Within the Mid-Atlantic United States, widespread landscape disturbance during European colonization resulted in erosion and subsequent storage of legacy sediments within river valleys and floodplains, altering their form, function, and flora. Previous studies of precolonial river corridors have influenced river restoration designs and targets throughout the region, but the generalizability of these studies into other physiographic settings, such as the Coastal Plain, is unknown. Therefore, our study investigated the physical form and riparian vegetation of precolonial stream corridors located within the Coastal Plain of Anne Arundel County, Maryland, documenting changes from preto colonial and postcolonial time periods. Our study provides evidence of buried, precolonial riparian ecosystems with dates ranging between 750 years to 8000 years Before Present. These valley bottom ecosystems were likely a dynamic patch mosaic, largely dominated by dense Alnus (alder) scrub swamps with variable Poaceae (grass) and Cyperaceae (sedge) dominated meadows and both multi-threaded and single-threaded channel forms. These precolonial floodplains are buried by vast amounts of legacy sediment to the extent that pre-colonial sediments are largely not exposed in the modern valley bottom. Notably, the Coastal Plain precolonial corridors investigated in this study contrast to studies in the Piedmont physiographic region with precolonial sediments exposed in streambanks and with precolonial ecosystems described as herbaceous stream-wetlands. Our findings provide critical historical context as to the magnitude of alteration for modern stream channels and suggest an alternative precolonial ecosystem which can be used to inform restoration designs, management targets, and reestablishment of channel functional processes in areas of the Mid-Atlantic Coastal Plain.

Mangrove sediments are valuable archives of relative sea-level change if they can be distinguished in the stratigraphic record from other organic-rich depositional environments (e.g., freshwater swamps). Proxies for establishing environment of deposition can be poorly preserved (e.g., foraminifera) in mangrove sediment. Consequently, differentiating mangrove and freshwater sediment in the stratigraphic record is often subjective. We explore if biomarkers can objectively identify mangrove sediment with emphasis on their utility for reconstructing relative sea level. Our approach is specific to identifying in situ sediment, which has received less attention than identifying allochthonous mangrove organic matter. To characterize mangrove and non-mangrove (freshwater) environments, we measured n-alkane, sterol, and triterpenoid abundances in surface sediments at three sites in the Federated States of Micronesia. Elevated taraxerol abundance is diagnostic of sediment accumulating in mangroves and taraxerol is particularly abundant beneath monospecific stands of Rhizophora spp. Taraxerol was undetectable in freshwater sediment. Other triterpenoids are more abundant in mangrove sediment than in freshwater sediment. Using cores from Micronesian mangroves, we examine if biomarkers in sediments are indicative of in situ deposition in a mangrove, and have utility as a relative sea-level proxy. Taraxerol concentrations in cores are comparable to surface mangrove sediments, which indicates deposition in a mangrove. This interpretation is supported by pollen assemblages. Downcore taraxerol variability may reflect changing inputs from Rhizophora spp. rather than diagenesis. We propose that taraxerol is a proxy that differentiates between organic sediment that accumulated in mangrove vs. freshwater environments, lending it utility for reconstructing relative sea level.

Paleoecology studies provide pre-instrument data from the Everglades painting an informative picture of physical, biological, and ecological conditions prior to human intervention. Because Florida’s development history is relatively recent, and because observational data span only the last half-century, managers rely on paleoecology data as the basis for important decisions regarding multi-decadal and expensive restoration. Effective restoration depends strongly on the establishment of restoration targets, especially pre-development vegetation and hydropatterns (flow, depth, timing, distribution). Coring data were instrumental in the reconstruction of paleo hydrologic and vegetation trends in the ARM Loxahatchee National Wildlife Refuge, helping managers understand the magnitude and causes of 20th century problems. Similarly, sediment cores from the Big Cypress National Preserve led managers to understand that the development of marl prairies in Everglades National Park – critical habitat for the endangered Cape Sable Seaside Sparrow – was a 20th century phenomenon resulting from past water management practices. Finally, paleoecological and modeling studies in Florida Bay and the Everglades for the $20B+ Comprehensive Everglades Restoration plan established freshwater flow targets now used by managers. Although restoration of historic freshwater flow is not feasible, knowledge about Everglades hydrology and ecology prior to human intervention plays a pivotal role in the design, selection, and construction of restoration projects. Paleoecological data, coupled with decadal-scale monitoring and other long-term studies, provide the long-term perspective necessary to understand decadal, to centennial, and to millennial time-scale processes. While these data are cost-effective to procure, a long-term commitment to funding these types of studies is essential to provide the scientific foundation for restoration.

Building robust age–depth models to understand climatic and geologic histories from coastal sedimentary archives often requires composite chronologies consisting of multi-proxy age markers. Pollen chronohorizons derived from a known change in vegetation are important for age–depth models, especially those with other sparse or imprecise age markers. However, the accuracy of pollen chronohorizons compared to other age markers and the impact of pollen chronohorizons on the precision of age–depth models, particularly in salt marsh environments, is poorly understood. Here, we combine new and published pollen data from eight coastal wetlands (salt marshes and mangroves) along the Atlantic Coast of the United States (U.S.) from Florida to Connecticut to define the age and uncertainty of 17 pollen chronohorizons. We found that 13 out of 17 pollen chronohorizons were consistent when compared to other age markers (radiocarbon, radionuclide 137Cs and pollution markers). Inconsistencies were likely related to the hyperlocality of pollen chronohorizons, mixing of salt marsh sediment, reworking of pollen from nearby tidal flats, misidentification of pollen signals, and inaccuracies in or misinterpretation of other age markers. Additionally, in a total of 24 models, including one or more pollen chronohorizons, increased precision (up to 41 years) or no change was found in 18 models.

Determining hydrologic conditions prior to instrumental records is a challenge for restoration of freshwater ecosystems worldwide. Paleoecologic data provide this information on past conditions and when these data are used to adjust hydrologic models, allow conditions to be hindcast that may not be directly estimated from the paleo-data alone. In this context, the paleo-data provide real-world estimates as input to the models. Restoration of the Greater Everglades Ecosystem requires this understanding of the hydrology of the natural system prior to significant alterations due to water management and land use. Large scale models such as the Natural Systems Model (NSM 4.6.2) have been used by the South Florida Water Management District and other agencies responsible for restoration to estimate past hydrologic conditions; however, these models typically portray a drier natural system for the beginning of the 20th century than what is indicated by paleoecologic analyses and historical data. The purpose of this study is to estimate pre-20th century water levels, hydroperiods and flow in the freshwater wetlands of the Everglades by using pollen assemblage data in three sediment cores to adjust the Natural Systems Model. This study is designed to further test estimates of flow through the Everglades derived from analysis of sediment cores collected in Florida Bay. The results demonstrate that the NSM 4.6.2 underestimates water levels and hydroperiods in the Everglades compared to the paleo-adjusted NSM 4.6.2 model outputs. Flow models that use the paleo-adjusted water levels as input indicate flow through Shark River Slough in the late 19th century was approximately two times flow between 1990 and 2000, and flow through Taylor Slough was approximately three times flow between 1990 and 2000. The flow estimates derived from this study agree with the estimates derived from earlier studies using estuarine cores. This integration of paleoecologic information and hydrologic models provides resource managers with the best available estimates of past conditions and allows them to set realistic targets for restoration of freshwater ecosystems.

We examine the annual, seasonal, monthly, and diurnal climate responses to the land use change (LUC) in eastern United States and Cuba during four epochs (1650, 1850, 1920, and 1992) with ensemble simulations conducted with the RegCM4 regional climate model that includes the Biosphere Atmosphere Transfer Scheme (BATS1e) surface physics package (Dickinson et al., 1993). We derived the land use (LU) data sets by harmonizing a previous reconstruction (Steyaert & Knox, 2008) with updated observations and modeled potential vegetation. The eight‐member ensembles for each epoch were driven with randomly perturbed 1990–2002 atmospheric boundary conditions derived from the National Center for Environmental Prediction global reanalysis. LUC induces statistically significant climate responses across all epochs; the largest changes occur between 1850 and 1920 with the widespread conversion of forests in the United States and forests, grassland, and woody wetlands in Cuba to agriculture. The atmospheric feedback from the aggregated grid‐cell responses attributed to physical and biophysical parameters in BATS1e alters the circulation in the lower atmosphere, thereby propagating the LUC regionally. Depending on the season and location, the altered circulation reinforces, attenuates, or has little effect on surface responses. Relative to pre‐settlement (1650), the 1992 LU produces colder mean annual air temperature (−0.09 ± 0.16 °C) and increased precipitation (0.08 ± 0.09 mm day−1) over the United States, warmer (0.08 °C) and wetter (0.03 mm day−1) conditions over Florida, and warming (0.32 °C) and drying (−0.03 mm day−1) over Cuba, indicating that LUC has played a varying role in climate change over the region.

Examinations of soil traces associated with forensic evidence can be used to narrow potential source area(s) by characterizing features of the trace soil assemblage, some of which are limited to specific regions. Soil characteristics may be used to infer the likelihoods of the soil trace being derived from distinct areas within digital maps, including both maps of discrete classes such as formations on geologic maps and land cover, and continuous geospatial data, such as distance from a point source. Seldom do digital maps precisely represent the observable characteristics in a soil trace. Nevertheless, logical assigned likelihoods based on the correspondence between the mapped characteristics and the observed soil particulate assemblage permit creation of a model of the more probable sources of the soil trace. This approach is applied to a 2003 case in which forensic soil samples derived from digging tools were characterized for investigative leads and to narrow the search area of a clandestine grave. This grave site was located in 2005. The suspect traveled approximately 5,000km before arrest, so narrowing the prioritized search area for law enforcement would be beneficial. Soil examination and case circumstances were used to assign relative likelihoods within digital maps (GIS or Geographic Information Systems data) of geology, soil mineralogy, plant distributions, power plant locations, and proximity to the known travel path. The product of these individual probability maps generates joint probability models to narrow the recommended search area. The digital model output can be easily overlaid on infrastructure maps to aid law enforcement searches. Plain Language Summary Trace soil remaining on digging tools may be examined to aid law enforcement in narrowing search areas for clandestine graves. Properties of the particles within the soil reflect the geology, biology, and human activities of the grave area. The soil characteristics are used to identify some regions within digital maps as more likely sources of the soil. Combining multiple digital maps which have been designated with higher and lower priority regions based on the soil observation can be used to guide police search strategies. This approach is retrospectively applied to a case in which a suspect drove 5,000km over 6days, burying two bodies along the route. The investigative history, results of examination of less than 1g of soil, interpretations, and the processes of predicting the more likely grave locations are described as an example of probabilistic modeling for geographic attribution of forensic soils.

Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR rate of 0.67 ± 0.1 mm yr −1 between ~4.2–2.8 ka, 4–6 times lower than current rates. Despite low RSLR rates, the rapid mangrove to estuarine transgression was facilitated by a period of prolonged droughts and frequent storms. These findings suggest that with higher and accelerating RSLR today, enhanced climate variability could further hasten the loss of mangrove-lined coastlines, compounded by the reductions in natural flow to the coast caused by water management. Climate variability is nonlinear, and when superimposed on increases in RSLR, can complicate estimated trajectories of coastal inundation for resource management and urban planning.

First posted March 28, 2019 For additional information, contact: Florence Bascom Geoscience CenterU.S. Geological Survey926A National Center12201 Sunrise Valley DriveReston, VA This publication portrays the geology of the Hardeeville NW quadrangle and parts of the Brighton and Pineland quadrangles that are within Jasper County, South Carolina. The study area is located in the Atlantic Coastal Plain province, approximately 50 to 70 kilometers (km) inland from the coast. The data are compiled from geological field mapping, light detection and ranging (lidar) elevation data, cores, optically stimulated luminescence ages, radiocarbon ages, and biostratigraphic interpretations. Most of the study area is occupied by the valley of the Savannah River, and exposures of geologic units are very limited. Traditional geologic mapping in this area is difficult because of limited access, subdued topography, extensive swamps, and abundant vegetation.The Savannah River flows predominantly southeast, and forms most of the border between the States of South Carolina and Georgia. The river is approximately 483 km long and has a total drainage area of approximately 15,850 square km. Although upstream tributaries drain the southeastern side of the Appalachian Blue Ridge province, the Savannah River begins in the Piedmont province and then flows across the Atlantic Coastal Plain province to the Atlantic Ocean. For much of its extent, the modern channel of the Savannah River is located on the southwestern side of the river valley, and the southwestern bank of the valley is the active cut bank. Within the study area, the valley of the Savannah River trends southeast and is relatively straight. The valley has relatively low relief, although the southwestern valley wall is steeper and has greater relief than the northeastern valley wall.Elevations within the valley mostly range from 3 to 15 meters (m) above sea level, whereas elevations on the high terrace that forms the eastern margin of the Savannah River valley are 15 to 20 m above sea level. The width of the valley is 6 to 7 km in the northern part of the study area and expands to 10 to 12 km farther south. The modern river channel occupies the southwestern side of the valley, and some modern (active) creeks enter the river from the west. Sand hills and low-relief terraces are present to the east of the modern river channel, and the eastern side of the valley is characterized by abandoned meandering and linear channels. Fan-shaped deposits of sand and mud are present where relict (inactive) channels enter the eastern side of the valley. Abandoned meandering channels of low relief (<3 m) are also present to the east on the high terrace (>15 m elevation) that forms the eastern margin of the Savannah River valley. Within the study area, most of the Savannah River valley is covered by alluvial wetland community vegetation dominated by cypress and tupelo trees, although sand hills within the valley are covered by xeric sand community vegetation dominated by pine trees.

Carbon (C) standing stocks, C mass balance, and soil C burial in tidal freshwater forested wetlands (TFFW) and TFFW transitioning to low‐salinity marshes along the upper estuary are not typically included in “blue carbon” accounting, but may represent a significant C sink. Results from two salinity transects along the tidal Waccamaw and Savannah rivers of the U.S. Atlantic Coast show that total C standing stocks were 322–1,264 Mg C/ha among all sites, generally shifting to greater soil storage as salinity increased. Carbon mass balance inputs (litterfall, woody growth, herbaceous growth, root growth, and surface accumulation) minus C outputs (surface litter and root decomposition, gaseous C) over a period of up to 11 years were 340–900 g C · m−2 · year−1. Soil C burial was variable (7–337 g C · m−2 · year−1), and lateral C export was estimated as C mass balance minus soil C burial as 267–849 g C · m−2 · year−1. This represents a large amount of C export to support aquatic biogeochemical transformations. Despite reduced C persistence within emergent vegetation, decomposition of organic matter, and higher lateral C export, total C storage increased as forests converted to marsh with salinization. These tidal river wetlands exhibited high N mineralization in salinity‐stressed forested sites and considerable P mineralization in low‐salinity marshes. Large C standing stocks and rates of C sequestration suggest that TFFW and oligohaline marshes are considerably important globally to coastal C dynamics and in facilitating energy transformations in areas of the world in which they occur.

This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow and runoff, cave drip rates, biological productivity, assemblages of living organisms, and salinity. Centennial-scale hydroclimate anomalies are obtained by iteratively sampling the proxy data on each of thousands of age model realizations and determining the fractions of possible time series indicating that the century-smoothed data was anomalously wet or dry relative to the 100 BCE to 1900 CE mean. Results suggest regionally asynchronous wet and dry periods over multidecadal to centennial timescales and frequent periods of extended regional drought. Most sites indicate drying during previously documented multicentennial periods of warmer Northern Hemisphere temperatures, particularly in the western U.S., central U.S., and Canada. Two widespread droughts were documented by the NAHS: from 50 BCE to 450 CE and from 800 to 1100 CE. Major hydroclimate reorganizations occurred out of sync with Northern Hemisphere temperature variations and widespread wet and dry anomalies occurred during both warm and cool periods. We present a broad assessment of paleoclimate relationships that highlights the potential influences of internal variability and external forcing and supports a prominent role for Pacific and Atlantic Ocean dynamics on century-scale continental hydroclimate.

produced similar to 3000-year long relative sea-level (RSL) histories for two sites in North Carolina (USA) using foraminifera preserved in new and existing cores of dated salt-marsh sediment. At Cedar Island, RSL rose by similar to 2.4 m during the past similar to 3000 years compared to similar to 3.3 m at Roanoke Island. This spatial difference arises primarily from differential GIA that caused late Holocene RSL rise to be 0.1-0.2 mm/yr faster at Roanoke Island than at Cedar Island. However, a non-linear difference in RSL between the two study regions (particularly from similar to 0 CE to similar to 1250 CE) indicates that additional local-to regional-scale processes drove centennial-scale RSL change in North Carolina. Therefore, the Cedar Island and Roanoke Island records should be considered as independent of one another. Between-site differences on sub-millennial timescales cannot be adequately explained by non-stationary tides, sediment compaction, or local sediment dynamics. We propose that a period of accelerating RSL rise from similar to 600 CE to 1100 CE that is present at Roanoke Island (and other sites north of Cape Hatteras at least as far as Connecticut), but absent at Cedar Island (and other sites south of Cape Hatteras at least as far as northeastern Florida) is a local-to regional-scale effect of dynamic ocean and/or atmospheric circulation. (C) 2017 Elsevier Ltd. All rights reserved.

This study examines Holocene impacts of changes in climate, land use, and sea level rise (SLR) on sediment accretion, carbon accumulation rates (CAR), and vegetation along a transect of tidal freshwater forested wetlands (TFFW) to oligohaline marsh along the Waccamaw River, South Carolina (four sites) and along the Savannah River, Georgia (four sites). We use pollen, plant macrofossils, accretion, and CAR from cores, spanning the last 1,500-6,000 years to test the hypothesis that TFFW have remained stable throughout the late Holocene and that marshes transitioned from TFFW during elevated SLR during the Medieval Climate Anomaly, with further transformation resulting from colonial land use change. Results show low and stable accretion and CAR through much of the Holocene, despite moderate changes associated with Holocene paleoclimate. In all records, the largest observed change occurred within the last similar to 400 years, driven by colonial land clearance, shifting terrigenous sediment into riparian wetlands, resulting in order-of-magnitude increases in accretion and C accumulation. The oligohaline marshes transitioned from TFFW similar to 300-500 years ago, coincident with colonial land clearance. Postcolonial decreases in CAR and accretion occur because of watershed reforestation over the last century. All sites show evidence of recent (decades to century) swamp forest decline due to increasing salinity and tidal inundation from SLR. This study suggests that allochthonous sediment input during colonialization helped maintain TFFW but that current SLR rates are too high for TFFW to persist, although higher accretion rates in oligohaline marshes increase the resilience of tidal wetlands as they transition from TFFW to marsh.

Resource managers around the world are challenged to develop feasible plans for sustainable conservation and/or restoration of the lands, waters, and wildlife they administer – a challenge made greater by anticipated climate change and associated effects over the next century. Increasingly, paleoecologic and geologic archives are being used to extend the period of record of observed data and provide information on centennial to millennial scale responses to long-term drivers of ecosystem change. The development of paleoecology from an emerging field investigating past environments to a highly relevant applied science is reviewed and general examples of the application of paleoecologic research to resource management questions in diverse habitats and regions are provided. Specific examples of the application of paleoecologic research to the restoration of the Greater Everglades Ecosystem of south Florida (U.S.A) are presented. Conducting valuable scientific research that would benefit resource management decisions, however, is not enough. Scientists and resource managers need to be engaged in collaborative discussions from the beginning of the research process in order to ensure that management questions are being addressed and that the science reaches the people who will benefit from the information. Paleoecology and related disciplines provide an understanding of how ecosystems and individual species function and change over time in response to both natural and anthropogenic drivers. Information on pre-anthropogenic baseline conditions is provided by paleoecologic research, but it is the detection of long-term trends and cycles that allow resource managers to set realistic goals and targets by moving away from the fixed-point baseline concept to one of dynamic landscapes that anticipates and incorporates an expectation of change into decision-making.

To address a paucity of Common Era data in the Gulf of Mexico, we reconstructed ~1.1m of relative sea-level (RSL) rise over the past ~2000years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regional-scale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollution, 137Cs and pollen chronohorizons. Our proxy reconstruction was combined with tide-gauge data from four nearby sites spanning 1913–2014CE. Application of an Errors-in-Variables Integrated Gaussian Process (EIV-IGP) model to the combined proxy and instrumental dataset demonstrates that RSL fell from ~350 to 100BCE, before rising continuously to present. This initial RSL fall was likely the result of local-scale processes (e.g., silting up of a tidal flat or shallow sub-tidal shoal) as salt-marsh development at the site began. Since ~0CE, we consider the reconstruction to be representative of regional-scale RSL trends. We removed a linear rate of 0.3mm/yr from the RSL record using the EIV-IGP model to estimate climate-driven sea-level trends and to facilitate comparison among sites. This analysis demonstrates that since ~0CE sea level did not deviate significantly from zero until accelerating continuously from ~1500CE to present. Sea level was rising at 1.33mm/yr in 1900CE and accelerated until 2014CE when a rate of 2.02mm/yr was attained, which is the fastest, century-scale trend in the ~2000-year record. Comparison to existing reconstructions from the Gulf coast of Louisiana and the Atlantic coast of northern Florida reveal similar sea-level histories at all three sites. We explored the influence of compaction and fluvial processes on our reconstruction and concluded that compaction was likely insignificant. Fluvial processes were also likely insignificant, but further proxy evidence is needed to fully test this hypothesis. Our results indicate that no significant Common Era sea-level changes took place on the Gulf and southeastern Atlantic U.S. coasts until the onset of modern sea-level rise in the late 19th century.