Serial polygyny and colony genetic structure in the monogynous queenless ant Diacamma cyaneiventre

Serial polygyny, defined as the temporal succession of several reproductive females in a colony, occurs in some monogynous social insects and has so far attracted little attention. Diacamma cyaneiventre is a queenless ponerine ant found in the south of India. Colonies are headed by one singly mated worker, the gamergate. After the death of the gamergate or her absence following colony fission, the gamergate is replaced by a newly eclosed nestmate worker. After a replacement, colonies go through short-lived periods in which two matrilines of sisters co-occur. This is a situation which can be described as serial polygyny. To measure the consequences of serial polygyny, a genetic analysis was performed on 449 workers from 46 colonies of D. cyaneiventre using five microsatellite loci. The presence of more than one matriline among workers of the same nest was detected in 19% of colonies, indicating a recent change of gamergate. The average genetic relatedness among nestmate workers was 0.751 and did not significantly differ from the theoretical expectation under strict monogyny and monandry (0.75). A simple analytical model of the temporal dynamics of serial polygyny was developed in order to interpret these results. We show that the rate of gamergate turnover relative to the rate of worker turnover is the crucial parameter determining the level of serial polygyny and its effect on the genetic structure of colonies. This parameter, estimated from our data, confirms that serial polygyny occurs in D. cyaneiventre but is not strong enough to influence significantly the average genetic relatedness among workers.     

Helium isotopic constraints on simulated ocean circulations: implications for abyssal theories

There is ongoing controversy as to the dynamical significance of geothermal heat flow in shaping the abyssal circulation. In this paper, we gauge the impact of geothermal heating and vertical mixing parameterizations in the general circulation model OPA. The experiments are evaluated by comparing simulated mantle ³He with observations collected during the GEOSECS and WOCE programs. This tracer is particularly adapted to the validation of our numerical simulations because its injection into the ocean interior is tightly linked to geothermal processes. In agreement with previous studies, the model circulation is found very sensitive to the parameterization of the vertical mixing. The meridional overturning circulation (MOC) is globally intensified when moving from a constant mixing to a version with enhanced mixing near the ocean bottom, with the most drastic variation observed for AABW (+ 50%). Adding the geothermal heat flux mainly affects AABW circulation in the model, enhancing it all the more as the meridional circulation is slow (low vertical mixing), but proportionally less so when it is more vigorous (enhanced vertical mixing). This can be understood from the requirement of the abyssal ocean to maintain heat balance. The evaluation with mantle ³He simulations reveals that the version with low vertical mixing, with its sluggish circulation, produces unrealistically high a ³He isotopic composition. However, with a vertical mixing that is enhanced at depth, the ³He distribution falls within an acceptable range of values in the deep ocean. Finally, adding the geothermal heating to this enhanced mixing case provides a substantial improvement of the simulation of AABW in all basins but the Indian Ocean. ³He isotopic composition is then in good agreement with the observations. Taken jointly with observational estimates of the MOC intensity, these independent isotopic constraints suggest that both geothermal heating and enhanced diapycnal mixing at depth are key ingredients in the realistic simulation of abyssal circulation.     

Coexistence of oceanic predators on wintering areas explained by population-scale foraging segregation in space or time

Ecological niche theory predicts segregation mechanisms that mitigate potential competition between closely related organisms. However, little is known outside the breeding season, when central-place foraging animals may move on larger scales. This study tested for segregation mechanisms within the same 2007 inter-breeding period on three neighboring populations of avian predators from the southern Indian Ocean: Eastern Rockhopper Penguins Eudyptes filholi from Crozet and Kerguelen and Northern Rockhopper Penguins E. moseleyi from Amsterdam. Using state-of-the-art geolocation tracking and stable isotope analysis techniques, we quantified and compared the ecological niches in time, space, and diet. The three populations showed large-scale movements over deep oceanic waters near the Subantarctic Front, with generally little individual variation. The two neighboring populations of Eastern Rockhopper Penguins showed strikingly distinct distribution in space, while foraging in similar habitats and at the same trophic level (crustacean-eaters). In contrast, Northern Rockhoppers showed marked spatial overlap with birds of the sibling Eastern species, but their temporal delay of two months enabled them to effectively avoid significant overlap. Our results highlight parsimonious mechanisms of resource partitioning operating at the population level that may explain how animals from neighboring localities can coexist during the nonbreeding period.     

Beyond men and women: a critical perspective on gender and disaster

Consideration of gender in the disaster sphere has centred almost exclusively on the vulnerability and capacities of women. This trend stems from a polarised Western understanding of gender as a binary concept of man—woman. Such an approach also mirrors the dominant framing of disasters and disaster risk reduction (DRR), emphasising Western standards and practices to the detriment of local, non‐Western identities and experiences. This paper argues that the man—woman dichotomy is an insufficient construct with which to address the gendered dimensions of a disaster as it fails to capture the realities of diverse gender minorities in non‐Western contexts. The paper presents case studies from the Philippines, Indonesia, and Samoa, where gender minorities display specific patterns of vulnerability associated with their marginal positions in society, yet, importantly, also possess a wide array of endogenous capacities. Recognition of these differences, needs, skills, and unique resources is essential to moving towards inclusive and gender‐sensitive DRR.     

Modelling geosmin concentrations in three sources of raw water in Quebec, Canada

The presence of off-flavour compounds such as geosmin, often found in raw water, significantly reduces the organoleptic quality of distributed water and diverts the consumer from its use. To adapt water treatment processes to eliminate these compounds, it is necessary to be able to identify them quickly. Routine analysis could be considered a solution, but it is expensive and delays associated with obtaining the results of analysis are often important, thereby constituting a serious disadvantage. The development of decision-making tools such as predictive models seems to be an economic and feasible solution to counterbalance the limitations of analytical methods. Among these tools, multi-linear regression and principal component regression are easy to implement. However, due to certain disadvantages inherent in these methods (multicollinearity or non-linearity of the processes), the use of emergent models involving artificial neurons networks such as multi-layer perceptron could prove to be an interesting alternative. In a previous paper (Parinet et al., Water Res 44: 5847-5856, 2010), the possible parameters that affect the variability of taste and odour compounds were investigated using principal component analysis. In the present study, we expand the research by comparing the performance of three tools using different modelling scenarios (multi-linear regression, principal component regression and multi-layer perceptron) to model geosmin in drinking water sources using 38 microbiological and physicochemical parameters. Three very different sources of water, in terms of quality, were selected for the study. These sources supply drinking water to the Québec City area (Canada) and its vicinity, and were monitored three times per month over a 1-year period. Seven different modelling methods were tested for predicting geosmin in these sources. The comparison of the seven different models showed that simple models based on multi-linear regression provide sufficient predictive capacity with performance levels comparable to those obtained with artificial neural networks. The multi-linear regression model (R ²?=?0.657, <0.001) used only four variables (phaeophytin, sum of green algae, chlorophyll-a and potential Redox) in comparison with ten variables (potassium, heterotrophic bacteria, organic nitrogen, total nitrogen, phaeophytin, total organic carbon, sum of green algae, potential Redox, UV absorbance at 254 nm and atypical bacteria) for the best model obtained with artificial neural networks (R ²?=?0.843).     

Modelling tritium flux from water to atmosphere: application to the Loire River

Tritium (³H or T) is one of the major radionuclides released by nuclear power plants (NPP) into rivers. However, tritiated water (HTO) flux from water to air is seldom considered when assessing health effects of such releases. The aim of this paper is to present the result of a research program, called LORA, conducted on the Loire River (France). To improve our understanding of HTO flux from surface water to air, three field campaigns were organised during the NPP’s radioactive releases to measure simultaneously the activity concentrations in air on the riverbank, using an innovative system, and in river water. The measurements showed that during radioactive releases, water vapour was enriched in ³H. These results were used to calibrate exchange velocities. The average of these estimated exchange velocities was more than one order of magnitude higher than those calculated in the literature from indoor experiments. The variability of these values was also larger, showing that outdoor studies cover a wide range of conditions influencing HTO flux. No correlation was observed between exchanges velocities and meteorological conditions. However, there was a significant difference between day and night with a higher value observed during the day. Two approaches used to calculate HTO evaporation from water (i.e. the approach based on water evaporation and the approach considering that HTO follows its own concentration gradient) were included in a hydrodynamic model, which was used to evaluate HTO air activity along the Loire River. In conclusion, only the approach considering that HTO follows its own gradient led to a good agreement between measurements and predictions. A one-year simulation was done to estimate the contribution of this process to the dose. Its contribution can be considered as negligible in this case compared to the other pathways such as ingestion of water or foodstuffs.     

He mass spectrometry for very low-level measurement of organic tritium in environmental samples

The design, setup and performance of a mass spectrometric system for the analysis of low to very low-level tritium in environmental samples are described. The tritium concentration is measured indirectly by the ³He ingrowth from radioactive decay after complete initial degassing of the sample. The analytical system is fully computer-controlled and consists in a commercial helium isotope mass spectrometer coupled with a high vacuum inlet system. A detection limit of 0.15 Bq/kg is routinely obtainable for sample sizes of 20 g of water equivalent and an accumulation time of three months. Larger samples (and/or longer accumulation time) can be used to obtain lower detection limits. In addition to the benefit of a lower detection limit, another advantage of this non-destructive method lies in the simplicity of the analytical procedure which strongly limits the risk of contamination. An inter-comparison was successfully performed with the conventional beta counting technique on lyophilized grass samples, in a range of tritium concentrations of environmental interest. It shows that the ³He mass spectrometry method yields results that are fully consistent with the conventional liquid scintillation technique over a wide range of tritium concentrations.     

Stakeholder participation in sustainability assessment of non-wicked problems: The case of a future seaweed industry in Sweden

Acceptance by, and cooperation with relevant stakeholders in developing new sustainability initiatives when they are generally perceived as positive, is one of the keys for successful implementation of such new sustainability initiatives later on. It is remarkable, however, that ample literature exists about involving stakeholders in research projects focusing on problems with diverging views (controversy) around facts and values (wicked problems), but there is very little literature addressing whether and how to involve relevant stakeholders in case of initiatives where diverging norms and values do not play a (substantial) role, like in sustainability assessment for a future seaweed industry. This perspectives paper addresses that gap, and explores how to design such sustainability assessment, illustrated by how stakeholder interaction influenced the assessment and its results for a future seaweed industry in Sweden, followed by a discussion whether and how a similar approach may benefit sustainability assessment of other non-wicked sustainability initiatives.     

Multi-level modelling of chlorination by-product presence in drinking water distribution systems for human exposure assessment purposes

During drinking water treatment and distribution, chlorine reacts with organic matter occurring in water to form various chlorination by-products (CBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). This paper presents the occurrence of THMs and HAAs in different water distribution systems (DS) of the same region and their modelling for exposure assessment purposes. This study was conducted in eight DS supplying chlorinated water to the population of Québec City, Canada. These systems differ in type of water source (i.e. surface, ground or mixed water), in treatment applied at the plant, and in size and structure of the DS. Two spatio-temporal databases for THMs and HAAs were implemented, one for model development and the other for model validation. The analysis of the data demonstrates significant seasonal and spatial variations of these compounds. A multi-level statistical modelling approach was applied to estimate the ranges for occurrence of THMs and HAAs in the eight DS (i.e. a single model for the study region for each CBP species). The modelling approach integrates available or easily measurable parameters. For both THMs and HAAs, a two-level model considering a sampling-site random effect was selected among various models initially developed. The model capacity for estimating the presence of THMs and HAAs in drinking water and its usefulness for exposure assessment purposes in the studied region was demonstrated.