Singing performance,frequency matching and courtship success of long-tailed manakins (Chiroxiphia linearis)

We examined the relationship between song performance and courtship success in the lek-mating long-tailed manakin (Chiroxiphia linearis) of Costa Rica. Teams of male manakins form cooperative partnerships consisting of a dominant alpha male and a beta male partner with a variable number of subordinate affiliates. Each alpha and beta partnership performs a joint song virtually in unison, which attracts females to their lek arena. We quantified four aspects of song performance, including synchrony, degree of consistency in the alpha male's singing, degree of consistency in the beta male's singing, and degree of sound frequency matching between partners. When all four variables were included in a discriminant function analysis, average frequency matching alone was useful in discriminating between teams with high rates of visitation by females and those with low visitation rates. Only frequency matching was correlated with the rate at which females visited display lek arenas. We propose that the degree of frequency matching provides an unambiguous ideal against which dual-male courtship performance can be assessed. This aspect of song performance may provide information useful to females in assesing a potential mate's ability to form a cooperative long-term partnership.     

Semipermeable membrane devices accumulate conserved ratios of sterane and hopane petroleum biomarkers

Semipermeable membrane devices (SPMDs) are commonly used as a time-integrated measure of aqueous concentrations of persistent hydrophobic chemicals, including PAH, pesticides, dioxins, and PCBs. Another class of persistent hydrophobic chemicals is petroleum biomarker compounds (hopanes and steranes) that are used for hydrocarbon source identification and allocation. In this study three different passive sampling device designs were exposed to a complex hydrocarbon mixture (Alaska North Slope crude) in a laboratory experiment to determine uptake rates of biomarkers into SPMDs. In addition to the standard triolein filled SPMDs, iso-octane filled SPMDs (ISPMDs) and unfilled low-density polyethylene strips (PESDs) were tested. Uptake rates and effective sampling rates were determined for 53 compounds. There was little variation in sampling rates among the individual biomarkers; average values (ld(-1)) for hopanes were 0.43+/-0.07 (PESD), 0.33+/-0.06 (SPMD), and 0.44+/-0.03 (ISPMD) and average sterane sampling rates were 0.57+/-0.04 (PESD), 0.42+/-0.03 (SPMD), and 0.53+/-0.03 (ISPMD). The primary reason for biomarker analysis is for source discrimination of petroleum. Nineteen different diagnostic ratios were measured, and were found to be remarkably well conserved between the oil, water, and all three devices. This indicates that SPMDs, PESDs, and ISPMDs should each be effective for source discrimination studies of petroleum contamination.     

Remediating dicamba-contaminated water with zerovalent iron

Dicamba (3,6-dichloro-2-methoxybenzoicacid) is a highly mobile pre- and post-emergence herbicide that has been detected in ground water. We determined the potential of zerovalent iron (Fe0) to remediate water contaminated with dicamba and its common biological degradation product, 3,6-dichlorosalicylic acid (DCSA). Mixing an aqueous solution of 100 microM dicamba with 1.5% Fe0 (w/v) resulted in 80% loss of dicamba within 12 h. Solvent extraction of the Fe0 revealed that dicamba removal was primarily through adsorption; however when the Fe0 was augmented with Al or Fe(III) salts, dicamba was dechlorinated to an unidentified degradation product. In contrast to dicamba, Fe0 treatment of DCSA resulted in removal with some dechlorination observed. When DCSA was treated with Fe0 plus Al or Fe(III) salts, destruction was 100%. Extracts of this Fe0 treatment contained the same HPLC degradation peak observed with the Fe0 + Al or Fe(III) salt treatment of dicamba. Molecular modeling suggests that differences in removal and dechlorination rates between dicamba and DCSA may be related to the type of coordination complex formed on the iron surface. Experiments with 14C-labeled dicamba confirmed that Fe-adsorbed dicamba residues are available for subsequent biological mineralization (11% after 125 d). These results indicate that Fe0 could be potentially used to treat dicamba and DCSA-contaminated water.     

Using the bootstrap and fast Fourier transform to estimate confidence intervals of 2D kernel densities

Kernel density estimators are often used to estimate the utilization distributions (UDs) of animals. Kernel UD estimates have a strong theoretical basis and perform well, but are usually reported without estimates of error or uncertainty. It is intuitively and theoretically appealing to estimate the sampling error in kernel UD estimates using bootstrapping. However, standard equations for kernel density estimates are complicated and computationally expensive. Bootstrapping requires computing hundreds or thousands of probability densities and is impractical when the number of observations, or the area of interest is large. We used the fast Fourier transform (FFT) and discrete convolution theorem to create a bootstrapping algorithm fast enough to run on commonly available desktop or laptop computers. Application of the FFT method to a large (n>20,000) set of radio telemetry data would provide a 99.6% reduction in computation time (i.e., 1.6 as opposed to 444 hours) for 1000 bootstrap UD estimates. Bootstrap error contours were computed using data from a radio-collared polar bear (Ursus maritimus) in the Beaufort Sea north of Alaska.     

Dynamic model for the assessment of radiological exposure to marine biota

A generic approach has been developed to simulate dynamically the uptake and turnover of radionuclides by marine biota. The approach incorporates a three-compartment biokinetic model based on first order linear kinetics, with interchange rates between the organism and its surrounding environment. Model rate constants are deduced as a function of known parameters: biological half-lives of elimination, concentration factors and a sample point of the retention curve, allowing for the representation of multi-component release. The new methodology has been tested and validated in respect of non-dynamic assessment models developed for regulatory purposes. The approach has also been successfully tested against research dynamic models developed to represent the uptake of technetium and radioiodine by lobsters and winkles. Assessments conducted on two realistic test scenarios demonstrated the importance of simulating time-dependency for ecosystems in which environmental levels of radionuclides are not in equilibrium.     

A comparison of concentrations of polycyclic aromatic compounds detected in dust samples from various regions of the world

Settled house dust can be a source of human exposure to toxic polycyclic aromatic hydrocarbons (PAHs) through non-dietary ingestion and dermal contact. Information regarding the concentrations of various contaminants in house dust would be useful in estimating the risk associated with exposure to these compounds. This study reports on the surface loading, variability and distribution of PAHs in settled house dust collected from homes in three locations: Sumgayit, Azerbaijan; Shanxi Province, China; and southern Texas, United States. The highest PAH floor surface loadings were observed in China, followed by Azerbaijan and Texas. Median concentrations of high molecular weight (four ring and larger) PAHs ranged from a low of 0.11 microg/m(2) in Texas, to 2.9 microg/m(2) in Azerbaijan and 162 microg/m(2) in China. These trends in total surface loading and relative carcinogenicity indicate that the risk of health effects from exposure to PAHs in house dust is highest in the Chinese population and lowest in the Texas population. As anticipated, variability among dust samples from different houses within the same region was high, with coefficients of variation greater than 100%. Alkylated PAHs comprised 30-50% of the total mass of PAHs. Based on a comparison of the composition of specific components, PAHs in China and Azerbaijan were determined to be derived mainly from combustion sources rather than from unburned fossil fuels such as petroleum. These results, coupled with ongoing investigation of appropriate PAH exposure biomarkers in humans, will guide future efforts to identify ways to reduce exposures in the study areas.