acase@tulane.edu / Natural systems can be altered, over a wide range of time scales, through changes in environmental conditions. In the Mississippi Delta, which has been shaped by changes in sediment deposition and sea level at the land-ocean interface over the Holocene, changes to environmental conditions lead to state changes that can be observed in both modern ecosystems and the depositional record. Alluvial strata (which comprise the bulk of the world’s sedimentary record) can provide insight into past triggers for ecosystem state changes and can be compared to modern monitoring data to paint a fuller picture of system response to environmental change. Given the large potential impact of anthropogenic climate change on natural systems, this combination of modern and paleo-environmental information may improve our ability to predict future conditions.
This dissertation explores coastal and delta plain ecosystem responses to environmental change, particularly relative sea-level rise over annual to millennial timescales (Chapters 2 and 3) and rates of carbon storage by organic and clastic deposits in the Mississippi Delta (Chapter 4). Chapter 2 describes the results of an analysis of how subsidence and relative sea-level rise affect modern wetlands in coastal Louisiana. Using 274 rod surface-elevation table – marker horizon records, GPS measurements, and satellite altimetry data from the Gulf of Mexico, this chapter assesses present-day wetland vulnerability given current environmental conditions.
Chapter 3 describes an analysis of how changes in past environmental conditions, specifically variable rates of relative sea-level rise, impacted marshes in the Mississippi Delta throughout the Holocene. Using 355 sediment cores, this chapter identifies relative sea-level rise tipping points that lead to marsh collapse and a state shift from marsh to open water. Using 14C dating, foraminiferal assemblage analysis, and stable isotope geochemistry, this chapter also estimates the time necessary for reestablishment of terrestrial conditions after an initial marsh collapse and conversion to open water at one selected location. Together, these results provide a framework for projecting likely marsh response to future increased rates of relative sea-level rise in coastal Louisiana. The combination of these studies provides a more complete picture of modern and future wetland vulnerability in coastal Louisiana and provides unique insights into the limitations of short-term observational studies of marsh conditions for projecting long-term outcomes in response to environmental change.
Chapter 4 describes the results of a comparative analysis of carbon storage rates in organic and clastic deposits within the Holocene sedimentary record near Bayou Lafourche in the Mississippi Delta. Using 14C and OSL dating, elemental analysis, and bulk density measurements collected from three sediment cores, this chapter calculates carbon storage rates to determine the relative carbon storage efficiency of these deposits. This chapter provides an important comparison to similar work in deltaic deposits of the Wax Lake Delta. Furthermore, the high rates of carbon storage within the dominantly clastic deposits, which are interpreted as a proxy for planned sediment diversions in the region, provide an estimate for future carbon storage potential by these coastal restoration efforts. / 1 / Krista L. Jankowski
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_83024 |
| Date | January 2018 |
| Contributors | Jankowski, Krista L. (author), Törnqvist, Torbjörn E (Thesis advisor), School of Science & Engineering Earth and Environmental Sciences (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 123 |
| Rights | 6 months, Copyright is in accordance with U.S. Copyright law. |
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