<Emphasis Type="Italic">Cytherella</Emphasis> as a tool to reconstruct deep-sea paleo-oxygen levels: the respiratory physiology of the platycopid ostracod <Emphasis Type="Italic">Cytherella</Emphasis> cf. <Emphasis Type="Italic">abyssorum</Emphasis>

The reconstruction of past climates is a major challenge. One approach is the use of paleoceanography, which looks for clues to the past activity of deep-sea currents by associating them with the melting of the poles. In different sampling zones, fossil biomarkers are used to reconstruct the oxygenation levels of the sea bottom. Among the ostracods (crustaceans), the family Cytherellidae is considered to be resistant to significant decreases in oxygen and their fossil valves are used as biomarkers for oxygenation levels in the past. We studied the basic principles behind Cytherella cf. abyssorum’s ability to adapt to variations in water oxygenation levels in an attempt to determine what could differentiate it from other ostracods. Cytherella cf. abyssorum Sars 1866 has an activity level and ventilatory frequency only half that of ostracods studied previously. When subjected to a decrease in oxygenation, it demonstrates the beginnings of ventilatory adaptation which is unknown in the other studied ostracods. Some morpho-functional aspects are also remarkable, such as the presence of thick valves, which can close hermetically by means of powerful adductor muscles. Compared with already studied ostracods, Cytherella cf. abyssorum has, therefore, characteristics which suggest an ability to present increased resistance in hypoxia. We discuss these results in the paleoceanographical context by describing a scenario suggesting why an increased proportion of the ostracod population could indicate the existence of ocean bottoms with low oxygenation.     

Spatial and space-time scan statistics to detect low rate clusters of sex ratio

Whether general environmental exposures to endocrine disrupting chemicals (including pesticides and dioxin) might induce decreased sex ratios (male/female ratio at birth) is discussed. To address this issue, the authors looked for a space-time clustering test which could detect local areas of significantly low risk, assuming a Bernoulli distribution. As a matter of fact, if the endocrine disruptor hypothesis holds true, and if the sex ratio is a sentinel health event indicative of new reproductive hazards ascribed to environmental factors, then in a given region, either a cluster of low male/female ratio among newborn babies would be expected in the vicinity of polluting municipal solid waste incinerators (MSWIs) (supporting the dioxin hypothesis), or local clusters would be expected in some rural areas where large amounts of pesticides are sprayed. Among cluster detection tests, the spatial scan statistic has been widely used in various applications to scan for areas with high rates, and rarely (if ever) with low rates. Therefore, the goal of this paper was to check the properties of the scan statistics under a given scenario (Bernoulli distribution, search for clusters with low rates) and to assess its added value in addressing the sex ratio issue. This study took place in the Franche-Comté region (France), mainly rural, comprising three main MSWIs, among which only one had high dioxin emissions level in the past. The study population consisted of 192,490 boys and 182,588 girls born during the 1975–1999 period. On the whole, the authors conclude that: (i) spatial and space-time scan statistics provide attractive features to address the sex ratio issue; (ii) sex ratio is not markedly affected across space and does not provide a reliable screening measure for detecting reproductive hazards ascribed to environmental factors.     

A simulation study of the medium-term effects of field patterns on cross-pollination rates in oilseed rape (Brassica napus L.)

Gene flow between cultivars within a landscape may lead to impurities that reduce harvest value. In OSR, as for most crops, impurity rates are expected to depend on the spatial distribution of crops over the landscape. However, in contrast to other well-studied crops such as maize, OSR crops generate seed banks in European agro-ecosystems. Gene flow is thus a spatio-temporal process which depends on cropping systems. We therefore aimed at identifying spatial variables that have an effect on regional or local harvest impurities, taking account of the time since the introduction of OSR crops in the regions and of cropping system. Gene flow was simulated over 36 field patterns cultivated with either 15% or 30% of OSR fields, among which 10% or 50% were GM, for three contrasted cropping systems, with the GeneSys software already used for EU co-existence studies. Through regression analyses, we determined spatial and agronomic factors that most affected harvest impurity rates of non-GM OSR after one or seven years of OSR cultivation. The cropping system was the main factor explaining regional harvest impurity rates. Its importance increased after six years of OSR cultivation. For a given cropping system, the regional impurity rate after one year increased linearly with the current proportion of GM crop. In contrast, impurity rates after six years largely depended on the proportions of OSR crop (GM or not) in the two preceding years. During the first year of OSR cultivation, local impurity rates were mostly explained by the distance to the closest GM field. After six years, these rates were mostly explained by the density of GM volunteers in the analysed field and, to a lesser degree, to that of volunteers in neighbour non-OSR fields. Cropping systems were most important in determining impurity rates and the way impurity rates related to regional or local factors. Determination of isolation distances to ensure harvest purity should thus consider past history of OSR cultivation in the area and, in particular, how current or future cropping systems will manage volunteers. Regression quantiles were fitted to the simulated data to determine regional rules (i.e. the maximum regional area of GM OSR and isolation distances between GM and non-GM crops) as a function of the risk accepted by the decision-maker (i.e. the % of situations exceeding harvest impurity thresholds), the cropping system and the volunteer infestation.     

Sampling for weed spatial distribution mapping need not be adaptive

Weeds are species of interest for ecologists because they are competitors of the crop for resources but they also play an important role in maintaining biodiversity in agroecosystems. To study their spatial distribution at the field scale, only sampled observations are available due to the cost of sampling. Weeds sampling strategies are static. However, in the domain of spatial sampling, adaptive strategies have also been developed with, for some of them, an important on-line or off-line computational cost. In this article we provide answers to the following question: Are the current adaptive sampling methods efficient enough to motivate a wider use in practice when sampling a weed species at a field scale? We provide a comparison of the behaviour of 8 static strategies and 3 adaptive ones on four criteria: density class estimation, map restoration, spatial aggregation estimation, and sampling duration. From two weeds data sets, we estimated six contrasted Markov Random Field (MRF) models of weed density class spatial distribution and a model for sampling duration. The MRF models were then used to compare the strategies on a large set of simulated maps. Our main finding was that there is no clear gain in using adaptive sampling strategies rather than static ones for the three first criteria, and adaptive strategies were associated to longer sampling duration. This conclusion points out that for weed mapping, it is more important to build a good model of spatial distribution, than to propose complex adaptive sampling strategies.     

Early onset of vegetation growth vs. rapid green-up: impacts on juvenile mountain ungulates

Seasonal patterns of climate and vegetation growth are expected to be altered by global warming. In alpine environments, the reproduction of birds and mammals is tightly linked to seasonality; therefore such alterations may have strong repercussions on recruitment. We used the normalized difference vegetation index (NDVI), a satellite-based measurement that correlates strongly with aboveground net primary productivity, to explore how annual variations in the timing of vegetation onset and in the rate of change in primary production during green-up affected juvenile growth and survival of bighorn sheep (Ovis canadensis), Alpine ibex (Capra ibex), and mountain goats (Oreamnos americanus) in four different populations in two continents. We indexed timing of onset of vegetation growth by the integrated NDVI (INDVI) in May. The rate of change in primary production during green-up (early May to early July) was estimated as (1) the maximal slope between any two successive bimonthly NDVI values during this period and (2) the slope in NDVI between early May and early July. The maximal slope in NDVI was negatively correlated with lamb growth and survival in both populations of bighorn sheep, growth of mountain goat kids, and survival of Alpine ibex kids, but not with survival of mountain goat kids. There was no effect of INDVI in May and of the slope in NDVI between early May and early July on juvenile growth and survival for any species. Although rapid changes in NDVI during the green-up period could translate into higher plant productivity, they may also lead to a shorter period of availability of high-quality forage over a large spatial scale, decreasing the opportunity for mountain ungulates to exploit high-quality forage. Our results suggest that attempts to forecast how warmer winters and springs will affect animal population dynamics and life histories in alpine environments should consider factors influencing the rate of changes in primary production during green-up and the timing of vegetation onset.     

Towards improved socio-economic assessments of ocean acidification’s impacts

Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research.     

Earthworms highly increase ciprofloxacin mineralization in soils

This report shows that earthworms increase up to eight times the mineralization of the antibiotic ciprofloxacin in soils. Antibiotics are extensively used and disseminated in environmental compartments. Antibiotics may enter food chains and thus induce resistance in environmental and human commensal bacteria. The antibiotic ciprofloxacin is suspected to induce significant adverse effects on soil microbial processes, with possible consequences on soil functions. Nevertheless, little is known concerning the fate of ciprofloxacin in soils. Here, we studied the mineralization and distribution of the [2-¹⁴C]-ciprofloxacin in soil–plant–water systems where ciprofloxacin was applied by amendment of spiked pig slurry. Results show that a very weak microbial mineralization of the antibiotic, lower than 0.01 %, occurred after 84 days of incubation. By contrast, the addition of earthworms increased from 5 to 8 times ciprofloxacin mineralization during the following 84 days incubation. In addition, earthworm activity induced the transfer of 40 % of radioactive compounds from the upper to the lower layer of soil, modifying the distribution of the antibiotic within the soil profile. We conclude that earthworms can be used efficiently to mineralize ciprofloxacin and modify its distribution in soils. As a consequence, earthworms change the exposure of soil organisms to ciprofloxacin, and, in turn, the eco-toxicological impact of the antibiotic.