A Large-Eddy Simulation Study of the Convective Boundary Layer over Philadelphia during the 1999 Summer NE-OPS Campaign

This study presents a large-eddy simulation (LES) study of the convective boundary layer on August 1, 1999 over Philadelphia, PA during a summer ozone episode. The study is an evaluation of the Colorado State University's Regional Atmospheric Modeling System Version 4.3 (RAMS4.3) with the LES option using Northeast Oxidant and Particulate Study (NE-OPS) data. Simulations were performed with different imposed sensible heat fluxes at the ground surface. The model was initialized with the atmospheric sounding data collected at Philadelphia at 1230 UTC and model integrations continued till 2130 UTC. The resulting mean profiles of temperature and humidity obtained from the LES model were compared with atmospheric soundings, tethered balloon and aircraft data collected during the NE-OPS 1999 field campaign. Also the model-derived vertical profiles of virtual temperature were compared with NE-OPS Radio Acoustic Sounder System (RASS) data while the humidity profiles were compared with NE-OPS lidar data. The comparison of the radiosonde data with the LES model predictions suggests that the growth of the mixing layer is reasonably well simulated by the model. Overall, the agreement of temperature predictions of the LES model with the radiosonde observations is good. The model appears to underestimate humidity values for the case of higher imposed sensible heat flux. However, the humidity values in the mixing layer agree quite well with radiosonde observations for the case of lower imposed sensible heat flux. The model-predicted temperature and humidity profiles are in reasonable agreement with the tethered balloon data except for some small overestimation of temperature at lower layers and some underestimation of humidity values. However, the humidity profiles as simulated by the model agree quite well with the tethered balloon data for the case of lower imposed sensible heat flux. The model-predicted virtual temperature profile is also in better agreement with RASS data for the case of lower imposed sensible heat flux. The model-predicted temperature profile further agrees quite well with aircraft data for the case of lower imposed heat flux. However, the relative humidity values predicted by the model are lower compared with the aircraft data. The model-predicted humidity profiles are only in partial agreement with the lidar data. The results of this study suggest that the explicitly resolved energetic eddies seem to provide the correct forcing necessary to produce good agreement with observations for the case of an imposed sensible heat flux of 0.1 K m s^–1 at the surface.     

Numerical Investigation of Boundary-Layer Evolution and Nocturnal Low-Level Jets: Local versus Non-Local PBL Schemes

Numerical simulations of the evolution of the planetary boundary layer (PBL) and nocturnal low-level jets (LLJ) have been carried out using MM5 (version 3.3) with four-dimensional data assimilation (FDDA) for a high pollution episode in the northeastern United States during July 15–20, 1999. In this paper, we assess the impact of different parameterizations on the PBL evolution with two schemes: the Blackadar PBL, a hybrid local (stable regime) and non-local (convective regime) mixing scheme; and the Gayno–Seaman PBL, a turbulent kinetic energy (TKE)-based eddy diffusion scheme. No FDDA was applied within the PBL to evaluate the ability of the two schemes to reproduce the PBL structure and its temporal variation. The restriction of the application of FDDA to the atmosphere above the PBL or the lowest 8 model levels, whichever is higher, has significantly improved the predicted strength and timing of the LLJ during the night. A systematic analysis of the PBL evolution has been performed for the primary meteorological fields (temperature, specific humidity, horizontal winds) and for the derived parameters such as the PBL height, virtual potential temperature, relative humidity, and cloud cover fraction. There are substantial differences between the PBL structures and evolutions simulated by these two different schemes. The model results were compared with independent observations (that were not used in FDDA) measured by aircraft, RASS and wind profiler, lidar, and tethered balloon platforms during the summer of 1999 as part of the NorthEast Oxidant and Particle Study (NE-OPS). The observations tend to support the non-local mixing mechanism better than the layer-to-layer eddy diffusion in the convective PBL.     

Examination of model predictions at different horizontal grid resolutions

While fluctuations in meteorological and air quality variables occur on a continuum of spatial scales, the horizontal grid spacing of coupled meteorological and photochemical models sets a lower limit on the spatial scales that they can resolve. However, both computational costs and data requirements increase significantly with increasing grid resolution. Therefore, it is important to examine, for any given application, whether the expected benefit of increased grid resolution justifies the extra costs. In this study, we examine temperature and ozone observations and model predictions for three high ozone episodes that occurred over the northeastern United States during the summer of 1995. In the first set of simulations, the meteorological model RAMS4a was run with three two-way nested grids of 108/36/12 km grid spacing covering the United States and the photochemical model UAM-V was run with two grids of 36/12 km grid spacing covering the eastern United States. In the second set of simulations, RAMS4a was run with four two-way nested grids of 108/36/12/4 km grid spacing and UAM-V was run with three grids of 36/12/4 km grid spacing with the finest resolution covering the northeastern United States. Our analysis focuses on the comparison of model predictions for the finest grid domain of the simulations, namely, the region overlapping the 12 km and 4 km domains. A comparison of 12 km versus 4 km fields shows that the increased grid resolution leads to finer texture in the model predictions; however, comparisons of model predictions with observations do not reveal the expected improvement in the predictions. While high-resolution modeling has scientific merit and potential uses, the currently available monitoring networks, in conjunction with the scarceness of highly resolved spatial input data and the limitations of model formulation, do not allow confirmation of the expected superiority of the high-resolution model predictions.The U.S. Governments right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged.     

Numerical Investigation of the Effects of Boundary-Layer Evolution on the Predictions of Ozone and the Efficacy of Emission Control Options in the Northeastern United States

This paper examines the effects of two different planetary boundary-layer (PBL) parameterization schemes – Blackadar and Gayno–Seaman – on the predicted ozone (O₃) concentration fields using the MM5 (Version 3.3) meteorological model and the MODELS-3 photochemical model. The meteorological fields obtained from the two boundary-layer schemes have been used to drive the photochemical model to simulate O₃ concentrations in the northeastern United States for a three-day O₃ episodic period. In addition to large differences in the predicted O₃ levels at individual grid cells, the simulated daily maximum 1-h O₃ concentrations appear at different regions of the modeling domain in these simulations, due to the differences in the vertical exchange formulations in these two PBL schemes. Using process analysis, we compared the differences between the different simulations in terms of the relative importance of chemical and physical processes to O₃ formation and destruction over the diurnal cycle. Finally, examination of the photochemical model's response to reductions in emissions reveals that the choice of equally valid boundary-layer parameterizations can significantly influence the efficacy of emission control strategies.     

Soil Lead and Children’s Blood Lead Levels in Syracuse, NY, USA

A geo-referenced data set of 12 228 first-time blood lead screening values for Syracuse, NY, children was established for the 4-year period 1992–1996. Soil lead values were measured in a 600 m by 600 m tessellation grid covering the city. The two data sets were merged for evaluation of relationships between them. Strong seasonal variation in blood lead levels suggests the importance of contaminated soils as an exposure source. When the data were aggregated at a large geographic scale (3 km²), a logarithmic model showed an R² of > 0.65 for the regression of geometric mean blood lead on median soil lead values. Results showed a striking similarity to those obtained by Mielke et al. (1999) for a study in New Orleans, LA, USA.     

Offshore spawning by the portunid crabScylla serrata (Crustacea: Decapoda)

The portunid crabScylla serrata (Forskål) is shown to migrate offshore to spawn. Records of 447S. serrata caught as bycatch by trawlers in the tropical waters of northern Australia were analysed with respect to area, depth, distance offshore and month of capture as well as the sex and size of the crabs and whether the females were ovigerous. The crabs were caught mainly in three areas that correspond to the tiger prawn trawl fishery, at between 10 and 60 m depth (mean 28.5 m), 3 to 95 km offshore (mean 17.9 km). Most (87%) of the crabs were captured in October and November, which suggests they move offshore in September and October. No crabs were reported from offshore by February. Over 97% of the crabs caught offshore were female, of these 61.5% were ovigerous. The size range of females (100–109 to 200–209 mm carapace-width size classes) and males (120–129 to 200–209 mm carapace-width size classes) caught was similar. The frequent occurrence in coastal waters of females that are larger than the modal size at spawning, as well as mature females with spent ovaries, suggests that many females return to the coast after spawning. Although some species of portunid crab are euryhaline, mature females of estuarine species migrate to the sea to spawn. The migration byS. serrata described here is far more extensive than would be required to reach sea water salinities; it probably provides a dispersal mechanism for larvae to enable the megalopa stage to recruit to habitats distant from those of the parents.     

Dynamic environ analysis of compartmental systems: A computational approach

Ecosystems are often modeled as stocks of matter or energy connected by flows. Network environ analysis (NEA) is a set of mathematical methods for using powers of matrices to trace energy and material flows through such models. NEA has revealed several interesting properties of flow–storage networks, including dominance of indirect effects and the tendency for networks to create mutually positive interactions between species. However, the applicability of NEA is greatly limited by the fact that it can only be applied to models at constant steady states. In this paper, we present a new, computationally oriented approach to environ analysis called dynamic environ approximation (DEA). As a test of DEA, we use it to compute compartment throughflow in two implementations of a model of energy flow through an oyster reef ecosystem. We use a newly derived equation to compute model throughflow and compare its output to that of DEA. We find that DEA approximates the exact results given by this equation quite closely – in this particular case, with a mean Euclidean error ranging between 0.0008 and 0.21 – which gives a sense of how closely it reproduces other NEA-related quantities that cannot be exactly computed and discuss how to reduce this error. An application to calculating indirect flows in ecosystems is also discussed and dominance of indirect effects in a nonlinear model is demonstrated.     

Determination of the optimum MM5 configuration for long term CMAQ simulations of aerosol bound pollutants in Europe

Realistic meteorological fields are a prerequisite for the determination of pollutant concentrations and depositions by means of a chemistry transport model. Different configurations of the 5th generation NCAR/Penn State University mesoscale meteorological model MM5 were tested to determine the optimum set up for long term hindcasts that cover several months up to years. Four dimensional data assimilation (FDDA) significantly enhances the spatio temporal representation of temperature, humidity and wind. Best agreement with radiosonde observations could be achieved when temperature, humidity and wind were grid nudged every 6 h. The quality of the resulting meteorological fields showed no significant systematic temporal or spatial variation over Europe in a model run of the year 2000. It was found that the hydrological cycle was not correctly reproduced by the model when no nudging was applied. The relevant model run showed too high relative humidity and too high rainfall when compared to observations. This led to considerably lower aerosol concentrations close to ground and a shift in the deposition patterns of particle bound pollutants like the carcinogenic benzo(a)pyrene (B(a)P). Guest Editor: Dr. S. T. Rao.     

Surface zooplankton dynamics and community structure in the Gulf of Aqaba (Eilat), Red Sea

Winter and summer zooplankton maxima were observed on both near-reef and offshore sampling sites in the northern part of the Gulf of Aqaba, with summer maxima smaller than those of winter and more characterized by larval forms. Near-reef zooplankton biomass was generally several times greater than that observed 2 km offshore. During 1987, a near-reef maximum of 155 ind. or 12.2 g wet biomass m^–3 was observed in March, while 103 ind. or 8.5 g wet biomass m^–3 was observed in July. In the same year, 2 km offshore a maximum of 53 ind. or 2.5 g wet biomass m^–3 was observed in February, while a maximum of 33 ind. or 0.5 g wet biomass m^–3 was noted in July. The following year, 1988, the near-reef zooplankton abundances were little changed, but offshore zooplankton abundances were much higher (317 m^–3). During 1987, the dominant winter (March) forms near the reef were gammarid amphipods, at maximum concentrations of 100 ind. m^–3, where the summer (July) maximum was composed primarily of mysids (34 m^–3), gammarid amphipods (30 m^–3), and fish eggs (24 m^–3). The offshore winter zooplankton fauna was characterized by copepods and appendicularians, each at a maximum concentrations of ca 13 ind. m^–3, while the summer maximum was dominated by brachyuran zoea (31 m^–3). Though the 1988, winter near-reef zooplankton community compositions were similar to those of 1987, the offshore zooplankton fauna was dominated by ostracods, which were relatively rare in previous years. Preliminary data suggests that holoplanktonic forms like chaetognaths, copepods and appendicularians, at an offshore site exhibit different patterns of vertical migration than those near the reef. This different behavior may result from different species compositions of these taxa or from high concentrations of pseudoplanktonic bentho-neritic peracarid crustaceans.Please address correspondence and reprint requests to T. Echelman, Marine Science Research Center, State University of New York, Stony Brook, New York 11794-5000, USA     

Larval supply of shorefishes to nursery habitats around Lee Stocking Island,Bahamas. I. Small-scale distribution patterns

Plankton nets moored in tidal channels around Lee Stocking Island, Bahamas, were used to monitor larval supply from Exuma Sound to benthic habitats on Great Bahama Bank in the winter months (December–February) of 1990–1991 and 1991–1992. A total of 10376 fishes were collected in 1990–1991 from 58 taxa; in 1991–1992, 13358 fishes were collected from 56 taxa. Vertical distributions of 16 dominant taxa suggested that most settlement-stage fishes were concentrated in surface waters Six taxa showed no yearxdepth interaction; of Fese, five were sigmficantly more abundant in the surface nets. Eight of the ten taxa with significant yearxdepth interactions displayed a tendency to be more abundant in surface layers than in sub-surface collections during the first year, but were more evenly distributed across surface and sub-surface collections in the second year of sampling. Larval supply of six taxa showed significant coherency over spatial scales from 0.5 to 1.5 km. Over scales up to 5 km, however, larval supply became largely decoupled at the daily level. Significant inter-annual variability in the vertical and horizontal distributions of settlement-stage fishes suggests that behavior may play a major role in determining larval supply in tropical shorefishes.     

A study on the Spatial Distribution of Nitrogen and Phosphorus Balance, and Regional Nitrogen Flow Through Crop Production

The spatial distribution patterns of the nitrogen and phosphorus input/intake amounts in crop production within two small basins are examined, based upon a cropping unit distribution map that is obtained from remote sensing data analysis. Firstly, we examine the availability and suitability of approaches to the spatial distribution analysis of cultivation patterns classified from material flow characteristics of crop production using seasonal remote-sensing data. Secondly, material flow units in crop production are grouped according to the cultivation patterns obtained from the remote-sensing data analysis. Consequently, the spatial patterns of the amounts of both nitrogen and phosphorus inputs/intakes through crop production on farmland are examined and their spatial distribution maps are prepared according to the material flow units. In addition, we developed a nitrogen flow and runoff model and the model is simulated based on the examination of the results of spatial distribution patterns of the material flow units. The annual nitrogen runoff from small catchments, where various crops are cultivated, varies from 2.7 kg ha^–1 year^–1 to 108 kg ha^–1 year^–1 and the annual balanced losses of nitrogen in small catchments varied from –30 kg ha^–1 year^–1 to 101 kg ha^–1 year^–1. Also, the monthly changes in soil nitrogen of each material flow unit is estimated at –55 kg ha^–1 as a maximum decrease and 114 kg ha^–1 as a maximum increase. These results indicate that the spatial distribution patterns of nutrient input and intake through agricultural activities should be considered when analyzing the material flows and nutritient movement in soil–water systems in rural areas for watershed environmental control and regional agricultural management.     

Ultrasonic tracking of Greenland sharks,<Emphasis Type="Italic"> Somniosus microcephalus</Emphasis>, under Arctic ice

Six Greenland sharks, Somniosus microcephalus (Bloch and Schneider, 1801), 190–355 cm fork length, were tracked under land-fast sea ice off northern Baffin Island (73.2°N; 85.3°W) between 16 and 28 May 1999, using ultrasonic telemetry. The sharks were tracked continuously for periods of 5.5–13.0 h, with the tracks of two individuals lasting 31.4 and 42.8 h, respectively, each with an interval when the track was lost. Several sharks dove after release and moved along the ocean bottom for the duration of the tracking period, while others varied their movements regarding course and depth. Two sharks made repeated visits to within 11 m of the ice–water interface from deeper water. The tracked sharks exhibited no apparent depth or temperature preferences, and pooled data indicated that sharks remained deep during the morning and gradually moved into shallower depths through the afternoon and night. Rates of descent (average=0.099 m s^–1) were significantly greater than rates of ascent (average=0.058 m s^–1) for all sharks, and the average rate of horizontal movement over ground was estimated as 0.215 m s^–1. Based on the movements of tracked sharks and information contained in the literature, S. microcephalus may prey on seals in areas covered by land-fast sea ice.Communicated by J.P. Grassle, New Brunswick     

Lead pollution in soils adjacent to homes in Tampa,Florida

In the United States, the study of lead pollution in soil has focused on older cities throughout the industrialised northern tier of states often referred to as the rust belt. Researchers have not studied the magnitude and extent of contamination in the newly developed portions of the sunbelt region of the south. In order to assess the significance of lead pollution in soils in these areas, an analysis of the lead content in 146 soil samples collected at a one km grid throughout residential portions of Tampa, Florida was undertaken. The results reveal that lead contaminated (>500 g g^–1) soil is present in the older portions of the city and near expressways. A comparison of the results with data collected in an older, northern city demonstrates that the magnitude and extent of the contamination in Tampa are less than found in the larger rust belt city. However, the presence of hazardous levels of lead in soil collected in Tampa is evidence that sunbelt cities must address lead pollution in the urban environment.     

On the latent state estimation of nonlinear population dynamics using Bayesian and non-Bayesian state-space models

Nonlinear state-space models have been increasingly applied to study population dynamics and data assimilation in environmental sciences. State-space models can account for process error and measurement error simultaneously to correct for the bias in the estimates of system state and model parameters. However, few studies have compared the performance of different nonlinear state-space models for reconstructing the state of population dynamics from noisy time series. This study compared the performance of the extended Kalman filter (EKF), unscented Kalman filter (UKF) and Bayesian nonlinear state-space models (BNSSM) through simulations. Synthetic population time series were generated using the theta logistic model with known parameters, and normally distributed process and measurement errors were introduced using the Monte Carlo simulations. At higher levels of nonlinearity, the UKF and BNSSM had lower root mean square error (RMSE) than the EKF. The BNSSM performed reliably across all levels of nonlinearity, whereas increased levels of nonlinearity resulted in higher RMSE of the EKF. The Metropolis–Hastings algorithm within the Gibbs algorithm was used to fit the theta logistic model to synthetic time series to estimate model parameters. The estimated posterior distribution of the parameter θ indicated that the 95% credible intervals included the true values of θ (=0.5 and 1.5), but did not include 1.0 and 0.0. Future studies need to incorporate the adaptive Metropolis algorithm to estimate unknown model parameters for broad applications of Bayesian nonlinear state-space models in ecological studies.     

Accumulation of selenium in sugarcane (Sachharum officinarum Linn.) in seleniferous areas of Punjab,India

A survey was conducted during 1986–88 to assess the level and pattern of accumulation of selenium in sugarcane plants in seleniferous areas of Punjab (India). Total and water-extractable (available) selenium ranged from 0.55 to 2.58 (mean 1.43 ± 0.67) mg kg^–1 and from 0.02 to 0.05 (mean 0.033 ± 0.007) mg kg^–1, respectively, in seleniferous areas. Corresponding values from non-seleniferous areas were 0.23–0.55 (mean 0.36 ± 0.08) mg kg^–1 and 0.015–0.025 (mean 0.020 ± 0.003) mg kg^–1, respectively. Sugarcane tops from seleniferous areas accumulated high levels of selenium ranging from 7.9 to 67.5 mg kg^–1. These selenium levels were 6–14 times higher than those from non-seleniferous areas. During the early stages of growth (June), the selenium content was highest but decreased during the months of July and August and then did not change up to maturity. In the seleniferous areas sugarcane tops and canes at maturity contained 5.7–9.5 and 1.8–2.1 mg Se kg^–1, respectively. However, the tops and canes of plants growing near the permanent boundary (bundh) contained 9.5–18.8 and 2.1–2.4 mg Se kg^–1, respectively.In a field experiment on sugarcane, application of gypsum up to 1 ton ha^–1 resulted in a significant reduction of selenium content in sugarcane tops as well as in the cane. Selenium content in sugarcane tops at maturity was reduced from 15.16 to 5.08 mg kg^–1 by applying gypsum of 1 ton ha^–1.     

Population biology of hyperbenthic crustaceans in a cold water environment (Conception Bay,Newfoundland). II.<Emphasis Type="Italic"> Acanthostepheia malmgreni</Emphasis> (Amphipoda)

Seasonal population dynamics of the gammarid Acanthostepheia malmgreni Goës in Conception Bay, Newfoundland, were examined from October 1998 to November 2000. This species exhibited a 2.5-year life span, with the reproductive cycle correlating with seasonal phytoplankton flux. Females were semelparous and died following a 5-month brooding period and the subsequent release of juveniles in April and May. The biennial life cycle of this population should result in the presence of two cohorts in the hyperbenthos at any given time. However, the cohorts alternated in strength from year to year, which affected annual density, biomass and production during the study period. Densities were 64±87 ind. per 100 m³ in 1999 and 491±492 ind. per 100 m³ (mean±SD) in 2000. Secondary production was estimated at 18–44 mg C m^–2 in 1999 and 180–311 mg C m^–2 in 2000. The annual P/B ratios were 0.89 and 2.27 in 1999 and 2000, respectively. Growth varied both among and within cohorts, with different life-history stages exhibiting variable growth rates ranging from 0 to 12 mg dry mass month^–1.Communicated by J.P. Grassle, New Brunswick     

From data and theory to environmental models and indices formation

A prerequisite for environmental indices is that they represent environmental pressure, and the state of, and impact on environmental conditions. In other words, they should capture as much as possible of the cause-effect chains they represent and relate pressure and effect to criteria of environmental quality. The approach proposed in the article attempts to link the pressure–state–impact–response framework of indicators to the integrated environmental model, based on the method of response function (MRF). The MRF allows to construct purposeful, credible models from data and prior knowledge or information. The data are usually time series observations of system inputs and outputs, and sometimes of internal states. The output of such models is presented with highly aggregated environmental indices, reflecting the main pressure–state–impact–response cause-effect chains. The proposed approach is illustrated with the example of soil erosion indices.     

Annual abundance and biomass of aloricate ciliates in tropical neritic waters off Kingston,Jamaica

The daily abundance of aloricate ciliates at Lime Cay, Jamaica, a shallow neritic site, ranged from 29 to 118 × 10⁶ m^–2 (0.97 to 3.93 × 10⁶ m^–3) between November 1985 and November 1986. Biomass was converted to kilojoules (1 kcal=4.1855 kJ) assuming 42% carbon, 20.15 kJ (g dry wt)^–1, and 20% cell shrinkage. Biomass ranged from 0.40 to 3.00 kJ m^–2 (13.3 to 100 J m^–3; 0.28 to 2.08µg C l^–1) with an annual mean of 1.11 kJ m^–2 (36.8 J m^–3; 0.764µg C l^–1). Nanociliates (<20µm equivalent spherical diameter, ESD) dominated abundance, but microciliates (> 20µm ESD) dominated biomass.Strombidium, Strobilidium, Tontonia andLaboea species were conspicuous taxa. Annual production estimates of the aloricate assemblage, based on literature growth rates, ranged from 404 kJ m^–2 yr^–1 (37 J m^–3 d^–1) to 1614 kJ m^–2 yr^–1 (147 J m^–3 d^–1). A compromise estimate of 689 kJ m^–2 yr^–1 (i.e., 63 J m^–3 d^–1) is comparable to other estimates from tropical and subtropical regions. A model of annual energy flow through 11 planktonic compartments suggests the total ciliate assemblage (aloricates and tintinnines) to be as productive as metazoan herbivores and metazoan carnivores.     

Probabilistic movement model with emigration simulates movements of deer in Nebraska, 1990–2006

Movements of deer can affect population dynamics, spatial redistribution, and transmission and spread of diseases. Our goal was to model the movement of deer in Nebraska in an attempt to predict the potential for spread of chronic wasting disease (CWD) into eastern Nebraska. We collared and radio-tracked >600 white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus) in Nebraska during 1990–2006. We observed large displacements (>10 km) for both species and sexes of deer, including migrations up to 100 km and dispersals up to 50 km. Average distance traveled between successive daily locations was 166 m for male and 173 for female deer in eastern Nebraska, and 427 m for male and 459 for female deer in western Nebraska. Average daily displacement from initial capture point was 10 m for male and 14 m for female deer in eastern Nebraska, and 27 m for male and 28 m for female deer in western Nebraska. We used these data on naturally occurring movements to create and test 6 individual-based models of movement for white-tailed deer and mule deer in Nebraska, including models that incorporated sampling from empirical distributions of movement lengths and turn angles (DIST), correlated random walks (CRW), home point fidelity (FOCUS), shifting home point (SHIFT), probabilistic movement acceptance (MOVE), and probabilistic movement with emigration (MOVEwEMI). We created models in sequence in an attempt to account for the shortcomings of the previous model(s). We used the Kolmogrov–Smirnov goodness-of-fit test to verify improvement of simulated annual displacement distributions to empirical displacement distributions. The best-fit model (D = 0.07 and 0.08 for eastern and western Nebraska, respectively) included a probabilistic movement chance with emigration (MOVEwEMI) and resulted in an optimal daily movement length of 350 m (maximum daily movement length of 2800 m for emigrators) for eastern Nebraska and 370 m (maximum of 2960 m) for western Nebraska. The proportion of deer that moved as emigrators was 0.10 and 0.13 for eastern and western Nebraska, respectively. We propose that the observed spread of CWD may be driven by large movements of a small proportion of deer that help to establish a low prevalence of the disease in areas east of the current endemic area. Our movement models will be used in a larger individual-based simulation of movement, survival, and transmission of CWD to help determine future surveillance and management actions.     

The diving behaviour of brooding king penguins (<Emphasis Type="Italic">Aptenodytes patagonicus</Emphasis>) from the Falkland Islands: variation in dive profiles and synchronous underwater swimming provide new insights into their foraging strategies

The diving behaviour of king penguins (Aptenodytes patagonicus) was studied on the Falkland Islands, where a small population (ca. 300 fledglings year^–1) is located at the geographical limit of their breeding range. King penguins rearing newly hatched chicks were equipped with time-depth recorders before leaving for sea. In total, 20,175 dives >3 m were recorded from 12 birds during 15 foraging trips with a mean duration of 5.7±2.3 days. The majority of the trips was directed up to 500 km to the northeast of the breeding colony in slope waters of, and oceanic waters beyond, the Patagonian shelf. Mean time spent underwater accounted for 42±9% of the foraging trip. Mean dive depth achieved was 55±16 m; maximum dive depth recorded was 343 m. Mean dive duration was 159±25 s; maximum dive duration was 480 s. The mean vertical distance covered was 140±65 km trip^–1; and on average birds covered 25 km day^–1. Synchronous diving behaviour was observed in two birds for a period of about 24 h after leaving the colony. Dive depth correlated positively with: (1) light intensity, (2) dive duration and (3) vertical velocities, thus confirming previous findings obtained from conspecifics at other breeding sites and indicating comparable diving behaviour. However, separation of dives according to their profile—V-, U-, or W-shaped—revealed significant differences between certain dive parameters. For a given depth range, bottom time was longer and vertical velocities higher in W-dives than in U-dives. This, together with a higher number of W-dives at dawn and dusk, suggests that foraging is more effective during W-dives than U-dives, and during twilight. These findings imply that king penguins have to make more complex decisions, individually and socially, on the performance of the subsequent dive than previously thought.Communicated by O. Kinne, Oldendorf/Luhe