High natural fusion rates in a botryllid ascidian

Many benthic colonial invertebrates have the ability to fuse and form chimeras with compatible colonies. Botryllid ascidians are model organisms for the study of the evolution of and molecular basis for allorecognition, and fusion rates have been determined for different populations and species by random sampling and fusion testing between individuals. However, natural fusion rates over time have not been documented. Nine settlement panels were deployed in Salem Harbor, Massachusetts, USA and Botrylloides violaceus settlement, growth, and fusion monitored from July to mid-August 2007. Seventy-three percent of the recruits observed fused with at least one other colony, while 4% neither fused nor were overgrown. Multifused colonies were not observed to grow faster than single colonies when growth was calculated as increase in size beyond the summation of fused entities; however, they were significantly larger. These results suggest that larvae settle in clumps of compatible individuals, and that large subtidal colonies may be the result of high numbers of fusions between compatible colonies.     

SIMULATED ANNEALING WITH MEMORY AND DIRECTIONAL SEARCH FOR GROUND WATER REMEDIATION DESIGN1

ABSTRACT: Review of recent literature indicates an emergence in the use of combinatorial methods such as simulated annealing in ground water management during the past nine to ten years. While previous studies demonstrated the feasibility of using these methods, a general finding was that computational processing requirements were inordinately high relative to gradient‐based methods. An enhanced annealing algorithm was developed and used to demonstrate the potential for greatly improving the computational efficiency of simulated annealing as an optimization method for ground water management applications. The algorithm incorporates “directional search” and “memory” capabilities. Selecting search directions based on better understanding of the current neighborhood of the configuration space was shown to improve algorithm performance. Also, “memory” concepts derived from the Tabu Search Method show particular promise for improving the rate and quality of convergence. Performance of the enhanced annealing method was evaluated and the resultant management method was demonstrated using an example from the literature.     

El Niño periods increase growth of juvenile white seabass (<Emphasis Type="Italic">Atractoscion nobilis</Emphasis>) in the Southern California Bight

Studies of the impact of El Niño periods on marine species have usually focused on negative, highly visible effects, e.g., decreasing growth rates or increasing mortality due to a decline in primary productivity in typically nutrient rich upwelling zones; but positive effects related to elevated water temperature are also known. This study examined how the growth rate of juvenile white seabass, Atractoscion nobilis, responded to changes in ocean temperature in an El Niño period (1997–1998) in the northern portion of the Southern California Bight, USA. Growth rates of juvenile white seabass during their first 4 years of life were estimated as the slopes of linear relationships between body mass and age (from otoliths) of 800 fish collected at 11 stations throughout the bight. Growth rates differed significantly among cohorts hatched in 1996–2001. Specifically, white seabass that hatched in 1996 and 1997 grew significantly faster than those that hatched in 1998, 1999, and 2001. These differences in growth rates of cohorts appeared to be driven by variation in sea-surface temperature (SST). Growth rates averaged over the first three or 4 years of life were significantly positively correlated to average daily SST during the first 1–4 years of life. Increased growth of juvenile white seabass during the warm El Niño period likely provided a number of benefits to this warm-temperate species. This study demonstrated that some species will benefit from these warm-water periods despite reduced system-wide primary production.     

Exploratory Analysis of the Winter Chemistry of Five Lakes on the North Slope of Alaska1

Abstract: Lakes are important water resources on the North Slope of Alaska. Freshwater is required for oilfield production as well as exploration, which occurs largely on ice roads and pads. Since most North Slope lakes are shallow, the quantity and quality of the water under ice at the end of winter are important environmental management issues. Currently, water‐use permits are a function of the presence of overwintering fish populations, and their sensitivity to low oxygen concentrations. Sampling of five North Slope lakes during the winter of 2004‐2005 shed some light on the winter chemistry of four lakes that were used as water supplies and one undisturbed lake. Field analysis was conducted for oxygen, conductivity, pH, and temperature throughout the lake depth, as well as ice thickness and water depth. Water samples were retrieved from the lakes and analyzed for Na, Ca, K, Mg, Fe, dissolved‐organic carbon, and alkalinity in the laboratory. Lake properties, rather than pumping, were the best predictors of oxygen depletion, with the highest dissolved‐oxygen levels maintained in the lake with the lowest concentration of constituents. Volume weighted mean dissolved‐oxygen concentrations ranged from 4 to 94% of saturation in March. Dissolved oxygen and specific conductance data suggested that the lakes began to refresh in May.     

Acute toxic hazard evaluations of glyphosate herbicide on terrestrial vertebrates of the oregon coast range

GOAL, SCOPE AND BACKGROUND: The degree to which dose responses of model organisms (lab rodents) can adequately predict dose responses of free-ranging wild mammals or amphibians is unknown, and the relative sensitivity of such species to body loading of a toxicant such as glyphosate is seldom reported. For relative effects of dosage, we compare sensitivity of nine wild vertebrate species to effects of high doses of glyphosate in Swiss-Webster laboratory mice both by gavage and by intraperitoneal injection. We also evaluate sublethal effects of herbicide exposure on behavior and reproductive success of one mammal and one amphibian species. METHODS: Comparisons of acute toxicity of glyphosate were made with intraperitoneal dosings of technical glyphosate isopropylamine salt to nine species of terrestrial vertebrates (five amphibians, four mammals) and compared with responses in Swiss-Webster laboratory mice. Animals collected from sites that had no recent herbicide application were allowed 7-14 days to equilibrate in captivity before treatment. RESULTS: Median lethal dose ranged from 800 to 1,340 mg kg(-1) in mammals, and 1,170 to >2,000 mg kg(-1) in amphibians, with Oregon vole being the most sensitive. White lab mice were in the middle of the mammalian range. Tailed frog, at >2,000 mg kg(-1) was the least sensitive. Calibration of IP sensitivity to oral administration by gavage indicated that roughly four times as much glyphosate must be administered to obtain a comparable estimate of lethality. Administration by gavage in highly concentrated solutions tended to cause physical injury, hence may prove less useful as a relative indicator of toxicity. When sublethal dosages were given to roughskin newts or chipmunks, mobility and use of cover appeared largely unaffected. DISCUSSION: Direct toxic effects of spraying glyphosate under normal forest management seem unlikely for the nine species examined. Nor could we detect significant indirect effects of exposure on behavior and use of cover features in two species. There may be effects on other aspects of the field biology of these animals, such as reproductive rates, which we did not investigate. Recent field data indicate that changes in habitat quality following herbicide application can result in high reproductive activity in species associated with the grasses and forbs that proliferate following field applications. CONCLUSIONS: When compared to field data on body burdens of wild mammals exposed after aerial application of glyphosate at maximum rates in forests, there seems to be a large margin of safety between dosages encountered and those causing either death or limitation of movement, foraging or shelter. RECOMMENDATIONS AND PERSPECTIVES: Margins of safety for small mammals and amphibians appear to be large under any probable exposure scenarios, however our results indicate high variability in responses among species. Uncertainty introduced into field studies from unknown sources of mortality (e.g, likely predation) must be considered when interpreting our results.     

Formaldehyde Dose-Response in Healthy Nonsmokers

Industrial, commercial, and domestic levels of formaldehyde exposure range from <0.1 to >5.0 ppm. Irritation of the eyes and upper respiratory tract predominate, and bronchoconstriction is described in case reports. However, pulmonary function and irritant symptoms together have not been assessed over a range of HCHO concentrations in a controlled environment. We investigated dose response in both symptoms and pulmonary function associated with 3-h exposures to 0.0-3.0 ppm HCHO in a controlled environmental chamber. Ten subjects were randomly exposed to 0.0, 0.5, 1.0, and 2.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise and nine additional subjects were randomly exposed to 0.0,1.0,2.0, and 3.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise. Significant dose-response relationships in odor and eye irritation were observed (p < 0.05). Nasal flow resistance was increased at 3.0 ppm (p < 0.01), but not at 2.0 ppm HCHO. There were no significant decrements in pulmonary function (FVC, FEV₁, FEF_25-75%, SGaw) or increases in bronchial reactivity to methacholine (log PD_35SGaw) with exposure to 0.5-3.0 ppm HCHO at rest or to 2.0 ppm HCHO with exercise.     

Evidence of degradation of polybrominated biphenyls in soil samples from michigan

Abstract

Soil samples obtained from the former polybrominated biphenyls (PBB) manufacturing site in Michigan were analyzed by gas chromatography and gas chromatography with mass spectrometric detection. The results indicate significant degradation of the PBB residue in the soil sample. The soil sample with the highest concentration of PBB has the greatest degree of degradation. Principal degradation products include 2,3’,4,4’,5‐pentabromo‐biphenyl, 2,2’,4,4’,5‐pencabromobiphenyl and two unidentified tetrabromobiphenyls.

The degradation pattern observed supports a photochemical decomposition mechanism. These degraded residues may be more toxic than the original Firemaster residues. The implications of the results are discussed.     

Application of an improved method for the analysis of pesticides and their metabolites in the urine of farmer applicators and their families

As the annual use of pesticides in the United States has escalated, public health agencies have become increasingly concerned about chronic pesticide exposure. However, without reliable, accurate analytical methods for biological monitoring, low-level chronic exposures are often difficult to assess. A method for measuring simultaneously the urinary residues of as many as 20 pesticides has been significantly improved. The method uses a sample preparation which includes enzyme digestion, extraction, and chemical derivatization of the analytes. The derivatized analytes are measured by using gas chromatography coupled with isotope-dilution tandem mass spectrometry. The limits of detection of the modified method are in the high pg/L - low μg/L range, and the average coefficient of variation (CV) of the method was below 20% for most analytes, with approximately 100% accuracy in quantification. This method was used to measure the internal doses of pesticides among selected farmer applicators and their families. Definite exposure and elimination patterns (i.e., an increase in urinary analyte levels following application and then a gradual decrease to background levels) were observed among the farmer applicators and many of the family members whose crops were treated with carbaryl, dicamba, and 2,4-D esters and amines. Although the spouses of farm workers sometimes exhibited the same elimination pattern, the levels of the targeted pesticides or metabolites found in their urine were not outside the ranges found in the general U.S. population (reference range). The farmer applicators who applied the pesticides and some of their children appeared to have higher pesticide or metabolite levels in their urine than those found in the general U.S. population, but their levels were generally comparable to or lower than reported levels in other occupationally exposed individuals. These results, however, were obtained from a nonrandom sampling of farm residents specifically targeted to particular exposures who may have altered their practices because they were being observed; therefore, further study is required to determine if these results are representative of pesticide levels among residents on all farms where these pesticides are applied using the same application techniques. Using this method to measure exposure in a small nonrandom farm population allowed differentiation between overt and background exposure. In addition, the important role of reference-range information in distinguishing between various levels of environmental exposure was reaffirmed.     

Arthropod community organization and development in pear

Arthropod communities in pear are conceptualized as hierarchically organized systems in which several levels of organization or subsystems can be recognized between the population level and the community as a whole. An individual pear tree is taken to be the community habitat with arthropod subcommunities developing on leaf, fruit, and wood subcommunity habitats. Each subcommunity is composed of trophically organized systems of populations. Each system of populations is comprised of a functional group or guild of phytophagous arthropods that use the habitat primarily for feeding but also for overwintering or egg deposition, and associated groups of specialized predators, parasitoids, and hyperparasitoids. Several species move from one subcommunity to another during the course of community development and thus integrate community subsystems. Community development or change in organization through time is conceptualized as being jointly determined by the development of the habitat and the organization of the species pool. The influence of habitat development on community development within a species pool is emphasized in this research. Seasonal habitat development is expressed as change in the kinds and biomasses of developmental states of wood, leaf, and fruit subcommunity habitats. These changes are accompanied by changes in the kinds, biomasses, and distributions of associated community subsystems.