Coastal Plain Ecoregion Research Articles

Spatiotemporal patterns of forest pollinator diversity across the southeastern United States

AbstractAimEfforts to understand how pollinating insect diversity is distributed across large geographic areas are rare despite the importance of such work for conserving regional diversity. We sought to relate the diversity of bees (Hymenoptera: Apoidea), hover flies (Diptera: Syrphidae), and butterflies (Lepidoptera) to ecoregion, landscape context, canopy openness, and forest composition across southeastern U.S. forests.LocationNineteen experimental forests across nine states in the southeastern U.S.MethodsWe established 5–7 plots on each experimental forest. In each, we sampled pollinators monthly (March–September) using coloured pan traps, and collected data on local forest characteristics. We used the National Land Cover Database (NLCD) to quantify surrounding landcover at different spatial scales.ResultsBee richness was negatively correlated with both the amount of conifer (pine) forest and the extent of wetlands in the surrounding landscape but was positively correlated with canopy openness. Hover flies and butterflies were less sensitive to landscape context and stand conditions. Pollinator communities differed considerably among ecoregions, with those of the Central Appalachian and Coastal Plain ecoregions being particularly distinct. Bee richness and abundance peaked 2 months earlier in Central Appalachia than in the Coastal Plain and Southeastern Mixed Forest ecoregions.Main ConclusionsOur findings reveal ecoregional differences in pollinator communities across the southeastern U.S. and highlight the importance of landscape context and local forest conditions to this diverse fauna. The closed broadleaf forests of Appalachia and the open conifer‐dominated forests of the Coastal Plain support particularly distinct pollinator communities with contrasting seasonality. Our results suggest pine forests may reduce pollinator diversity in regions historically dominated by broadleaf forests. However, efforts to create more open canopies can help improve conditions for pollinators in planted pine forests. Research exploring associations between forest pollinators and different broadleaf tree taxa is needed to better anticipate the impacts of various management activities.

Ecogeographic Variation in Physical Traits of White-Tailed Deer

A growing body of work has revealed that differences in body size of ungulates follow ecoregion and soil boundaries and that these size differences are nutritionally influenced. Currently, it is unclear if these patterns of body size result from differences in quantity or quality of forage produced. We quantified differences in white-tailed deer (Odocoileus virginianus Zimm.) body mass and antler size captured at four sites in South Texas, United States. We sampled available forage to determine if long-term differences in average body and antler size could be explained by forage quantity or quality, or some combination of the two. Data collected from 2011 to 2019 indicated female body mass was > 3 kg smaller on the eastern edge of the Coastal Sand Plain ecoregion as compared with those from the western transition zone of the Coastal Sand Plain and Tamaulipan Thornscrub ecoregions. Similarly, male body mass and antler size were > 6 kg and > 20 cm smaller, respectively, in coastal habitats compared with more interior sites. We found that forb biomass, browse and forb diversity, and the nutritional landscape, quantified using digestible energy, crude protein, phosphorus, and neutral detergent fiber, differed between sites. However, differences between sites were inconsistent with predictions that would have supported our hypothesis. Overall, we found no support for the hypothesis that forage quantity drives ecogeographic variation in physical traits of white-tailed deer but were unable to fully refute or support the hypothesis that forage quality, specifically plant diversity, drives ecogeographic variation in physical traits of ungulates.

Implications of Declining Ground Water and Water Quality in the Greater Okefenokee Swamp Basin for Survival and Recovery of Federally Endangered and Threatened Marine and Aquatic Species and Critical Habitat in the US Southeastern Coastal Plain Ecoregion—Part 2

Implications of Declining Ground Water and Water Quality in the Greater Okefenokee Swamp Basin for Survival and Recovery of Federally Endangered and Threatened Marine and Aquatic Species and Critical Habitat in the US Southeastern Coastal Plain Ecoregion—Part 2

Implications of Declining Ground Water and Water Quality in the US Southeastern Coastal Plain Ecoregion and Areawide Environmental Impact Statement Required for Mining in the Greater Okefenokee Swamp Basin—Part 1

Karst aquifers occur worldwide and exhibit groundwater flow responses that differ considerably from aquifers lacking fractures, bedding planes, and other karst conduits where significant and rapid groundwater flow can occur. The regional, karst Floridan aquifer system underlies the United States (US) Southeastern Coastal Plain Physiographic Region and exhibits hydrologic interconnections with overlying surficial aquifers and throughout other zones of the aquifer system, as is characteristic of other karst aquifer systems. Anthropogenic groundwater declines in this regional karst aquifer system have been documented in published literature for decades, but the impacts of those declines in this coastal plain region and the embedded ecosystems that provide essential and critical habitat for native, endemic, and federally endangered and threatened species have not been considered previously. Those anthropogenic groundwater declines reduce surfacewater levels and flows due to the capture of both groundwater and overland flow of surfacewater, resulting in induced recharge through semi-confining zones and interbasin flow through fractures and other karst conduits. This case study identifies examples from the Greater Okefenokee Swamp Basin study area and comparison areas of how those declines result in loss of historic base flow to surface waters and other capture of surface waters, ultimately increasing saltwater intrusion. Those results alter and degrade the physical, chemical, and biological integrity of the nation’s waters, in violation of the US Clean Water Act (CWA) of 1972. Historic groundwater declines from mining and other anthropogenic groundwater withdrawals from this regional karst aquifer system already threaten the survival and recovery of federally endangered and threatened species, as well as existing and proposed critical habitat for those species within this regional extent, in violation of the Endangered Species Act (ESA) of 1973. This case study and its companion publication (Part 2) appear to be the first to provide scientific support for this regional karst aquifer system as the unifying factor in habitat responses to irreversible groundwater impacts on aquatic and marine ecosystems. These adverse impacts strongly suggest that the extent of the regional Floridan aquifer system should be designated as the Southeastern Coastal Plain Ecoregion for the purpose of managing natural resources. Mining activities continue to expand in our study area, which is the Greater Okefenokee Swamp Basin. Despite that fact, no comprehensive Areawide Environmental Impact Statement (AEIS), similar to the AEIS required for phosphate mining within the Central Florida Phosphate District (CFPD) approximately a decade ago has been conducted for any of the numerous mining projects that are occurring and are proposed within the Greater Okefenokee Swamp Basin. This case study also provides examples of why a comprehensive AEIS is essential to consider all of the adverse direct, indirect, and cumulative impacts of those mining activities to the CWA, the ESA, and the irreversible losses to local economies, because federal agencies responsible for considering those adverse impacts rely on public comments to identify those adverse impacts. The mining activities authorized throughout the regional Floridan aquifer system under Category 44 Nationwide Permits (NWP) result in the same type of adverse impacts as the mining activities evaluated under Individual Permits in that region. Therefore, those Category 44 NWP mining activities also should be required to obtain Individual Permits and be evaluated under an AEIS in the Greater Okefenokee Swamp Basin. This case study also describes how Florida’s assumption of the CWA Section 404 regulatory authority in 2020 severs four sub-basins within the Greater Okefenokee Swamp Basin study area at the state line between Florida and Georgia.

First documentation of Dichanthelium caerulescens (Poaceae) for the vascular flora of Louisiana, U.S.A.

Dichanthelium caerulescens is documented for the first time in Louisiana, as the result of floristic fieldwork performed in 2019 through 2021. Louisiana records extend the range of D. caerulescens westward by approximately 265 mi (426.5 km) into the Western Gulf Coastal Plain ecoregion. These findings also identify a new habitat, coastal prairie, utilized by D. caerulescens.

Gopher tortoise (Gopherus polyphemus) resource selection within a private working pine (Pinus spp.) forest landscape

Private working forest landscapes provide wildlife habitat and understanding how species interact with these landscapes is critical to identifying conservation opportunities. The gopher tortoise (Gopherus polyphemus; hereafter, tortoise) is a species endemic to the Coastal Plain ecoregion of the southeastern United States, with private working pine (Pinus spp.) forests encompassing a substantive portion of area within the species’ range. Although private working pine forests contain tortoises, uncertainty exists about how tortoises use these landscapes. Specifically, there is limited information regarding tortoise habitat associations within these landscapes relative to current forest management practices. Therefore, we used radio telemetry data from 55 adult tortoises collected over 3 years to estimate resource selection within a private working forest landscape dominated by planted loblolly pine (Pinus taeda) stands in the Upper Coastal Plain ecoregion of Georgia, USA. The strongest predictor of resource selection by tortoises was proximity to permanently open areas, specifically a utility right-of-way and areas adjacent to unpaved forest roads and, to a lesser extent, areas of higher elevation containing soils suitable for tortoises. On our study area, we identified permanently open areas as an important landscape component to adult tortoises. Although adult tortoises persist within these landscapes, more work is needed to understand tortoise recruitment in private working pine forest landscapes.

Prioritization of Vulnerable Species Under Scenarios of Anthropogenic-Driven Change in Georgia's Coastal Plain

Abstract Effective management of wildlife populations benefits from an understanding of the long-term vulnerability of species to anthropogenic stressors. Exposure to potential habitat change is one measure of vulnerability that wildlife managers often use to assess and prioritize individual species or groups of species for resource allocation or direct management actions. We used species distribution models for 15 species occurring in the coastal plain ecoregion of Georgia to estimate the current amount and distribution of potential habitat and then predict exposure to changes in habitat due to inundation from sea level rise (using the Sea Level Affecting Marshes model) and urban growth (using the Slope Land-use Excluded Urban Topology Hillshade Growth model) for four future time points. Our results predict that all focal species were likely to experience some exposure to habitat change from either sea level rise or urbanization, but few species will experience high exposure to change from both stressors. Species that use salt marsh or beach habitats had the highest predicted exposure from sea level rise (25–69%), while species that use more inland habitats had the highest predicted exposure to urban growth (10–20%). Our models are a resource for managers considering tradeoffs between prioritization schemes under two future stressors. Results suggest that managers may need to prioritize species (or their habitats) based on the predicted magnitude of habitat loss, while also contextualizing prioritization with respect to the current amount of available protected habitat and species global vulnerability.

Differences in distribution and community structure of plant-parasitic nematodes in pecan orchards between two ecoregions of Georgia.

In Georgia, pecans are commercially grown in the Piedmont and Coastal Plain ecoregions which are characterized by sandy-loam, sandy, and/or clay soils. If well-drained, these soils are suitable for pecan production, but the soil characteristics differ enough between ecoregions in which the plant-parasitic nematode (PPN) communities could differ substantially. We studied PPN communities in pecan orchards to evaluate the potential for ecoregion differences. In total, 11 genera (Helicotylenchus, Hemicycliophora, Heterodera, Hoplolaimus, Meloidogyne, Mesocriconema, Pratylenchus, Paratylenchus, Paratrichodorus, Tylenchorhynchs, Xiphenema) were recovered from pecan orchards in the Piedmont and Coastal Plain ecoregions. However, Non-Metric Multi-Dimensional Scaling ordination, Multi-Rank Permutation Procedure, and Indicator Species Analyses indicated that the pecan PPN communities strongly differed between ecoregions and that different genera were strongly associated with different ecoregions. For 9 of the 11 PPN genera, the maximum counts occurred in Coastal Plain locations, suggesting that the well-drained sandy soils of the Coastal Plain and comparatively ill-drained red clay soils of the Piedmont may be conducive and unfavorable for movement/reproduction of PPNs, respectively.

Status of an Anomalous Population of Northern Long-Eared Bats in Coastal North Carolina

AbstractThe northern long-eared bat Myotis septentrionalis was discovered in coastal North Carolina in 2007. Work began in 2015 to document the species' distribution and behavior in eastern North Carolina, and the known range of the species has expanded from 4 coastal counties to 19. Captures occurred in all months of the year and mostly occurred in or adjacent to wetland forest. Captures occurred exclusively in the Middle Atlantic Coastal Plain ecoregion of the state, and the species has not been documented in the Southeastern Plains or Piedmont ecoregions. The lack of captures in the middle of the state suggests spatially disjunct populations in North Carolina. The bats were observed to be active throughout most of the winter and roosted in trees. During late fall–winter 2015–2018, 43 bats were tracked to 165 winter roost trees located mostly in wetland forest. The species' winter activity in coastal North Carolina represents a novel survival strategy as opposed to the hibernation behavior it is assumed to use in the rest of its range. This portion of the state is nearly devoid of caves or mines suitable for hibernacula, but has milder winters with insect activity. During spring 2019, 21 reproductive females were captured in the northern coastal plain and tracked to 64 maternity roost trees located mostly in wetland forest. Pregnant females began to be captured on April 25 and juveniles on June 16, indicating that pups are likely born in late May. Swab samples collected during late fall–winter from species susceptible to white-nose syndrome provided no evidence of Pseudogymnoascus destructans. Since northern long-eared bats in coastal North Carolina are active most of the winter and not dependent upon caves or mines for hibernation, they are likely not susceptible to white-nose syndrome. With the species in sharp decline elsewhere due to white-nose syndrome, this coastal population may serve as a refugium.

Quantifying the Impacts of Land-Use and Climate on Carbon Fluxes Using Satellite Data across Texas, U.S.

Climate change and variability, soil types and soil characteristics, animal and microbial communities, and photosynthetic plants are the major components of the ecosystem that affect carbon sequestration potential of any location. This study used NASA’s Soil Moisture Active Passive (SMAP) Level 4 carbon products, gross primary productivity (GPP), and net ecosystem exchange (NEE) to quantify their spatial and temporal variabilities for selected terrestrial ecosystems across Texas during the 2015–2018 study period. These SMAP carbon products are available at 9 km spatial resolution on a daily basis. The ten selected SMAP grids are located in seven climate zones and dominated by five major land uses (developed, crop, forest, pasture, and shrub). Results showed CO2 emissions and uptake were affected by land-use and climatic conditions across Texas. It was also observed that climatic conditions had more impact on CO2 emissions and uptake than land-use in this state. On average, South Central Plains and East Central Texas Plains ecoregions of East Texas and Western Gulf Coastal Plain ecoregion of Upper Coast climate zones showed higher GPP flux and potential carbon emissions and uptake than other climate zones across the state, whereas shrubland on the Trans Pecos climate zone showed lower GPP flux and carbon emissions/uptake. Comparison of GPP and NEE distribution maps between 2015 and 2018 confirmed substantial changes in carbon emissions and uptake across Texas. These results suggest that SMAP carbon products can be used to study the terrestrial carbon cycle at regional to global scales. Overall, this study helps to understand the impacts of climate, land-use, and ecosystem dynamics on the terrestrial carbon cycle.

Changes in Vegetation Cover of the Arctic National Wildlife Refuge Estimated from MODIS Greenness Trends, 2000–18

Abstract Trends and transitions in the growing-season normalized difference vegetation index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor at 250-m resolution were analyzed for the period from 2000 to 2018 to understand recent patterns of vegetation change in ecosystems of the Arctic National Wildlife Refuge (ANWR) in Alaska. Statistical analysis of changes in the NDVI time series was conducted using the breaks for additive seasonal and trend method (BFAST). This structural change analysis indicated that NDVI breakpoints and negative 18-yr trends in vegetation greenness over the years since 2000 could be explained in large part by the impacts of severe wildfires. At least one NDVI breakpoint was detected in around 20% of the MODIS pixels within both the Porcupine River and Coleen River basins of the study area. The vast majority of vegetation cover in the ANWR Brooks Range and coastal plain ecoregions was detected with no (positive or negative) growing-season NDVI trends since the year 2000. Results suggested that most negative NDVI anomalies in the 18-yr MODIS record have been associated with early spring thawing and elevated levels of surface moisture in low-elevation drainages of the northern ANWR ecoregions.

Assessment of northern bobwhite survival and fitness in the West Gulf Coastal Plain ecoregion.

In the West Gulf Coastal Plains (WGCP) northern bobwhite (Colinus virginianus) are declining faster than range-wide averages and such declines have been linked to the consequences of land management. Management for the endangered red-cockaded woodpecker (Picoides borealis) has benefitted northern bobwhite by restoring mature pine-grassland ecosystems in some areas of the region. However, at Felsenthal National Wildlife Refuge, Crossett, Arkansas, USA, the bobwhite population was not increasing despite the availability of seemingly suitable habitat from management for the endangered species. To understand factors that may be affecting bobwhite survival on Felsenthal National Wildlife Refuge we conducted a telemetry study and assessed summer survival, brood survival, and nest success from 1 April– 11 August in 2013 and 1 April– 15 August in 2014. We also calculated home-range sizes and measured microhabitat characteristics around nests. Summer survival rates were 71% (SE = 0.17) and 47% (SE = 0.14); while nest success was 47% (SE = 0.02) and 100% for 2013 and 2014, respectively. Between years, both 95% and 50% kernel home-ranges were not different (pooled, 63.92±6.07 ha and 14.94±1.75 ha); however minimum convex polygon home-range sizes were (113.8 ± 20.1 ha in 2013; and 393.1 ± 49.0 ha in 2014, P < 0.001). Only numerical differences in microhabitat vegetation characteristics of nest sites and non- nest sites were observed. We suggest management for red-cockaded woodpeckers supports bobwhite populations but only as a buffer against more severe declines. Since bobwhites are declining range-wide, we believe areas federally managed for red-cockaded woodpeckers will become increasingly more important for sustaining regional bobwhite population levels.

Tanglehead in Southern Texas: A Native Grass with an Invasive Behavior

On the Ground • Tanglehead is a native bunchgrass with a pan-tropical distribution. Historically, tanglehead was common but not abundant in southern Texas and was considered a decreaser whose presence indicated good range condition. • Beginning in the late 1990s, the Texas Coastal Sand Plain ecoregion witnessed dramatic increases in the abundance and distribution of tanglehead: thousands of acres of former grasslands were replaced by dense monotypic stands of tanglehead, reducing habitat quality for livestock and wildlife. • Our research has focused on understanding factors related to tanglehead's expansion, its effects on habitat quality, and management practices that can improve range condition and habitat quality.

Growth responses of narrow or broad site adapted tree species to a range of resource availability treatments after a full harvest rotation

Understanding the processes driving forest productivity is a critical element in our efforts to maximize production of biomass and wood products and more efficiently utilize resources required for plant growth. We examined above and belowground growth and productivity of four tree species – eastern cottonwood (Populus deltoides), American sycamore (Platanus occidentalis), sweetgum (Liquidambar styraciflua), and loblolly pine (Pinus taeda) – receiving irrigation and fertilization in the Upper Coastal Plain ecoregion of South Carolina, USA. Trees received treatments throughout an entire intensively-managed harvest rotation, which was nine years for cottonwood and sycamore, and 11years for sweetgum and loblolly pine. Fertilization and irrigation positively affected growth and productivity of all tree species. Fertilization alone led to increases in stem volume index of up to 329% for cottonwood, 376% for sycamore, 261% for sweetgum, and 49% for loblolly pine. Loblolly pine grew the largest of all species tested, and sweetgum was the largest hardwood. Net primary productivity was driven by leaf and fine root tissue production. When accounting for the effect of tree size, belowground biomass decreased with increasing resource availability in sweetgum and loblolly pine, but not cottonwood or sycamore. These results help explain complex relationships between above and belowground tissues in woody species, and indicate that both ontogeny and resource availability can mediate allocation to belowground tissues.

Prioritizing watersheds for conservation actions in the southeastern coastal plain ecoregion.

The aim of this study was to apply and evaluate a recently developed prioritization model which uses the synoptic approach to geographically prioritize watersheds in which Best Management Practices (BMPs) can be implemented to reduce water quality problems resulting from erosion and sedimentation. The model uses a benefit-cost framework to rank candidate watersheds within an ecoregion or river basin so that BMP implementation within the highest ranked watersheds will result in the most water quality improvement per conservation dollar invested. The model was developed to prioritize BMP implementation efforts in ecoregions containing watersheds associated with the USDA-NRCS Conservation Effects Assessment Project (CEAP). We applied the model to HUC-8 watersheds within the southeastern Coastal Plain ecoregion (USA) because not only is it an important agricultural area but also because it contains a well-studied medium-sized CEAP watershed which is thought to be representative of the ecoregion. The results showed that the three HUC-8 watersheds with the highest rankings (most water quality improvement expected per conservation dollar invested) were located in the southern Alabama, northern Florida, and eastern Virginia. Within these watersheds, measures of community attitudes toward conservation practices were highly ranked, and these indicators seemed to push the watersheds to the top of the rankings above other similar watersheds. The results, visualized as maps, can be used to screen and reduce the number of watersheds that need further assessment by managers and decision-makers within the study area. We anticipate that this model will allow agencies like USDA-NRCS to geographically prioritize BMP implementation efforts.

Remote detection of small wetlands in the Atlantic coastal plain of North America: Local relief models, ground validation, and high-throughput computing

Isolated wetlands are ecologically important freshwater ecosystems that occur frequently throughout the Atlantic coastal plain ecoregions of North America. Known to support 86 species recognized by the US Fish and Wildlife Service as threatened or endangered, isolated wetlands are a conservation priority in the United States and elsewhere. They are often obscure and methods to detect them at the spatial scales necessary for systematic conservation planning and forest management have been time consuming, cost ineffective, or too coarse-filter. To fill existing information gaps and develop a repeatable, high-resolution methodology, we subjected LiDAR elevation data to custom relief models designed to elucidate fine-scale geomorphology, specifically small, localized changes in concavity, as a location predictor. Because fine grain size and large spatial extent can impose processing limits in landscape-level analysis, we executed our workflow in a high-throughput computing (HTC) environment, which achieved a 91× time-savings over our 55,000ha study area. We conducted field validation at 114 randomly selected sites to measure model commission (14.9%), approximate omission (5.3%) error rates and estimate wetland boundaries. Depressional wetlands predicted in this study (n=4610) were mostly small (x¯=0.37±0.69ha) and previously unmapped sites. The mapping accuracy of this effort (85.1%) suggests that local relief models captured slight geomorphologic changes that successfully predict wetland boundaries in low-relief ecosystems. Many small wetlands are centers of biodiversity in forested landscapes and such analyses will provide information and improved methods for landscape-scale management and conservation.

Estimating reference nutrient criteria for Maryland ecoregions

Management of stream nutrients is becoming increasingly important in order to protect both water quality and aquatic resources throughout the USA. Using an extensive water quality database from the long-term Maryland Biological Stream Survey (MBSS), we describe nutrient relationships to landscape characteristics as total nitrogen (TN) and total phosphorus (TP) of small-order, non-tidal streams in USEPA L2 and L3 ecoregions in Maryland and by MBSS stream order at the L2 and L3 ecoregion levels. To protect stream ecosystem integrity, preliminary reference nutrient estimates (TN and TP) as percentiles (25th of all stream reaches and 75th of stream reference reaches) for the six Maryland L3 ecoregions are: Blue Ridge TN 0.29 and 0.64mg/L, TP 0.0065 and 0.0090mg/L; Central Appalachians TN 0.40 and 1.0mg/L, TP 0.0060 and 0.015mg/L; Middle Atlantic Coastal Plains TN 0.93 and 2.5mg/L, TP 0.094 and 0.065mg/L; Northern Piedmont TN 1.6 and 1.8mg/L, TP 0.010 and 0.015mg/L; Ridge and Valley TN 0.40 and 0.98mg/L, TP 0.0063 and 0.012mg/L; and Southeastern Plains TN 0.33 and 0.82mg/L, TP 0.016 and 0.042mg/L. High levels of both TN and TP are present in many streams found in non-tidal watersheds associated with all Maryland ecoregions, but are especially elevated in the Northern Piedmont and Middle Atlantic Coastal Plain ecoregions, with the latter second-order streams (average TN > 2.9mg/L) significantly higher than all other ecoregion-order combinations. Across all six ecoregions, mean nutrient loading for both TN and TP was generally equivalent in first-order streams to nutrient concentrations seen in both second- and third-order streams, indicating a definite need to increase efforts in preventing nutrients from entering first-order streams. Small-order stream nutrient levels are the drivers for subsequent TN and TP inputs into the upper freshwater tidal reaches of the Chesapeake Bay, resulting in a potential risk for altered estuarine ecosystems.

Interregional variation in urbanization-induced geomorphic change and macroinvertebrate habitat colonization in headwater streams

Urban land use alters channel morphometry, particle size structure, and sediment-transport dynamics in stream ecosystems, thereby degrading the habitat of aquatic organisms. However, stream form varies substantially among geoclimatic settings, and, thus, the degree of negative effects induced by urbanization may be region-specific. Biota in streams of the Coastal Plain ecoregion of the eastern US consistently show greater tolerance to urban land use than do biota of the adjacent Piedmont, potentially because of a disparity in geomorphic degradation between ecoregions. We quantified channel morphometry, particle mobility, sediment deposition, and floodwater chemistry in similarly sized rural and urban streams of both ecoregions to detect differences in urbanization-induced geomorphic change. Macroinvertebrate rates of recolonization in patches of disturbed benthic habitat also were monitored. No differences in channel morphometry were observed among treatment groups. Riffle particle sizes were significantly larger in urban than in rural Piedmont streams, but a corresponding disparity was absent in Coastal Plain streams. Particle mobility increased in urban settings uniformly between ecoregions. However, transported particles were substantially larger in Piedmont streams. Sediment deposition was higher overall in Coastal Plain streams but more affected by urbanization in Piedmont streams. Macroinvertebrate density in the disturbed habitat rose faster over time in Coastal Plain than in Piedmont streams. Results suggest that geomorphic degradation is greater in Piedmont streams and that organisms may be adapted to benthic instability in Coastal Plain streams. In addition, our findings demonstrate that ecosystem-scale responses of streams to urbanization may vary inherently among geoclimatic settings.

Mercury in South Carolina Fishes, USA

The South Carolina Department of Health and Environmental Control has collected, processed, and analyzed fish tissue total mercury (Hg) since 1976. For this study, skin-on-filet data from 1993 to 2007 were examined to determine biotic, spatial and temporal trends in tissue Hg levels for SC fishes. Because of the relatively high number of tissue Hg values below the analytical detection limits interval censored regression and censored least absolute deviations were used to construct several models to characterize trends. Large pelagic, piscivorous fish species, such as bowfin (Amia calva Linnaeus 1766), had higher levels of tissue Hg than smaller omnivorous species. Estuarine species had relatively low levels of tissue Hg compared to freshwater species, while two large open ocean species, king mackerel (Scomberomorus cavalla Cuvier 1829) and swordfish (Xiphias gladius Linnaeus 1758), had higher tissue Hg readings. For a given fish species, length was an important predictor of tissue Hg with larger individuals having higher levels than smaller individuals. The USEPA Level III ecoregion and water body type from where the fishes were collected were important in predicting the levels of tissue Hg. The Middle Atlantic Coastal Plain ecoregion had fishes with the highest levels of tissue Hg, while the Piedmont and Southern Coastal Plain ecoregions had the lowest. For a given ecoregion, large reservoirs and regulated rivers had fish with lower levels of tissue Hg than unregulated rivers. For reservoirs, the size of the impoundment was a significant predictor of tissue mercury with small reservoirs having higher levels of tissue mercury than large reservoirs. Landuse and water chemistry accounted for differences seen in fish of various ecoregions and waterbody types. Sampling locations associated with a high percentage of wetland area had fish with high levels of tissue Hg. Correlation analysis showed a strong positive relationship between tissue Hg levels and water column iron, total organic carbon, ammonia, and total kjedahl nitrogen, and a negative relationship with alkalinity, dissolved oxygen and pH. Results from principle component analysis revealed patterns between waterbody type and water chemistry variables that suggests hydrologic modification can have profound effects on the levels of fish tissue Hg in riverine systems. From 1993 to 2007, fish tissue Hg levels have trended lower. A spike in tissue Hg levels was observed in 2003-2005. The drying and rewetting of the landscape after the 2002 drought is hypothesized to have caused an increase in the methylation efficiencies of the system.

Distribution of Breeding Shorebirds on the Arctic Coastal Plain of Alaska

Available information on the distribution of breeding shorebirds across the Arctic Coastal Plain of Alaska is dated, fragmented, and limited in scope. Herein, we describe the distribution of 19 shorebird species from data gathered at 407 study plots between 1998 and 2004. This information was collected using a single-visit rapid area search technique during territory establishment and early incubation periods, a time when social displays and vocalizations make the birds highly detectable. We describe the presence or absence of each species, as well as overall numbers of species, providing a regional perspective on shorebird distribution. We compare and contrast our shorebird distribution maps to those of prior studies and describe prominent patterns of shorebird distribution. Our examination of how shorebird distribution and numbers of species varied both latitudinally and longitudinally across the Arctic Coastal Plain of Alaska indicated that most shorebird species occur more frequently in the Beaufort Coastal Plain ecoregion (i.e., closer to the coast) than in the Brooks Foothills ecoregion (i.e., farther inland). Furthermore, the occurrence of several species indicated substantial longitudinal directionality. Species richness at surveyed sites was highest in the western portion of the Beaufort Coastal Plain ecoregion. The broad-scale distribution information we present here is valuable for evaluating potential effects of human development and climate change on Arctic-breeding shorebird populations.