Molecular structure and biodegradation kinetics of linear alkylbenzene sulphonates in sea water

The present paper describes the results of the application of the biodegradation test proposed by the United States Environmental Protection Agency (USEPA) “Biodegradability in sea water” Office of Prevention, Pesticides, and Toxic Substances (OPPTS) 835.3160, to Linear Alkylbenzene Sulphonate (LAS), the synthetic surfactant with the highest consumption volume on a world-wide basis. High performance liquid chromatography (HPLC) has been employed for the separation and quantification of the different homologues and isomers of the surfactant. Water from the Bay of Cádiz (South–West of the Iberian peninsula) has been used as test medium. The results indicate how both lag and t ₅₀ time shows a significant linear relationship with the length of the alkyl chain of the homologue; the effect of this is that the homologues of longer chain length not only begin to degrade first but also degrade at a faster rate. Regarding the isomeric composition, it is observed that as the percentage of biodegradation increases, there is an increase in the proportion of internal isomers, in comparison with the isomeric relationships of the original test substance     

Mineralization of Surfactants by the Microbiota of Submerged Plant Detritus

In wetlands and canopied bodies of water, plant detritus is an important source of carbon and energy. Detrital materials possess a large surface area for sorption of dissolved organics and are colonized by a large and diverse microbiota. To examine the biodegradation of surfactants by these microorganisms, submerged oak leaves were obtained from a laundromat wastewater pond, its overflow, and a pristine control pond. Leaves were cut into disks and incubated in sterile water amended with 50 μg of ¹⁴C-labeled linear alkylbenzene sulfonate (LAS), linear alcohol ethoxylate, stearyltrimethyl ammonium chloride, distearyldimethyl ammonium chloride, benzoic acid, or mixed amino acids per liter. Sorption of the test compounds to the detritus and evolution of ¹⁴CO₂ were followed with time. All of the compounds sorbed to the detritus to various degrees, with LAS and stearyltrimethyl ammonium chloride the most sorptive and benzoic acid the least. All compounds were mineralized without a lag. With leaves from the laundromat wastewater pond, half-lives were 12.6 days for LAS, 8.4 days for linear alcohol ethoxylate, 14.2 days for stearyltrimethyl ammonium chloride, 1.0 days for benzoic acid, and 2.7 days for mixed amino acids. Mineralization of LAS and linear alcohol ethoxylate by control pond leaves was slower and exhibited an S-shaped rather than a typical first-order pattern. This study shows that detritus represents a significant site of surfactant removal in detritus-rich systems.     

Fish Gill Respiratory Cells in Culture: A New Model for Cl−-secreting Epithelia

Primary cultures of sea bass gill cells grown on permeable membranes form a confluent, polarized, functional tight epithelium as characterized by electron microscopy and electrophysiological and ion transport studies. Cultured with normal fetal bovine serum (FBS) and mounted in an Ussing chamber, the epithelium presents a small short-circuit current (I _sc : 1.4 ± 0.3 μA/cm²), a transepithelial voltage (V _t ) of 12.7 ± 2.7 mV (serosal positive) and a high transepithelial resistance (R _t : 12302 ± 2477 Ω× cm²). A higher degree of differentiation and increased ion transport capacities are observed with cells cultured with sea bass serum: numerous, organized microridges characteristic of respiratory cells are present on the apical cell surface and there are increased I _sc (11.9 ± 2.5 μA/cm²) and V _t (25.9 ± 1.7 mV) and reduced R _t (4271 ± 568 Ω× cm²) as compared with FBS-treated cells. Apical amiloride addition (up to 100 μm) had no effect on I _sc . The I _sc , correlated with an active Cl⁻ secretion measured as the difference between ³⁶Cl⁻ unidirectional fluxes, was partly blocked by serosal ouabain, bumetanide, DIDS or apical DPC or NPPB and stimulated by serosal dB-cAMP. It is concluded that the chloride secretion is mediated by a Na⁺/K⁺/2Cl⁻ cotransport and a Cl⁻/HCO₃ ⁻ exchanger both responsible for Cl⁻ entry through the basolateral membrane and by apical cAMP-sensitive Cl⁻ channels. This study gives evidence of a functional, highly differentiated epithelium in cultures composed of fish gill respiratorylike cells, which could provide a useful preparation for studies on ion transport and their regulation. Furthermore, the chloride secretion through these cultures of respiratorylike cells makes it necessary to reconsider the previously accepted sea water model in which the chloride cells are given the unique role of ion transport through fish gills. Received: 12 July 1996/Revised: 5 November 1996     

Biodegradation kinetics of LAS in river water

This article reports the biodegradation kinetics of linear alkylbenzene sulfonates (LAS) in river water. The authors used the ‘river die-away' test method and high performance liquid chromatography to monitor LAS concentrations as functions of time in a series of tests systems. Controlled variables included initial LAS concentrations and incubation temperature. The kinetic parameters computed from the experimental data demonstrated strong correlations (r²>0.99) with theoretical values computed from the kinetic model presented in this paper. The proposed model accurately predicts concentrations of non-biodegradable substrate and the maximum specific microbial growth rate.     

Biodegradation of nonionic and anionic surfactants in domestic wastewater under simulated sewer conditions

The ultimate disposition of chemicals discarded down the drain can be substantially impacted by their fate in the sewer, but to date limited data have been published on the biodegradability of chemicals in sewer systems. The recently established OECD 314 guideline (Simulation tests to assess the biodegradability of chemicals discharged in wastewater, 2008) contains a simulation method (314A) for evaluating the biodegradation of chemicals in sewage under simulated sewer conditions. This research used the OECD 314A method to evaluate the rates and pathways of primary and ultimate biodegradation of a suite of ¹⁴C-labeled homologues representing four classes of high volume surfactants including nonionic alkyl ethoxylates (AE), and anionic alkyl ethoxysulfates (AES), alkyl sulfate (AS) and linear alkyl benzene sulfonate (LAS). All the tested homologues exhibited >97 % loss of parent, formation of metabolites, and some level (16–94 %) of CO₂ production after being incubated 96–100 h in raw domestic wastewater. Comparison of C₁₂E₃, C₁₄E₃, and C₁₆E₃ showed that the first order biodegradation rate was affected by alkyl chain length with rates ranging from 6.8 h^?1 for C₁₂E₃ to 0.49 h^?1 for C₁₆E₃. Conversely, comparison of C₁₄E₁, C₁₄E₃, and C₁₄E₉ showed that the number of ethoxy units did not impact the biodegradation rate. AES and AS degraded quickly with first order kinetic rates of 1.9–3.7 and 41 h^?1 respectively. LAS did not exhibit first order decay kinetics and primary degradation was slow. Biodegradation pathways were also determined. This work shows that biodegradation in the sewer has a substantial impact on levels of surfactants and surfactant metabolites that ultimately reach wastewater treatment plants.     

Fate of the Benzene Ring of Linear Alkylbenzene Sulfonate in Natural Waters

The biodegradability of linear alkylbenzene sulfonate (LAS) was studied in water samples collected from a receiving stream at locations above and below the discharge of a municipal wastewater treatment plant. Rates of primary biodegradation were determined for a commercial LAS mixture by a modified methylene blue-active substance method. Rates of LAS ultimate degradation were determined by radiochemical methods, using a C₁₂ LAS homolog uniformly labeled with ¹⁴C in the benzene ring. The C₁₂ LAS was tested at low concentrations (50 and 500 μg/liter) comparable to those existing in the receiving stream. Loss of methylene blue-active substance response over time occurred rapidly in water samples containing sediment collected from below the treatment plant, with an estimated half-life for LAS of 0.23 days. Evolution of ¹⁴CO₂ during mineralization of the benzene ring occurred rapidly in the same samples, with a half-life for the benzene ring of 0.73 day. Mineralization of the benezene ring was also observed in river water containing no sediments and in river water and sediment samples collected from above the treatment plant. However, the rate of degradation was reduced in these cases, with half-lives for ring carbon ranging from 1.4 to 14 days. Although LAS degradation was enhanced in the presence of sediments, adsorption of LAS to the clay-silt fraction of river sediments was low, and most of the radioactivity was bound to biomass.     

Inhibition of Biogas Production by Alkyl Benzene Sulfonates (LAS) in a Screening Test for Anaerobic Biodegradability

The effect of the inoculum source on the digestion of linear alkylbenzene sulfonates (LAS) under anaerobic conditions has been investigated. The potential for primary and ultimate LAS biodegradation of anaerobic sludge samples obtained from wastewater treatment plants (WWTPs) of different geographical locations was studied applying a batch test system. It was found that only 4–22% of the LAS added to the batch anaerobic digesters was primarily transformed suggesting a poor primary degradation of the LAS molecule in anaerobic discontinuous systems. Regarding ultimate biodegradation, the addition of LAS to the batch anaerobic digesters caused a reduction on the extent of biogas production. Significant differences in the inhibition extent of the biogas production were observed (4–26%) depending on the sludge used as inoculum. Effect of the surfactant on the anaerobic microorganisms was correlated with its concentration in the aqueous phase. Sorption of LAS on anaerobic sludge affects its toxicity by depletion of the available fraction of the surfactant. LAS content on sludge was related to the total amount of calcium and magnesium extractable ions. The presence of divalent cations promote the association of LAS with anaerobic sludge reducing its bioavailability and the extent of its inhibitory effect on the biogas production.     

Fecundity,reproductive rate,longevity, and intrinsic rate of increase of an aphidiid parasitoidLysiphlebia mirzai

A life-table was constructed for a little known aphidiid waspLysiphlebia mirzai, a parasitoid of cereal aphid,Rhopalosiphum maidis. The female parasitoid survived 6.4 ± 1.17 (SD) days and oviposited intensively 4.0 ± 0.47 days. The total fecundity rate, R_t, was 169.2 ± 6.94 mummies/female and net reproductive rate, R_o, was 92.70 female offspring/female. The intrinsic total fecundity rate, r_t, and intrinsic rate of natural increase, r_m, the finite rate of total fecundity, λ^t, and finite rate of increase, λ^m, was 0.27048, 0.24155, 1.31059 and 1.27322 respectively. The mean generation time (18.75 days) and doubling time of the population (2.87 days) was slightly higher than other aphidiids studied so far. The proportion of female progenies decreased significantly on the successive oviposition days.      

Microcalorimetry as a diagnostic and analytical tool for the assessment of biodegradation of 2,4-D in a liquid medium and in soil

The biodegradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) byPseudomonas cepacia was assessed by microcalorimetry in a liquid medium and in sterilized soil at 25°C under aerobic conditions. It was found that thermograms of the rate of heat evolved versus time (dQ/dt versust) can be used as a diagnostic tool to identify the timet ₁ required for the primary biodegradation of 2,4-D and the timet _f required for the completion of the biodegradation activity in a liquid medium as well as in soil. Microcalorimetry can also be used as an analytical tool to monitor the progress of 2,4-D consumption during the biodegradation process in a liquid medium and to measure the importance of the soil sorption/desorption of intermediate metabolites. A new concept called bioeffort was defined as the product of the biodegradation time (t) and the biomass concentration (X) at that time. This concept was used to predict either the biomass concentration required or the duration of the primary biodegradation of 2,4-D in soil from the data obtained from a liquid medium.     

Gallium uptake by transferrin and interaction with receptor 1

The kinetics and thermodynamics of Ga(III) exchange between gallium mononitrilotriacetate and human serum transferrin as well as those of the interaction between gallium-loaded transferrin and the transferrin receptor 1 were investigated in neutral media. Gallium is exchanged between the chelate and the C-site of human serum apotransferrin in interaction with bicarbonate in about 50 s to yield an intermediate complex with an equilibrium constant K ₁ = (3.9 ± 1.2) × 10⁻², a direct second-order rate constant k ₁ = 425 ± 50 M⁻¹ s⁻¹ and a reverse second-order rate constant k ₋₁ = (1.1 ± 3) × 10⁴ M⁻¹ s⁻¹. The intermediate complex loses a single proton with proton dissociation constant K _1a = 80 ± 40 nM to yield a first kinetic product. This product then undergoes a modification in its conformation which lasts about 500 s to produce a second kinetic intermediate, which in turn undergoes a final extremely slow (several hours) modification in its conformation to yield the gallium-saturated transferrin in its final state. The mechanism of gallium uptake differs from that of iron and does not involve the same transitions in conformation reported during iron uptake. The interaction of gallium-loaded transferrin with the transferrin receptor occurs in a single very fast kinetic step with a dissociation constant K _d = 1.10 ± 0.12 μM and a second-order rate constant k _d = (1.15 ± 0.3) × 10¹⁰ M⁻¹ s⁻¹. This mechanism is different from that observed with the ferric holotransferrin and suggests that the interaction between the receptor and gallium-loaded transferrin probably takes place on the helical domain of the receptor which is specific for the C-site of transferrin and HFE. The relevance of gallium incorporation by the transferrin receptor-mediated iron-acquisition pathway is discussed.     

Effect of mutation on helper T-cells and viral population: A computer simulation model for HIV

Summary A Monte Carlo simulation is proposed to study the dynamics of helper T-cells (N _H) and viral (N _V) populations in an immune response model relevant to HIV. Cellular states are binary variables and the interactions are described by logical expressions. Viral population shows a nonmonotonic growth before reaching a constant value while helper T-cells grow to a constant after a relaxation/reaction time. Initially, the population of helper cells grows with time with a power-law, N _H ∼t ^β, before reaching the steady-state; the growth exponent β increases systematically (β ≈ 1 – 2) with the mutation rate (P _mut≈0.1–0.4). The critical recovery time (t _c) increases exponentially with the viral mutation, t _c≈Ae ^αP _mut , with α=4.52±0.29 in low mutation regime and α=15.21±1.41 in high mutation regime. The equilibrium population of helper T-cell declines slowly with P _mut and collapses at ∼ 0.40; the viral population exhibits a reverse trend, i.e., a slow increase before the burst around the same mutation regime.     

Mineralization of Surfactants by Microbiota of Aquatic Plants

The biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) by the microbiota associated with duckweed (Lemna minor) and the roots of cattail (Typha latifolia) was investigated. Plants were obtained from a pristine pond and a pond receiving wastewater from a rural laundromat. Cattail roots and duckweed plants were incubated in vessels containing sterile water amended with [¹⁴C]LAS, [¹⁴C]LAE, or ¹⁴C-labeled mixed amino acids (MAA). Evolution of ¹⁴CO₂ was determined over time. The microbiota of cattail roots from both ponds mineralized LAS, LAE, and MAA without lag periods, and the rates and extents of mineralization were not significantly affected by the source of the plants. Mineralization of LAS and LAE was more rapid in the rhizosphere than in nearby root-free sediments, which exhibited differences as a function of pond. The microbiota of duckweed readily mineralized LAE and MAA but not LAS. The rate and extent of mineralization were not affected by the source of the duckweed.     

Degradation and mineralization of petroleum by two bacteria isolated from coastal waters

Within the framework of a study on the oil biodegradation potential of the sea the ability of a Flavobacterium sp. and Brevibacterium sp. to metabolize a paraffinic crude oil and a chemically defined hydrocarbon mixture was investigated. Major components of the crude oil were identified by combination gas chromatography and mass spectrometry. The rate and extent of total hydrocarbon biodegradation was measured. In addition, CO₂ evolution from the crude oil was continuously monitored in a shaker-mounted gas train arrangement. Degradation started after a 2 to 4 day lag period, and reached its maximum within two weeks. At this time up to 60% of the crude oil and 75% of the model hydrocarbon mixture, each added at the level of 1 ml per 100 ml artificial sea water, were degraded. Mineralization(conversion to CO₂) was slightly lower due to formation of products and bacterial cell material. n-Paraffins were preferentially degraded as compared to branched chain hydrocarbons. Biodegradation of n-paraffins in the range of C₁₂ to C₂₀ was simultaneous; no diauxie effects were observed.     

Flow-Dependent Activation of Maxi K+ Channels in Apical Membrane of Rabbit Connecting Tubule

The Ca²⁺-activated maxi K⁺ channel was found in the apical membrane of everted rabbit connecting tubule (CNT) with a patch-clamp technique. The mean number of open channels (NP _o ) was markedly increased from 0.007 ± 0.004 to 0.189 ± 0.039 (n= 7) by stretching the patch membrane in a cell-attached configuration. This activation was suggested to be coupled with the stretch-activation of Ca²⁺-permeable cation channels, because the maxi K⁺ channel was not stretch-activated in both the cell-attached configuration using Ca²⁺-free pipette and in the inside-out one in the presence of 10 mm EGTA in the cytoplasmic side. The maxi K⁺ channel was completely blocked by extracellular 1 μm charybdotoxin (CTX), but was not by cytoplasmic 33 μm arachidonic acid (AA). On the other hand, the low-conductance K⁺ channel, which was also found in the same membrane, was completely inhibited by 11 μm AA, but not by 1 μm CTX. The apical K⁺ conductance in the CNT was estimated by the deflection of transepithelial voltage (ΔV _t ) when luminal K⁺ concentration was increased from 5 to 15 mEq. When the tubule was perfused with hydraulic pressure of 0.5 KPa, the ΔV _t was only −0.7 ± 0.4 mV. However, an increase in luminal fluid flow by increasing perfusion pressure to 1.5 KPa markedly enhanced ΔV _t to −9.4 ± 0.9 mV. Luminal application of 1 μm CTX reduced the ΔV _t to −1.3 ± 0.6 mV significantly in 6 tubules, whereas no significant change of ΔV _t was recorded by applying 33 μm AA into the lumen of 5 tubules (ΔV _t =−7.2 ± 0.5 mV in control vs.ΔV _t =−6.7 ± 0.6 mV in AA). These results suggest that the Ca²⁺-activated maxi K⁺ channel is responsible for flow-dependent K⁺ secretion by coupling with the stretch-activated Ca²⁺-permeable cation channel in the rabbit CNT. Received: 21 August 1997/Revised: 20 March 1998     

Use of Rice Husk as Bulking Agent in Bioremediation of Automobile Gas Oil Impinged Agricultural Soil

Evaluation of rice husk (RH) as bulking agent in bioremediation of automobile gas oil (AGO) hydrocarbon polluted agricultural soil using renewal by enhanced natural attenuation (RENA) as control was the subject of the present investigation. The effect of different parameters such as total petroleum hydrocarbon (TPH), dehydrogenase activity (DHA), optical density and pH on bioremediation performance were evaluated. The studied parameters such as microbial dynamics, percentage degradation and DHA were found to be higher in RH-amended system and differed significantly with control at P < 0.05. RH resulted in high removal efficiency of 97.85 ± 0.93% under a two-month incubation period, while RENA had lesser removal efficiency of 53.15 ± 3.81%. Overall hydrocarbon biodegradation proceeded very slowly in the RENA particularly from week 0 to 4. Experimental data perfectly fitted into the first-order kinetic and generated high r² values (0.945), first-order degradation constant (0.47 day^?1), and shorter degradation half-life (1.50 d)—t_1/2 = Ln2/K and Ln2 numerically equals to 0.693 and hence written as 0.693/K. Micrococcus luteus and Rhizopus arrhizus were isolated in the present study, which displayed extreme AGO hydrocarbon biodegradative abilities. The use of RH in hydrocarbon-polluted soil significantly increased biodegradation rate and resulted in effective AGO cleanup within 2 months period. Therefore, RH provides an alternative source of bioremediation material in field application for abundant petroleum hydrocarbon soil pollution.     

Population Dynamics of Spotted Owls in the Sierra Nevada,California

ABSTRACT The California spotted owl (Strix occidentalis occidentalis) is the only spotted owl subspecies not listed as threatened or endangered under the United States Endangered Species Act despite petitions to list it as threatened. We conducted a meta-analysis of population data for 4 populations in the southem Cascades and Sierra Nevada, California, USA, from 1990 to 2005 to assist a listing evaluation by the United States Fish and Wildlife Service. Our study areas (from N to S) were on the Lassen National Forest (LAS), Eldorado National Forest (ELD), Sierra National Forest (SIE), and Sequoia and Kings Canyon National Parks (SKC). These study areas represented a broad spectrum of habitat and management conditions in these mountain ranges. We estimated apparent survival probability, reproductive output, and rate of population change for spotted owls on individual study areas and for all study areas combined (meta-analysis) using model selection or model-averaging based on maximum-likelihood estimation. We followed a formal protocol to conduct this analysis that was similar to other spotted owl meta-analyses. Consistency of field and analytical methods among our studies reduced confounding methodological effects when evaluating results. We used 991 marked spotted owls in the analysis of apparent survival. Apparent survival probability was higher for adult than for subadult owls. There was little difference in apparent survival between male and female owls. Model-averaged mean estimates of apparent survival probability of adult owls varied from 0.811 ± 0.021 for females at LAS to 0.890 ± 0.016 for males at SKC. Apparent survival increased over time for owls of all age classes at LAS and SIE, for adults at ELD, and for second-year subadults and adults at SKC. The meta-analysis of apparent survival, which included only adult owls, confirmed an increasing trend in survival over time. Survival rates were higher for owls on SKC than on the other study areas. We analyzed data from 1,865 observations of reproductive outcomes for female spotted owls. The proportion of subadult females among all territorial females of known age ranged from 0.00 to 0.25 among study areas and years. The proportion of subadults among female spotted owls was negatively related to reproductive output (no. of young fledged/territorial F owl) for ELD and SIE. Eldorado study area and LAS showed an alternate-year trend in reproductive output, with higher output in even-numbered years. Mean annual reproductive output was 0.988 ± 0.154 for ELD, 0.624 ± 0.140 for LAS, 0.478 ± 0.106 for SIE, and 0.555 ± 0.110 for SKC. Eldorado Study Area exhibited a declining trend and the greatest variation in reproductive output over time, whereas SIE and SKC, which had the lowest reproductive output, had the lowest temporal variation. Meta-analysis confirmed that reproductive output varied among study areas. Reproductive output was highest for adults, followed by second-year subadults, and then by first-year subadults. We used 842 marked subadult and adult owls to estimate population rate of change. Modeling indicated that Λ _t (Λ _t is the finite rate of population change estimated using the reparameterized Jolly–Seber estimator [Pradel 1996]) was either stationary (LAS and SIE) or increasing after an initial decrease (ELD and SKC). Mean estimated Λ _t for the 4 study areas was 1.007 (95% CI = 0.952–1.066) for ELD; 0.973 (95% CI = 0.946–1.001) for LAS; 0.992 (95% CI = 0.966–1.018) for SIE; and 1.006 (95% CI = 0.947–1.068) for SKC. The best meta-analysis model of population trend indicated that Λ varied across time but was similar in trend among the study areas. Our estimates of realized population change (Δ _t ; Franklin et al. 2004), which we estimated as the product 1 λ₃, were based on estimates of Λ _t from individual study areas and did not require estimating annual population size for each study area. Trends represented the proportion of the population size in the first year that remained in each subsequent year. Similar to λ₄ on which they were based, these λ_k-1 showed evidence of decline over the study period for LAS and SIE. The best model indicated recruitment of male and female adult and subadults varied from 0.10 to 0.31 new territorial individuals at time t/number of territorial individuals at time t–1 and similarly among areas. We also conducted a population viability analysis (PVA) based on results of our meta-analysis. This PVA was of limited utility for ELD and SKC study areas because 95% confidence intervals on the probability of decline or increase spanned the interval [0, 1] within 5–10 years. When we restricted inferences to 7 years, estimated probability of a >10% decline for SIE was 0.41 (95% CI = 0.09–0.78); for LAS the probability was 0.64 (95% CI = 0.27–0.94). In contrast, estimated probability of a >10% increase in 7 years for SIE was 0.23 (95% CI = 0.01–0.55) and for LAS was 0.10 (95% CI = 0.00–0.34). For comparisons, we simulated a PVA for a hypothetical population with mean Λ = 1.0 and the same temporal variation as observed in our owl populations. Our PVA suggested that both the SIE and LAS populations had higher probabilities of declining in a 7-year period than increasing but that it would be difficult to determine if a population was in a slight gradual decline. Our analysis and the repository of information on our 4 study populations provide a data-rich template for managers to monitor impacts of future management actions on the owl. Specifically, our data can be used to evaluate the effect of management strategies on spotted owls that are being implemented by the United States Forest Service to reduce the risk of wildfire in the Sierra Nevada ecosystem. Our information also provides baseline information for evaluating the status of the owl for potential listing as a threatened species by the United States Fish and Wildlife Service. RESUMEN El búho californiano manchado (Strix occidentalis occidentalis) es la única subespecie de búhos manchados que no está listada como amenazada o en peligro de extinción en el Acta de E.E.U.U. para las Especies en Peligro de Extinción a pesar de las peticiones para que sea incluida en la lista como una especie amenazada. Nosotros realizamos un meta-análisis de los datos de la población de 4 poblaciones del sur de Cascades y de la Sierra Nevada, California desde 1990 hasta 2005 como ayuda a una evaluación de listado hecha por el U.S Fish and Wildlife Service. Nuestras áreas de estudio (de norte a sur) estuvieron localizadas en el Bosque Nacional Lassen (LAS), en el Bosque Nacional Eldorado (ELD), en el Bosque Nacional Sierra (SIE) y en los Parques Nacionales Sequoia y Kings Canyon (SKC). Estas áreas de estudio representaron un amplio espectro del hábitat y de las condiciones de manejo en estas cadenas de montañas. Nosotros calculamos la probabilidad de supervivencia aparente, el volumen de reproducción y el cambio en la tasa de población de los búhos manchados en áreas de estudio individuales y para todas las áreas de estudio combinadas (meta-análisis) utilizando selección de modelos o promediando modelos basados en la estimación de máxima probabilidad. Seguimos un protocolo formal para realizar este análisis que fuera similar a otros meta-análisis con búhos manchados. La consistencia del campo y los métodos analíiticos en nuestros estudios redujeron la confusión de efectos metodológicos al evaluar los resultados. Utilizamos 991 búhos manchados marcados en el análisis de supervivencia aparente. La probabilidad de supervivencia aparente fue más alta para búhos adultos que para subadultos. Hubo poca diferencia en la supervivencia aparente entre hembras y machos. Para los modelos promediados, los cálculos de la media de la probabilidad de supervivencia aparente para búhos adultos tuvo una variación de 0.811 ± 0.021 para hembras en LAS a 0.890 ± 0.016 para machos en SKA. La supervivencia aparente aumentó con el tiempo para los búhos de todos los grupos de edad en LAS y SIE, para adultos en ELD, y para subadultos del segundo año y para adultos en SKC. El meta-análisis de supervivencia aparente, que incluyó únicamente a búhos adultos, confirmó una tendencia al aumento en la supervivencia con el tiempo. Las tasas de supervivencia fueron más altas para los búhos en SKC que en las otras áreas de estudio. Analizamos información de 1.865 observaciones de resultados de reproducciones para búhos manchados hembra. La proporción de hembras subadultas entre todas las hembras territoriales de edad conocida fluctuó de 0.00 a 0.25 a través de las áreas de estudio y de los años. La proporción de subadultos entre los búhos manchados hembra estuvo relacionada negativamente con el volumen de reproducción (número de pichones emplumados por búho hembra territorial) para ELD y SIE. ELD y LAS mostraron una tendencia anual alternada en el volumen de reproducción, con un volumen mayor en los años pares. La media del volumen de reproducción anual fue 0.988 ± 0.154 para ELD, 0.624 ± 0.140 para LAS, 0.478 ± 0.106 para SIE y 0.555 ± 0.154 para SKC. ELD exhibió una tendencia a disminuir y la variación más alta en el volumen de reproducción a través del tiempo; mientras que SIE y SKC, que tuvieron el más bajo volumen de reproducción, tuvieron la menor variación temporal. El meta-análisis confirmó que el volumen de reproducción varió entre las áreas de estudio. El volumen de reproducción fue más alto para adultos, seguido por subadultos del segundo año, y luego por subadultos del primer año. Nosotros utilizamos 842 búhos marcados, adultos y subadultos, para calcular el índice de cambio de la población. La selección de modelos indicó que Λ _t era, o relativamente fija (LAS y SIE) o aumentaba después de una disminución inicial (ELD y SKC). La media calculada Λ _t para las cuatro áreas de estudio fue: 1.007 (95% CI = 0.952–1.066) para ELD; 0.973 (95% CI = 0.946–1.001) para LAS; 0.992 (95% CI = 0.966–1.018) para SIE; y 1.006 (95% CI = 0.947–1.068) para SKC. El mejor modelo de meta-análisis de la tendencia de población indicó que Λ variaba con el tiempo pero que era una tendencia similar entre las áreas de estudio. Nuestros cálculos sobre el cambio de población realizado (Δ _t ) se basaron en los cálculos de Λ _t de las áreas de estudio individuales y no requirieron calcular el tamaño de la población anual para cada área de estudio. Las tendencias representaron la proporción del tamaño de la población en el primer año que permaneció en cada año subsiguiente. De manera similar a λ_t, en la que se basaron, éstas Δ_t mostraron evidencia de disminución durante el período de estudio para LAS y SIE. El mejor modelo de reclutamiento indicado, el reclutamiento de búhos machos y hembras, adultos y subadultos, varió de 0.10 a 0.31 individuos territoriales nuevos al tiempo t por el número de individuos territoriales al tiempo t–1 y de manera similar entre las otras áreas. También realizamos un análisis de viabilidad de población (PVA) basado en los resultados de nuestro meta-análisis. Este análisis PVA fue de limitada utilidad para las áreas de estudio ELD y SKC porque el 95% de intervalos de confiabilidad en la probabilidad de disminución o aumento extendió el intervalo [0, 1] de 5–10 años. Cuando restringimos las inferencias a 7 años, la probabilidad estimada de a >10% de disminución para SIE fue 0.41 (95% CI = 0.09–0.78); para LAS la probabilidad fue 0.64 (95% CI = 0.27–0.94). En contraste, la probabilidad estimada de un >10% de aumento en 7 años para SIE fue 0.23 (95% CI = 0.01–0.55) y para LAS fue 0.10 (95% CI = 0.00–0.34). Para comparar, simulamos un PVA para una población hipotética con una media Λ = 1.0, y con la misma variación temporal observada en nuestras poblaciones de búhos. Nuestro PVA sugirió que ambas poblaciones SIE y LAS tenían, en un período de 7 años, mayores probabilidades de disminución que de aumento, pero que sería muy difícil determinar si alguna de las poblaciones estaba en una ligera disminución gradual. El depósito de información de nuestras 4 áreas de estudio provee una plantilla rica en información para que los administradores monitoreen los impactos de acciones futuras en el manejo de los búhos (por ejemplo, nuevas estrategias de manejo del Plan de Sierra Nevada Forest). También provee evidencia importante para evaluar el estatus del búho para su potencial inclusión en el listado de especies amenazadas. RÉSUMÉ Le hibou tacheté californien (Strix occidentalis occidentalis) est la seule sous-espèce de hibou tacheté ne figurant pas sur la liste des animaux menacés ou vulnérables sous la Loi des Espèces en Danger des Etats-Unis malgré des pétitions pour l'inscrire sur cette liste en tant que sous-espèce menacée. Nous avons effectué une méta-analyse des données de population pour 4 populations dans le sud des Cascades et dans la Sierra Nevada, en Californie de 1990 à 2005 pour aider une évaluation de leur statut établie par les Services des Eaux et Forêts des Etats-Unis. Nos aires d'étude (du nord au sud) étaient dans la forêt nationale Lassen (LAS), la forêt nationale Eldorado (ELD), la forêt nationale Sierra (SIE), et les parcs nationaux Sequoia et Kings Canyon (SKC). Ces aires d'étude représentaient un large échantillon des conditions de l'habitat et de la gestion dans ces chaînes de montagnes. Nous avons estimé la probabilité de survie apparente, le succès de reproduction, et le taux de changement de la population pour les hiboux tachetés dans chaque aire d'étude individuelle et dans toutes les aires réunies (méta–analyse) en utilisant la sélection de modèles ou le calcul de la moyenne des modèles basé sur une estimation du maximum de vraisemblance. Pour effectuer cette analyse nous avons suivi un protocole rigoureux similaire à d'autres méta-analyses de hiboux tachetés. La cohérence des observations de terrain et des méthodes analytiques entre ces études a réduit les effets méthodologiques confondants lors des évaluations des résultats. Nous avons utilisé 991 hiboux tachetés marqués dans l'analyse de survie apparente. La probabilité de survie apparente a été plus élevée pour les hiboux adultes que pour les sous-adultes. Il y a eu peu de différence pour ce qui est de la survie apparente entre les hiboux mâles et femelles. La moyenne des estimations de la probabilité de survie apparente des hiboux adultes basée sur la moyenne des modèles a varié entre 0,811 ± 0,021 pour les hiboux femelles à LAS et 0,890 ± 0,016 pour les hiboux mâles à SKC. La survie apparente a augmenté avec le temps pour les hiboux de toutes les classes d'âge à LAS et SIE, pour les adultes à ELD, et pour les sous-adultes de deux ans et les adultes à SKC. La méta-analyse de survie apparente, qui comprenait seulement des hiboux adultes, a confirmé une tendance croissante de survie avec le temps. Les taux de survie étaient plus élevés pour les hiboux de SKC que pour ceux des autres aires d'étude. Nous avons analysé les données obtenues à partir de 1 865 observations de succès de reproduction de hiboux tachetées femelles. La proportion des hiboux femelles sous-adultes parmi toutes les femelles territoriales d'àge connu a varié de 0,00 à 0,25 selon les aires et les années d'étude. La proportion des sousadultes parmi les hiboux tachetés femelles a été négativement corrélée avec le succès de reproduction (nombre de jeunes hiboux par femelle territoriale) pour ELD et SIE. La forêt nationale Eldorado et la forêt nationale Lassen ont montré une tendance à alterner selon un cycle biennal pour ce qui est du succès de reproduction, avec un taux plus élevé pendant les années paires. La moyenne du succès de reproduction annuel était de 0,988 ± 0,154 pour ELD, de 0,624 ± 0,140 pour LAS, de 0,478 ± 0,106 pour SIE, et de 0,555 ± 0,110 pour SKD. La forêt nationale Eldorado a montré une tendance décroissante ainsi que la plus grande variation dans le succès de reproduction avec le temps, alors que SIE et SKC, qui ont eu le succès de reproduction le plus bas, ont connu la variation temporelle la plus basse. La méta-analyse a confirmé que le succès de reproduction variait selon les aires d'étude. Le succès de reproduction a été le plus élevé pour les adultes, puis pour les sous-adultes de deux ans, et ensuite pour les sous-adultes d'un an. Nous avons utilisé 842 hiboux marqués, adultes et sous-adultes, pour estimer le taux de changement de la population. La modélisation a indiqué que Λ _t était soit stationnaire (LAS et SIE), soit croissant après une baisse initiale (ELD et SKC). La moyenne estimée Λ _t pour les 4 aires d'étude était: 1,007 (95% IC = 0,952–1,066) pour ELD; 0,973 (95% IC = 0,946–1,001) pour LAS; 0,992 (95% IC = 0,966–1,018) pour SIE; et 1,006 (95% IC = 0,947–1,068) pour SKC. Le meilleur modèle de méta-analyse pour la tendance de la population a indiqué que Λ variait selon le temps mais suivait la même tendance selon les aires d'étude. Nos estimations du changement de population réalisé (Δ _t ) étaient fondées sur les estimations de Λ _t des aires d'étude individuelles et n'ont pas nécessité d'estimation de la taille annuelle de la population pour chaque aire d'étude. Les tendances représentaient la proportion de la taille de la population pendant la première année qui s'est maintenue chaque année subséquente. De même que λ_t sur lesquels ils étaient fondés, ces δ_t ont apporté des preuves de déclin pendant la période d'étude pour LAS et SIE. Le meilleur modèle a indiqué que le recrutement des hiboux adultes et sous-adultes mâles et femelles variait de 0,10 à 0,31 nouveaux individus territoriaux à un temps t pour un nombre d'individus territoriaux à un temps t-1 et qu'il en était de même dans chaque aire. Nous avons également procédé à une analyse de viabilité de la population (AVP) fondée sur les résultats de notre méta-analyse. Cette AVP a été d'une utilité limitée pour les aires d'étude ELD et SKC parce que les intervalles de confiance de 95% sur la probabilité du déclin ou de la croissance couvraient l'intervalle [0, 1] sur une période de 5 à 10 ans. Lorsque nous avons réduit les inférences à 7 ans, la probabilité estimée d'un déclin >10% pour SIE était de 0,41 (95% IC = 0,09–0,78); pour LAS la probabilité était de 0,64 (95% IC = 0,27–0,94). Al'opposé, la probabilité estimée d'une croissance >10% en 7 ans pour SIE était de 0,23 (95% IC = 0,01–0,55) et pour LAS elle était de 0,10 (95% IC = 0,00–0,34). Afin de comparer, nous avons simulé une AVP pour une population hypothétique ayant une moyenne Λ = 1,0 et la même variation temporelle que celle observée dans nos populations de hiboux. Notre AVP a suggéré que les populations de SIE et de LAS avaient de plus grandes probabilités de déclin que de croissance sur une période de 7 ans, mais qu'il serait difficile de déterminer si une population présentait un léger déclin graduel. La collecte des informations pour nos 4 aires d'étude foumit aux personnes chargées de la gestion un modèle riche de données permettant de suivre l'impact sur les hiboux des actions de gestion à l'avenir (par exemple, les nouvelles stratégies de gestion du Plan pour la Forêt de Sierra Nevada). Cette collecte foumit également des preuves importantes afin d'évaluer le statut du hibou pour une classification potentielle sur la liste des espèces menacées.     

Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean

Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of 1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K ⁻¹ _par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values were twice as high within K ⁻¹ _par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within K ⁻¹ _par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K ⁻¹ _par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean, especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences. Accepted: 27 August 1999     

On the use of non-linear regression with the logistic equation for changes with time of percentage root length colonized by arbuscular mycorrhizal fungi

For the regression of sigmoid-shaped responses with time t of colonization C of roots by arbuscular mycorrhizal fungi, C=C _p/1+[e ^−k(t−ti) ] is the most useful form of the logistic equation. At the time of inflection t _i the slope is maximal and directly proportional to the product of the colonization plateau C _p and the abruptness k of the curve. Coefficient k has a high value when the curve rises abruptly following and preceding long shallow phases. The logistic equation has a curve that is symmetrical about t _i such that C=C _p/2 at inflection. Although the logistic equation can generate a good fit to many data sets for changes in colonization with time, there are cases that are not sigmoid and the logistic equation does not apply. For sigmoid curves, the lag in the development of colonization is directly related to both t _i and k but not to the plateau and not to the value of the maximum slope. Higher values of k or t _i reflect longer lag. When considered alone, t _i and k do not fully summarize the lag in colonization, and so a numerical method to combine them is presented here which allows lag to be compared between curves. In this method, the lag is evaluated by calculating the time during early colonization when the slope equals half of the value of the maximum slope. In summary, use of the logistic equation for regression of sigmoid curves of colonization with time allows numerical comparison between curves of the lag, the period of steep ascent, and the plateau. The logistic equation does not model directly the fundamental processes at work in the development of the mycorrhizae. Instead, it can be used as described here to gain insight into the colonization process by comparing the dynamics of that colonization for different species under various conditions. Accepted: 20 October 2000     

Assessment of oxidative stress biomarkers – neuroprostanes and dihomo-isoprostanes – in the urine of elite triathletes after two weeks of moderate-altitude training

This randomized and controlled trial investigated whether the increase in elite training at different altitudes altered the oxidative stress biomarkers of the nervous system. This is the first study to investigate four F₄-neuroprostanes (F₄-NeuroPs) and four F₂-dihomo-isoprostanes (F₂-dihomo-IsoPs) quantified in 24-h urine. The quantification was carried out by ultra high pressure liquid chromatography-triple quadrupole-tandem mass spectrometry (UHPLC-QqQ-MS/MS). Sixteen elite triathletes agreed to participate in the project. They were randomized in two groups, a group submitted to altitude training (AT, n?=?8) and a group submitted to sea level training (SLT) (n?=?8), with a control group (Cg) of non-athletes (n?=?8). After the experimental period, the AT group triathletes gave significant data: 17-epi-17-F_2t-dihomo-IsoP (from 5.2?±?1.4?μg/mL 24?h^?1 to 6.6?±?0.6?μg/mL 24?h^?1), ent-7(RS)-7-F_2t-dihomo-IsoP (from 6.6?±?1.7?μg/mL 24?h^?1 to 8.6?±?0.9?μg/mL 24?h^?1), and ent-7-epi-7-F_2t-dihomo-IsoP (from 8.4?±?2.2?μg/mL 24?h^?1 to 11.3?±?1.8?μg/mL 24?h^?1) increased, while, of the neuronal degeneration-related compounds, only 10-epi-10-F_4t-NeuroP (8.4?±?1.7?μg/mL 24?h^?1) and 10-F_4t-NeuroP (5.2?±?2.9?μg/mL 24?h^?1) were detected in this group. For the Cg and SLT groups, no significant changes had occurred at the end of the two-week experimental period. Therefore, and as the main conclusion, the training at moderate altitude increased the F₄-NeuroPs- and F₂-dihomo-isoPs-related oxidative damage of the central nervous system compared to similar training at sea level.     

Photosynthetic limitations of a halophyte sea aster (<Emphasis Type="Italic">Aster tripolium</Emphasis> L) under water stress and NaCl stress

To understand the mechanisms of salt tolerance in a halophyte, sea aster (Aster tripolium L.), we studied the changes of water relation and the factors of photosynthetic limitation under water stress and 300 mM NaCl stress. The contents of Na⁺ and Cl^- were highest in NaCl-stressed leaves. Leaf osmotic potentials (Ψ _s) were decreased by both stress treatments, whereas leaf turgor pressure (Ψ _t) was maintained under NaCl stress. Decrease inΨ _s without any loss ofΨ _t accounted for osmotic adjustment using Na⁺ and Cl^- accumulated under NaCl stress. Stress treatments affected photosynthesis, and stomatal limitation was higher under water stress than under NaCl stress. Additionally, maximum CO₂ fixation rate and O₂ evolution rate decreased only under water stress, indicating irreversible damage to photosynthetic systems, mainly by dehydration. Water stress severely affected the water relation and photosynthetic capacity. On the other hand, turgid leaves under NaCl stress have dehydration tolerance due to maintenance of Ψ _t and photosynthetic activity. These results show that sea aster might not suffer from tissue dehydration in highly salinized environments. We conclude that the adaptation of sea aster to salinity may be accomplished by osmotic adjustment using accumulated Na⁺ and Cl^-, and that this plant has typical halophyte characteristics, but not drought tolerance. Electronic Publication