East Coast Sites Research Articles

Isolation, small population size, and management influence inbreeding and reduced genetic variation in K’gari dingoes

Small island populations are vulnerable to genetic decline via demographic and environmental stochasticity. In the absence of immigration, founder effects, inbreeding and genetic drift are likely to contribute to local extinction risk. Management actions may also have a greater impact on small, closed populations. The demographic and social characteristics of a species can, however, delay the impact of threats. K’gari, a ~ 1 660 km2 island off the Australian east coast and UNESCO World Heritage Site (Fraser Island 1842–2023), supports an isolated population of approximately 70–200 dingoes that represent an ideal opportunity to explore the small island paradigm. To examine temporal and spatial patterns of genetic diversity in this population we analysed single nucleotide polymorphism (SNP) genotype data (72 454 SNPS) for 112 K’gari dingoes collected over a 25-year period (1996 to 2020). Genetic diversity was lower in K’gari dingoes than mainland dingoes at the earliest time point in our study and declined significantly following a management cull in 2001. We did not find any spatial genetic patterns on the island, suggesting high levels of genetic connectivity between socially discrete packs. This connectivity, combined with the social structure and behaviour of dingoes, may act in concert to buffer the population from the impacts of genetic drift in the short term. Nevertheless, a general decline in genetic variation via inbreeding and drift has occurred over the past 20 years which we suggest should be considered in any future management planning for the population. Monitoring patterns of genetic variation, together with a clearer understanding of the social ecology of K’gari dingoes, will aid in the development of measurable genetic targets set over ecologically meaningful timelines, and help ensure continued survival of this culturally important population.

Reference monopile designs for US East Coast sites supporting the IEA 15 MW reference turbine using a novel conceptual design methodology

A novel conceptual design methodology was developed and implemented to design twelve reference monopile foundations, compatible with the IEA 15 MW reference turbine. The designs are position-specific, corresponding to planned, US East Coast, wind energy development areas. The monopiles were designed considering the fatigue limit state (FLS), ultimate limit state (ULS), serviceability limit state (SLS), and natural frequency analysis (NFA), following an intentionally reduced subset of design load cases (DLCs) in IEC 61400-3-1. In 11 of 12 cases, the diameter and wall thicknesses of the monopile foundations were found to be determined by FLS criteria. The exception was one position subjected to a combination of breaking waves and a large significant wave height. For the 11 positions governed entirely by FLS, the maximum ULS utilization ratios varied between 0.63 and 0.81, indicating significant reserve capacity for the ultimate limit state. Fatigue damage during turbine idling was found to be an important contributor to lifetime fatigue damage, despite having a relatively small probability of occurrence. The novel design methodology described herein includes a preliminary FLS assessment step, which was found to be an efficient way to select an initial foundation geometry, while providing a 92% improvement in computational efficiency.

The Arctic and the future Arctic? Soundscapes and marine mammal communities on the east and west sides of Svalbard characterized through acoustic data

The Svalbard Archipelago, Norway, is warming rapidly, resulting in environmental change that is likely already affecting the underwater soundscape, a critical habitat feature for marine mammals. Baseline information about current sound levels is needed to monitor future changes. Fixed-location recorders were used in this study to characterize the soundscape and study the occurrence and phenology of marine mammals at two locations within Svalbard. Kongsfjorden (2017-2018), on the west coast, has already undergone vast environmental change, whereas M2 (2019-2020), on the east coast, remains more Arctic. The results of the study reveal that the soundscapes and species assemblages differed markedly west vs east. In the west, Arctic species were detected from winter to summer and migrant marine mammal species were detected occasionally through the autumn. In the east, Arctic species were detected constantly on an almost year-round basis, and a few migrant species were detected during summer. Vessels were detected more often in the west than in the east, in accordance with AIS traffic data that indicated more boat traffic in Kongsfjorden in the west than in the east of the archipelago. In terms of soundscapes, geophonies (wind, ice) were the main factors determining the sound energy at both locations. Kongsfjorden’s soundscape was characterized by glacier-melt sounds with moderate levels of anthropogenic noise and some biophonies (marine mammals). At M2, sea-ice noises shaped the soundscape, which was otherwise dominated by biophonies from Arctic marine mammals. At the east coast site there was little impact from anthropophonies (vessels). This study provides information on Svalbard’s current underwater soundscape, which is likely to be transformed in the future due to ongoing climate change, with the west coast reflecting future conditions in many Arctic regions if ship-traffic is not regulated.

Modeling the mechanisms of conifer mortality under seawater exposure.

Relative sea level rise (SLR) increasingly impacts coastal ecosystems through the formation of ghost forests. To predict the future of coastal ecosystems under SLR and changing climate, it is important to understand the physiological mechanisms underlying coastal tree mortality and to integrate this knowledge into dynamic vegetation models. We incorporate the physiological effect of salinity and hypoxia in a dynamic vegetation model in the Earth system land model, and used the model to investigate the mechanisms of mortality of conifer forests on the west and east coast sites of USA, where trees experience different form of sea water exposure. Simulations suggest similar physiological mechanisms can result in different mortality patterns. At the east coast site that experienced severe increases in seawater exposure, trees loose photosynthetic capacity and roots rapidly, and both storage carbon and hydraulic conductance decrease significantly within a year. Over time, further consumption of storage carbon that leads to carbon starvation dominates mortality. At the west coast site that gradually exposed to seawater through SLR, hydraulic failure dominates mortality because root loss impacts on conductance are greater than the degree of storage carbon depletion. Measurements and modeling focused on understanding the physiological mechanisms of mortality is critical to reducing predictive uncertainty.

The extreme forest fires in California/Oregon in 2020: Aerosol optical and physical properties and comparisons of aged versus fresh smoke

Wildfire activity in the western United States during August to October 2020 was exceptional in terms of the fire severity and area burned. Extremely dry biomass fuels from near historic multi-year drought conditions were further exacerbated with very hot and dry conditions in 2020. These conditions when coupled with strong offshore flow allowed many ignitions to grow into extremely large and severe wildfires. Long-term monitoring at a few AERONET sites in California showed that the number of days with high Aerosol Optical Depth at 440 nm (AOD440>1) in 2020 was greater than any other year going back to the beginning of the data records in 2002. A wide range of fine mode particle volume median radii were retrieved from AERONET data over the course of these fires suggesting significant variability in combustion conditions and aging processes. Additionally, the fine mode radii in some of these smoke plumes in 2020 were very large especially at high AOD (∼0.22–0.32 μm volume median radius), likely due to both coagulation and condensation occurring during aging at very high particulate concentrations. The largest fine mode particle radii combined with narrow distributions resulted in some very rare AOD spectra showing peak AOD at 500 nm and decreasing to lower AOD at both shorter and longer wavelengths. The most extreme retrieved size distributions and associated measured AOD spectra were principally observed in long-distance transported smoke plumes from these western United States fires at sites in Colorado, Maryland and Virginia, possibly due to further aging during transport. Additionally, strong absorption was sometimes observed at short wavelengths with much lower single scattering albedo at 440 nm compared to 675 nm in some plumes consistent with significant brown carbon (BrC) and/or coated black carbon (BC) absorption in biomass burning particles. This strong spectral absorption signature observed at some California sites and dates remained similarly strong in some smoke plumes observed at some east coast sites in Maryland and Virginia, thereby suggesting that the lifetime of these particular BrC and/or coated BC absorbing species was greater than 5 days.

Northern and southern blacklegged (deer) ticks are genetically distinct with different histories and Lyme spirochete infection rates

Lyme borreliosis (LB) is the archetypal emerging zoonosis and is dependent on transmission by ticks in the genus Ixodes. Understanding the origin, maintenance, and spread of these ticks contributes much to our understanding of the spread of LB and other disease agents borne by these ticks. We collected 1232 Ixodes scapularis ticks from 17 east coast sites ranging from New Hampshire to Florida and used mtDNA, three nuclear genetic loci, and incorporated Bayesian analyses to resolve geographically distinct tick populations and compare their demographic histories. A sparse, stable, and genetically diverse population of ticks in the Southeastern US, that is rarely infected with the agent of LB is genetically distinct from an abundant, expanding, and comparatively uniform population in the Northeast, where epidemic LB now constitutes the most important vector borne disease in the United States. The contrasting geography and demography of tick populations, interpreted in the context of the geological history of the region, suggests that during the last glacial period such ticks occupied distinct refugia, with only the northern-most site of refuge giving rise to those ticks and pathogens now fueling the epidemic.

Changes over time and changes yet to come

Change over time is of primary interest for ecologists and managers. Change can be positive and is often part of nature's flux, but it can also be negative if arising from impacts that push ecosystems beyond net sustainability. Researchers work long and hard to develop methodologies to gain insight into how much change is part of acceptable flux and how much is unacceptable impact; and monitoring change is also essential to identify levels of recovery over time after restorative management interventions and, in many cases, to fully test hypotheses. This issue's interview with Mike Dodkin, retired naturalist ranger and pest species officer, touches on all these themes as he recollects projects over a 40-year period. Mike was there during the period of social change that saw mineral sand mining on Australia's east coast sites destined for dedication as national parks post-mining. His role not only included finding ways to reduce mining impacts and attain recovery, but also involved starting up new restoration projects to overcome damage that occurred many decades previously – all such projects which will take many decades hence to be fully realized. In a similar vein in this issue, Brad Farmilio and colleagues report about changes in plant composition after 10 years of monitoring in grazed native pastures in south-eastern Australia after an incentive scheme to reduce impacts on grassland remnants; Richard van Dongen and colleagues observe changes in native vegetation on Dirk Hartog Island, Western Australia many years after removal of non-native herbivores; and, Andrew Carter and Laura Ruykys document a gradual eradication of introduced predators in a fenced reserve in South Australia The passage of time is also important to fully test new hypotheses. Hannah Franklin and colleagues in New Zealand tested the capacity of a range of native riparian plants to take up nitrogen and propose a framework for selecting species that can best buffer farm runoff into streams. Longer term study of riparian plantings based on this model will provide valuable insights, as will application of the value-based arguments for seascape repair put forward by Vishnu Prahalad and colleagues in this issue's second feature and Linda Luck and colleagues’ longer term testing of residual herbicides to reduce Gamba Grass populations in northern Australia. Indeed, all our interventions to improve the functionality of impaired ecosystems could be considered tests of hypotheses, including the core hypothesis that interventions can make a positive difference. Ian McLeod and colleagues acted on an informed hunch in North Queensland that relocation of coral colonies displaced by a cyclone would result in recovery, and all the indicators are pointing to success in this case and many others. In this and many cases involving lower-to-establish species or processes, only time and ongoing monitoring will tell. For example, longer time frames have proven to be useful in the detection by Tai White-Tony and colleagues of long-term patterns of establishment of tree species after mine site restoration in the Jarrah Forest in Western Australia – as well as to allow Kimberly McCallum and colleagues to assess the relationship between the configuration of planted species and their effective pollination in South Australian revegetation sites, many years after plant establishment. With the passage of time also comes change in personnel, such that longitudinal studies and ongoing nurturing of long-term recovery require commitments by institutions that persist beyond the working lives of individuals. It is hard to overstate the need for future managers and researchers to recognize the amount of past work that has gone into many studies and into securing the current condition of many sites. We need to firmly but gently remind current and future generations that long-term effort in these areas is a multi-generational compact.

Long‐Term Measurements Show Little Evidence for Large Increases in Total U.S. Methane Emissions Over the Past Decade

AbstractRecent studies show conflicting estimates of trends in methane (CH4) emissions from oil and natural gas (ONG) operations in the United States. We analyze atmospheric CH4measurements from 20 North American sites in the National Oceanic and Atmospheric Administration Global Greenhouse Gas Reference Network and determined trends for 2006–2015. Using CH4vertical gradients as an indicator of regional surface emissions, we find no significant increase in emissions at most sites and modest increases at three sites heavily influenced by ONG activities. Our estimated increases in North American ONG CH4emissions (on average approximately 3.4 ± 1.4 %/year for 2006–2015, ±σ) are much smaller than estimates from some previous studies and below our detection threshold for total emissions increases at the east coast sites that are sensitive to U.S. outflows. We also find an increasing trend in ethane/methane emission ratios, which has resulted in major overestimation of oil and gas emissions trends in some previous studies.

Influence of Regional Water Temperature Variability on the Flowering Phenology and Sexual Reproduction of the Seagrass Zostera marina in Korean Coastal Waters

Increasing sea surface temperature due to global climate change is a major threat to the growth and survival of many temperate seagrasses, while cold-water upwelling can potentially ameliorate high-temperature stress on temperate seagrass meadows during growing seasons. Seagrasses in the coasts of Korea are increasingly influenced by rising water temperatures and water temperature anomalies in recent decades due to climate change, but the impacts of such events on reproductive phenology of seagrasses remain poorly understood. We investigated the reproductive phenology and sexual reproduction of Zostera marina in four seagrass meadows along the coasts of Korea. Two study sites were located on the south coast where water temperature shows significant warming trends, while two other study sites were located on the east coast where coastal cold-water upwelling is prevalent. Water temperature exhibited stronger seasonality with cooler winter and warmer summer in the south coast sites than in the east coast sites. Cold-water upwelling events occurred frequently along the east coast of Korea, leading to anomalously cool water temperatures during the growing season. Z. marina flowering was prolonged and/or precocious at the east coast sites relative to the south coast sites. The mean flowering period was 5–7.5 months at the east coast sites and 3.5 months at the south coast sites. Moreover, reproductive shoot density and biomass, as well as the corresponding flowering frequency and reproductive efforts were much higher (2–3 times) at the east coast sites than at the south coast sites. Consequently, the potential seed production was higher in the east coast sites than in the south coast sites. Overall, high summer water temperature appeared to reduce sexual reproduction of Z. marina in the south coast sites, while regional cold-water upwelling on the east coast changed seasonal temperature patterns and decreased summer temperature highs, consequently provided a relatively long period of optimal water temperature for production of reproductive shoots. Regional water temperature variability has an important role in shifting the flowering responses of seagrass, which could affect the long-term stability and maintenance of seagrass meadows via the regulation of the sexual-asexual reproductive trade-off.

A Cloud Based Epidemiology Network to Investigate Geographical Dynamics of Respiratory Disease

Background Real-time data collection of respiratory disease is important for understanding the spatiotemporal dynamics of disease transmission in the US. Healthcare professionals use tools such as FluView to help identify local pathogen circulation; however, these tools are limited to syndromic surveillance, and track a limited set of pathogens. Understanding respiratory disease dynamics requires 1) a large, pathogen rich data set 2) geographically dispersed data sources, and 3) fine temporal resolution. Here we utilize FilmArray® Trend, a research epidemiology system containing exported data from FilmArray® Respiratory Panel (RP) tests, to investigate geographic patterns of 20 common pathogens.Methods Over 6,000,000 individual pathogen assays from 19 clinical sites were exported to the Trend database from 2013 to present. Trend data were smoothed and normalized to produce the time series of pathogen incidence. A cross-correlation analysis was performed to compare sites to one another and determine offset of pathogen incidence. The results were plotted on a map of the US with visual indicators of correlation strength and directional movement as defined by cross-correlation lag values.ResultsThe respiratory pathogens detected by the FilmArray RP test show a diverse set of spatial and temporal behaviors Most striking was the spread of the virus Coronavirus OC43, and Respiratory Syncytial Virus (RSV), with RSV traveling from east coast sites to west coast sites across the US over 20 days. In contrast Parainfluenza virus 3 (PIV3) shows a small cross-correlation lag across all of the Trend sites during the regular summer season, indicating near simultaneous onset of detection nationwide. A localized cluster of PIV3 in the winter of 2016 was observed in the midwest and west, identifying the significance of localized regional trends.Conclusion FilmArray Trend shows great promise in deciphering spatiotemporal dynamics of these common respiratory pathogens. This system can identify localized outbreaks and directional movement of pathogens over time. Future work with finer geographic distribution of contributing sites will aide in making conclusions regarding spatial dynamics of all 20 RP pathogens. Other pathogen transmission models may also be explored using this data set.Disclosures C. Cook, BioFire Diagnostics: Employee, Salary. A. Wallin, BioFire Defense: Employee, Salary. A. Faucett, BioFire Diagnostics: Employee, Salary. L. Meyers, BioFire Diagnostics: Employee, Salary

Factors influencing the long-term dynamics of larval sea lice density at east and west coast locations in Scotland

Sea lice (Copepoda: Caligidae) are marine copepods that parasitize finfish, and in cases of high infestation can result in severe epithelial damage and mortality. In Scotland, 2 species of sea louse, Lepeophtheirus salmonis and Caligus elongatus, pose a significant economic burden to the marine Atlantic salmon aquaculture industry and potentially impact wild salmonids. The purpose of this study was to determine how the density of pelagic sea lice is affected by external variables, in order to improve our understanding of sea lice dynamics. Long-term data from 2 sampling sites on the east and west coasts of Scotland were modelled independently in conjunction with environmental and anthropogenic variables. Statistical analysis identified that at the east coast site, the most influential factor affecting lice density was salinity. On the west coast, salinity, rainfall and farmed salmon production year were most influential. Molecular and morphological techniques also showed that the individuals recorded on the east coast were C. elongatus, a generalist copepod parasite, whereas only the salmonid-specific L. salmonis were found on the west. These results reiterate the role of environmental factors in influencing sea lice dynamics, and that salmonids are the primary hosts of sea lice on the west coast, but there could be non-salmonid host species as well as salmonid species influencing east coast sea lice densities.

Effect of tidal regime on the thermal tolerance of the marine gastropod Lunella smaragda (Gmelin 1791)

The tidal cycle around New Zealand results in spring low tides consistently occurring during the hottest part of the day (mid-afternoon) in north-eastern New Zealand, and during the cooler dawn/dusk periods in the north-west of the country. We hypothesised that due to mid-afternoon spring low tides, intertidal populations residing at north-eastern sites would show greater thermotolerance than their north-west conspecifics. To test this we used the marine gastropod, Lunella smaragda, which were collected from sites on both the East and West coasts of the Auckland region and exposed to an acute heat shock. Thermotolerance was measured as survivorship (LT50), drop down time (time to heat coma) and thermal stability of the anaerobic energy producing enzyme Tauropine dehydrogenase. Furthermore, temperature loggers were deployed at each site so as to record and compare thermal regimes among sites. A strong temperature spike associated with spring low tide was found at all sites, and maximal temperatures of all East coast sites were higher than West coast sites (in some case by up to 10°C). In terms of thermotolerance, mortality of L. smaragda occurred at 42°C leading to 100% mortality at 45°C. However, comparison of LT50 showed snails were equally thermotolerant regardless of site of collection. Similar results were found in TDH thermal stability with animals from all sites showing an approximately 80% decrease in enzyme activity after 10min exposure to 42°C. Whilst drop down times were different among sites these were correlated with animal size as opposed to site of collection. Thus, East coast populations of L. smaragda appear no more thermotolerant than their West coast counterparts. Such a result is concerning as maximal temperatures at East coast sites already exceed the LT50 values of L. smaragda recorded in the lab suggesting these populations have less of a thermal safety margin.

The creation of a comprehensive metocean data set for offshore wind turbine simulations

AbstractA database of meteorological and ocean conditions is presented for use in offshore wind energy research and design. The original data are from 23 ocean sites around the USA and were obtained from the National Data Buoy Center run by the National Oceanic and Atmospheric Administration. The data are presented in a processed form that includes the variables of interest for offshore wind energy design: wind speed, significant wave height, wave peak‐spectral period, wind direction and wave direction. For each site, a binning process is conducted to create conditional probability functions for each of these variables. The sites are then grouped according to geographic location and combined to create three representative sites, including a West Coast site, an East Coast site and a Gulf of Mexico site. Both the processed data and the probability distribution parameters for the individual and representative sites are being hosted on a publicly available domain by the National Renewable Energy Laboratory, with the intent of providing a standard basis of comparison for meteorological and ocean conditions for offshore wind energy research worldwide. Copyright © 2015 John Wiley & Sons, Ltd.

Prevalence of Salmonella spp. and thermophilic Campylobacter spp. in the small Asian mongoose (Herpestes javanicus) in Barbados, West Indies.

From April to July 2005, rectal swabs were collected from 48 free-ranging small Asian mongooses (Herpestes javanicus) on the east and south coasts of Barbados and analyzed for Salmonella and Campylobacter spp. Salmonella was recovered in 21.12% (7/33) of mongooses at the east-coast site and 26.67% (4/15) at the south-coast site. Four serotypes were isolated: Salmonella enterica serovar Rubislaw, Kentucky, Javiana, and Panama. One east-coast sample of 11 tested for Campylobacter was positive (9.09%). These results indicate that mongooses in Barbados are carriers and shedders of Salmonella and Campylobacter spp. and are a potential wildlife reservoir for these enteropathogens.

Fate and Transport of Polycyclic Aromatic Hydrocarbons in Upland Irish Headwater Lake Catchments

Polycyclic aromatic hydrocarbons (PAHs) are a concern due to their carcinogenicity and propensity for transboundary atmospheric transport. Ireland is located on the western periphery of Europe and assumed to receive clean Atlantic air. As such, it has been used as an atmospheric reference for comparison to other regions. Nonetheless, few studies have evaluated concentrations of PAHs within the Irish environment. In the current study, PAHs were measured at five upland (500–800 masl) headwater lake catchments in coastal regions around Ireland, remote from industrial point source emissions. Semipermeable membrane devices were deployed in lakes for a 6-month period in July 2009, and topsoils were sampled from each catchment during October 2010. The concentrations of PAHs were low at most study sites with respect to other temperate regions. Homologue groups partitioned between lake and soil compartments based on their molecular weight were: “lighter” substances, such as Phenanthrene and Fluorene, were found in higher proportions in lakes, whereas “heavier” compounds, such as Chrysene and Benz[a]anthracene, were more prominent in soils. Concentrations of PAHs were highest at the east coast sites, potentially due to contributions from historical transboundary and regional combustion sources.

A survey of pathogens and metazoan parasites on wild sea trout (Salmo trutta) in Scottish waters

AbstractUrquhart, K., Pert, C. C., Fryer, R. J., Cook, P., Weir, S., Kilburn, R., McCarthy, U., Simons, J., McBeath, S. J., Matejusova, I., and Bricknell, I. R. 2010. A survey of pathogens and metazoan parasites on wild sea trout (Salmo trutta) in Scottish waters. – ICES Journal of Marine Science, 67: 444–453. In all, 300 wild sea trout were sampled from three east coast and two west coast sites around Scotland over a 3-year period to establish the prevalence and the abundance of bacteria, viruses, and ecto- and endoparasites. No bacterial pathogens were isolated from any fish. One fish tested positive for viral pathogens (infectious pancreatic necrosis virus). The viral agent syncytium, resulting from aquareovirus infection, was found in four fish from the east coast. The parasitic fauna consisted of three classes of ectoparasite, Monogenea, Isopoda, and Copepoda, and four classes of endoparasite, Cestoda, Digenea, Nematoda, and Acanthocephala. Sea trout from the east coast sites were larger than those from the west coast. The abundance of Lepeophtheirus salmonis, Hysterothylacium aduncum, and Anisakis sp. was significantly greater at the east coast sites. The only parasite found in significantly greater numbers at a west coast site was Pomphorhynchus laevis.

Use of Landscape Fabric to Manage Diaprepes Root Weevil in Citrus Groves

ABSTRACT Experiments were conducted at 3 sites in Florida to determine whether landscape fabric, used as soil mulch, can reduce damage to citrus trees by Diaprepes abbreviates. The mulches were intended to prevent newly hatched weevil larvae from entering the soil to feed on roots and to prevent teneral adult weevils from exiting the soil to initiate egg-laying. The weight of aboveground parts of trees at a site heavily infested by D. abbreviatus on the east coast was 70% larger (P ≤ 0.05) for trees grown for 3 years on mulched compared to unmulched soil. Mulching did not affect the amount of feeding damage to roots at the east coast site, suggesting that mulched trees tolerated the damage better than trees in bare soil. Small plot size and relatively narrow fabric dimensions at the east coast site may have facilitated the entry of neonate larvae into soil. At a site on the Central Ridge with low weevil population density, average trunk cross-sectional area of 5-year-old mulched trees was 31% greater (P <...

Summertime buildup and decay of lightning NOx and aged thunderstorm outflow above North America

This study explores the upper tropospheric anticyclone above eastern North America and its influence on the summertime buildup and decay of lightning NOx (LNOx) and thunderstorm outflow. LNOx transport is simulated with a particle dispersion model that releases a LNOx tracer from the locations of millions of cloud‐to‐ground lightning flashes during May–September 2004 and 2006. On average, upper tropospheric zonal flow in May transitions to a closed anticyclone above northern Mexico and the southern United States in July that strengthens in August and rapidly decays in September. Concentrations of the LNOx tracer reach a maximum above the southern United States and Gulf of Mexico in July and August. Fourteen study sites across North America exhibit high day‐to‐day variability of the LNOx tracer in the upper troposphere during summer, with the sites most heavily influenced by the North American summer monsoon having the greatest background concentrations. During late spring and September the western sites have low concentrations with little variability. In general, the west coast sites plus Barbados have the most aged thunderstorm outflow, while the east coast sites have the least aged outflow. More than 80% of summertime upper tropospheric NOx above the eastern United States is produced by lightning. To produce the best available observation‐based view of upper troposphere NOx above North America, measurements from six aircraft campaigns are combined in a single composite plot. The modeled upper tropospheric NOx matches the general continental‐scale distribution of NOx in the composite plot, supporting the dominant role of LNOx in the simulations.

SEASCAPE-DEPENDENT SUBTIDAL–INTERTIDAL TROPHIC LINKAGES

In this study, we test in southern New Zealand a conceptual model of food web linkage that is seascape dependent, which can explain some of the variability in rocky shore community structure among sites and coasts. Using a comparative-experimental approach at local and distant sites we demonstrate that mobile subtidal predators (fish and crabs) can exert strong predation pressure on small mussels in the low tidal zone, but only in sites where the seascape includes subtidal reefs. On intertidal benches with adjacent subtidal reefs (+SR), 60-100% of small (5-15 mm) transplanted mussels were removed within a day from experimental tiles on the low shore when unprotected from predation, compared to fully caged controls that had approximately 100% survival over several months. In partial cages that exclude fish but not crabs, survivorship was intermediate. In contrast, on benches without subtidal reefs (-SR) 40-100% of mussels survived for months, even if unprotected. This difference is expressed in lower cover (0-60%) of mussels on rocks at +SR benches compared to -SR benches (70-99%). The central to northern west coast of the South Island is composed mostly of -SR benches, and predation on small mussels there was low and similar to the -SR benches on the east coast, whereas the +SR benches on the east coast had much greater predation. This contrasts to other studies in New Zealand that examined only predation on larger mussels by seastars and concluded that predation is strong on the west coast and weak on the east coast. Excluding large predators from low-shore areas with new recruits for a year in one +SR site showed longer-term predation effects on their abundance and cover. Short-term sampling at the east coast sites showed that mussel settlement was greater in -SR compared to +SR sites, providing some evidence that seascapes may also affect settlement. Overall, predation depended on the local seascape and ultimately affected community structure via suppression of effective recruitment rates. This study emphasizes the importance of predation on early life stages of basal species and the influence of seascapes on top-down interactions between subtidal predators and their intertidal prey.

A springtime comparison of tropospheric ozone and transport pathways on the east and west coasts of the United States

We have conducted a study to determine the influence of Asian pollution plumes on free tropospheric ozone above the west coast of the United States during spring. We also explored the additional impact of North American emissions on east coast free tropospheric ozone. Long‐term ozone monitoring sites in the United States are few, but we obtained ozonesonde profiles from Trinidad Head on the west coast, Huntsville, Alabama, in the southeast, and Wallops Island, Virginia, on the east coast. Additional east coast ozone profiles were measured by the MOZAIC commercial aircraft at Boston, New York City, and Philadelphia. Kilometer‐averaged ozone was compared between Trinidad Head and the three east coast sites (MOZAIC, Wallops Island, and Huntsville). Only in the 0–1 km layer did the MOZAIC site have a statistically significant greater amount of ozone than Trinidad Head. Likewise only the 0–1 and 1–2 km layers had greater ozone at Wallops Island and Huntsville in comparison to Trinidad Head. While Wallops Island did show greater ozone than Trinidad Head at 6–9 km, this excess ozone was attributed to a dry air mass sampling bias. A particle dispersion model was used to determine the surface source regions for each case, and the amount of anthropogenic NOx tracer that would have been emitted into each air mass. Transport times were limited to 20 days to focus on the impact of direct transport of pollution plumes from the atmospheric boundary layer. As expected, the amount of NOx tracer emitted into the east coast profiles was much greater in the lower and mid troposphere than at the west coast. At various altitudes at both coasts there existed a significant positive correlation between ozone and the NOx tracer, but the explained variance was generally less than 30%. On the east coast, Wallops Island had the weakest relationship between ozone and the NOx tracer, while Huntsville had the strongest. During spring, differences in photochemistry and transport pathways in the lowest 2 km of the troposphere results in an extra 5–14 ppbv of ozone on the east coast in comparison to Trinidad Head. However, despite differing amounts of NOx tracer from Asia and North America in the free troposphere, we found no significant difference in free tropospheric ozone between the east and west coasts of the United States during spring.