Search Results (51)

Driven by the need to expand urban/industrial complexes, and/or mitigate anticipated environmental impacts (e.g., tropical storms), many coastal countries have long implemented large-scale land reclamation initiatives. Some areas, like coastal Louisiana, USA, have relied heavily on restoration activities (i.e., beneficial use of dredged material) to counter extensive long-term wetland loss. Despite these prolonged engagements, the quantifiable benefits of these activities have lacked comprehensive documentation. Therefore, this study leveraged remote sensing data and advanced machine learning techniques to enhance the classification and evaluation of restoration efficacy within the wetlands adjacent to the Mississippi River’s Southwest Pass (SWP). By utilizing air- and space-borne imagery, land and water data were extracted and used to compare land cover changes during two distinct restoration periods (1978 to 2008 and 2008 to 2020) to historical trends. The classification methods employed achieved an overall accuracy of 85% with a Cohen’s kappa value of 0.82, demonstrating substantial agreement beyond random chance. To further assess the success of the SWP reclamation efforts in a global context, broad-based land cover data were generated using biennial air- and space-borne imagery. Results show that restoration activities along SWP have resulted in a significant recovery of degraded wetlands, accounting for approximately a 30 km² increase in land area, ranking among the most successful land reclamation projects in the world. The findings from this study highlight beneficial use of dredged material as a critical component in large-scale, recurring restoration activities aimed at mitigating degradation in coastal landscapes. The integration of remote sensing and machine learning methodologies provides a robust framework for monitoring and evaluating restoration projects, offering valuable insights into the optimization of ecosystem services. Overall, the research advocates for a holistic approach to coastal restoration, emphasizing the need for continuous innovation and adaptation in restoration practices to address the dynamic challenges faced by coastal ecosystems globally. Full article

The increasing demand for food and rapid population growth have made advanced crop monitoring essential for sustainable agriculture. Deep learning models leveraging multispectral satellite imagery, like Sentinel-2, provide valuable solutions. However, transferring these models to diverse regions is challenging due to phenological differences in crop growth stages between training and target areas. This study proposes the Adaptive Month Matching (AMM) method to align the phenological stages of crops between training and target areas for enhanced transfer learning in cropland segmentation. In the AMM method, an optimal Sentinel-2 monthly time series is identified in the training area based on deep learning model performance for major crops common to both areas. A month-matching process then selects the optimal Sentinel-2 time series for the target area by aligning the phenological stages between the training and target areas. In this study, the training area covered part of the Mississippi River Delta, while the target areas included diverse regions across the US and Canada. The evaluation focused on major crops, including corn, soybeans, rice, and double-cropped winter wheat/soybeans. The trained deep learning model was transferred to the target areas, and accuracy metrics were compared across different time series chosen by various phenological alignment methods. The AMM method consistently demonstrated strong performance, particularly in transferring to rice-growing regions, achieving an overall accuracy of 98%. It often matched or exceeded other phenological matching techniques in corn segmentation, with an average overall accuracy across all target areas exceeding 79% for cropland segmentation. Full article

Coastal wetlands face threats from climate change-induced flooding and biological invasions. Plants respond to these stressors through changes in their phytochemical metabolome, but it is unclear whether stressors affecting one tissue compartment (e.g., leaves) create vulnerabilities in others (e.g., roots) or elicit similar responses across tissues. Additionally, responses to multiple simultaneous stressors remain poorly understood due to the focus on individual metabolites in past studies. This study aims to elucidate how the phytochemical metabolome of three Phragmites australis (Cav.) lineages, common in the Mississippi River Delta, responds to flooding and infestation by the non-native scale insect Nipponaclerda biwakoensis (Kuwana). Among these lineages, one is non-native and poses a threat to North American wetlands. Results indicate that metabolomic responses are highly specific, varying with lineage, tissue type, stressor type, and the presence of multiple stressors. Notably, the non-native lineage displayed high chemical evenness, while the other two showed stressor-dependent responses. The 10 most informative features identified by a machine learning model showed less than 1% overlap with known metabolites linked to water and herbivory stress, underscoring gaps in our understanding of plant responses to environmental stressors. Our metabolomic approach offers a valuable tool for identifying candidate plant genotypes for wetland restoration. Full article

Here, we review the functioning and importance of deltaic coastal systems in the northern and southern Gulf of Mexico and how petroleum activities have impacted these two important systems. The Mississippi and Usumacinta-Grijalva Deltas are areas of high biological productivity and biodiversity that support the two largest fisheries in the Gulf. The north central Gulf receives inflow from the Mississippi river, the largest discharge in North America. The Mississippi Delta covers about 10,000 km². The Usumacinta-Grijalva River is the second highest freshwater input to the Gulf and discharges to the Usumacinta-Grijalva/Laguna de Terminos deltaic complex. These two areas are the largest petroleum producing regions in the Gulf, involving both inshore and offshore production. Petroleum activities impact coastal ecosystems in two important ways. In inshore areas dominated by coastal wetlands, there has been enormous physical disruption of the natural environment that affected hydrology and system functioning. In both inshore and offshore areas, spilled oil and release of high salinity produced water has led to widespread toxic pollution. Documentation of petroleum activity impacts on coastal marine ecosystems is much more advanced in the Mississippi Delta. Here, we describe how petroleum production impacts coastal ecosystems and discuss how restoration and management can restore the functioning of impacted coastal ecosystems. Full article

The Mississippi Delta region has worse population health outcomes, including higher overall cardiovascular and infant mortality rates. Water quality has yet to be considered as a factor in these health disparities. The objective of this paper is to determine overall differences in basic water quality indicators, electrolytes of cardiovascular importance, trace elements, heavy metals, and radioactive ions of groundwater in delta and non-delta counties in states along the Mississippi River. Data were sourced from the major-ions dataset of the U.S. Geological Survey. We used the Wilcoxon rank sum test to determine the difference in water quality parameters. Overall, delta counties had lower total dissolved solids (TDS) (47 and 384 mg/L, p-value < 0.001), calcium (7 and 58 mg/L; p-value < 0.001), magnesium (2 and 22 mg/L; p-value < 0.001), and potassium (1.57 and 1.80 mg/L; p-value < 0.001) and higher sodium (38 mg/L and 22 mg/L; p-value < 0.001) compared to non-delta counties. Overall, there were no statistical differences in trace elements, heavy metals, and radioactive ions across delta versus non-delta counties. These results underscore the need for further epidemiological studies to understand if worse health outcomes in delta counties could be partially explained by these parameters. Full article

The Mississippi River Delta Front (MRDF) is a subaqueous apron of rapidly deposited and weakly consolidated sediment extending from the subaerial portions of the Birdsfoot Delta of the Mississippi River, long characterized by mass-wasting sediment transport. Four (4) depositional environments dominate regionally (an undisturbed topset apron, mudflow gully, mudflow lobe, and prodelta), centering around mudflow distribution initiated by a variety of factors (hurricanes, storms, and fluid pressure). To better understand the spatiotemporal scales of the events as well as the controlling processes, eight cores (5.8–8.0 m long) taken offshore from the South Pass (SP) and the Southwest Pass (SWP) were analyzed for gamma density, grain size, sediment fabric (X-radiography), and geochronology (²¹⁰Pb/¹³⁷Cs radionuclides). Previous work has focused on the deposition of individual passes and has been restricted to <3 m core penetration, limiting its geochronologic completeness. Building on other recent studies, within the mudflow gully and lobe cores, the homogeneous stepped profiles of ²¹⁰Pb activities and the corresponding decreased gamma density indicate the presence of gravity-driven mass failures. ²¹⁰Pb/¹³⁷Cs indicates that gully sedimentary sediment accumulation since 1953 is greater than 580 cm (sediment accumulation rate [SAR] of 12.8 cm/y) in the southwest pass site, and a lower SAR of the South Pass gully sites (2.6 cm/y). This study shows that (1) recent dated mudflow deposits are identifiable in both the SWP and SP; (2) SWP mudflows have return periods of 10.7 y, six times more frequent than at the SP (66.7 y); (3) ²¹⁰Pb inventories display higher levels in the SWP area, with the highest focusing factors in proximal/gully sedimentation, and (4) submarine landslides in both study areas remain important for sediment transport despite the differences in sediment delivery and discharge source proximity. Full article

The response of coastal wetlands to sea-level rise (SLR) largely depends on the tolerance of individual plant species to inundation stress and, in brackish and freshwater wetlands, exposure to higher salinities. Phragmites australis is a cosmopolitan wetland reed that grows in saline to freshwater marshes. P. australis has many genetically distinct haplotypes, some of which are invasive and the focus of considerable research and management. However, the relative response of P. australis haplotypes to SLR is not well known, despite the importance of predicting future distribution changes and understanding its role in marsh response and resilience to SLR. Here, we use a marsh organ experiment to test how factors associated with sea level rise—inundation and seawater exposure—affect the porewater chemistry and growth response of three P. australis haplotypes along the northern Gulf of Mexico coast. We planted three P. australis lineages (Delta, European, and Gulf) into marsh organs at five different elevations in channels at two locations, representing a low (Mississippi River Birdsfoot delta; 0–13 ppt) and high exposure to salinity (Mermentau basin; 6–18 ppt) for two growing seasons. Haplotypes responded differently to flooding and site conditions; the Delta haplotype was more resilient to high salinity, while the Gulf type was less susceptible to flood stress in the freshwater site. Survivorship across haplotypes after two growing seasons was 42% lower at the brackish site than at the freshwater site, associated with high salinity and sulfide concentrations. Flooding greater than 19% of the time led to lower survival across both sites linked to high concentrations of acetic acid in the porewater. Increased flood duration was negatively correlated with live aboveground biomass in the high-salinity site (χ² = 10.37, p = 0.001), while no such relationship was detected in the low-salinity site, indicating that flood tolerance is greater under freshwater conditions. These results show that the vulnerability of all haplotypes of P. australis to rising sea levels depends on exposure to saline water and that a combination of flooding and salinity may help control invasive haplotypes. Full article

Many Mississippi River Delta studies have shown recent declines in fluvial sediment load from the river and associated land loss. In contrast, recent sedimentary processes on the subaqueous delta are less documented. To help address this knowledge gap, multicores were collected offshore from the three main river outlets at water depths of 25–280 m in June 2017 just after the peak river discharge period, with locations selected based on 2017 U.S. Geological Survey seabed mapping. The coring locations included the undisturbed upper foreset, mudflow lobes, gullies, and the undisturbed prodelta. Nine multicores were analyzed for Beryllium-7 activity, and four cores were analyzed for excess Thorium-234 activity via gamma spectrometry, granulometry and X-radiography. Our results indicate a general trend of declining ⁷Be and ²³⁴Th activities and inventories with increasing distance from sources and in deeper water. The core X-radiographs are graded from the predominantly physically stratified nearshore to the more bioturbated offshore, consistent with the sedimentation patterns. Sediment focusing assessed via the ⁷Be and ²³⁴Th sediment inventories shows preferential sedimentation in gully and lobe environments, whereas the upper foreset and prodelta focusing factors are relatively depleted. Overall, short-term sediment deposition from the main fluvial source remains active offshore from all three major river outlets, despite the overall declining river load. Full article

Sediment cores were collected from a mudflow lobe (80 m water depth) offshore of the Mississippi River’s Southwest Pass in 2017 to better understand the sedimentology near the lobe entraining the SS Virginia shipwreck (sunk by a German U-boat in 1942) and surrounding Mississippi River delta front. Core analyses included ²¹⁰Pb/¹³⁷Cs geochronology, granulometry, and X-radiography. Sediment accumulation rates (SAR) calculated from excess ²¹⁰Pb activity in multicores are 0.22–0.29 cm/y at seabed depths less than 20 cm and 0.29–0.51 cm/y at depths greater than 20 cm. Accumulation rates for ¹³⁷Cs have been ~0.15 to ~0.37 cm/y since 1954 and 1963, respectively. Sediment accumulation rates from ²¹⁰Pb, ¹³⁷Cs geochronology and indicators of relative sedimentation and bioturbation from X-radiographs suggest that rates of sediment accumulation near the Virginia have declined since the mid-20th century. This may be explained by the multi-decade downslope mass transport of the mudflow lobe in which the shipwreck is embedded and decreases in sediment supply delivered offshore from the Mississippi river. Mass transport calculations of the Virginia lobe derived from core properties and published lobe advection rates suggest downslope mass transport is far higher than sediment resupply from the Mississippi river, consistent with recent studies of delta retreat. Full article

Deltaic landscapes go through cycles of birth, growth, decline, and death governed by intertwined geological, biological, and ecological processes. In this study, we tracked deltaic lobes in the Balize Mississippi River Delta, Louisiana, USA, over 28 years (1984–2012). Hydrologic and geomorphic patterns as well as sustained patterns of wetland plant richness, diversity, and biomass are described. Plant diversity and biomass were modeled by nMDS ordination. Taxa (53) were harvested and dried (116,706 g) from 965 (0.25 m²) plots and divided into three groups: I. four foundation species, corresponding to 78.9% of the total harvest; II. nine pioneer species, corresponding to 13.6% of the total harvest; and III. all other taxa, corresponding to 7.5% of the total harvest (eight miscellaneous grasses, eight miscellaneous sedges, and twenty-four miscellaneous herbs). Autogenic/allogenic processes (sedimentation, subsidence, plant colonization, and succession events) affected composition and biomass. Eleven important species were identified. Taxon richness increased on mudflats during primary succession (fifteen to twenty-five taxa per site), then declined to fewer than five taxa per site. The niche space theory explained patterns of community change, with a similar total biomass/yr (~500 g/m²/yr) at all study sites. Quantile regression analyses showed that the water quality and quantity of the Mississippi River influenced biomass, especially in springtime waters. Stochastic events (storms, herbivory, salt burn, and flood pulses) impacted biomass. Long-term studies like this are required in a future of climate unknowns. Full article

Coastal Louisiana is currently experiencing high rates of wetland loss and large-scale ecosystem restoration is being implemented. One of the largest and most novel restoration projects is a controlled sediment diversion, proposed to rebuild and sustain wetlands by diverting sediment- and nutrient-rich water from the Mississippi River. However, the impact of this proposed sediment diversion on the nutrient budget of the receiving basin is largely unknown. A water quality model was developed to investigate the impact of the planned Mid-Barataria Sediment Diversion on the nutrient budget of the Barataria Basin (herein referred to as ‘the Basin’). The model results indicate that the planned diversion will increase TN and TP pools by about 38% and 17%, respectively, even with TN and TP loadings that increase by >300%. Water quality model results suggest that the increase of nutrients in the basin will be mitigated by increased advection transport (i.e., decreased residence time from ~170 days to ~40 days, leading to greater flushing) and increased removal via assimilation, denitrification, and settling within the Basin. Advection transport resulted in higher TN removal in the Basin than other processes, such as uptake or denitrification. Approximately 25% of the additional TN loading and 30% of the additional TP loading were processed within the Basin through the assimilation of phytoplankton and wetland vegetation, denitrification, and burial in the sediment/soils. These nutrient budgets help to better understand how the planned large-scale sediment diversion project may change the future ecological conditions within the estuaries of coastal Louisiana and near-shore northern Gulf of Mexico. Full article

Sediment deposition in river channels from various topographic conditions has been one of the major contributors to water quality impairment through non-point sources. Soil is one of the key components in sediment loadings, during runoff. Yazoo River Watershed (YRW) is the largest watershed in Mississippi. Topography in the watershed has been classified into two types based on land-use and slope conditions: Delta region with a slope ranging from 0% to 3% and Bluff hills with a slope exceeding 10%. YRW spans over 50,000 km²; the Soil and Water Assessment Tool (SWAT) was used to estimate soil-specific sediment loss in the watershed. Soil predominance was based on spatial coverage; a total of 14 soil types were identified, and the sediment contributed by those soils was quantified. The SWAT model was calibrated and validated for streamflow, sediment, Total Nitrogen (TN), Total Phosphorus (TP), and Crop yield for soybeans. Model performance was evaluated using the Coefficient of determination (R²), Nash and Sutcliffe Efficiency index (NSE), and Mean Absolute Percentage Error (MAPE). The performance was good for streamflow, ranging between 0.34 and 0.83, and 0.33 and 0.81, for both R² and NSE, respectively. Model performance for sediment and nutrient was low-satisfactory as R² and NSE ranged between 0.14 and 0.40, and 0.14 and 0.35, respectively. In the case of crop yield, model performance was satisfactory during calibration and good for validation with an R² of 0.56 and 0.76 and with a MAPE of 11.21% and 10.79%, respectively. Throughout YRW, soil type Smithdale predicted the highest sediment loads with 115.45 tons/ha/year. Sediment loss in agricultural fields with a soybean crop was also analyzed, where soil type Alligator predicted the highest with 8.37 tons/ha/year. Results from this study demonstrate a novel addition to the scientific community in understanding sediment loads based on soil types, which can help stakeholders in decision-making toward soil conservation and improving the environment. Full article

Groundwater (GW) in the Mississippi Delta has some of the highest phosphorus (P) concentrations measured in the U.S. Chemical data collected from GW and surface water (SW) sites were compared to understand factors affecting P concentrations. Spatial instability in Delta GWs indicates that P sources vary. High P measurements in shallow wells near rivers, in shallow nested wells compared to deeper nested wells, and P fluctuations in wells over time suggest that the land surface may be a greater source of P in shallow groundwater than natural geological deposits. Widespread reducing conditions in shallow GW, long-term P applications to the land surface, and shallow wells being proximal to streams are possible covarying explanatory variables. Potential SW to GW pathways of P include leaching and preferential flow paths; however, GW interactions with SW via irrigation, although unnatural, can result in P deposition on soils and later transport to SW or GW. GW tracer data indicate that irrigation return flows can exceed natural baseflow discharge to some streams in late summer. Studies are needed to confirm the degree that P is mobilized from soils and bed sediment to shallow GW and to determine how declines in GW levels resulting from irrigation affect ecological services in SW. Full article

This study characterizes the spatial patterns of the overall and monthly trends in sea surface temperature (SST) and chlorophyll-a (Chl-a) of the Gulf of Mexico (GoM) to investigate the seasonal variations in oceanic climate trends. We also investigate the trends in mesoscale eddies using three parameters to identify ocean-eddy-related energetic features in their area, strength, and intensity. Multidecadal remote-sensing-based observations of monthly SST, Chl-a, and sea surface height are used to detect trends at both basin and grid scales. Prominent warming trends are found in most regions of the GoM in all months, with the largest trends in the northern GoM. Winter cooling trends are also detected along the Texas and Florida coast. The overall summer warming trend (~0.22 °C/decade) is larger than the winter trend (~0.05 °C/decade), suggesting seasonal variations of increase in SST with warming. Chl-a trends and variations are confined on the continental shelf and slope in the northern GoM. The largest increase trends are found near the Mississippi River Delta. No obvious Chl-a trend is detected in the deepwater of the GoM, consistent with previous studies. Small but significant changes are found in eddy characteristics, indicating the eddy activities might be slowly affected by climate change in the GoM. The detailed monthly trends at per-grid scale are valuable for regional resource management, environmental protection, and policy making in the GoM. Full article

Hurricanes are one of the most devastating earth surface processes. In 2020 and 2021, Hurricanes Zeta and Ida pounded the Mississippi River Delta in two consecutive years, devastated South Louisiana, and raised tremendous concerns for scientists and stakeholders around the world. This study presents a high-resolution spatial-temporal analysis incorporating planialtimetric data acquired via LIDAR, drone, and satellite to investigate the shoreline dynamics near Port Fourchon, Louisiana, the eye of Ida at landfall, before and after the beach nourishment project and recent hurricane landfalls. The remote sensing analysis shows that the volume of the ~2 km studied beachfront was reduced by 240,858 m³ after consecutive landfalls of Hurricanes Zeta and Ida in 2020 and 2021, while 82,915 m³ of overwash fans were transported to the backbarrier areas. Overall, the studied beach front lost almost 40% of its volume in 2019, while the average dune crest height was reduced by over 1 m and the shoreline retreated ~60 m after the two hurricane strikes. Our spatial-temporal dataset suggests that the Louisiana Coastal Protection and Restoration Authority’s (CPRA’s) beach nourishment effort successfully stabilized the beach barrier at Port Fourchon during the hurricane-quiescent years but was not adequate to protect the shoreline at the Mississippi River Delta from intense hurricane landfalls. Our study supports the conclusion that, in the absence of further human intervention, Bay Champagne will likely disappear completely into the Gulf of Mexico within the next 40 years. Full article