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Microplastics are a growing concern in the natural environment as plastic production and improper disposal have greatly increased since the first widespread use of plastic in 1950. Previous studies have investigated the amount of plastic found within organisms, the water column, and surface sediments, but few studies are available that investigate microplastics within the sedimentary column. This study seeks to determine the abundance of microplastics and their rate of deposition in two coastal Louisiana estuaries (Bay Champagne and Little Lake) that are influenced by the petroleum, shipping, and commercial fishing industries. Samples from two short sediment cores were treated for microplastic analysis following NOAA removal techniques. Microplastics were identified visually and confirmed using FTIR spectroscopy. Three morphotypes of microplastic were found throughout the sediment column in the cores (fibers, fragments, and sheets), with a high concentration near the surface and a major decrease downcore. Of the two sites, Little Lake had a much higher total abundance of microplastics than Bay Champagne, likely due to its proximity to New Orleans and the active commercial fishery. Interestingly, both sites had trace amounts of microplastic in basal samples, in sediment much older than 1950. Their presence is likely attributable to bioturbation by burrowing organisms, although sediment reworking by high energy disturbance events (i.e., hurricanes) or human activity is also possible. Microplastic presence within these highly productive estuarine waters is a major ecological issue and understanding the possible sources and sinks of microplastics is critical in addressing this growing problem of environmental pollution. [ABSTRACT FROM AUTHOR]

The world's most extensive and active deltas, Louisiana's wetlands, are deteriorating rapidly due to multiple stressors. Their ecological and anthropogenic histories on a multimillennial timescale have not been thoroughly documented. This study investigates hydrological and anthropogenic impacts on southern Louisiana wetlands to guide future efforts toward environmental restoration. A 3.6 m sediment core (JOYWMA) extracted from a freshwater wetland adjacent to Lake Pontchartrain yielded a 5000‐year record. Multiproxy data indicate four distinct stages, with the earliest period representing an oyster reef (~4.5 cal yr bp) marked by elevated Ca and Sr concentrations. Evolution to a freshwater marsh occurred 4.5–4.0 cal yr bp during the St. Bernard delta progradation, marked by increased Zr and Br concentrations. The site transitioned to a lake due to the isolation from the St. Bernard delta and local subsidence (4.0–2.0 cal yr bp), marked by increased Ti, Fe, Mn and K concentrations. The site altered to a cypress swamp after 2.0 cal yr bp due to increased sediment supply during the St. Bernard subdelta progradation. Both natural (delta progradation and subsidence) and anthropogenic (fire, deforestation) stressors have impacted the site over the last 4500 years. Delta‐switching of the Mississippi River caused the significant geomorphological and ecological changes. [ABSTRACT FROM AUTHOR]

Few studies have documented the characteristics of fluvial flooding-induced storm deposits associated with a modern hurricane. Hurricane Harvey (2017) caused extensive flooding in coastal Texas due to a combination of storm surge and heavy precipitation. This study investigates the depositional process associated with Hurricane Harvey by means of loss-on-ignition (LOI) and X-ray fluorescence (XRF) analyses of 9 short cores and 17 surface samples collected from the San Bernard National Wildlife Refuge (SBNWR), Texas. Hurricane Harvey caused the largest flood within SBNWR over the last 28 years, and freshwater flooding from the San Bernard River was the predominant cause of this inundation. A distinct washover sand layer is lacking at all coring sites, but the intrusion of seawater can still be detected by a peak in the chlorine/bromine (Cl/Br) ratio of most sediment cores. Our study shows that Cl/Br ratios are higher in coastal environments than in terrestrial environments, thereby confirming that this elemental ratio can be used as a salinity indicator and, as a corollary, evidence of marine intrusion into lower-salinity environments. The ensuing phase of freshwater flooding and fluvial sedimentation is represented by a distinct flood deposit in only three cores, but is absent or indistinct in most cores. The elusiveness of the Harvey fluvial flood deposit can be explained by the relatively low discharge and suspended sediment load of the San Bernard River, the uneven distribution of this event deposit, and its indistinctiveness with the underlying deposits laid down by previous flood events. [ABSTRACT FROM AUTHOR]

ABSTRACT Yao, Q.; Liu, K.-B., and Ryu, J., 2018. Multi-proxy Characterization of Hurricane Rita and Ike Storm Deposits in a Coastal Marsh in the Rockefeller Wildlife Refuge, Southwestern Louisiana. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 841–845. Coconut Creek (Florida), ISSN 0749-0208. In 2005 and 2008, Hurricanes Rita and Ike made landfalls as category 3 and 2 hurricanes to the west of Rockefeller Wildlife Refuge (RWR) in southwestern Louisiana. In 2013, three ~30 cm sediment monoliths dominated by brown clay were recovered along a ~30 m transect perpendicular to the shoreline from the RWR. Each monolith contains two distinct light-colored calcareous storm deposits that are attributable to these two landfalling hurricanes. Loss-onignition and X-ray fluorescence (XRF) analyses were performed on all three sediment monoliths to study the sedimentological and geochemical characteristics of these two storm deposits. The geochemical results show that the storm deposits are characterized by higher-than-average values of Ca, Sr, Zr, and carbonates and low percentages of water and organics. In addition, remote sensing images show that the rate of average shoreline retreat at the RWR is ~14.5 m/yr from 1998 to 2017, and 19 m/year and 25.5 m/yr during the Hurricane Rita and Ike years, respectively. Both loss-on-ignition and XRF results also show that despite being a stronger storm, the Hurricane Rita layers are much thinner than those of Hurricane Ike in all monoliths. Remote sensing data support our interpretation that Hurricane Rita caused significant shoreline erosion and coastal recession in 2005, rendering the sampling locations at least 30 m closer to the ocean and thereby more susceptible to storm surges when Hurricane Ike struck in 2008. Thus, these results suggest that site-to-sea distance is an important factor in determining the thicknesses of storm deposits in coastal wetlands, particularly along shorelines undergoing rapid marine transgression. [ABSTRACT FROM AUTHOR]

ABSTRACT Ryu, J.; Bianchette, T.A.; Liu, K.-B.; Yao, Q., and Maiti, K.D., 2018. Palynological and Geochemical Records of Environmental Changes in a Taxodium Swamp near Lake Pontchartrain in Southern Louisiana (USA) during the Last 150 Years. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 381–385. Coconut Creek (Florida), ISSN 0749-0208. The hydrological and environmental histories of estuarine wetlands in southern Louisiana are not well-documented. To better understand their local developmental processes, a 59 cm sediment core (WMA-1) was extracted from a bald cypress (Taxodium distichum) swamp located approximately 800 m west of Lake Pontchartrain. This area has been heavily influenced by human activities, and is susceptible to inundation from storm surges from Lake Pontchartrain as well as fluvial and lacustrine processes. 210Pb analysis indicates that WMA-1 has a sedimentation rate of 0.39 cm/year, consistent with the detection of a 137Cs peak at 18 cm depth. Sedimentological and geochemical analyses reveal two distinct sedimentological facies: an organic-rich dark brown peat unit from 0 to 29 cm containing low concentrations of terrestrial elements (e.g., Ti, and Fe), and a clay unit from 29 to 59 cm with elevated concentrations of most elements (e.g., Sr, Cl, Ti, Mn, and Fe). The pollen assemblage in the clay section is dominated by TCT (mainly Taxodium), but it is replaced by Salix and wetland herbaceous taxa in the overlying peat. The Taxodium swamp was present at the site at least 150 years ago, and was replaced by Salix and other bottomland hardwood trees and wetland herbs due to a decrease in water level around AD 1940. While climate may have played a role, this hydrological change was most likely caused by the significant regional human activities during the last 100 years. Two thin clay layers (at 3–5 cm, 14–19 cm) embedded in the upper peat section were likely deposited from hurricanes Isaac (2012) and Betsy (1969): two events responsible for heavy rain and significant storm-surge flooding. Our findings suggest that human activities are capable of altering local wetland hydrology and ecology, while the clay layers represent hurricane-induced floods at the site during the past century. [ABSTRACT FROM AUTHOR]

Yao, Q.; Liu, K.-B., and Ryu, J., 2018. Multi-proxy Characterization of Hurricane Rita and Ike Storm Deposits in a Coastal Marsh in the Rockefeller Wildlife Refuge, Southwestern Louisiana. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 841–845. Coconut Creek (Florida), ISSN 0749-0208. In 2005 and 2008, Hurricanes Rita and Ike made landfalls as category 3 and 2 hurricanes to the west of Rockefeller Wildlife Refuge (RWR) in southwestern Louisiana. In 2013, three ~30 cm sediment monoliths dominated by brown clay were recovered along a ~30 m transect perpendicular to the shoreline from the RWR. Each monolith contains two distinct light-colored calcareous storm deposits that are attributable to these two landfalling hurricanes. Loss-onignition and X-ray fluorescence (XRF) analyses were performed on all three sediment monoliths to study the sedimentological and geochemical characteristics of these two storm deposits. The geochemical results show that the storm deposits are characterized by higher-than-average values of Ca, Sr, Zr, and carbonates and low percentages of water and organics. In addition, remote sensing images show that the rate of average shoreline retreat at the RWR is ~14.5 m/yr from 1998 to 2017, and 19 m/year and 25.5 m/yr during the Hurricane Rita and Ike years, respectively. Both loss-on-ignition and XRF results also show that despite being a stronger storm, the Hurricane Rita layers are much thinner than those of Hurricane Ike in all monoliths. Remote sensing data support our interpretation that Hurricane Rita caused significant shoreline erosion and coastal recession in 2005, rendering the sampling locations at least 30 m closer to the ocean and thereby more susceptible to storm surges when Hurricane Ike struck in 2008. Thus, these results suggest that site-to-sea distance is an important factor in determining the thicknesses of storm deposits in coastal wetlands, particularly along shorelines undergoing rapid marine transgression. [ABSTRACT FROM AUTHOR]

Ryu, J.; Bianchette, T.A.; Liu, K.-B.; Yao, Q., and Maiti, K.D., 2018. Palynological and Geochemical Records of Environmental Changes in a Taxodium Swamp near Lake Pontchartrain in Southern Louisiana (USA) during the Last 150 Years. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 381–385. Coconut Creek (Florida), ISSN 0749-0208. The hydrological and environmental histories of estuarine wetlands in southern Louisiana are not well-documented. To better understand their local developmental processes, a 59 cm sediment core (WMA-1) was extracted from a bald cypress (Taxodium distichum) swamp located approximately 800 m west of Lake Pontchartrain. This area has been heavily influenced by human activities, and is susceptible to inundation from storm surges from Lake Pontchartrain as well as fluvial and lacustrine processes. 210Pb analysis indicates that WMA-1 has a sedimentation rate of 0.39 cm/year, consistent with the detection of a 137Cs peak at 18 cm depth. Sedimentological and geochemical analyses reveal two distinct sedimentological facies: an organic-rich dark brown peat unit from 0 to 29 cm containing low concentrations of terrestrial elements (e.g., Ti, and Fe), and a clay unit from 29 to 59 cm with elevated concentrations of most elements (e.g., Sr, Cl, Ti, Mn, and Fe). The pollen assemblage in the clay section is dominated by TCT (mainly Taxodium), but it is replaced by Salix and wetland herbaceous taxa in the overlying peat. The Taxodium swamp was present at the site at least 150 years ago, and was replaced by Salix and other bottomland hardwood trees and wetland herbs due to a decrease in water level around AD 1940. While climate may have played a role, this hydrological change was most likely caused by the significant regional human activities during the last 100 years. Two thin clay layers (at 3–5 cm, 14–19 cm) embedded in the upper peat section were likely deposited from hurricanes Isaac (2012) and Betsy (1969): two events responsible for heavy rain and significant storm-surge flooding. Our findings suggest that human activities are capable of altering local wetland hydrology and ecology, while the clay layers represent hurricane-induced floods at the site during the past century. [ABSTRACT FROM AUTHOR]

Relative sea-level (RSL) rise associated with decreased fluvial sediment discharge and increased hurricane activity have contributed to the high rate of shoreline retreat and threatened coastal ecosystems in Port Fourchon, Louisiana, USA. This study, based on QuickBird/drone images (2004–2019) and LIDAR data (1998–2013), analyzed the impacts of shoreline dynamics on mangroves (Avicennia germinans) and marshes before and after the initiation of a beach nourishment project in 2013. The coastal barrier and dune crest migrated landward between 1998 and 2013. Meanwhile, the dune crest height increased between 1998 and 2001, then decreased in 2013, probably due to hurricane impacts. The total sediment volume along this sandy coastal barrier presented an overall trend of decline in the 1998–2013 period, resulting in a wetlands loss of ~15.6 ha along 4 km of coastline. This has led to a landward sand migration onto muddy tidal flats occupied by Avicennia germinans (1.08 ha) and Spartina (14.52 ha). However, the beach nourishment project resulted in the advancement of the beach barrier from Nov/2012 to Jan/2015, followed by a relatively stable period between Jan/2015 and Mar/2019. Additionally, both the dune crest height and sediment volume increased between 2013 and 2019. This set of factors favored the establishment and expansion of mangroves (3.2 ha) and saltmarshes (25.4 ha) along the backbarrier environments after 2013, allowing the tidal flats to keep pace with the RSL rise. However, waves and currents caused shoreline erosion following the beach nourishment project between Oct/2017 and Nov/2019, threatening wetlands by resuming the long-term process of shoreline retreat. [ABSTRACT FROM AUTHOR]