Movements,behavior, and habitat utilization of yellowfin tuna (<Emphasis Type="Italic">Thunnus albacares</Emphasis>) in the northeastern Pacific Ocean,ascertained through archival tag data

Sixty-eight yellowfin tuna, Thunnus albacares, (60-135 cm fork length) were caught and released with implanted archival tags offshore off Baja California, Mexico, during October 2002 and October 2003. Thirty-six fish (53%) were recaptured and the data were downloaded from all 36 recovered tags. Time at liberty ranged from 9 to 1,161 days, and the data were analyzed for the 20 fish that were at liberty for 154 or more days. The accuracy in the position estimates, derived from light-level longitude data and sea-surface temperatures (SSTs) based latitude, is about 0.41° in longitude and 0.82° in latitude, in this region. The movement paths, derived from position estimates, for the 20 yellowfin indicated that 19 (95%) remained within 1,445 km of their release locations. The estimated mean velocity along movement paths was 77 km/day. The southern and northern seasonal movement paths observed for yellowfin off Baja California are influenced by the seasonal movements of the 18°C SST isotherm. Cyclical movements to and from suitable spawning habitat (≥24°C SST) was observed only for mature fish. For the 12 fish that demonstrated site fidelity, the mean 95 and 50% utilization distributions were 258,730 km² and 41,260 km², respectively. Evaluations of the timed depth records resulted in discrimination of four distinct behaviors. When exhibiting type-1 diving behavior (78.1% of all days at liberty) the fish remained at depths less than 50 m at night and did not dive to depths greater than about 100 m during the day. Type-2 diving behavior (21.2% of all days at liberty) was characterized by ten or more dives in excess of 150 m during the day. Type-2 diving behavior is apparently a foraging strategy for fish targeting prey organisms of the deep-scattering layer during the day, following nighttime foraging within the mixed layer on the same prey. Yellowfin tuna exhibited occasional deep-diving behavior, and some dives exceeded 1,000 m, where ambient temperatures were less than 5°C. Surface-oriented behavior, defined as the time fish remained at depths less than 10 m for more than 10 min, were evaluated. The mean number and duration of surface-oriented events per day for all fish was 14.3 and 28.5 min, respectively. Habitat utilization of yellowfin, presented as monthly composite horizontal and vertical distributions, indicates confined geographical distributions, apparently resulting from an affinity to an area of high prey availability. The vertical distributions indicate greater daytime depths in relation to a seasonally deeper mixed layer and a greater proportion of daytime at shallower depths in relation to a seasonally shallower mixed layer.     

Pilot-scale constructed wetlands for petroleum-contaminated groundwater.

A pilot study was conducted to determine the feasibility of using constructed treatment wetlands to remediate recovered groundwater from the subsurface of a former refinery site. The pilot system consisted of four subsurface flow treatment cells operated in an upward vertical flow mode and equipped with subsurface aeration lines. The treatment system showed minimal capability for methyl-tert-butyl ether removal, but did effectively remove total petroleum hydrocarbons-deisel range organics and total benzene, toluene, ethylbenzene, and o-, m-, and p-xylenes (total BTEX). Effluent benzene concentrations were less than 0.05 mg/L in 70% of the samples from a treatment cell using subsurface aeration and a wetland sod amendment. Based on 1 year of operating data, cumulative mass removal approached 80% for benzene and 88% for total BTEX.     

MODELING INFILTRATION WITH VARYING HYDRAULIC CONDUCTWITY UNDER SIMULATED RAINFALL CONDITIONS1

ABSTRACT: Physically-based models are extensively used to simulate the infiltration process under varied field conditions. Most models are based on the deterministic nature of input parameters related to the flow process (such as hydraulic conductivity). These models yield poor predictions of infiltration rates because they do not include the field-scale variations of flow parameters. The paper presents an approach for integrating the field-scale variability of hydraulic conductivity with an infiltration model to simulate infiltration under the rainfall conditions. A model describing the spatial structure of hydraulic conductivity has been developed using stochastic techniques. The stochastic structure of hydraulic conductivity was then incorporated in the Green-Ampt and Mein-Larson infiltration model. The model outputs on the instantaneous infiltration rates and cumulative infiltration were evaluated using the field infiltration data measured under simulated rainfall conditions. The results show that the combined model is capable of rep. resenting the instantaneous infiltration rates and cumulative infiltration of the study soils. The model may, therefore, be used to simulate the rainfall infiltration process for spatially-variable soils under the field conditions.     

Characterization and optimization of an online system for the simultaneous measurement of atmospheric water-soluble constituents in the gas and particle phases

In this work we present the results of extensive characterization and optimization of the Ambient Ion Monitor-Ion Chromatograph (AIM-IC) system, an instrument developed by URG Corp. and Dionex Inc. for simultaneous hourly measurements of the water-soluble chemical composition of atmospheric fine particulate matter (PM(2.5)) and associated precursor gases. The sampling assembly of the AIM-IC consists of an inertial particle size-selection assembly, a parallel-plate wet denuder (PPWD) for the collection of soluble gases, and a particle supersaturation chamber (PSSC) for collection of particles, in series. The analytical assembly of the AIM-IC consists of anion and cation IC units. The system detection limits were determined to be 41 ppt, 5 ppt, and 65 ppt for gas phase NH(3(g)), SO(2(g)), and HNO(3(g)) and 29 ng m(-3), 3 ng m(-3), and 45 ng m(-3) for particle phase NH(4)(+), SO(4)(2-), and NO(3)(-) respectively. From external trace gas calibrations with permeation sources, we determined that the AIM-IC is biased low for NH(3(g)) (11%), SO(2(g)) (19%), and HNO(3(g)) (12%). The collection efficiency of SO(2(g)) was found to strongly depend on the composition of the denuder solution and was found to be the most quantitative with 5 mM H(2)O(2) solution for mixing ratios as high as 107 ppb. Using a cellulose membrane in the PPWD, the system responded to changes in SO(2(g)) and HNO(3(g)) within an hour, however for NH(3(g)), the timescale can be closer to 20 h. With a nylon membrane, the instrument response time for NH(3(g)) was significantly improved, becoming comparable to the responses for SO(2(g)) and HNO(3(g)). Performance of the AIM-IC for collection and analysis of PM(2.5) was evaluated by generating known number concentrations of ammonium sulfate and ammonium nitrate particles (with an aerodynamic diameter of 300 nm) under laboratory conditions and by comparing AIM-IC measurements to measurements from a collocated Aerosol Mass Spectrometer (AMS) during a field-sampling campaign. On average, the AIM-IC and AMS measurements agreed well and captured rapid ambient concentration changes at the same time. In this work we also present a novel inlet configuration and plumbing for the AIM-IC which minimizes sampling inlet losses, reduces peak smearing due to sample carryover, and allows for tower-height sampling from the base of a research tower.     

A spectrophotometric method for detection of enzymatic degradation of thin polymer films

An assay method has been developed for monitoring the enzymatic degradation of thin films of translucent polymers. The method was based on the observation that when a solution-cast film of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was exposed to a solution of a depolymerase fromPseudomonas lemoignei, the surface of the film roughened and the film became visibly turbid. This increase in turbidity could be measured spectrophotometrically and was reproducible during the initial stage of degradation. Turbidity correlated very closely with film weight loss early in the degradation but reached a maximum value before extensive degradation had taken place. For a given set of films, this correlation was independent of the concentration of the enzyme used, although it did vary with the mode of enzyme exposure. The turbidity was associated with the exposure of crystalline domains due to the removal of amorphous material from the film surface. The increase in crystallinity at the surface was verified by attenuated total reflectance infrared spectroscopy (ATRIR). In conjunction with SEM, weight loss, and ATRIR, the film turbidity assay provided much semiquantitative insight into the mechanism of the enzymatic degradation reaction. This assay was used to study the enzymatic degradation of films of PHBV solution blended with cellulose acetate esters (CAE). The presence of only 25% of CAE of degree of substitution 2.9 severely hampered the enzymatic degradability of PHBV, a result which is consistent with the environmental degradation of these same samples exposed to activated sludge.     

Development and Application of Computer Simulation Tools for Ecological Risk Assessment

Based on a review of available models for ecological risk estimation, most are site-specific and their applications are limited. However, general models, which can be easily adapted to other sites, remain few, in addition, they are simple and associated with significant uncertainties. In this paper, an approach is introduced for an ecological risk assessment (ERA) model that can be modified for site-specific conditions. Using computer simulation as a screening tool for ecological risk assessment can assist environmental managers and policy decision-makers in the planning and implementation of potentially highly focused assessments and remediation, should the ERA dictate the need. The model was integrated with a Windows-based interface and interactive database management system (DBMS) as a user-friendly software package. In addition, based on trophic sources, a food web has been integrated into the framework of the DBMS. In an effort to evaluate the model, a case study was implemented to characterize the effects on an ecosystem of replacing electroplated chromium coatings with sputtered tantalum at U.S. Army Yuma and Aberdeen Proving Grounds. Potential exposure pathways included ingestion, inhalation, and dermal absorption for terrestrial animals; root and foliar uptake for plants; and direct absorption for aquatic species. Overall, results showed that the most significant exposure resulted from molybdenum and hexavalent chromium, which posed higher risks to select aquatic and terrestrial species at both sites. On the other hand, tantalum (with vanadium as the surrogate) resulted in the least risk to all receptors within the studied areas. A sensitivity analysis demonstrated that soil-water distribution coefficients have a significant impact on the results. Based on the results, neither molybdenum nor chromium are recommended as a coating in gun barrels, and further study would be essential to address any affected firing range area. Tantalum is recommended for use, although for those species receiving a slight adverse risk, field investigations that include receptor sampling maybe necessary once soil/sediment and water sampling validates projected concentrations.     

Characterization and enzymatic degradation of a cross-linked bacterial polyester

The bacterial polyester, poly(-hydroxybutyrate-co--hydroxyvalerate) (PHB/V), was cross-linked with 1, 5, 7, 10, 20, and 30 wt% benzoyl peroxide by thermal decomposition reactions. Solvent extractions were carried out to determine the cross-linked fractions of the films. The sol/gel data were used to estimate cross-link densities. Films of PHB/V cross-linked with 10% benzoyl peroxide were placed in contact with purified depolymerase A secreted byP. lemoignei. These samples exhibited weight loss rates which were half that of un-cross-linked PHB/V, but the network was degraded completely by the enzyme. The results of this study suggest that anendo-type enzymatic degradation may occur, in addition to theexo-type activity, which is normally presumed to occur with theP. lemoignei depolymerase system.     

Competitive interactions between two fucoid algae with different growth forms,<Emphasis Type="Italic"> Fucus serratus</Emphasis> and<Emphasis Type="Italic"> Himanthalia elongata</Emphasis>

Competitive interactions between two fucoid algae with different growth forms, Fucus serratus L. and Himanthalia elongata (L.) S.F. Gray were examined both in the laboratory and on a shore of the Isle of Man, Irish Sea. The growth of germlings of both species declined with increasing density, irrespective of whether they were with cohorts or rival species, indicating that intra- and interspecific competition occurred between germlings. H. elongata suppressed the performance of F. serratus at the germling stage by virtue of its larger initial size, and at the mushroom stage by forming a miniature canopy with the caps of the adjacent plants. In a field experiment, the mortality of H. elongata juveniles generally increased in mixtures with F. serratus and was highest when F. serratus were 50% of the plants. At the juvenile stage, the negative effect of F. serratus on H. elongata was more severe than the other way round. This was because F. serratus grows predominantly upwards, whereas H. elongata had already begun to expand laterally at the distal end. If F. serratus survives in sparse mixed stands with H. elongata juveniles, it can overgrow them and inhibit their subsequent survivorship and growth, probably by both shading and physical sweeping. H. elongata and F. serratus maintain their discrete monospecific stands because of the varying outcomes of mutual competitive exclusion resulting from their differing growth patterns. Thus it is possible for them to co-occur at a similar shore height.Communicated by O. Kinne, Oldendorf/Luhe     

Correlates of extra-pair fertilization success in hooded warblers

We examined correlates of extra-pair fertilization (EPF) success in the hooded warbler (Wilsonia citrina), a species where females pursue extra-pair matings. The good genes hypothesis predicts that females choose extra-pair mates with morphological or behavioral traits that reflect differences in male genetic quality. EPFs were common, as 35.3% (42/119) of broods contained extra-pair young (EPY) and 26.7% (95/356) of nestlings were the result of EPFs. There was a strong skew in male EPF success which increased the variance in annual male mating success 2–3 fold. However, male morphology did not predict EPF success, as extra-pair males were not older or larger than the males they cuckolded. Likewise, there were no significant correlations between the proportion of extra-pair young in a brood and male size or age. The good genes hypothesis predicts that high-quality males will be consistently preferred as genetic mates, but the number of young sired by a male with his social mate was not consistent from one year to the next. There was a significant negative correlation between female age and proportion of EPY produced, which could result if older females obtain higher-quality social mates. We found no strong evidence that females choose extra-pair mates for good genes, but females may use behavioral rather than morphological cues to assess relative male quality. Received: 31 May 1996 / Accepted after revision: 17 October 1996