Delmarva Peninsula Research Articles

Loess in the mid-Atlantic region, USA

AbstractLoess is common in the Mid-Atlantic region of the United States south of the Late Wisconsinan glacial border particularly along rivers draining the glaciated areas of Pennsylvania, New Jersey, and New York. The broadest deposits occur on the flat landscapes of the Delmarva Peninsula in Maryland where two episodes of deposition have been identified. The earlier Miles Point Loess has a limited distribution and is buried by the more widespread Paw Paw Loess. OSL and 14C dates place deposition of the Miles Point Loess during MIS 3. The well developed paleosol formed in the Miles Point Loess acts as a stratigraphic marker. The Paw Paw Loess buries Clovis age cultural materials which date deposition to the end of the Pleistocene. Loess deposits and paleosols are critical in understanding regional landscape evolution, Late Pleistocene environments, and early North American cultural history. Mapping the extent of loess in the Mid-Atlantic using the Natural Resources Conservation Service’s gSSURGO database overrepresents loess in some areas and underrepresents in others.

Estimation of Forest Canopy Height and Aboveground Biomass from Spaceborne LiDAR and Landsat Imageries in Maryland

Mapping the regional distribution of forest canopy height and aboveground biomass is worthwhile and necessary for estimating the carbon stocks on Earth and assessing the terrestrial carbon flux. In this study, we produced maps of forest canopy height and the aboveground biomass at a 30 m spatial resolution in Maryland by combining Geoscience Laser Altimeter System (GLAS) data and Landsat spectral imageries. The processes for calculating the forest biomass included the following: (i) processing the GLAS waveform and calculating spatially discrete forest canopy heights; (ii) developing canopy height models from Landsat imagery and extrapolating them to spatially contiguous canopy heights in Maryland; and, (iii) estimating forest aboveground biomass according to the relationship between canopy height and biomass. In our study, we explore the ability to use the GLAS waveform to calculate canopy height without ground-measured forest metrics (R2 = 0.669, RMSE = 4.82 m, MRE = 15.4%). The machine learning models performed better than the principal component model when mapping the regional forest canopy height and aboveground biomass. The total forest aboveground biomass in Maryland reached approximately 160 Tg. When compared with the existing Biomass_CMS map, our biomass estimates presented a similar distribution where higher values were in the Western Shore Uplands region and Folded Application Mountain section, while lower values were located in the Delmarva Peninsula and Allegheny Mountain regions.

A Retrospective Statistical Analysis of Second Primary Cancers in the Delmarva Peninsula, U.S.A.

A significant percentage of cancer survivors develop a second primary cancer. Using data of deceased patients provided by the Peninsula Regional Medical Center, a retrospective statistical analysis was conducted to investigate whether the type of the first cancer affects the occurrence time and type of the second primary cancer. Cancer patients were stratified according to the first cancer type, and the time elapsed between the first and second cancer diagnosis was examined to see if there are statistically significant differences. Histograms of second cancer occurrence times for lung and bronchus, breast and melanoma-skin cancers are strongly skewed right while those for prostate and urinary bladder cancers have lower right skewness. Both one-way analysis of variance test and Kruskal-Wallis test show a p-value below the significance level of 0.05, confirming that the first cancer type affects the second cancer occurrence time. For each first cancer type, the most common types of the second primary cancer are identified. About 40% of breast cancer and lung and bronchus cancer survivors develop a second primary cancer of the same type. 25% of melanoma-skin cancer survivors develop the same cancer again and 17% of them develop a second melanoma cancer. In contrast, less than 1% of prostate cancer survivors develop a second prostate cancer and only 14% of urinary bladder cancer survivors develop the same cancer again. Lung and bronchus cancer is one of the most prevalent second cancer types regardless of the first cancer type.

Fluxes of nitrous oxide and nitrate from agricultural fields on the Delmarva Peninsula: N biogeochemistry and economics of field management

The effects of two agricultural conservation practices on nitrous oxide (N2O) fluxes to the atmosphere and nitrate (NO3−) fluxes to groundwater were compared to conventional practices. The conservation practices were application of 80% of recommended nitrogen (N) and planting of winter cover crops. N2O fluxes were measured by static chambers, and NO3− fluxes were calculated using measured NO3− concentrations from tile lines and estimated groundwater yields. During the growing season, one of the five 80% N treatments showed significantly reduced N2O fluxes compared to the 100% N control, whereas three of the five 80% N treatments showed significantly reduced NO3− concentrations compared to the 100% N application. The 80% N treatment resulted in reduced crop yields of 5–26% and average economic losses of US$366ha−1 for corn and US$153ha−1 for winter wheat. In three winter cover-crop treatments there were two significant reductions in fall N2O fluxes compared to no-cover-crop controls, and tile drain NO3− concentrations were also significantly lower in autumn. The N2O fluxes were a function of soil temperature, moisture, and fertilizer applications (r2=0.49, p<0.001). Integrating N2O and NO3− fluxes to the annual time scale without conservation measures resulted in mean export of 15±8kgN2O-Nha−1y−1 and 36±6kg NO3-Nha−1y−1. Adding an 80% N conservation treatment reduced N2O fluxes by 79% and NO3− fluxes by 22%, whereas adding cover crops had smaller effects (11% for N2O, 9% for NO3−). However, cover crops were more cost-effective, averaging US$53 (kgN)−1 compared to the 80% fertilizer treatment (US$77 (kgN)−1) due to large economic losses for corn. The state of Maryland (MD) subsidizes cover crops, making the practice even more cost-effective at US$15 (kgN)−1, emphasizing the importance of farmer-friendly policies.

Estimating restorable wetland water storage at landscape scales.

Globally, hydrologic modifications such as ditching and subsurface drainage have significantly reduced wetland water storage capacity (i.e., volume of surface water a wetland can retain) and consequent wetland functions. While wetland area has been well documented across many landscapes and used to guide restoration efforts, few studies have directly quantified the associated wetland storage capacity. Here, we present a novel raster-based approach to quantify both contemporary and potential (i.e., restorable) storage capacities of individual depressional basins across landscapes. We demonstrate the utility of this method by applying it to the Delmarva Peninsula, a region punctuated by both depressional wetlands and drainage ditches. Across the entire peninsula, we estimated that restoration (i.e., plugging ditches) could increase storage capacity by 80%. Focusing on an individual watershed, we found that over 59% of restorable storage capacity occurs within 20 m of the drainage network, and that 93% occurs within 1 m elevation of the drainage network. Our demonstration highlights widespread ditching in this landscape, spatial patterns of both contemporary and potential storage capacities, and clear opportunities for hydrologic restoration. In Delmarva and more broadly, our novel approach can inform targeted landscape-scale conservation and restoration efforts to optimize hydrologically mediated wetland functions.

PAH, PCB, TPH and mercury in surface sediments of the Delaware River Estuary and Delmarva Peninsula, USA

Surface sediment concentrations of polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB), total petroleum hydrocarbons (TPH) and mercury, were compared from two areas with contrasting land use history, the industrial Delaware Estuary and the rural Delmarva Peninsula (USA). TPH in the Delaware (38–616mg/kg) and saturate/aromatic fractions suggested petroleum/industrial sources compared to biogenic sources in the Delmarva coastal control (<34–159mg/kg). Within the Delaware the ∑PAH18 ranged from 3749 to 22,324μg/kg with isomeric ratios indicative of petroleum combustion source/s, conversely, those in the Delmarva (5–2139μg/kg) also yielded relatively higher perylene that were consistent with natural background levels derived from vegetation/coal combustion source/s. ∑PCB(tri-hepta) concentrations in the Delmarva (0.6–6.5μg/kg) were less than the threshold effect concentration (TEC), whereas the Delaware had received much higher PCB loading (18.1–136.8μg/kg) as evidenced by a significantly higher amounts in some samples (>TEC).

Topographic and physicochemical controls on soil denitrification in prior converted croplands located on the Delmarva Peninsula, USA

Topographic and soil physiochemical characteristics exert substantial controls on denitrification, and the effect of these controls is especially evident in fertilized agricultural lands. To depict these controls at a landscape scale for decision support applications, metrics (i.e., proxies) must be developed based on commonly available geospatial data. In this study, we carried out an observational study on denitrification potential (DP) and capacity (DC) in three actively farmed crop fields that were converted from forested wetlands (i.e., prior converted croplands). The combined effects of ten topographic and physiochemical factors, including three topographic attributes (relief, topographic wetness index, and positive openness), two soil texture indices (sand and clay), and five soil properties (soil moisture, pH, electrical conductivity, soil organic carbon and total nitrogen), on DP and DC were analyzed. The three topographic attributes were developed using a digital elevation model (DEM) derived from light detection and ranging (LiDAR) data. Nitrate and carbon addition led to a doubling in DP compared to DC without soil amendment. Topography explained the greatest amount of variation in DP across the three sites. The relationship between topography and DP may partly be explained through the relatively robust relationships between topography and soil moisture, texture, and carbon content. Soil electrical conductivity (EC) exhibited the highest correlation with DC (r2=35%). DP and DC were higher under drought conditions with low soil moisture, relative to average conditions with relatively higher soil moisture, which may be related to the substantial increase in soil EC under drought conditions. However, DP and DC were less responsive to soil EC at sandy sites that tended to have low soil moisture. Results of this study suggest that the spatial-temporal variations in denitrification at these croplands were primarily caused by complex interactions between soil properties and landscape position. Topographic metrics derived from LiDAR data have the potential to improve understanding of denitrification variability at the landscape scale.

Automated Quantification of Surface Water Inundation in Wetlands Using Optical Satellite Imagery

We present a fully automated and scalable algorithm for quantifying surface water inundation in wetlands. Requiring no external training data, our algorithm estimates sub-pixel water fraction (SWF) over large areas and long time periods using Landsat data. We tested our SWF algorithm over three wetland sites across North America, including the Prairie Pothole Region, the Delmarva Peninsula and the Everglades, representing a gradient of inundation and vegetation conditions. We estimated SWF at 30-m resolution with accuracies ranging from a normalized root-mean-square-error of 0.11 to 0.19 when compared with various high-resolution ground and airborne datasets. SWF estimates were more sensitive to subtle inundated features compared to previously published surface water datasets, accurately depicting water bodies, large heterogeneously inundated surfaces, narrow water courses and canopy-covered water features. Despite this enhanced sensitivity, several sources of errors affected SWF estimates, including emergent or floating vegetation and forest canopies, shadows from topographic features, urban structures and unmasked clouds. The automated algorithm described in this article allows for the production of high temporal resolution wetland inundation data products to support a broad range of applications.

The influence of data characteristics on detecting wetland/stream surface-water connections in the Delmarva Peninsula, Maryland and Delaware.

The dependence of downstream waters on upstream ecosystems necessitates an improved understanding of watershed-scale hydrological interactions including connections between wetlands and streams. An evaluation of such connections is challenging when, (1) accurate and complete datasets of wetland and stream locations are often not available and (2) natural variability in surface-water extent influences the frequency and duration of wetland/stream connectivity. The Upper Choptank River watershed on the Delmarva Peninsula in eastern Maryland and Delaware is dominated by a high density of small, forested wetlands. In this analysis, wetland/stream surface water connections were quantified using multiple wetland and stream datasets, including headwater streams and depressions mapped from a lidar-derived digital elevation model. Surface-water extent was mapped across the watershed for spring 2015 using Landsat-8, Radarsat-2 and Worldview-3 imagery. The frequency of wetland/stream connections increased as a more complete and accurate stream dataset was used and surface-water extent was included, in particular when the spatial resolution of the imagery was finer (i.e., <10 m). Depending on the datasets used, 12% to 60% of wetlands by count (21% to 93% of wetlands by area) experienced surface-water interactions with streams during spring 2015. This translated into a range of 50% to 94% of the watershed contributing direct surface water runoff to streamflow. This finding suggests that our interpretation of the frequency and duration of wetland/stream connections will be influenced not only by the spatial and temporal characteristics of wetlands, streams and potential flowpaths, but also by the completeness, accuracy and resolution of input datasets.

Using column experiments to examine transport of As and other trace elements released from poultry litter: Implications for trace element mobility in agricultural watersheds

Trace elements are added to poultry feed to control infection and improve weight gain. However, the fate of these trace elements in poultry litter is poorly understood. Because poultry litter is applied as fertilizer in many agricultural regions, evaluation of the environmental processes that influence the mobility of litter-derived trace elements is critical for predicting if trace elements are retained in soil or released to water. This study examined the effect of dissolved organic carbon (DOC) in poultry litter leachate on the fate and transport of litter-derived elements (As, Cu, P and Zn) using laboratory column experiments with soil collected from the Delmarva Peninsula (Mid-Atlantic, USA), a region of intense poultry production. Results of the experiments showed that DOC enhanced the mobility of all of the studied elements. However, despite the increased mobility, 60–70% of Zn, As and P mass was retained within the soil. In contrast, almost all of the Cu was mobilized in the litter leachate experiments, with very little retention in soil. Overall, our results demonstrate that the mobility of As, Cu, Zn and P in soils which receive poultry litter application is strongly influenced by both litter leachate composition, specifically organic acids, and adsorption to soil. Results have implications for understanding fate and transport of trace elements released from litter application to soil water and groundwater, which can affect both human health and the environment.

Observations of the reduction in surface artifact frequency as a result of multimodal plowing

AbstractThe frequency and distribution of plowzone artifacts are compared with the timing and duration of two plow modes at two study locales on the Delmarva Peninsula, United States. Our results indicate that historic moldboard plowing created a maximum plowzone of ca. 0.30 m, in which artifacts were retained over time. Later, soil‐conservative chisel plowing mixed the top ca. 0.15 m of soil, creating a shallow, minimum plowzone. With time and repeated plowing, our data suggest that the number of artifacts at the surface diminished via a combination of vertical mixing and/or degradation, physical and chemical weathering, and avocational collecting. When moldboard plowing is reapplied to fields after decades of chisel plowing, the historic maximum plowzone is inverted and the surface is re‐saturated with artifacts. This inverted maximum plowzone retains an inherent pattern of artifact transport from moldboard plowing, which supports other studies that have measured such displacements over time. Our results suggest that the frequency of artifacts observed at the surface of agricultural fields, or lack thereof, is a likely outcome of natural and mechanical processes, and removal within the minimum plowzone. This inevitable depletion of artifacts may have negative repercussions for many research designs that systematically sample the plowzone.

Identification of Type A Influenza Viruses from Wild Birds on the Delmarva Peninsula, 2007-10.

Wild waterfowl and shorebirds in the Delaware-Maryland-Virginia (Delmarva) Peninsula region within the Atlantic Flyway were sampled as part of the Early Detection of Highly Pathogenic H5N1 Avian Influenza (AI) in Wild Migratory Birds program. The U.S. Department of Agriculture (USDA) and state wildlife agencies submitted 7858 samples for AI virus (AIV) testing by real-time reverse transcription PCR (rRT-PCR) to the University of Delaware Poultry Health System from April 2007 to March 2011. Virus isolation attempts were performed on samples with matrix gene cycle threshold (Ct) values ≤33.9. Using rRT-PCR, AIV was detected in 14% (1091/7857) of the samples. In species with sample sizes >100, American black duck ( Anas rubripes ; 28%), ruddy turnstone ( Arenaria interpres ; 27%), American green-winged teal ( Anas crecca ; 21%), semipalmated sandpiper ( Calidris pusilla ; 27%), greater snow goose ( Chen caerulescens atlanticus; 12%), mallard ( Anas platyrhynchos ; 10%), and northern pintail ( Anas acuta ; 14%) showed the highest rates of AIV detection. Forty-two AIVs were recovered from eight species: American black duck, mallard, ruddy turnstone, American green-winged teal, greater snow goose, Canada goose ( Branta canadensis ), ring-necked duck ( Aythya collaris ), and mallard × American black duck ( Anas platyrhynchos × Anas rubripes ). Recovered H5 (n = 2) and H7 (n = 2) viruses were found to be low pathogenicity by the USDA National Veterinary Services Laboratory. Additional AIVs represented a diversity of subtype combinations: H1-H4, H6, and H10 and H11 and N subtypes N1-N9 and N6-N9. The rate of AIV recovery from swabbings was inversely related to Ct value, ranging from 50% for Ct values of 16.0-18.9 to 5.1% for Ct values of 31-33.9.

A complete history of the establishment of Japanese sika deer on the Delmarva Peninsula: 100 years post-introduction

While many non-native species immediately express their negative qualities which encourage their management (even attempted eradication), some have long lag periods before the population begins to grow out of control. Sika deer have been problematic in many places where they were introduced as novelties or games species through hybridization or aggressive interactions with native deer. In attempt to better manage these species we need to know their native ecosystem. We provide evidence through summarized literature of the manner in which sika deer arrived on Delmarva from Yakushima Island in Japan via a multi-generational stopover in the United Kingdom. We also add morphological and genetic support that confirm the origins and help describe the path of introduction of sika deer to Maryland. We also summarize the growth and change in population size(s) over the last 100 years. This historic understanding is an essential part of coping with the persistent growth of a large, aggressive herbivore that is currently being managed as a game species. We summarize the possible impacts of sika deer including the displacement of native white-tailed deer. The management of this species needs to be carefully observed as they continue to spread throughout the critical saltmarsh of the Delmarva Peninsula.

Two new pinicolous Arthonia (Arthoniaceae; Arthoniomycetes) from the Delmarva Peninsula of the Atlantic Coastal Plain in eastern North America

Abstract Two new non-lichenized Arthonia are described from the branches and wood of pine trees (Pinus spp.) in the Coastal Plain of southeastern North America. Arthonia samdykeana is a characterized by its lack of photobiont, large irregularly shaped ascomata, and 6–9(–10–12)-celled ascospores that are macrocephallic. Arthonia gutberletiana is characterized by its lack of photobiont, black circular apothecia with persistent margins, hyaline 2-celled ascospores and occurrence on pine wood.

Integrating Radarsat-2, Lidar, and Worldview-3 Imagery to Maximize Detection of Forested Inundation Extent in the Delmarva Peninsula, USA

Natural variability in surface-water extent and associated characteristics presents a challenge to gathering timely, accurate information, particularly in environments that are dominated by small and/or forested wetlands. This study mapped inundation extent across the Upper Choptank River Watershed on the Delmarva Peninsula, occurring within both Maryland and Delaware. We integrated six quad-polarized Radarsat-2 images, Worldview-3 imagery, and an enhanced topographic wetness index in a random forest model. Output maps were filtered using light detection and ranging (lidar)-derived depressions to maximize the accuracy of forested inundation extent. Overall accuracy within the integrated and filtered model was 94.3%, with 5.5% and 6.0% errors of omission and commission for inundation, respectively. Accuracy of inundation maps obtained using Radarsat-2 alone were likely detrimentally affected by less than ideal angles of incidence and recent precipitation, but were likely improved by targeting the period between snowmelt and leaf-out for imagery collection. Across the six Radarsat-2 dates, filtering inundation outputs by lidar-derived depressions slightly elevated errors of omission for water (+1.0%), but decreased errors of commission (−7.8%), resulting in an average increase of 5.4% in overall accuracy. Depressions were derived from lidar datasets collected under both dry and average wetness conditions. Although antecedent wetness conditions influenced the abundance and total area mapped as depression, the two versions of the depression datasets showed a similar ability to reduce error in the inundation maps. Accurate mapping of surface water is critical to predicting and monitoring the effect of human-induced change and interannual variability on water quantity and quality.

Molecular Detection of Avian Influenza Virus from Sediment Samples in Waterfowl Habitats on the Delmarva Peninsula, United States.

Avian influenza viruses (AIV) affect many species of birds including waterfowl and may persist in sediment in aquatic habitats. Sediment samples were collected from two areas representative of prime migration and overwintering waterfowl habitat in Dorchester County, Maryland in the fall and winter of 2013-2014. Samples were screened for the presence of AIV via reverse transcriptase-quantitative PCR targeting the matrix gene. Although 13.6% of sediment samples were positive for the AIV matrix gene across all collection dates and locations, differences in detection were noted with location and collection season. Percentage of AIV-positive sediment samples recovered corresponded to trends in waterfowl abundance at collection sites both temporally and spatially. These findings provide further support for the assertion that the presence of AIV in the aquatic environment is likely affected by the total number, site-specific density, and array of waterfowl species.

Nutrient biofilters in the Virginia Coastal Plain: Nitrogen removal, cost, and potential adoption pathways

Excess nonpoint source nutrient loss presents one of the most vexing water management challenges for water quality managers. Agriculture is the single largest contributor of nutrients to the Chesapeake Bay, and achieving nutrient reduction targets for agriculture will be costly. Biofilters offer new opportunities to reduce nutrient loads from artificially drained agricultural land. Nutrient biofilters consist of organic carbon (C) medium, typically woodchips, that when saturated with nitrogen (N)-enriched waters supports the activity of naturally occurring soil microorganisms that convert bioavailable N into N gases via denitrification. This study estimates the cost and N removal effectiveness for a biochar-amended woodchip biofilter draining a 10 ha (25 ac) field planted in a corn (<i>Zea mays</i> L.)–soy (<i>Glycine max</i> [L.] Merr.) rotation in eastern Virginia as well as for alternative design scenarios for biofilters ranging 25 to 150 m³ (883 to 5,297 ft³) with either woodchips alone or biochar-amended woodchip C substrates. Nitrogen removal effectiveness is estimated using modeled site-specific influent loads and N removal effectiveness estimates derived from experimental trials in a pilot scale system on the Delmarva Peninsula. This analysis estimates N removal costs as a function of biofilter size, which directly relates to residence time, per unit of N removed. Modeled N removal estimates over a five-year period (2009 to 2013) for five bed volumes range from 88 to 391 kg (194 to 862 lb) for the woodchip biofilters (21% to 95% removal) and 132 to 412 kg (291 to 908 lb) for the biochar-amended woodchip biofilters (32% to 100% removal) of the 412 kg total N load exported to the biofilters during the five-year period. The N removal costs range from US$15 to US$48 kg⁻¹ y⁻¹ (US$6.82 to US$21.82 lb⁻¹ yr⁻¹) for the woodchip biofilter and US$15 to US$33 kg⁻¹ y⁻¹ (US$6.82 to US$15 lb⁻¹ yr⁻¹) for biochar-amended woodchip filters. While biofilters are determined to be cost-effective for N removal compared to conventional agricultural best management practices, agricultural producers may be reluctant to voluntarily adopt biofilters because of the relatively high initial installation costs and the lack of direct incentive payments for pollutant removal effectiveness. Nutrient trading programs offer some potential to enhance adoption, but not in the immediate future.

Monitoring of wetland inundation dynamics in the Delmarva Peninsula using Landsat time-series imagery from 1985 to 2011

Wetlands provide important ecosystem services, the provision of which is largely controlled by fluctuations in inundation and soil saturation. Inundation is highly dynamic and can vary substantially through time in response to multiple drivers, including precipitation and evapotranspiration. This research focused on developing a practical and effective framework for regional, long-term monitoring of wetland inundation dynamics using airborne LiDAR intensity data (Lang et al., 2013) and Landsat time-series imagery. Subpixel water fraction (SWF) maps indicating the percent of surface water within each 30-m pixel were generated on an annual basis over the entire Delmarva Peninsula on the East Coast of the United States from 1985 to 2011. Comprehensive accuracy assessments of the SWF maps were conducted using historical high-resolution aerial photography to determine the reference condition. The assessment resulted in an estimated root mean square error (RMSE) of 7.78% for the sample of open water areas (mean SWF was ~40% for this region of the map). Moreover, a separate accuracy assessment targeting inundation in wetlands (i.e. presence or absence of water) yielded an overall accuracy of 93%. Accuracies derived indicated that Landsat data can be calibrated to accurately extract long-term water information at the regional scale. Characteristics of inundation were examined with respect to different wetland types defined by water regime and dominant vegetation types, as well as different physical drivers. Results showed that tidal wetlands typically exhibited more intensive inundation than nontidal wetlands, and a higher degree of inundation was associated with emergent wetlands compared to wetland areas dominated by woody vegetation. Analysis of change drivers revealed that tide exerted a statistically significant influence on coastal inundation with r2 values of 32–36% and p<0.01, whereas inundation changes in inland wetland areas were in part driven by precipitation with r2 values of 25–34% and p<0.08. Because an up-to-date archive of Landsat imagery is globally available and LiDAR data are becoming increasingly more affordable, the developed framework can be easily implemented to generate a continuous inundation record in many regions of the globe to assist in ongoing and future studies focused on wetland hydrology and wetland management.

Annulus Formation and Growth of Atlantic Surfclam (Spisula solidissima) Along a Latitudinal Gradient in the Western North Atlantic Ocean

ABSTRACT Age data play an important role in the Atlantic surfclam [Spisula solidissima (Dillwyn, 1817)] stock assessment and their accuracy depends on understanding the periodicity and timing of annulus formation. In the United States, the surfclam stock area spans approximately 5° latitude in the northwest Atlantic. In recent years, surfclams at the southern end of this area have undergone changes in abundance, distribution, and growth, all likely due to increasing ocean temperature. To determine whether the periodicity or timing of annulus formation has also changed, shells from live surfclams were collected during every month of the year from three regions spanning 4° latitude: southern New England (northernmost), New Jersey (middle), and the Delmarva Peninsula (southernmost). Edge analysis and marginal increment analysis indicated a single annulus was formed each year in each region and by all age groups, verifying surfclams can still be aged reliably throughout the managed area. Some regional or ages...

Low Pathogenic Avian Influenza Viruses in Wild Migratory Waterfowl in a Region of High Poultry Production, Delmarva, Maryland.

Migratory waterfowl are natural reservoirs for low pathogenic avian influenza viruses (AIVs) and may contribute to the long-distance dispersal of these pathogens as well as spillover into domestic bird populations. Surveillance for AIVs is critical to assessing risks for potential spread of these viruses among wild and domestic bird populations. The Delmarva Peninsula on the east coast of the United States is both a key convergence point for migratory Atlantic waterfowl populations and a region with high poultry production (>4,700 poultry meat facilities). Sampling of key migratory waterfowl species occurred at 20 locations throughout the Delmarva Peninsula in fall and winter of 2013-14. Samples were collected from 400 hunter-harvested or live-caught birds via cloacal and oropharyngeal swabs. Fourteen of the 400 (3.5%) birds sampled tested positive for the AIV matrix gene using real-time reverse transcriptase PCR, all from five dabbling duck species. Further characterization of the 14 viral isolates identified two hemagglutinin (H3 and H4) and four neuraminidase (N2, N6, N8, and N9) subtypes, which were consistent with isolates reported in the Influenza Research Database for this region. Three of 14 isolates contained multiple HA or NA subtypes. This study adds to the limited baseline information available for AIVs in migratory waterfowl populations on the Delmarva Peninsula, particularly prior to the highly pathogenic AIV A(H5N8) and A(H5N2) introductions to the United States in late 2014.