Physical Sciences and Mathematics Commons^™

Abundance, Stable Isotopic Composition, And Export Fluxes Of Doc, Poc, And Dic From The Lower Mississippi River During 2006-2008, Yihua Cai, Laodong Guo, Xuri Wang, George Aiken

Faculty Publications

Sources, abundance, isotopic compositions, and export fluxes of dissolved inorganic carbon (DIC), dissolved and colloidal organic carbon (DOC and COC), and particulate organic carbon (POC), and their response to hydrologic regimes were examined through monthly sampling from the Lower Mississippi River during 2006–2008. DIC was the most abundant carbon species, followed by POC and DOC. Concentration and δ¹³C of DIC decreased with increasing river discharge, while those of DOC remained fairly stable. COC comprised 61 ± 3% of the bulk DOC with similar δ¹³C abundances but higher percentages of hydrophobic organic acids than DOC, suggesting its …

Assessing Biogeochemical Impacts And Environmental Conditions Associated With Cross-Shelf High Chlorophyll Plumes In The Northern Gulf Of Mexico, Erin Brooke Jones

Dissertations

The northern Gulf of Mexico is a complex marine system subject to episodic physical phenomena such as loop current eddies. Flow fields generated by these eddies can result in cross-shelf exchanges between riverine influenced shelf waters and the offshore water column. This study considers the impacts of high chlorophyll plumes (HCPs) resulting from cross-shelf exchanges to the bio-optical properties of affected waters and how these plumes are influenced by their environment. The seasonal, interannual and decadal chlorophyll cycles of the Gulf of Mexico and the northern Gulf of Mexico are described to provide context for evaluating the ecological effects of …

Slides: Six Decades Of Texas Water Planning, Ronald Kaiser

Innovations in Managing Western Water: New Approaches for Balancing Environmental, Social and Economic Outcomes (Martz Summer Conference, June 11-12)

Presenter: Ronald Kaiser, Professor of Water Law and Policy, Chair of Graduate Water Degree Program, Texas A&M University

32 slides

Sub-Marine Sediment Instability Near Southwest Pass Of The Mississippi River: Evidence Of Mass Movements From Raciochemistry And Other Proxies, Gregory Paul Keller

LSU Master's Theses

Mass wasting events are an important geomorphic control on the Mississippi River Delta Front. Short multicores (<50cm) and longer gravity cores (<3m) were collected seaward of the Southwest Pass of the Mississippi River Delta and were analyzed to assess the frequency, extent, and potential causes of submarine mass wasting events. Cores were analyzed for radionuclide activity, grain size, and density at 2cm resolution. Short-term sedimentation rates calculated from 7-Be are 2-16cm/y, while longer-term accumulation from 210-Pb are only 1.3-7.3 cm/y. In most cores, 210-Pb activity steadily decreases downcore without displaying a “stairstep” nature. However, seven cores have layers of low 210-Pb activity stratigraphically above layers with higher activity. In a gravity core from a mudflow gully, 210-Pb steadily decreases for the upper 70 cm before stabilizing for the remaining 150 cm. Clay content generally ranges between 25-40% and sand ranges between 5-15% with silt making up the rest of each sample. Sediment accumulation rates derived from 210-Pb in the short cores indicate that proximity to the river mouth has stronger influence than depositional environment (mudflow gully, depositional lobe, prodelta). This finding may be explained by rapid sedimentation rates coupled with a reduced tropical cyclone activity over the delta in the last seven years (2006-2013) which is a known cause of mass wasting events. The regions of decreased 210-Pb activity may be evidence of scavenging effects of plume sedimentation because they do not correspond with decreases in clay fraction. The layer of homogenized activity below 70cm in the gully core corresponds with a layer of decreased density. This layer occurs at a depth equivalent to 9-18 years, indicating mixing on a decadal scale from mudflows. These results may be explained by a lack of recent mass failures corresponding with lulls in tropical cyclone activity over the delta, preceded by a period of more active hurricane-driven mudflow activity.

If You Build It, What Will Come? Assessing The Avian Response To Wetland Restoration In The Mississippi River Bird’S Foot Delta Through Multiple Measures Of Density And Biodiversity, Lauren Rae Sullivan

LSU Master's Theses

Multiple wetland restoration and enhancement techniques are used in Louisiana to combat land loss and provide habitat for waterbirds. We investigated the avian response to three wetland restoration techniques in the Lower Mississippi Bird’s Foot Delta to determine if the different habitat types resulted in differences in the value of edge habitat. Species richness, guild richness, total bird density, bird density by foraging guild, and bird abundance relative to distance from the marsh edge was compared among (i) crevasse splays, a type of sediment diversion which allow the river to build new wetlands, (ii), beneficial use of dredged material marshes, …