Importance of Local and Regional Scales in Shaping Mycobacterial Abundance in Freshwater Lakes.

Biogeographical studies considering the entire bacterial community may underestimate mechanisms of bacterial assemblages at lower taxonomic levels. In this context, the study aimed to identify factors affecting the spatial and temporal dynamic of the Mycobacterium, a genus widespread in aquatic ecosystems. Nontuberculous mycobacteria (NTM) density variations were quantified in the water column of freshwater lakes at the regional scale (annual monitoring of 49 lakes in the Paris area) and at the local scale (2-year monthly monitoring in Créteil Lake) by real-time quantitative PCR targeting the atpE gene. At the regional scale, mycobacteria densities in water samples ranged from 6.7 × 103 to 1.9 × 108 genome units per liter. Density variations were primarily explained by water pH, labile iron, and dispersal processes through the connection of the lakes to a river. In Créteil Lake, no spatial variation of mycobacterial densities was noticed over the 2-year monthly survey, except after large rainfall events. Indeed, storm sewer effluents locally and temporarily increased NTM densities in the water column. The temporal dynamic of the NTM densities in Créteil Lake was associated with suspended solid concentrations. No clear seasonal variation was noticed despite a shift in NTM densities observed over the 2012-2013 winter. Temporal NTM densities fluctuations were well predicted by the neutral community model, suggesting a random balance between loss and gain of mycobacterial taxa within Créteil Lake. This study highlights the importance of considering multiple spatial scales for understanding the spatio-temporal dynamic of bacterial populations in natural environments.

Environmental factors associated with phytoplankton succession in a Mediterranean reservoir with a highly fluctuating water level.

Eutrophication and harmful algal blooms have become a worldwide environmental problem. Understanding the mechanisms and processes that control algal blooms is of great concern. The phytoplankton community of Karaoun Reservoir, the largest water body in Lebanon, is poorly studied, as in many freshwater bodies around the Mediterranean Sea. Sampling campaigns were conducted semi-monthly between May 2012 and August 2013 to assess the dynamics of its phytoplankton community in response to changes in physical-chemical and hydrological conditions. Karaoun Reservoir is a monomictic waterbody and strongly stratifies between May and August. Changes in its phytoplankton community were found to be a result of the interplay between water temperature, stratification, irradiance, nutrient availability and water level. Thermal stratification established in spring reduced the growth of diatoms and resulted in their replacement by green algae species when nutrient availability was high and water temperatures lower than 22 °C. At water temperature higher than 25 °C and low nutrient concentrations in summer, blooms of the cyanobacterium Microcystis aeruginosa occurred. Despite different growth conditions in other lakes and reservoir, cyanobacterium Aphanizomenon ovalisporum dominated at temperatures lower than 23 °C in weakly stratified conditions in early autumn and dinoflagellate Ceratium hirundinella dominated in mixed conditions, at low light intensity and a water temperature of 19 °C in late autumn. We believe that the information presented in this paper will increase the knowledge about phytoplankton dynamics in the Mediterranean region and contribute to a safer usage of reservoir waters.

Assessment of two non-invasive techniques for measuring turbulent benthic fluxes in a shallow lake.

Benthic fluxes refer to the exchange rates of nutrients and other compounds between the water column and the sediment bed in aquatic ecosystems. Their quantification contributes to our understanding of aquatic ecosystem functioning. Near-bed hydrodynamics plays an important role at the sediment-water interface, especially in shallow lakes, but it is poorly considered by traditional measuring techniques of flux quantification, such as sediment incubations. Thus, alternative sampling techniques are needed to characterize key benthic fluxes under in-situ hydrodynamic conditions. This study aimed to evaluate the performance of two promising methods: relaxed eddy accumulation (REA) and mass transfer coefficient (MTC). We applied them in a hyper-eutrophic shallow lake to measure the fluxes of ammonium, phosphate, iron, and manganese ions. For the first time, REA revealed hourly nutrient flux variations, indicating a strong lake biogeochemical dynamics at short time-scales. Daily average fluxes are of similar orders of magnitude for REA and MTC for ammonium (24 and 42 mmol m2 d-1), manganese (1.0 and 0.8), and iron (0.8 and 0.7) ions. They are one order of magnitude higher than fluxes estimated from sediment incubations, due to the difficulty in reproducing in-situ oxygen and hydrodynamic conditions in the laboratory. Although the accuracy of both techniques needs to be improved, the results revealed their potential: REA follows the short-term biogeochemical dynamics of sediments, while MTC could be widely used for lake monitoring because of its simpler implementation.

Diagnosis and Management of Pregnant Women With Placental Abruption and Neonatal Outcomes.

Background Placenta abruptio (PA) remains a serious materno-fetal complication. According to progress realized in maternal-fetal medicine, we aimed to evaluate the diagnosis and management of PA and neonatal outcomes. Methods We conducted a retrospective study that involved all the patients that were diagnosed with PA in a tertiary maternity hospital between 2006 and 2013. Data were analyzed to determine mean and standard deviation and statistically analyzed using the Chi-square test. Results In total, 201 patients were diagnosed with PA out of 35184 deliveries (0.56%). The mean age of patients was 30 years and most of them were multiparous (56.2%). Thirty-six out of 201 patients (17.9%) smoked tobacco or consumed alcohol during the pregnancy. Three patients came from their homes. Twenty-eight patients had preeclampsia and 105 presented with high blood pressure. Furthermore, 117 patients presented metrorrhagia (58.2%) and 39% of patients exhibited abdominal pain. We reported fetal heart rate abnormalities in 57% of the cases. Ultrasound examination revealed PA in only 48 patients (23.9%). One hundred eighty out of 201 patients (84.6%) underwent an emergency caesarean section. One hundred sixty-seven fetuses were born prematurely. Thirteen out of 201 fetuses died, and 98 newborns needed neonatal resuscitation. In total, 31 fetuses had an umbilical artery (UA) with pH ≤ 7 (31/188). The mean time for delivery was 18.7 min. However, UA pH did not differ when the delivery time was shorter (p = 0.09). Seventy-six percent of cases came from their homes. The mean UA pH was significantly lower for PA cases who came from their homes compared to hospitalized women (p = 0.0015). Histological examination of the placenta confirmed the diagnosis in 71 out of 148 cases (47.9%). The mean duration of hospital stay of the newborns was 17 days. Conclusion PA remains a serious materno-fetal emergency with a bad fetal prognosis for many newborns. Many fetuses either died or exhibited severe acidosis. Clinical signs and radiological images of PA are absent in many cases. There was more fetal acidosis for mothers who came from their homes at the time of delivery. We recommend that the delivery should not be delayed and a cesarean section must be the preferred mode of delivery. Pregnant women with vascular and metabolic diseases should be carefully monitored and informed on the risk of PA.

Multiple square sutures for postpartum hemorrhage: results and hysteroscopic assessment.

OBJECTIVE: The purpose of this study was to evaluate the efficiency and morbidity of multiple square sutures in severe postpartum hemorrhage. STUDY DESIGN: A retrospective study encompassed 30 multiple square sutures that were performed for severe postpartum hemorrhage in 26,605 deliveries in a tertiary maternity center. The main outcome measures were the ability to stop hemorrhage and the assessment of the uterine cavity by hysteroscopy at 3 months. RESULTS: Multiple square sutures stopped postpartum hemorrhage in 28 of 30 cases (93%). Twenty women underwent hysteroscopy after multiple square sutures. Eight women (40%) did not have intrauterine adhesions. Nine women (45%) had thin and localized intrauterine adhesions that were removed easily by the tip of the hysteroscope; 2 women had moderate intrauterine adhesions that were resected. One patient had endometritis followed by severe intrauterine adhesions. CONCLUSION: Multiple square sutures are effective and safe for the control of severe postpartum hemorrhage and for uterine conservation in most cases. Although some patients had moderate or severe adhesions, a normal uterine cavity or minimal intrauterine adhesions that were removed easily were the most frequent findings at hysteroscopy. A prospective study may be helpful to compare the safety and efficiency of square and brace sutures.

Impact of Escherichia coli from stormwater drainage on recreational water quality: an integrated monitoring and modelling of urban catchment, pipes and lake.

In recent years, recreational waterbodies are increasingly favoured in urban areas. In spite of the growing concerns for maintaining the required bathing water quality, the impacts of stormwater drainage are still poorly controlled. In this context, this study originally develops an integrated urban catchment-pipes-lake monitoring and modelling approach to simulate the impacts of microbial quality from stormwater drainage on recreational water quality. The modelling system consists of three separated components: the urban catchment component, the 3D lake hydrodynamic component and the 3D lake water quality component. A series of processes are simulated in the model, such as rainfall-discharge, build-up, wash-off of Escherichia coli (E. coli) on urban surfaces, sewer flows, hydrothermal dynamics of lake water and transport and mortality of E. coli in the lake. This integrated model is tested for an urban catchment and its related recreational lake located in the Great Paris region. Continuous monitoring and samplings were performed at the stormwater drainage outlet and three different sites in the lake. Comparing the measured data with simulation results over 20 months, the modelling system can correctly represent the E. coli dynamics in the stormwater sewer systems and in the lake. Although uncertainties related to parameter values, pollution sources and E. coli mortality processes could be further discussed, the good performance of this modelling approach emphasizes a promising potential for urban bathing water quality management.

Linking phytoplankton pigment composition and optical properties: A framework for developing remote-sensing metrics for monitoring cyanobacteria.

This study has been performed in the framework of a research program aiming to develop a low-cost aerial sensor for the monitoring of cyanobacteria in freshwater ecosystems that could be used for early detection. Several empirical and mechanistic remote-sensing tools have been already developed and tested at large scales and have proven useful in monitoring cyanobacterial blooms. However, the effectiveness of these tools for early detection is hard to assess because such work requires the detection of low concentrations of characteristic pigments amid complex ecosystems exhibiting several confounding factors (turbidity, blooms of other species, etc.). We developed a framework for performing high-throughput measurements of the absorbance and reflectance of small volumes (∼ = 20 mL) of controlled mixtures of phytoplankton species and studied the potential of this framework to validate remote-sensing proxies of cyanobacteria concentration. The absorption and reflectance spectra of single and multiple cultures carried a specific signal that allowed for the quantitative analysis of culture mixes. This specific signal was shown to be related to known pigment absorbance spectra. The concentrations of chlorophyll-a and -b, phycocyanin and phycoerythrin could be obtained from direct absorbance measurements and were correlated with the concentration obtained after pigment extraction (R2 ≥ 0.96 for all pigments). A systematic test of every possible two-band and three-band normalized difference between optical indices was then performed, and the coincidental correlation with chlorophyll-b (absent in cyanobacteria) was used as an indicator of non-specificity. Two-band indices were shown to suffer from non-specificity issues and could not yield strong and specific relationships with phycocyanin or phycoerythrin (maximum R2 < 0.5). On the other hand, the three-band modified normalized difference indices yielded strong specific relationships (R2 > 0.8).

On the successful use of a simplified model to simulate the succession of toxic cyanobacteria in a hypereutrophic reservoir with a highly fluctuating water level.

Many freshwater bodies worldwide that suffer from harmful algal blooms would benefit for their management from a simple ecological model that requires few field data, e.g. for early warning systems. Beyond a certain degree, adding processes to ecological models can reduce model predictive capabilities. In this work, we assess whether a simple ecological model without nutrients is able to describe the succession of cyanobacterial blooms of different species in a hypereutrophic reservoir and help understand the factors that determine these blooms. In our study site, Karaoun Reservoir, Lebanon, cyanobacteria Aphanizomenon ovalisporum and Microcystis aeruginosa alternatively bloom. A simple configuration of the model DYRESM-CAEDYM was used; both cyanobacteria were simulated, with constant vertical migration velocity for A. ovalisporum, with vertical migration velocity dependent on light for M. aeruginosa and with growth limited by light and temperature and not by nutrients for both species. The model was calibrated on two successive years with contrasted bloom patterns and high variations in water level. It was able to reproduce the measurements; it showed a good performance for the water level (root-mean-square error (RMSE) lower than 1 m, annual variation of 25 m), water temperature profiles (RMSE of 0.22-1.41 °C, range 13-28 °C) and cyanobacteria biomass (RMSE of 1-57 µg Chl a L-1, range 0-206 µg Chl a L-1). The model also helped understand the succession of blooms in both years. The model results suggest that the higher growth rate of M. aeruginosa during favourable temperature and light conditions allowed it to outgrow A. ovalisporum. Our results show that simple model configurations can be sufficient not only for theoretical works when few major processes can be identified but also for operational applications. This approach could be transposed on other hypereutrophic lakes and reservoirs to describe the competition between dominant phytoplankton species, contribute to early warning systems or be used for management scenarios.

Dynamics of the toxin cylindrospermopsin and the cyanobacterium Chrysosporum (Aphanizomenon) ovalisporum in a Mediterranean eutrophic reservoir.

Chrysosporum ovalisporum is a cylindrospermopsin toxin producing cyanobacterium that was reported in several lakes and reservoirs. Its growth dynamics and toxin distribution in field remain largely undocumented. Chrysosporum ovalisporum was reported in 2009 in Karaoun Reservoir, Lebanon. We investigated the factors controlling the occurrence of this cyanobacterium and vertical distribution of cylindrospermopsin in Karaoun Reservoir. We conducted bi-weekly sampling campaigns between May 2012 and August 2013. Results showed that Chrysosporum ovalisporum is an ecologically plastic species that was observed in all seasons. Unlike the high temperatures, above 26 °C, which is associated with blooms of Chrysosporum ovalisporum in Lakes Kinneret (Israel), Lisimachia and Trichonis (Greece) and Arcos Reservoir (Spain), Chrysosporum ovalisporum in Karaoun Reservoir bloomed in October 2012 at a water temperature of 22 °C during weak stratification. Cylindrospermopsin was detected in almost all water samples even when Chrysosporum ovalisporum was not detected. Chrysosporum ovalisporum biovolumes and cylindrospermopsin concentrations were not correlated (n = 31, r² = -0.05). Cylindrospermopsin reached a maximum concentration of 1.7 µg L⁻¹. The vertical profiles of toxin concentrations suggested its possible degradation or sedimentation resulting in its disappearance from the water column. The field growth conditions of Chrysosporum ovalisporum in this study revealed that it can bloom at the subsurface water temperature of 22 °C increasing the risk of its development and expansion in lakes located in temperate climate regions.

Estimating the risk of cyanobacterial occurrence using an index integrating meteorological factors: application to drinking water production.

The sudden appearance of toxic cyanobacteria (CB) blooms is still largely unpredictable in waters worldwide. Many post-hoc explanations for CB bloom occurrence relating to physical and biochemical conditions in lakes have been developed. As potentially toxic CB can accumulate in drinking water treatment plants and disrupt water treatment, there is a need for water treatment operators to determine whether conditions are favourable for the proliferation and accumulation of CB in source waters in order to adjust drinking water treatment accordingly. Thus, a new methodology with locally adaptable variables is proposed in order to have a single index, f(p), related to various environmental factors such as temperature, wind speed and direction. The index is used in conjunction with real time monitoring data to determine the probability of CB occurrence in relation to meteorological factors, and was tested at a drinking water intake in Missisquoi Bay, a shallow transboundary bay in Lake Champlain, Québec, Canada. These environmental factors alone were able to explain a maximum probability of 68% that a CB bloom would occur at the drinking water treatment plant. Nutrient limitation also influences CB blooms and intense blooms only occurred when the dissolved inorganic nitrogen (DIN) to total phosphorus (TP) mass ratio was below 3. Additional monitoring of DIN and TP could be considered for these source waters prone to cyanobacterial blooms to determine periods of favourable growth. Real time monitoring and the use of the index could permit an adequate and timely response to CB blooms in drinking water sources.

Modelagem da Lagoa da Pampulha: uma ferramenta para avaliar o impacto da bacia hidrográfica na dinâmica do fitoplâncton / Modelling Lake Pampulha: a tool for assessing the catchment area impacts on the phytoplankton dynamics

RESUMO No processo de urbanização, o aumento na proporção de superfícies impermeabilizadas e as mudanças no uso do solo são responsáveis por maiores volumes e velocidades do escoamento superficial, refletindo em uma maior capacidade de arraste e em um maior aporte de nutrientes nos corpos d'água receptores. O objetivo deste trabalho foi implementar uma ferramenta matemática capaz de reproduzir o impacto de mudanças na bacia hidrográfica sobre a dinâmica do fitoplâncton em um lago urbano. Neste artigo são apresentados o desenvolvimento e os resultados de um modelo integrado constituído de um modelo hidrológico, para simular vazões escoadas em uma bacia hidrográfica, e de um modelo hidrodinâmico e ecológico, para simular a biomassa fitoplanctônica em um corpo d'água urbano. A Lagoa da Pampulha (Belo Horizonte, Minas Gerais), escolhida como estudo de caso, foi intensamente monitorada, assim como sua bacia de drenagem, entre outubro de 2011 e junho de 2013. Os dados obtidos foram utilizados para calibrar e validar ambos os modelos. Os resultados obtidos com o modelo hidrológico mostraram-se coerentes com as medidas realizadas em campo (o coeficiente de Nash variou entre 0,70 e 0,88). O modelo da lagoa representou corretamente a evolução da comunidade fitoplanctônica (erro médio absoluto normalizado: 0,25-0,42 e o coeficiente de Pearson: 0,82-0,89; p<0,0001). O monitoramento e a modelagem da lagoa mostraram que a proliferação de cianobactérias é bastante perturbada pelas desestratificações térmicas que ocorrem na lagoa em virtude de eventos meteorológicos. A ferramenta de simulação desenvolvida possui potencial para avaliar diferentes cenários de mudança das condições climáticas e das características da bacia, podendo auxiliar na gestão dos corpos d'água situados em meio urbano.

ABSTRACT In urban areas the increasing imperviousness is responsible for rising runoff volume and speed, leading to a greater capacity to load nutrients and pollutants into reservoirs. In order to study the impacts of catchment changes on the phytoplankton dynamics in urban lakes, a modelling approach in which a hydrological model is connected to an ecological lake model is proposed for Lake Pampulha (Brazil). In this paper we present the methodology used to link both models. Lake Pampulha and its catchment area were intensively monitored between October 2011 and June 2013 in order to provide data for the calibration and validation of both models. The results of the hydrologic model showed good agreement with the in situ measurements, and the Nash coefficient ranged from 0.70 to 0.88. The lake ecological model have successfully represented the cyanobacteria dynamics (normalized mean average error: 0.25-0.42, Pearson coefficient: 0.82-0.89, p<0.0001). Monitoring and modelling showed that cyanobacteria blooms are quite disturbed by water column mixing caused by rain events. The mathematical tool developed here can be used to assess different scenarios of climate changes or catchment area changes and can be very helpful for the management of urban water resources.

The complex phase behaviour of suspensions of goethite (alpha-FeOOH) nanorods in a magnetic field.

In 1902, Majorana reported the magneto-optical properties of aqueous colloidal suspensions of mixed iron oxides. Oddly enough, the magnetic-field induced birefringence displayed a non-monotonic dependence upon field intensity. This behaviour was later interpreted as due to the existence in these sols of at least two different chemical species. During the course of our studies of mineral liquid crystals, we have revisited this problem by examining aqueous suspensions of pure goethite (alpha-FeOOH) nanorods. Although they are comprised of a single chemical species, these suspensions show the same odd behaviour reported by Majorana. Moreover, we show that, as the volume fraction increases, the suspensions have an isotropic liquid/nematic/rectangular columnar phase sequence, with first-order transitions between these phases. The non-monotonic dependence of the field-induced birefringence can be explained by the existence of a remanent magnetic moment of the nanorods and the negative anisotropy of their magnetic susceptibility. Therefore, the nanorods align parallel to a weak field but realign perpendicular to the field beyond Bc approximately 375 mT. In addition, other interesting phenomena appear upon application of a magnetic field: the disordered (i.e. isotropic in zero-field) phase becomes highly anisotropic and difficult to distinguish from the nematic phase. Both phases then acquire not only quadrupolar order but also dipolar order. The rectangular columnar phase is strongly stabilised versus the nematic one. Our experimental observations raise new theoretical questions about the phase diagram of these suspensions with respect to volume fraction and magnetic field intensity.