Predicted impact of ocean acidification on a marine invertebrate: elevated CO<Subscript>2</Subscript> alters response to thermal stress in sea urchin larvae

Ocean acidification (OA) and the biological consequences of altered seawater chemistry have emerged as a significant environmental threat to healthy marine ecosystems. Because a more acidic ocean interferes with fixation of calcium carbonate to form shells or calcified skeletons, future ocean chemistry may significantly alter the physiology of calcifying marine organisms. These alterations may manifest themselves directly in the calcification process, or have synergistic effects with other environmental factors such as elevated temperatures. New tools permit us to explore subtle changes in gene expression patterns in response to environmental conditions. We raised sea urchins (Strongylocentrotus franciscanus) under conditions simulating future atmospheric CO₂ levels of 540 and 970 ppm. When larvae raised under elevated CO₂ conditions were subjected to 1-h acute temperature stress, their ability to mount a physiological response (as measured by expression of the molecular chaperone hsp70) was reduced relative to those raised under ambient CO₂ conditions. These results represent the first use of gene expression assays to study the effects of OA on sea urchin development. They highlight the importance of looking at multiple environmental factors simultaneously as this approach may reveal previously unsuspected biological impacts of atmospheric changes.     

Macro- and mesoherbivores prefer native seaweeds over the invasive brown seaweed <Emphasis Type="Italic">Sargassum muticum</Emphasis>: a potential regulating role on invasions

Herbivory has a strong impact on algal distribution, abundance and community structure and may influence the establishment and spread of introduced seaweed species. In this study, we assess the potential regulating role of herbivory on one of the most invasive brown seaweeds: Sargassum muticum. Multiple choice feeding experiments were conducted with 13 native seaweeds, S. muticum and 5 herbivore species from the Northwest, Southwest and South of Portugal. S. muticum was always the least or among the least preferred seaweeds and attained one of the highest growth rates of the tested seaweeds, with and without herbivores. The addition of herbivores increased the number of cases by 40% in which the invader had higher growth rates. Our results suggest that low grazing pressure on S. muticum by the recipient herbivore community may give the invader a competitive advantage over at least part of the native seaweed community, thereby contributing to the invasiveness of S. muticum along the Portuguese coast.     

Estimation of urban sensible heat flux using a dense wireless network of observations

The determination of the sensible heat flux over urban terrain is challenging due to irregular surface geometry and surface types. To address this, in 2006–07, a major field campaign (LUCE) took place at the école Polytechnique Fédérale de Lausanne campus, a moderately occupied urban site. A distributed network of 92 wireless weather stations was combined with routine atmospheric profiling, offering high temporal and spatial resolution meteorological measurements. The objective of this study is to estimate the sensible heat flux over the built environment under convective conditions. Calculations were based on Monin–Obukhov similarity for temperature in the surface layer. The results illustrate a good agreement between the sensible heat flux inferred from the thermal roughness length approach and independent calibrated measurements from a scintillometer located inside the urban canopy. It also shows that using only one well-selected station can provide a good estimate of the sensible heat flux over the campus for convective conditions. Overall, this study illustrates how an extensive network of meteorological measurements can be a useful tool to estimate the sensible heat flux in complex urban environments.     

Effects of experimental protocol on global vegetation model accuracy: A comparison of simulated and observed vegetation patterns for Asia

Prognostic vegetation models have been widely used to study the interactions between environmental change and biological systems. This study examines the sensitivity of vegetation model simulations to: (i) the selection of input climatologies representing different time periods and their associated atmospheric CO₂ concentrations, (ii) the choice of observed vegetation data for evaluating the model results, and (iii) the methods used to compare simulated and observed vegetation. We use vegetation simulated for Asia by the equilibrium vegetation model BIOME4 as a typical example of vegetation model output. BIOME4 was run using 19 different climatologies and their associated atmospheric CO₂ concentrations. The Kappa statistic, Fuzzy Kappa statistic and a newly developed map-comparison method, the Nomad index, were used to quantify the agreement between the biomes simulated under each scenario and the observed vegetation from three different global land- and tree-cover data sets: the global Potential Natural Vegetation data set (PNV), the Global Land Cover Characteristics data set (GLCC), and the Global Land Cover Facility data set (GLCF). The results indicate that the 30-year mean climatology (and its associated atmospheric CO₂ concentration) for the time period immediately preceding the collection date of the observed vegetation data produce the most accurate vegetation simulations when compared with all three observed vegetation data sets. The study also indicates that the BIOME4-simulated vegetation for Asia more closely matches the PNV data than the other two observed vegetation data sets. Given the same observed data, the accuracy assessments of the BIOME4 simulations made using the Kappa, Fuzzy Kappa and Nomad index map-comparison methods agree well when the compared vegetation types consist of a large number of spatially continuous grid cells. The results of this analysis can assist model users in designing experimental protocols for simulating vegetation.     

Evaluation of discrete host–parasitoid models for diamondback moth and Diadegma semiclausum field time population density series

The performance of discrete mathematical models to describe the population dynamics of diamondback moth (DBM) (Plutella xylostella L.) and its parasitoid Diadegma semiclausum was investigated. The parameter values for several well-known models (Nicholson–Bailey, Hassell and Varley, Beddington, Free and Lawton, May, Holling type 2, 3 and Getz and Mills functional responses) were estimated. The models were tested on 20 consecutive sets of time series data collected at 14 days interval for pest and parasitoid populations obtained from a highland cabbage growing area in eastern Kenya. Model parameters were estimated from minimized squared difference between the numerical solution of the model equations and the empirical data using Powell's method. Maximum calculated DBM growth rates varied between 0.02 and 0.07. The carrying capacity determined at 16.5 DBM/plant by the Beddington et al. model was within the range of field data. However, all the estimated parameter values relating to the parasitoid, including the instantaneous searching rate (0.07–0.28), per capita searching efficiency (0.20–0.27), search time (5.20–5.33), handling time (0.77–0.90), and parasitism aggregation index (0.33), were well outside the range encountered empirically. All models evaluated for DBM under Durbin–Watson criteria, except the May model, were not autocorrelated with respect to residuals. In contrast, the criteria applied to the parasitoid residuals showed strong autocorrelations. Thus, these models failed to estimate parasitoid dynamics. We conclude that the interactions of the DBM with its parasitoid cannot be explained by any of the models tested. Two factors may be associated with this failure. First, the parasitoid in this integrated biological control system may not be playing a major role in regulating DBM population. Second, and perhaps more likely, poor correlations reflect gross inadequacies in the theoretical assumptions that underlie the existing models.     

Characterization of Santa Catarina (Brazil) coal with respect to human health and environmental concerns

The current paper presents the concentration, distribution, and modes of occurrence of trace elements of 13 coals from south Brazil. The samples were collected in the state of Santa Catarina. Chemical analyses and the high ash yields indicate that all studied coals are rich in mineral matter, with SiO₂ and Al₂O₃ dominating as determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Quartz is the main mineral species and is associated with minor levels of feldspars, kaolinite, hematite, and iron-rich carbonates. The contents of trace elements, including As, Pb, Cd, Ni, Cr, Mn, Be, V, U, Zn, Li, Cu, Tl, and Ni, in coals were determined. A comparison of ranges and means of elemental concentrations in Santa Catarina, Brazil, and world coals shows that the ranges of most elements in Santa Catarina coal are very close to the usual worldwide concentration ranges in coal.     

Protection of the vehicle cab environment against bacteria, fungi and endotoxins in composting facilities

Microbial quality of air inside vehicle cabs is a major occupational health risk management issue in composting facilities. Large differences and discrepancies in protection factors between vehicles and between biological agents have been reported. This study aimed at estimating the mean protection efficiency of the vehicle cab environment against bioaerosols with higher precision. In-cab measurement results were also analysed to ascertain whether or not these protection systems reduce workers' exposure to tolerable levels. Five front-end loaders, one mobile mixer and two agricultural tractors pulling windrow turners were investigated. Four vehicles were fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system. The four others were only equipped with pleated paper filter without pressurisation. Bacteria, fungi and endotoxins were measured in 72 pairs of air samples, simultaneously collected inside the cab and on the outside of the cab with a CIP 10-M sampler. A front-end loader, purchased a few weeks previously, fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system, and with a clean cab, exhibited a mean protection efficiency of between 99.47% CI 95% [98.58-99.97%] and 99.91% [99.78-99.98%] depending on the biological agent. It is likely that the lower protection efficiency demonstrated in other vehicles was caused by penetration through the only moderately efficient filters, by the absence of pressurisation, by leakage in the filter-sealing system, and by re-suspension of particles which accumulated in dirty cabs. Mean protection efficiency in regards to bacteria and endotoxins ranged between 92.64% [81.87-97.89%] and 98.61% [97.41-99.38%], and between 92.68% [88.11-96.08%] and 98.43% [97.44-99.22%], respectively. The mean protection efficiency was the lowest when confronted with fungal spores, from 59.76% [4.19-90.75%] to 94.71% [91.07-97.37%]. The probability that in-cab exposure to fungi exceeded the benchmark value for short-term respiratory effects suggests that front-end loaders and mobile mixers in composting facilities should be fitted with a pressurisation and HEPA filtration system, regardless of whether or not the facility is indoors or outdoors. Regarding the tractors, exposure inside the cabs was not significantly reduced. However, in this study, there was a less than 0.01% risk of exceeding the bench mark value associated with fungi related short-term respiratory effects during an 1-h per day windrow turning operation. Pressurisation and a HEPA filtration system can provide safe working conditions inside loaders and mobile mixer with regard to airborne bacteria, fungi and endotoxins in composting facilities. However, regular thorough cleaning of the vehicle cab, as well as overalls and shoes cleaning, and mitigation of leakage in the filter-sealing system are necessary to achieve high levels of protection efficiency.     

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO₂ levels: the added value of the isotope (δ¹³C and δ¹⁸O CO₂; δ¹³C and δD CH₄) approach

We are presenting here a multi-isotope approach (δ¹³C and δ¹⁸O of CO₂; δ¹³C and δD of CH₄) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO₂ levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH₄ oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH₄ is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH₄ oxidation by the methanotrophic bacteria. δ¹³C of CO₂ samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.     

First report on chlorinated pesticide deposition in a sediment core from a small lake in central Chile.

This paper presents a first report on chlorinated pesticide deposition analyzed through sedimentary records in a small mesotrophic lake (Chica de San Pedro) in central Chile. The sediment core was sliced and dated using 210Pb, 137Cs and pollen analyses. Organochlorine pesticides were analyzed by gas chromatography with electron capture detection (GC-ECD). From these results, pesticide deposition over the last 50 years was estimated. No pesticides were detected below the 1940 slice of the core. Concentrations were in the range 0.640-1.4 ng/g d.w. for total DDTs, 0.046-0.362 ng/g d.w. for lindane and 0.015-0.310 ng/g d.w. for alpha-hexachlorohexane. Highest concentrations of pp'DDT were found in 1993-1996 and higher concentrations of pp'-DDE and pp'-DDD were found in the seventies (1972-1978). Total organic carbon (TOC) normalized data were used for statistical analysis. Although significant correlation was observed between concentrations of DDE and DDD, no correlation was found for DDT, suggesting that it had a different source. Factorial analysis grouped DDE together with DDD, while DDT was grouped together with gamma- and alpha-HCH. Total DDT fluxes were highest during the 1970s, while those for HCHs have been increasing in the 1990s. In Chile, organochlorine compounds were banned in 1985, and the historical deposition patterns seem to indicate that such measures have been effective. On the other hand, results point out a relatively new occurrence of pp'-DDT in the watershed, but the source remains unknown.