, Avicennia-dominated, and a mix of the two, focusing on habitat use and …

Numerical Experiment Of Sediment Dynamics Over A Dredged Pit On The Louisiana Shelf, Nazanin Chaichitehrani

LSU Doctoral Dissertations

Sediment transport over Sandy Point dredge pit in the northern Gulf of Mexico was examined using field measurements and a finely resolved numerical model. Delft3D model with well-vetted computational grid and input parameters was used. Numerical experiments were performed to examine the effect of wind-generated waves, wind-driven currents and their interaction on sediment dynamics in our study area during a cold front in November 2014 and fair-weather conditions between July and August of 2015. Sediment dispersal from the lower Mississippi River, sediment resuspension, transport and deposition with high spatial and temporal resolution were simulated. A reliable satellite-derived near-surface suspended particulate …

Natural And Anthropogenic Impacts On Sediment Dynamics And Preservation In Contrasting Mississippi Deltaic Coastal Environments, Jiaze Wang

LSU Doctoral Dissertations

Deltas worldwide share the same sinking problem in face of pressure from natural and anthropogenic activities. Many restoration strategies are being planned or have been implemented in the coasts around the world. However, many conventional hard structure constructions are energy-intensive. There are also associated uncertainties and limitations on the effectiveness and sustainability of these restoration plans. Soft or ecological engineering strategies normally take advantage of or mimic the coastal system self-response and feedbacks to natural and anthropogenic activities. The successful implementation of soft strategies relies on process-based studies on the change of complex coastal system. In addition, post-implementation monitoring work …

Dinoflagellate Cysts Track Eutrophication In The Northern Gulf Of Mexico, Andrea M. Price, Melissa M. Baustian, R. Eugene Turner, Nancy N. Rabalais, Gail L. Chmura

Faculty Publications

We examined organic-walled dinoflagellate cysts from one 210Pb-dated sediment core and 39 surface sediment samples from the northern Gulf of Mexico to determine the relationship between nutrient enrichment and cyst assemblages in this region characterized by oxygen deficiency. The core spans from 1962 to 1997 and its sampling location is directly influenced by the Mississippi River plume. Surface sediments were collected in 2006, 2007, 2008, and 2014 and represent approximately 1 to 4 years of accumulation. A total of 57 cyst taxa were recorded, and four heterotrophic taxa in particular were found to increase in the top section (1986–1997) of …

Paleoenvironmental Reconstruction Using Coral Microatolls (Sp. Siderastrea Siderea) From The Gulf Of Gonâve, Haiti, Gilman Reno Ouellette Jr.

LSU Doctoral Dissertations

Natural and anthropogenic climate changes present unique and serious risks to society. In order to plan and implement adaptation and mitigation strategies successfully, regional manifestations of broad-scale climate changes must be understood robustly. The Caribbean region contains part of the Western Hemisphere Warm Pool (WHWP), a major sea surface temperature (SST) feature that plays a key role in North Atlantic climate. Climate variability in the Caribbean is captured poorly by climate models, due in part to a lack of continuous, multidecadal instrumental climate records from the region. I explored three research questions in this dissertation: Does non-systematic bias exist in …

How Dredge Pits Evolve Over Time: A Look At Their Geomorphologic Evolution And Infilling Processes, Patrick Robichaux

LSU Master's Theses

As coastal environments become more susceptible to land loss through accelerating sea level rise and subsidence, new restoration methods harnessing borrowed sediment are more valuable than ever. Mud-capped dredge pits (MCDPs) are a relatively new source of restoration-quality sediment that has only recently been utilized for beach and barrier island restorations in Louisiana. Because MCDPs have been in use for less than two decades in only a handful sites, little is understood about their evolution over decadal timescales. To improve our understanding of MCDPs after they are dredged, we have conducted a suite of geophysical surveys including bathymetry, sidescan sonar, …

The Changshu Declaration On Wetlands, R. Eugene Turner, Jos T. A. Verhoeven, Ania Grobicki, Jenny Davis, Shuqing An

Faculty Publications

No abstract provided.

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

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

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 …

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 …

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

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

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

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

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

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) …