Parramore Island Research Articles

Contribution of longshore sand exchanges to mesoscale barrier-island behavior: Insights from the Virginia Barrier Islands, U.S. East Coast

The development of coastal adaptation pathways along sandy barrier-island coasts requires an understanding of multi-decadal barrier morphodynamics in response to forcings such as sea-level rise, sediment fluxes, and storminess. Long- and cross-shore sand exchanges among barrier-system compartments (shorefaces, beaches, dunes, tidal inlets, backbarrier lagoons) and between adjacent barrier islands can play a fundamental role in barrier-system morphology and resilience to sea-level rise. We explore these dynamics through investigation of historical areal changes within the 13 largely undeveloped Virginia Barrier Islands of the United States Mid-Atlantic Coast. We pair subaerial island areas mapped from historical surveys and modern aerial and satellite imagery with representative island thicknesses determined from stratigraphic and lidar-derived elevation data to estimate volumetric changes through time. Overall, the Virginia Barrier Islands lost ~3.4% (16 × 106 m3) of their 1887 C.E. volume between 1887 and 2017 C.E. The loss from three central islands (Parramore, Hog, and Cobb)—historically characterized by rotational behavior—was 43% (79 × 106 m3). In particular, Parramore Island continuously decreased in volume over the 20th and 21st centuries. In contrast, growth of Assateague and northern Wallops islands (located at the northern, updrift end of the island chain) from 1887 to 2017 C.E. resulted in a volume increase of ~59 × 106 m3. Whereas the Virginia Barrier Islands as a whole modestly decreased in size (and thus volume) directly in response to storm impacts and accelerating relative sea-level rise since the mid-1800s, the differential behavior of islands south of Assateague suggests more regional controls on coastal geomorphic behavior. Specifically, we identify the roles of antecedent substrate, sand trapping and changing wave-refraction patterns associated with the growth of Assateague Island, and inter-island sand exchanges in response to changing updrift barrier-scale behaviors. These findings help to better understand the underlying mechanisms behind state changes of barrier islands; in particular, the mechanisms by which geomorphic change along one barrier island influences those located several to tens of kilometers downdrift. This highlights the need to consider coastal beach and sand management over long reaches, even in systems which are largely unaffected by development, nourishment, and shoreline hardening.

Long-Term Community Dynamics Reveal Different Trajectories for Two Mid-Atlantic Maritime Forests

Maritime forests are threatened by sea-level rise, storm surge and encroachment of salt-tolerant species. On barrier islands, these forested communities must withstand the full force of tropical storms, hurricanes and nor’easters while the impact is reduced for mainland forests protected by barrier islands. Geographic position may account for differences in maritime forest resilience to disturbance. In this study, we quantify two geographically distinct maritime forests protected by dunes on Virginia’s Eastern Shore (i.e., mainland and barrier island) at two time points (15 and 21 years apart, respectively) to determine whether the trajectory is successional or presenting evidence of disassembly with sea-level rise and storm exposure. We hypothesize that due to position on the landscape, forest disassembly will be higher on the barrier island than mainland as evidenced by reduction in tree basal area and decreased species richness. Rate of relative sea-level rise in the region was 5.9 ± 0.7 mm yr−1 based on monthly mean sea-level data from 1975 to 2017. Savage Neck Dunes Natural Area Preserve maritime forest was surveyed using the point quarter method in 2003 and 2018. Parramore Island maritime forest was surveyed in 1997 using 32 m diameter circular plots. As the island has been eroding over the past two decades, 2016 Landsat imagery was used to identify remaining forested plots prior to resurveying. In 2018, only plots that remained forested were resurveyed. Lidar was used to quantify elevation of each point/plot surveyed in 2018. Plot elevation at Savage Neck was 1.93 ± 0.02 m above sea level, whereas at Parramore Island, elevation was lower at 1.04 ± 0.08 m. Mainland dominant species, Acer rubrum, Pinus taeda, and Liquidambar styraciflua, remained dominant over the study period, with a 14% reduction in the total number of individuals recorded. Basal area increased by 11%. Conversely, on Parramore Island, 33% of the former forested plots converted to grassland and 33% were lost to erosion and occur as ghost forest on the shore or were lost to the ocean. Of the remaining forested plots surveyed in 2018, dominance switched from Persea palustris and Juniperus virginiana to the shrub Morella cerifera. Only 46% of trees/shrubs remained and basal area was reduced by 84%. Shrub basal area accounted for 66% of the total recorded in 2018. There are alternative paths to maritime forest trajectory which differ for barrier island and mainland. Geographic position relative to disturbance and elevation likely explain the changes in forest community composition over the timeframes studied. Protected mainland forest at Savage Neck occurs at higher mean elevation and indicates natural succession to larger and fewer individuals, with little change in mixed hardwood-pine dominance. The fronting barrier island maritime forest on Parramore Island has undergone rapid change in 21 years, with complete loss of forested communities to ocean or conversion to mesic grassland. Of the forests remaining, dominant evergreen trees are now being replaced with the expanding evergreen shrub, Morella cerifera. Loss of biomass and basal area has been documented in other low elevation coastal forests. Our results indicate that an intermediate shrub state may precede complete loss of woody communities in some coastal communities, providing an alternative mechanism of resilience.

Reconstructing Coastal Sediment Budgets From Beach‐ and Foredune‐Ridge Morphology: A Coupled Field and Modeling Approach

AbstractPreserved beach and foredune ridges may serve as proxies for coastal change, reflecting alterations in sea level, wave energy, or past sediment fluxes. In particular, time‐varying shoreface sediment budgets have been inferred from the relative size of foredune ridges through application of radiocarbon and optically stimulated luminescence dating to these systems over the last decades. However, geochronological control requires extensive field investigation and analysis. Purely field‐based studies might also overlook relationships between the mechanics of sediment delivery to the shoreface and foredune ridges, missing insights about sensitivity to changes in sediment budget. We therefore propose a simple geomorphic model of beach/foredune‐ridge and swale morphology to quantify the magnitude of changes in cross‐shore sediment budget, employing field measurements of ridge volume, ridge spacing, elevation, and shoreline progradation. Model behaviors are constrained by the partitioning of sediment fluxes to the shoreface and foredune ridge and can be used to reproduce several cross‐shore patterns observed in nature. These include regularly spaced ridges (“washboards”), large singular ridges, and wide swales with poorly developed ridges. We evaluate our model against well‐preserved ridge and swale systems at two sites along the Virginia Eastern Shore (USA): Fishing Point, for which historical records provide a detailed history of shoreline progradation and ridge growth, and Parramore Island, for which a relatively more complex morphology developed over a poorly constrained period of prehistoric growth. Our results suggest this new model could be used to infer the sensitivity of field sites across the globe to variations in sediment delivery.

Insights into barrier-island stability derived from transgressive/regressive state changes of Parramore Island, Virginia

Barrier islands and their associated backbarrier ecosystems front much of the U.S. Atlantic and Gulf coasts, yet threshold conditions associated with their relative stability (i.e., state changes between progradation, erosion, and landward migration) in the face of sea-level rise remain poorly understood. The barrier islands along Virginia's Eastern Shore are among the largest undeveloped barrier systems in the U.S., providing an ideal natural laboratory to explore the sensitivity of barrier islands to environmental change. Details about the developmental history of Parramore Island, one of the longest (12 km) and widest (1.0–1.9 km) of these islands, provide insight into the timescales and processes of barrier-island formation and evolution along this mixed-energy coast. Synthesis of new stratigraphic (vibra-, auger, and direct-push cores), geospatial (historical maps, aerial imagery, t-sheets, LiDAR), and chronologic (optically stimulated luminescence, radiocarbon) analyses reveals that Parramore has alternated between periods of landward migration/erosion and seaward progradation during the past several thousand years. New chronology from backbarrier and barrier-island facies reveals that Parramore Island has existed in some form for nearly 5000 years. Following a period of rapid overwash-driven retrogradation, and coinciding with a period of slow relative sea-level rise (~1 mm/ yr), Parramore stabilized ~1000 years ago in partial response to pinning by and sediment delivery from erosion of a Pleistocene-aged antecedent high. Following pinning, Parramore built seaward through development of successive progradational beach and dune ridges. Morphological and historical evidence suggests that these processes were interrupted by inlet formation—possibly associated with an interval of enhanced storminess—at least three times during this period. Following inlet closure in the early 1800s, island progradation was rapid, with Parramore Island reaching its maximum width ca. 150 years ago. It has since switched states again, undergoing accelerating erosion (~12 m/ yr since 1980). The relative youth of Parramore Island is in contrast to many East Coast barrier islands, which generally reached their present positions about 3500–2000 years ago. Moreover, these results demonstrate that the apparent robustness and stability of Parramore are ephemeral features of an island that has undergone multiple state changes within the last 1000 years. Finally, they refine current knowledge of the roles of antecedent topography, sediment delivery rates, storms, and sea-level rise in barrier-island stability and resilience to future climate change.

Prevalence of psammoma bodies in meninges and choroid plexuses of raccoons (Procyon lotor) from Parramore Island, Virginia.

Microscopic evidence of multifocal mineralizations (psammoma bodies) were seen in brains of 33/53 (62%) raccoons (Procyon lotor) necropsied on Parramore Island, Virginia. Most mineralized foci had concentric laminations and were present in small capillaries of meninges of the brain (15/33), in choroid plexus (3/33), or at both these sites (13/33). In 2 raccoons, the lesions were confined to the meninges of the proximal cervical spinal cord. In most cases, the affected vessels appeared to have been completely occluded. However, no evidence of ischemic changes in the brain parenchyma was seen, and none of the raccoons had abnormal neurologic signs prior to euthanasia. The condition appears to be a common incidental histopathologic finding in raccoons from the eastern United States. Although the exact cause of this condition is not known, a primary vascular insult with resultant dystrophic mineralization of the affected vessels is suspected.

First North American field release of a vaccinia-rabies glycoprotein recombinant virus.

Following nearly 10 yr of extensive laboratory evaluation, a vaccinia-rabies glycoprotein (V-RG) vaccine was the first recombinant virus to undergo limited North American field release on 20 August 1990. The free-ranging raccoon population on Parramore Island (Virginia, USA) was exposed to a high density (10 baits/ha) of vaccine-laden baits distributed on a 300 ha vaccination area. An annual total of 887 raccoons were live-trapped for sedation, physical examination and blood collection for rabies antibody determination; there was no evidence of adverse effects or lesions due to the vaccine. Age and sex distributions, mean body weights, and live-capture histories of raccoons from the vaccination and non-baited control areas were compared. There were no statistically significant differences in survivorship between the baited and non-baited areas, nor between rabies antibody-positive and antibody-negative raccoons from the vaccination area. There was no trend in field mortality that suggested an association with either tetracycline or sulfadimethoxine, used as biomakers, or with vaccine contact determined by antibody status. No gross or histopathologic lesions due to the vaccine were demonstrated among a subsample of live-trapped raccoons collected for gross necropsy, biomarker analysis, histopathologic examination, and V-RG virus isolation attempts. Recovery of V-RG virus was limited to the tonsils of two biomarker-positive, clinically healthy raccoons collected from the vaccination area for postmortem examination on days 2 and 4 following bait distribution. These data reinforce the extensive body of safety data on the V-RG virus and extend it to include field evaluation where vaccine is offered free-choice in abundance, in baits designed to attract free-ranging raccoons, in a relatively simple ecosystem.

Borrelia burgdorferi in Eastern Virginia: Comparison between a Coastal and Inland Locality

In Virginia, Borrelia burgdorferi was more prevalent in a site along the Atlantic Ocean, near Maryland, than in an inland site near Williamsburg and Yorktown. At the coastal site on Assateague Island, B. burgdorferi was isolated from 4.2% of 475 animals sampled, including four species of small mammals. Serologic tests indicated that 25-37% of the small rodents assayed had been exposed to B. burgdorferi. Immunofluorescence antibody assays specific for B. burgdorferi showed spirochete infection in Ixodes scapularis and Dermacentor variabilis but not in other species of ticks also examined from this site. At another coastal site (Parramore Island), no evidence of Peromyscus leucopus was found, no immature specimens of I. scapularis were collected, and no isolations were made from numerous raccoons or small mammals sampled. Borrelia burgdorferi infection was found in one I. cookei nymph, but not in numerous specimens of I. scapularis or other tick species from this locality. At the inland site between Williamsburg and Yorktown, B. burgdorferi was isolated from two small mammal species and antibodies to B. burgdorferi were found in only 7-10% of the small mammals sampled. Ixodes scapularis were less abundant at this locality than at the Assateague Island site. Borrelia burgdorferi spirochetes were found in I. scapularis and a single nymph of Amblyomma americanum, but not in any of numerous specimens of four other species. Infection with B. burgdorferi was found in 20% of unfed adult I. scapularis from vegetation, but in only 0.2% of numerous adults from hunter-killed deer. Infection in immature ticks was much lower than at Assateague Island. Borrelia burgdorferi may be more prevalent along the Atlantic coast than in inland areas. Isolations, seroprevalence, immature I. scapularis densities, and spirochete infection rates in ticks were higher at the Assateague Island site than the Williamsburg/Yorktown site. Consequently, the risk of human exposure to Lyme disease may be higher in some parts of the coastal area than elsewhere in Virginia. Overall, B. burgdorferi is less intense in Virginia than in the northeastern United States.

Factors Contributing to the Decline of Pinus taeda on a Virginia Barrier Island

JOHNSON S. R. AND D. R. YOUNG (Department of Biology, Virginia Commonwealth University, Richmond, VA 23284). Factors contributing to the decline of Pinus taeda on a Virginia barrier island. Bull. Torrey Bot. Club 120: 431-438. 1993.-Age structure, recruitment, salinity effects and tolerance to shading were examined for Pinus taeda (loblolly pine) to evaluate factors that may be contributing to a decline in abundance on Hog Island. Recruitment characteristics differed considerably when compared to Parramore Island, also within the Virginia barrier island system. Tree age structure was discontinuous, with almost no seedlings on Hog Island. Sixty percent of the trees were 30 to 50 years old and no trees were greater than 80 years in age, whereas the Parramore population ranged continuously from seedlings to trees over 100 years old. Laboratory experiments indicated that seeds survive at least four weeks in oceanstrength saltwater (30 ppt) when in cones and that seeds germinated when treated with diluted (10 ppt) saltwater, suggesting the possibility of colonization after oceanic transport. However, salinity did reduce stomatal conductance in seedlings, indicating salt intolerance. Seed germination and early seedling growth were reduced at low photon flux densities, typical of the shaded environment beneath dense vegetation on Hog Island. Population decline on Hog Island is probably the combined result of the scattered distribution of trees and low recruitment, in conjunction with the constraints of salinity and shading, as well as a variety of factors that contribute to the severe maritime island environment.

First Report of a Demodex sp. in Raccoons (Procyon lotor)

Demodex spp. mites were seen in skin sections of 5 of 53 raccoons (Procyon lotor) necropsied on Parramore Island, Virginia (USA). In all infections, mites were present in the skin over the lower legs; in one raccoon they also were located in a follicle of a vibrissa. None of the raccoons had Demodex-related gross lesions. Histopathologically, minimal lesions were seen in the affected follicles. This is the first documentation of Demodex spp. in raccoons.

Fade statistics and propagation events at C band for two overwater, line‐of‐sight propagation paths over a 1‐year period

We examine signal fading statistics over a 1‐year period corresponding to two overwater, line‐of‐sight, propagation links in the mid‐Atlantic coast of the United States. These links are composed of a transmitter on a tower at Parramore Island, Virginia, operating at 4.7 GHz, sending simultaneous CW signals to two receiver systems located on a lighthouse and a lookout tower on Assateague Beach, Virginia, at distances of 44 and 39 km, respectively. The receiving sites are separated by approximately 5 km. Cumulative fade distributions corresponding to yearly, monthly, and diurnal time scales were derived. The annual distributions showed fades in excess of 49 and 54 dB during approximately 7.7 hours of the year, for the lighthouse and lookout tower links, respectively. Fade duration statistics corresponding to sustained attenuation events were also derived. These events, which were arbitrarily defined as having fades relative to free space powers in excess of 20 dB for durations of 2 hours or more, are believed to be generally due to extreme subrefractive conditions. Analysis of synoptic weather conditions and nearby rawinsonde data during four sustained deep fading periods showed atmospheric conditions consistent with extreme subrefraction, where the refractivity height profiles had positive lapse rates. A measured refractivity profile, having a positive lapse rate, was injected into a propagation model based on an approximation to the scalar Helmholtz wave equation, and fade levels in the vicinity of the antenna locations were calculated. Although the refractivity profile was measured during an earlier period in the vicinity of the links, it was obtained over the water and showed an extreme positive lapse rate in refractivity, indicating that such profiles do in fact occur. Furthermore, the calculated fades were noted to have the same range of values as measured during the sustained deep fade events, showing consistency with the hypothesis that severe subrefraction may be the cause of these events.

Borrelia burgdorferi in Ticks (Acari: Ixodidae) from Coastal Virginia

Ixodid ticks removed from hosts and from vegetation during March-November 1987 at sites in coastal Virginia and North Carolina were examined for Borrelia burgdorferi. B. burgdorferi was evident in nine (22%) Ixodes cookei Packard removed from rice rats (Oryzomys palustris), a white-footed mouse (Peromyscus leucopus), and raccoons (Procyon lotor); four (6%) Amblyomma americanum (L.) removed from raccoons; and two (3%) Dermacentor variabilis (Say) removed from a raccoon and a rice rat. B. burgdorferi was also detected in Ixodes dentatus Marx removed from a brown thrasher (Toxostoma rufum), a Carolina wren (Thryothoros ludovicianus), and a towhee (Piplio erythrophthalamus); and in Haemaphysalis leporispalustris (Packard) removed from a brown thrasher and a white-throated sparrow (Zonotrichia albicollis) netted at Kiptopeke Beach, Va. Two Ixodes dammini Spielman, Clifford, Piesman & Corwin were collected on Parramore Island; one specimen was examined for spirochetes, and it was infected with B. burgdorferi. No spirochetes were detected in host-seeking A. americanum and Amblyomma maculatum Koch removed from vegetation. The plasma of one P. leucopus and sera obtained from two P. lotor contained antibodies to B. burgdorferi. All infected ticks and the seroreactive hosts were collected from the Eastern Shore of Virginia.

Lung Lesions in an Opossum (Didelphis virginiana) Associated with Capillaria didelphis

An opossum (Didelphis virginiana) live-trapped on Parramore Island, Virginia was infected with the lung parasite Capillaria didelphis. Lung lesions associated with this parasite were extensive and consisted of numerous areas with central necrosis deep within the parenchyma. Necrotic foci were present around airways and consisted of a mixture of inflammatory cells and cellular debris, adult nematodes and many bipolar eggs. This parasite causes severe verminous pneumonia in the opossum.

Proposed field evaluation of a rabies recombinant vaccine for raccoons (Procyon lotor): site selection, target species characteristics, and placebo baiting trials.

Prior to a limited field application of an orally-administered vaccinia-rabies glycoprotein (V-RG) recombinant virus vaccine for wildlife, background data were obtained for the proposed site on Parramore Island, Virginia (USA). Mammalian target and nontarget species, potentially at risk for exposure to vaccine were inventoried. Placebo baiting trials with a fishmeal polymer bait resulted in high bait disturbance (88 to 100%), primarily by raccoons (Procyon lotor), with infrequent visitation and no evidence of bait consumption by deer (Odocoileus virginianus), small mammals or avian species. Definitive bait acceptance rates by raccoons (indicative of bait ingestion) were difficult to accurately determine based exclusively on premolar and vibrissae samples collected antemortem from live-trapped raccoons for tetracycline and rhodamine B biomarker analyses, respectively. Bait acceptance rate was more accurately determined during a pilot baiting trial conducted on North Island, South Carolina, when mandibles (postmortem samples) were examined for tetracycline incorporation. Parasitologic findings in raccoons on Parramore Island included Hepatozoan procyonis, Phagicola angrense and Physaloptera rara and a variety of incidental microscopic lesions, and provided baseline pathological data for comparison subsequent to V-RG vaccine application. A population density estimate of one raccoon/2.7 ha was calculated using mark-recapture data for comparison after vaccine deployment. Limited reproductive data, including estimates of pregnancy rates by palpation, the number of live kits/litter live-trapped with previously pregnant raccoons or observed in the dens of radio-collared raccoons, was gathered to assess the effect of proposed oral vaccination with V-RG vaccine. Home ranges were assessed by radio-telemetry of 15 raccoons; all radio-collared raccoons currently reside on Parramore Island.(ABSTRACT TRUNCATED AT 250 WORDS)

The Parramore Island Mounds of Virginia

O N A series of large-scale aerial photographs covering the Atlantic coast a striking complex of moundlike features was observed, which seemed to be particularly well developed and numerous on Parramore Island, Virginia. No description of these features could be found in the literature. This is not surprising, however, since Parramore, a relatively isolated island, is privately owned and visits are restricted. Natural low mounds elsewhere that appear to have features in common with the Parramore Island mounds have been reported by Veatch,' Rich,2 Melton,3 Dietz,4 and others, who attributed the origin of the mounds they described to different causes. But unlike these mounds, those of Parramore Island seemed to be still in process of formation, and it was believed that their mode of origin could therefore be established. If so, the controversy over the history of mounds found elsewhere under similar environmental circumstances would be clarified. To understand better the nature of mounds in general and to ascertain the possible origin of the Parramore Island mounds, a brief review of the literature is desirable. A comparison will be drawn between the general types and the Virginia mounds, and previously suggested modes of origin will be described so that the probable mode can be more clearly established.

Some Features Common to Sand Bars on Modern Coasts and in Geologic Column: ABSTRACT

Sand bars which have features and distribution similar to sand bars on modern coast lines are being recognized as oil reservoirs in many parts of the geologic column, and their occurrence is in many widely spaced areas. A knowledge of modern sand bars, therefore, should aid the discovery and development of oil fields in ancient sand bars. Systems of sand bars are common features of many coasts of the world. They are particularly well developed on the Atlantic and Gulf coasts of the United States. Except for an attachment, commonly at one end, the bars are separated from the mainland by lagoons or marshes, many of which range from ½ to 5 miles in width. The width of some lagoons, however, is 30 miles or more. The length of many bars on the Atlantic Coast ranges from 4 to 8 miles, others from 15 to 30 miles, and on the Gulf Coast from a few to more than 100 miles. The individual bars are separated by narrow water channels called tidal inlets, which connect the ocean with the lagoons. The inlets are kept open by tidal currents which surge in and out through the inlets twice daily. Longshore currents, which are produced by waves striking the coast at an angle, operate on the seaward side of the bars. They transport sand along the shore, and lengthen the bars at one end. At the same time the tidal currents at the inlets tend to limit the extension of the bars. The result is that the end of an individual bar is extended along shore beyond the end of the next bar on the coast, but slightly seaward of it; thus producing an en echelon arrangement of the bars. Offset features are particularly well developed on the south shore of Long Island, where a westward longshore current has extended the western end of each bar westward beyond the adjacent bar. Many bars on the Atlantic Coast are characterized by ridges of sand that trend parallel with the shore; the ridges commonly are capped by dunes and are separated by long marsh strips or slashes. These are growth ridges and are produced by addition of sand to the seaward side of the bars. Growth End_Page 210------------------------------ ridges are prominent at Cape Henry, Virginia, Bogue Island, Parramore Island, and elsewhere on the Atlantic Coast and at many places on the Gulf Coast. Beach sands on modern coasts are well sorted within individual beds or laminae. On the other hand, there is considerable range in grain size from laminae to laminae. The beach sands are composed chiefly of grains of quartz but contain minor amounts of a great variety of minerals. Beach sands on modern coasts are transitory features that are modified by every storm. It is truly remarkable that many similar sand bodies of the geologic past have been so perfectly preserved in the geologic column. A few examples include the so-called shoestring oil sands in the Cherokee shale of Pennsylvanian age in Kansas and Oklahoma. These sand bodies have many features of the modern coastal sands. The length of one system of these sands is 150 miles. Some of the sand bodies in the Cretaceous system in the Denver basin of Colorado and Nebraska, and in the Powder River basin of Wyoming and the somewhat younger Cretaceous sands in the San Juan basin in New Mexico appear to have had a similar origin. End_of_Article - Last_Page 211------------