Palynological and Geochemical Records of Environmental Changes in a Taxodium Swamp near Lake Pontchartrain in Southern Louisiana (USA) during the Last 150 Years

Ryu, Junghyung; Bianchette, Thomas A.; Liu, Kam‐biu; Yao, Qiang; Maiti, Kanchan

doi:10.2112/si85-077.1

Cited by 15 publications

(17 citation statements)

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“…The ratio of Cl/Br has the highest score on both PC1 and PC2 axes; hence, it has the closest association with Wilma deposits. Many studies have revealed that although aqueous bromine (HOBr/OBr‐) is one of the most abundant element in seawater, it tends to react with organic matters in terrestrial environments, due to its higher electron density and smaller bond strength (Ryu et al, 2018; Westerhoff et al, 2004). On the contrary, chlorine (HOCl/OCl‐) is more abundant in inorganic environments (Donahoe et al, 1994; Tuthill et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

A Geochemical Record of Late‐Holocene Hurricane Events From the Florida Everglades

Yao

Liu

Rodrigues

et al. 2020

Water Resources Research

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A 5.25‐m sediment core SRM‐1 and 45 surface samples from mangrove forests at the Shark River Estuary in the Everglades National Park, Florida, were examined by using X‐ray fluorescence and carbon isotopic analyses to study the history of intense hurricane landfall during the Late‐Holocene. Significance testing of the surface samples in relation to storm deposits from Hurricane Wilma suggests that elemental concentration of Sr and Cl and the ratio of Cl/Br are the most sensitive indicators for major hurricane events in our study area. The geochemical data sets of core SRM‐1 identified five active periods of intense hurricane activities during the last 3,500 years at ~3,400–3,000, ~2,200–1,500, ~1,000–800, ~600–300, and ~150 calibrated years before present to present. This is the longest paleohurricane record to date from South Florida. Our results are consistent with the view that intense hurricane activities in South Florida were modulated by Intertropical Convergence Zone (ITCZ) movements, El Niño/Southern Oscillation (ENSO) activities, and North Atlantic Oscillation (NAO) strength. This study contributes to the methodological advancement in paleotempestological studies by demonstrating that geochemical signals, particularly signals of saltwater intrusions, can be preserved in the sediment profiles on millennial time‐scale and measured by X‐ray fluorescence techniques, thereby enabling more storm records to be produced from otherwise suboptimal sand‐limited coastal systems such as the Florida Everglades. More work needs to be done to explore the use of geochemical and stable isotopic analyses in detecting storm signals from sand‐limited coastal environments.

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Section: Discussionmentioning

confidence: 99%

A Geochemical Record of Late‐Holocene Hurricane Events From the Florida Everglades

Yao

Liu

Rodrigues

et al. 2020

Water Resources Research

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“…The record indicates that at least four major storms impacted the site over the past 1200 years. Paleotempestology studies from other marsh locations in Louisiana have demonstrated that major hurricanes are capable of depositing sediments into the coastal wetlands (Bianchette et al, 2016;Reese et al, 2008;Ryu et al, 2018). Based on the record of recent hurricanes that have made landfall near Bay Jimmy, it is possible to identify the storms that are likely to have deposited the anomalous sediments ( Figure 5).…”

Section: Potential Storm Impactsmentioning

confidence: 99%

“…Hurricanes normally deposit anomalous sediments through either overwash or flooding. Observations of such anomalous layers have been made in storm deposits from multiple sites that have been impacted by intense storm events (Bianchette et al, 2017;Braun et al, 2017;Liu et al, 2011;McCloskey et al, 2018;Reese et al, 2008;Ryu et al, 2018). The storms disturbed the vegetation in coastal Louisiana as is seen in the diminished pollen percentages of marsh vegetation such as Poaceae, Typha, and Cyperaceae accompanied by an increase in Cheno/Am, which are disturbance indicators.…”

Section: Environmental History Of Bay Jimmy Marshmentioning

confidence: 99%

A 1200-year history of environmental changes in Bay Jimmy area, coastal Louisiana, USA

Kiage

2019

The Holocene

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Paleoecological studies from the northern Gulf of Mexico (GOM) have mostly aimed at understanding long-term paleoenvironmental changes. Only a few studies have been performed in the southern United States focusing on paleoenvironmental changes during the common era. This study investigated paleoenvironmental changes in coastal Louisiana over the past 1200 years by utilizing proxy data, including loss-on-ignition (LOI) and pollen from a sediment core collected from a wetland in Bay Jimmy. The results indicate that the marsh in the study area was formed at ca. AD 1090 and has been primarily shaped by prevailing climatic conditions, including rare extreme events. At least four major hurricanes impacted the site over the 1200 years, including two that made landfall in recent times. The findings show that coastal Louisiana was warm and dry during the ‘Medieval Warm Period’ (ca. AD 950–1250). The environment after AD 1090 contained scattered Pinus and Juglans vegetation communities that were later succeeded by a closed forest that included Quercus and Morus. Red mangrove ( Rhizophora) was established in the vicinity of Bay Jimmy until shortly after cal AD 1450 and 1640. The pollen record indicates that the ‘Little Ice Age’ period (AD 1550–1850) was cold and dry, characterized by a more open vegetation community. There is evidence of forest disturbance that is marked by a rise in Ambrosia pollen in the 1700s, coinciding with the time of European settlement in North America. The presence of Ambrosia and Cheno/Am pollen throughout the record suggests that anthropogenic influence has been part of the fabric of the southern Louisiana landscapes throughout the 1200 years.

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“…For example, storm deposition caused by hurricanes can result in increased sedimentation rate and elevation in the region's wetlands, which will affect vegetation and biomass [45]. On the other hand, human activities, such as road construction, oil extraction, and timber harvesting, can affect the groundwater table and, consequently, vegetation and biomass, which would in turn affect soil property and sedimentation rate [46]. Biomass = f 3 (elevation, LULC, control variables), where Elevation = f 0 (sedimentation rate, subsidence rate, biomass)…”

Section: The Delta Cnh Modeling Frameworkmentioning

confidence: 99%

Understanding the Mississippi River Delta as a Coupled Natural-Human System: Research Methods, Challenges, and Prospects

Lam

Liu

et al. 2018

Water

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A pressing question facing the Mississippi River Delta (MRD), like many deltaic communities around the world, is: Will the system be sustainable in the future given the threats of sea level rise, land loss, natural disasters, and depleting natural resources? An integrated coastal modeling framework that incorporates both the natural and human components of these communities, and their interactions with both pulse and press stressors, is needed to help improve our understanding of coastal resilience. However, studying the coastal communities using a coupled natural-human system (CNH) approach is difficult. This paper presents a CNH modeling framework to analyze coastal resilience. We first describe such a CNH modeling framework through a case study of the Lower Mississippi River Delta in coastal Louisiana, USA. Persistent land loss and associated population decrease in the study region, a result of interplays between human and natural factors, are a serious threat to the sustainability of the region. Then, the paper describes the methods and findings of three studies on how community resilience of the MRD system is measured, how land loss is modeled using an artificial neural network-cellular automata approach, and how a system dynamic modeling approach is used to simulate population change in the region. The paper concludes by highlighting lessons learned from these studies and suggesting the path forward for analysis of coupled natural-human systems.

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Palynological and Geochemical Records of Environmental Changes in a Taxodium Swamp near Lake Pontchartrain in Southern Louisiana (USA) during the Last 150 Years

Cited by 15 publications

References 0 publications

A Geochemical Record of Late‐Holocene Hurricane Events From the Florida Everglades

A Geochemical Record of Late‐Holocene Hurricane Events From the Florida Everglades

A 1200-year history of environmental changes in Bay Jimmy area, coastal Louisiana, USA

Understanding the Mississippi River Delta as a Coupled Natural-Human System: Research Methods, Challenges, and Prospects

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