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Recent projections of global climate change necessitate improved methodologies that quantify shoreline variability. Updated analyses of shoreline movement provide important information that can aid and inform likely intervention policies. This paper uses the Analyzing Moving Boundaries Using R (AMBUR) technique to evaluate shoreline change trends over the time period 1856 to 2015. Special emphasis was placed on recent rates of change, during the 1994 to 2015 period of active storm conditions. Small segments, on the order of tens of kilometers, along two sandy barrier island regions on Florida’s Gulf and Atlantic coasts were chosen for this study. The overall average rate of change over the 159-year period along Little St. George Island was − 0.62 ± 0.12 m/year, with approximately 65% of shoreline segments eroding and 35% advancing. During periods of storm clustering (1994-2015), retreat rates along portions of this Gulf coast barrier accelerated to − 5.49 ± 1.4 m/year. Along the northern portion of Merritt Island on Florida’s Atlantic coast, the overall mean rate of change was 0.22 ± 0.08 m/year, indicative of a shoreline in a state of relative dynamic equilibrium. In direct contrast with the Gulf coast shoreline segment, the majority of transects (65%) evaluated along the oceanfront of Merritt Island over the long term displayed a seaward advance. Results indicate that episodes of clustered storm activity with fairly quick return intervals generally produce dramatic morphological alteration of the coast and can delay natural beach recovery. Additionally, the data show that tidal inlet dynamics, shoreline orientation, along with engineering projects, act over a variety of spatial and temporal scales to influence shoreline evolution. Further, the trends of shoreline movement observed in this study indicate that nearshore bathymetry—the presence of shoals—wields some influence on the behavior of local segments of the shoreline. [ABSTRACT FROM AUTHOR]

On September 18, Category 4 Hurricane Ian made landfall near Fort Myers Beach and Sanibel Island, two barrier islands on the northern Gulf of Mexico. In this paper, we present a novel set of observations from a post-event High Water Mark field survey as well as wavelet analysis of in-situ wave data. We also present a qualitative overview of some erosive effects and infrastructure damage. Measured peak surge elevations exceed 5 m, and wave plus surge elevations exceed 6.0 m (NAVD88). High Water Mark observations are consistent within the expected range produced by numerical hindcast models. A wavelet analysis, from one of the few wave records available during the storm, demonstrates the presence of long-period basin mode waves at a 40-min period. The 40-min wave appeared on the wave record before the storm surge, and the peak of this motion also occurred before the peak of the surge. In addition, the wavelet analysis reveals the presence of infragravity wave energy (periods between 30 s and 20 min). Together, these intermediate and long-period waves add over 40 cm to the total water level at peak energy. The measured field data shows a rapidly decreasing surge elevation within the first 300 m from the pre-storm shoreline, and we observe no statistically meaningful attenuation difference between the highly developed shoreline of Fort Myers and the more vegetated shoreline of Sanibel Island. However, the structural survey team observed more infrastructure damage in Fort Myers than Sanibel Island. • On September 28, 2022 Hurricane Ian made landfall in Fort Myers Beach and Sanibel Island, Florida, USA. • Post-storm, our field survey team observed High Water Mark (HWM) and wave impacts in these areas. • Wavelet analysis reveals a peak in energy near a 40-min period that arrived before the main surge. • Long-period motions have the potential to add at least 40 cm to the quasi-steady surge. • Field observations reveal a rapid decrease in wave impact observations in the first 300 m from the shoreline in both study sites. • Sanibel, more vegetated, and Fort Myers, more developed, showed no statistically meaningful difference in surge attenuation. • However, Fort Myers experienced higher infrastructure damage than Sanibel Island. [ABSTRACT FROM AUTHOR]

Barrier islands span 10% of the world's coastlines and dominate along the Atlantic and Gulf of Mexico coasts in the USA routinely exposed to storm surge. These islands serve as buffers between the open coast and the mainland, and protect the mainland from storm damage. During storms, significant morphological change can occur, including substantial erosion of the islands' vegetated dunes. In this study, the focus is on the influence of belowground biomass – namely dune plant roots – and dune topographic characteristics on barrier-island erosion during storms. The numerical model XBeach was employed to simulate storm-induced sediment transport. A parameter study was conducted by varying distance from the shoreline to the dune, dune shape, sediment grain size, and sediment mobility as an analogue for biomass. The influence of individual parameters and the collective impact of parameters were analyzed. The results help improve our knowledge of barrier island dynamics and lay a solid groundwork for future investigations. [ABSTRACT FROM AUTHOR]

Current ichnofacies models for shelf environments are largely based on analysis of ancient sedimentary deposits and have rarely been applied to studies of modern siliciclastic shelves. Siliciclastic shelf margins are key components of source rocks and unconventional shale plays that can be used as modern analogs to ancient systems. This paper examines the sedimentology and ichnology of shelf margin cores of the Mississippi River Delta containing strata formed during the 2004 (Ivan) and 2005 (Katrina and Rita) hurricane events in the Gulf of Mexico, together with those from the Kikori-Fly-Purari rivers in the Gulf of Papua, New Guinea and the Tūranganui-a-Kiwa/Poverty Bay shelf deposits of the Waipaoa River basin, offshore New Zealand. The cores provide examples of modern-day traces created by marine organisms on muddy shelves and are used to evaluate ichnological models that have been applied to determine sedimentation rates and depositional processes in ancient settings. In total, six facies were recognised based on lithology and ichnological characteristics: (1) laminated very fine sand, produced by waxing and waning currents, displaying scarce to moderate bioturbation; (2) laminated silty mud, formed by waxing and waning currents, exhibiting scarce, very low to moderate bioturbation; (3) normally graded sand and silt, created by suspension settling following a wave-enhanced sediment-gravity flow (WESGF), which reveals low to moderate bioturbation; (4) fluid mudflow/suspension settling deposits, characterised by structureless mud with low to high bioturbation; (5) biogenically mottled silty mud deposited by suspension settling which show high bioturbation intensity; and, (6) storm-generated facies of laminated sand formed by rapid sediment accumulation on the shelf. The different study areas show remarkably similar traces with variable intensity, diversity, abundance and distribution. The Mississippi River Delta cores are typified by Helminthopsis , Chondrites , Schaubcylindrichnus, Skolithos , Siphonichnus , navichnia, fugichnia and abundant bivalve shells. The deposits from the Gulf of Papua consist of Phycosiphon , Chondrites, Schaubcylindrichnus, Skolithos , Helminthopsis, Arenicolites, worm-like traces and abundant bivalve shell fragments. In addition to the traces and bivalves, Tūranganui-a-Kiwa/Poverty Bay shelf includes Asterosoma , Thalassinoides and gastropods. These traces are consistent with the newly defined Phycosiphon Ichnofacies (MacEachern and Bann, 2020), which characterise muddy prodelta settings. This research demonstrates that the neoichnology of modern shelf sediments match models developed from studies of ancient systems, and provides a robust tool for analysing and interpreting ancient shelf strata. • Four processes were interpreted to have formed the sediment facies in three continental shelves. • Facies from three different shelf margins display similar biogenic features with varying diversity and bioturbation. • Traces recognised to belong to recently proposed Phycosiphon Ichnofacies were recognised. • Link between sedimentation rate, bioturbation, facies and events processes is shown usingrectangular diagram. [ABSTRACT FROM AUTHOR]

Longitudinal data sets for population abundance are essential for studies of imperiled organisms with long life spans or migratory movements, such as marine turtles. Population status trends are crucial for conservation managers to assess recovery effectiveness. A direct assessment of population growth is the enumeration of nesting numbers and quantifying nesting attempts (successful nests/unsuccessful attempts) and emergence success (number of hatchlings leaving the nest) because of the substantial annual variations due to nest placement, predation, and storm activity. We documented over 133,000 sea turtle crawls for 50.9 km of Florida Gulf of Mexico coastline from 1982 to 2021 for a large loggerhead turtle nesting aggregation and a recovering remnant population of green sea turtles. Over time both species have emerged to nest significantly earlier in the year and green sea turtle nesting seasons have extended. Nest counts and hatchling production for both species have significantly increased, but the rate of emergence success of hatchlings leaving nests has not changed for loggerheads and has declined for green sea turtles. Sea level rise and coastal developments undoubtedly influence coastal habitats in the long-term, impacting nest site selection and potential recruitment from the loss of emerged hatchlings. However, the present indications for steady Gulf of Mexico recovery of loggerhead and green sea turtles counter findings of the Florida Atlantic coasts. This study indicates that effective conservation practices can be detected within time scales of 1–2 turtle generations. [ABSTRACT FROM AUTHOR]

Grand Bay estuary in coastal Mississippi and Alabama (USA) has undergone significant geomorphic changes over the last few centuries as a result of anthropogenic (bridge, road, and hardened shoreline construction) and climatic (extreme storm events) processes, which reduce freshwater input, sediment supply, and degrade barrier islands. To investigate how geomorphic changes may have altered the Grand Bay estuary, sediment push cores were collected for foraminiferal, sedimentological (organic matter content, grain-size distribution), and radiochemical (210Pb,137Cs, and 7Be) analyses. Clay normalized geochronologies were determined with a constant rate of supply model. Based on downcore age-depth relationships, select intervals were analyzed for foraminifera in order to assess alterations in the microfossil assemblage in Grand Bay estuary over the 20th Century. All estuarine samples were low diversity (species richness: 1–10; Fisher's alpha diversity: 0.14–1.75); two species, Ammotium salsum and Paratrochammina simplissima, dominated all downcore assemblages. Paratrochammina simplissima increased in abundance up-core from a minor subsidiary species (median = 4.7% at 19–20 cm) to dominant or co-dominant with A. salsum over the 20th and early 21st Centuries in six cores, comprising up to 60.7% of a single sample. The emerging dominance of P. simplissima since ~1950 along with the reduction of brackish-estuarine taxa and introduction of calcareous species signifies increased salinity and less marsh organic matter preserved in the sediments. While seasonal dissolution limits our ability to chronologically constrain the introduction of calcareous species, P. simplissima , a species not referenced in taxonomic data from the northern Gulf of Mexico until 2012, is well constrained, following its first occurrence in the 1930s. • Landscape changes contributed to surge in benthic, shallow-shelf foraminifera, Paratrochammina simplissima , in Grand Bay. • Multiple 210Pb sedimentation models were assessed for the development of chronologies due to sediment variability downcore. • Paper draws parallels between foraminiferal assemblage shifts and hydrologic and geomorphic changes over the past century. [ABSTRACT FROM AUTHOR]

Wang, P.; Adam, J.D.; Cheng, J., and Vallée, M., 2020. Morphological and sedimentological impacts of Hurricane Michael along the northwest Florida coast. Journal of Coastal Research, 36(5), 932–950. Coconut Creek (Florida), ISSN 0749-0208. On October 10, 2018, category 5 Hurricane Michael made landfall at Mexico Beach, generating a nearly 5-m storm surge. The greater landfall area is characteristic of a cuspate headland protruding into the Gulf of Mexico for up to 50 km. The headland is composed of several barrier islands with different orientations fronting a large estuary. The hurricane-impacted areas include densely developed small beachfront communities, modestly to sparsely developed shoreline communities, mostly pristine state parks, and a completely pristine national wildlife refuge. Therefore, Hurricane Michael provides an excellent opportunity to study the impact of an extreme storm over various coastal environments with different degrees of human developments. Because of the shoreline orientation and bathymetry changes induced by the headland, the wave field associated with the hurricane is complicated, with different locations for the highest wave and the landfall site where the surge and wind speed were the greatest. Numerical wave modeling revealed two wave-focusing points along the headland where barrier-island breaching occurred. Beach-dune erosion and impact to infrastructure were examined and compared among various natural–human coastal systems. The magnitude of dune erosion was mostly controlled by the storm wave height and prestorm beach width, but the height of the prestorm dune was not a determining factor. Sedimentological characteristics of storm deposits along the barrier islands, within Apalachicola Bay, and in the surrounding coastal marsh were examined using 116 sediment cores and 40 grab sediment samples. Characteristics of storm deposits and their preservation are described for various subenvironments, including beaches, dunes, interior wetlands, back-barrier bay, and coastal marsh along the landward side of the estuary. The landward penetrations of identifiable sandy overwash deposits were less than 150 m along the barrier islands and less than 30 m along the mainland marshes. These results should have potential implications on paleostorm study. [ABSTRACT FROM AUTHOR]

Beach and dune morphology are spatially and temporally variable, changing over a broad range of scales simultaneously. Strong wind, waves, and storm surge from Hurricane Harvey substantially eroded the beach and dunes along the Texas coast, causing significant scarps and berms. This paper presents information about how anthropogenic activity, such as driving on the beach, affected the response and recover of a barrier island with regard to the post-storm resiliency along the Texas-Gulf of Mexico coast by comparing two adjacent 7 km stretches of coast: a driving section and a limited-access section. A collection of field photos, aerial imagery, and a September 2016 LiDAR-derived digital elevation model (DEM) dataset provide information on pre-storm morphology, while field photos, taken only 3 days after Hurricane Harvey made landfall, and a structure-from-motion (SfM)-derived DEM and imagery provide qualitative and quantitative information about the post-storm morphology. While beach and dune erosion in the non-driving section was restricted entirely to the beach and incipient dune system, the driving section exhibited complex patterns of erosion and deposition along the beach and the entire foredune profile was altered. Despite the hurricane making landfall north of the study site and closer to the non-driving section, beach-dune erosion and scarping was greatest in the southern section which is accessible to public vehicles. Results demonstrate that human activity affects the response and recovery of the beach-dune system along the Gulf side of the island by decreasing alongshore variability in erosion-deposition and limiting vegetative and geomorphic recovery. Unlabelled Image • Driving on the beach affects beach-dune response to and recovery following a storm. • Non-driving areas show substantial evidence of recovery within 6 months post-storm. • Driving on the beach limits incipient foredune development and recovery. • Limiting low dune recovery can reinforce the effects of framework geology. [ABSTRACT FROM AUTHOR]

The large areal extent of hypoxia in the northern Gulf of Mexico has been partially attributed to substantial nitrogen (N) loading from the Mississippi River basin, which is driven by multiple natural and human factors. The available water quality monitoring data and most of the current models are insufficient to fully quantify N load magnitude and the underlying controls. Here we use a process‐based Dynamic Land Ecosystem Model to examine how multiple factors (synthetic N fertilizer, atmospheric N deposition, land use changes, climate variability, and increasing atmospheric CO2) have affected the loading and delivery of total nitrogen (TN) consisting of ammonium and nitrate (dissolved inorganic N) and total organic nitrogen from the Mississippi River basin during 1901–2014. The model results indicate that TN export during 2000–2014 was twofold larger than that in the first decade of twentieth century: Dissolved inorganic N export increased by 140% dominated by nitrate; total organic nitrogen export increased by 53%. The substantial enrichment of TN export since the 1960s was strongly associated with increased anthropogenic N inputs (synthetic N fertilizer and atmospheric N deposition). The greatest export of TN was in the spring. Although the implementation of N reduction has been carried out over the past three decades, total N loads to the northern Gulf of Mexico have not decreased significantly. Due to the legacy effect from historical N accumulation in soils and riverbeds, a larger reduction in synthetic N fertilizer inputs as well as improved N management practices are needed to alleviate ocean hypoxia in the northern Gulf of Mexico. Key Points: Over the period 1901‐2014, DIN and TON export from the Mississippi River basin increased by 85% and 60%, respectively. The Ohio River basin was largest contributor to the increase among seven subbasinsSynthetic N fertilizer application was the dominant contributor to increases in the export of DIN (70%) and TON (40%) since the 1970sThe highest DIN and TON export occurred in the spring, accounting for 39% and 36% of the total export from the MRB during 1990‐2014 [ABSTRACT FROM AUTHOR]

In response to the Deepwater Horizon oil spill, federal and state agencies conducted field studies to develop inputs for a shoreline deposition model used to estimate nearshore avian mortality resulting from the spill. A 2011 carcass drift study was designed to generate data on the likelihood that birds that died on the water would deposit along the northern Gulf of Mexico coast (rather than becoming lost at sea). In the case of the Deepwater Horizon oil spill, carcass losses at sea accounted for a significant portion of nearshore avian mortality. We evaluate the data collected during the Deepwater Horizon carcass drift study and compare the results obtained from the use of avian carcasses versus dummy carcasses (dummies) and the differences between those deployed nearshore versus further offshore. We conclude that, although the use of dummies provided valuable confirmation on the drift patterns of dead birds, dummies drifted greater distances, for longer periods of time, and were more likely to be observed beached compared to avian carcasses, with 64.6% of dummies beaching compared to 17.2% of carcasses. In response to future spills, researchers should account for these potential biases when incorporating dummy drift data into estimates of avian carcass loss. Further, none of the avian carcasses and dummies released more than 40 km from the shoreline made it to shore. In the northern Gulf of Mexico, carcasses that die on the waters farther offshore are unlikely to make it to shore to be captured in a deposition model; therefore, it may be appropriate to utilize a separate methodology to estimate offshore mortality. The applicability of these results to other spill events should be evaluated in the context of the specific spill characteristics. [ABSTRACT FROM AUTHOR]

The sand dunes found on coastal shores and barrier islands along the Northern Gulf of Mexico are important for protecting inland areas from wind and wave action, especially from tropical storms and hurricanes. The geomorphology of the dunes interacts with the plant community to create this dynamic coastal ecosystem. This study explored the processes that shape the foredunes, the youngest set of dunes where sediments are deposited by winds blowing up from the beach. These sands are thought to be slowed or trapped by early successional vegetation, leading to dune creation and growth. Our results suggest that the vegetative community is strongly associated with distance from the shore, where abiotic conditions are harshest closest to the ocean and gradually reduced moving toward the interior of the island. This deterministic community pattern appears to be maintained by the vegetation's ability to regenerate through time, especially in response to disturbances after heavy wind and wave action. A multifactorial germination experiment revealed strong differences among the germination rates of different species and the effects of salinity on species-specific germination rates. High rates of germination might be beneficial in colonizing open habitats following storms, where high salinity conditions are especially present. Understanding the patterns that shape vegetative community diversity should help guide restoration management in coastal dune systems and shed light on the importance of individual species and their function within the coastal ecosystem. [ABSTRACT FROM AUTHOR]

The Mississippi (MS) barrier island chain along the northern Gulf of Mexico coastline is subject to rapid changes in habitat, geomorphology and elevation by natural and anthropogenic disturbances. The purpose of this study was to compare habitat type coverage with respective elevation, geomorphic features and short-term change between the naturally-formed East Ship Island and the man-made Sand Island. Ground surveys, multi-year remotely-sensed data, habitat classifications and digital elevation models were used to quantify short-term habitat and geomorphic change, as well as to examine the relationships between habitat types and micro-elevation. Habitat types and species composition were the same on both islands with the exception of the algal flat existing on the lower elevated spits of East Ship. Both islands displayed common patterns of vegetation succession and ranges of existence in elevation. Additionally, both islands showed similar geomorphic features, such as fore and back dunes and ponds. Storm impacts had the most profound effects on vegetation and geomorphic features throughout the study period. Although vastly different in age, these two islands show remarkable commonalities among the traits investigated. In comparison to East Ship, Sand Island exhibits key characteristics of a natural barrier island in terms of its vegetated habitats, geomorphic features and response to storm impacts, although it was established anthropogenically only decades ago. [ABSTRACT FROM AUTHOR]

Khalil, S. M.; Finkl, C. W., and Raynie, R. C., 2013. Development of new rRestoration strategies for Louisiana barrier island systems, northern Gulf of Mexico, USA The rapid degradation of Louisiana's barrier island (BI) systems adversely impacts the vitality of strategic economic and biological resources (including aquatic habitat). Louisiana's BI systems have undergone landward migration through BI rollover, area loss and island narrowing as a result of complex interactions among land subsidence, sea-level rise, wave processes, inadequate sediment supply, and intense human disturbance. Consequently, the structural continuity of the BI shorelines has weakened as the islands narrowed, fragmented and, in some cases, submerged. Several multipronged restoration strategies are currently underway to develop effective interdisciplinary restoration projects that mitigate degradation of the Mississippi River delta plain and compensate for coastal land loss. Restoration of the BI systems requires strategies that protect interior wetlands and bolster the first lines of storm defense in a post- Hurricane Katrina-Rita-Gustav-Ike-Isaac and post-Deep Water Horizon era. Coastline degradation would have continued were it not for a series of massive barrier island restoration projects. Such efforts commonly consist of beach nourishment on the Gulfside and marsh creation on the bayside of barrier islands. Regionalizing monitoring, maintenance, and data management efforts support the still evolving scientific and engineering aspects of rebuilding BIs. [ABSTRACT FROM AUTHOR]

The stratigraphy of sections of three barrier island systems in the northeastern Gulf of Mexico (Apalachicola, Mississippi, and Chandeleur) have been mapped using geophysical and coring techniques to assess the influence of geologic variations in barrier lithosomes and adjoining inner shelf deposits on long-term rates of shoreline change at regional and local scales. Regional scale was addressed by comparing average geologic characteristics of the three areas with mean shoreline-change rates for each area. Regionally, differences in sand volume contained within the part of the barrier lithosome above sea level, sand volume on the inner shelf, and to a lesser extent, sediment grain size correlate with shoreline change rates. Larger sand volumes and coarser grain sizes are found where erosion rates are lower. Local scale was addressed by comparing alongshore variations in barrier island and inner shelf geology with alongshore variations in shoreline change. Locally, long-term shoreline change rates are highest directly shoreward of paleovalleys exposed on the inner shelf. While geology is not the sole explanation for observed differences in shoreline change along these three coastal regions, it is a significant contributor to change variability. [ABSTRACT FROM AUTHOR]

Aspects of northern Gulf of Mexico (NGOM) (Louisiana, Mississippi, Alabama, and Florida panhandle) processes and barrier islands that are pertinent to their geomorphologic response are contrasted with the broader knowledge base summarized by SCHWARTZ (1973) and LEATHERMAN (1979, 1985). Salient findings from studies documenting the short-term (storm-induced; timescales of hours, days, and weeks) and long-term (timescales of years, decades, and centuries) response of barrier island systems in the NGOM are synthesized into a conceptual model. The conceptual model illustrates the hypothetical evolution of three barrier island morphologies as they evolve through a typical Category 1-2 hurricane, including poststorm recovery (days to weeks) and long-term evolution (years to decades). Primary factors in barrier island geomorphologic response to storms, regardless of location, are the elevation of the island relative to storm (surge plus setup) elevation, and duration of the storm. Unique aspects of the NGOM barrier islands, compared with knowledge summarized for other barrier types, include (1) storm paths, wind speed, and large bays that create the potential for both Gulf and bayshore erosion and (2) in Louisiana and Mississippi, the potential for loading of the underlying substrate by the barrier island, which, through time, increases consolidation, relative sea level rise, overwash, morphologic change, and migration. We recommend that design of large-scale beach restoration projects incorporate the potential for (1) time-dependent consolidation of the underlying sediment due to project loading and future migration, (2) Gulf and bayshore erosion and overwash, and (3) eolian transport toward the Gulf from north winds. [ABSTRACT FROM AUTHOR]

Barrier-island chains worldwide are undergoing substantial changes, and their futures remain uncertain. An historical analysis of a barrier-island chain in the north-central Gulf of Mexico shows that the Mississippi barriers are undergoing rapid systematic land loss and translocation associated with: (1) unequal lateral transfer of sand related to greater updrift erosion compared to downdrift deposition; (2) barrier narrowing resulting from simultaneous erosion of shores along the Gulf and Mississippi Sound; and (3) barrier segmentation related to storm breaching. Dauphin Island, Alabama, is also losing land for some of the same reasons as it gradually migrates landward. The principal causes of land loss are frequent intense storms, a relative rise in sea level, and a sediment-budget deficit. Considering the predicted trends for storms and sea level related to global warming, it is certain that the Mississippi-Alabama (MS-AL) barrier islands will continue to lose land area at a rapid rate unless the trend of at least one causal factor reverses. Historical land-loss trends and engineering records show that progressive increases in land-loss rate correlate with nearly simultaneous deepening of channels dredged across the outer bars of the three tidal inlets maintained for deep-draft shipping. This correlation indicates that channel-maintenance activities along the MS-AL barriers have impacted the sediment budget by disrupting the alongshore sediment transport system and progressively reducing sand supply. Direct management of this causal factor can be accomplished by strategically placing dredged sediment where adjacent barrier-island shores will receive it for island nourishment and rebuilding. [ABSTRACT FROM AUTHOR]