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Abadie, E., Chiantella, C., Crottier, A., Rhodes, L., Masseret, E., Berteaux, T., et al. (2018). What are the main environmental factors driving the development of the neurotoxic dinoflagellate Vulcanodinium rugosum in a Mediterranean ecosystem (Ingril lagoon, France)? Harmful Algae, 75, 75–86.
Résumé: Vulcanodinium rugosum, a dinoflagellate developing in Ingril Lagoon (Mediterranean, France) is responsible for shellfish intoxications due to the neurotoxin pinnatoxin G. A one year survey (March 2012–April 2013) was conducted in this oligotrophic shallow lagoon and key environmental parameters were recorded (temperature, salinity and nutrients). The spatio-temporal distribution of V. rugosum in water column and on macrophytes was also determined. Planktonic cells of V. rugosum were observed at all sampling stations, but in relatively low concentrations (maximum of 1000 cell/L). The highest abundances were observed from June to September 2012. There was a positive correlation between cell densities and both temperature and salinity. Non-motile cells were detected on macrophytes, with a maximum concentration of 6300 cells/g wet weight. Nitrite and ammonium were negatively related to V. rugosum abundance whereas total nitrogen, total phosphorus and phosphates showed a positive correlation. Altogether, in situ results suggest that V. rugosum is rather thermophilic and that organic nutrients should be considered when studying the nutrition requirements for this noxious expanding dinoflagellate.
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Alfonso, S., Blanc, M., Joassard, L., Keiter, S. H., Munschy, C., Loizeau, V., et al. (2019). Examining multi- and transgenerational behavioral and molecular alterations resulting from parental exposure to an environmental PCB and PBDE mixture. Aquat. Toxicol., 208, 29–38.
Résumé: Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants extensively used during the 20th century and still present in aquatic environments despite their ban. Effects of exposure to these compounds over generations are poorly documented. Therefore, our aims were to characterize behavioral responses and underlying molecular mechanisms in zebrafish exposed to an environmentally relevant mixture of PCBs and PBDEs as well as in four unexposed offspring generations. Zebrafish (F0) were chronically exposed from the first meal onward to a diet spiked with a mixture containing 22 PCB and 7 PBDE congeners in proportions and concentrations reflecting environmental situations (Sigma PCBs = 1991 and Sigma PBDEs = 411 ng/g). Four offspring generations (F1 to F4) were obtained from this F0 and were not further exposed. Behavior was assessed at both larval and adult stages. Mechanisms related to behavioral defects (habenula maturation and c-fos transcription) and methylation (dnmts transcription) were monitored in larvae. Exposed adult F0 as well as F1 and F3 adults displayed no behavioral change while F2 expressed anxiety-like behavior. Larval behavior was also disrupted, Le. hyperactive after light to dark transition in F1 or hypoactive in F2, F3 and F4. Behavioral disruptions may be related to defect in habenula maturation (observed in F1) and change in c-fos transcription (observed in F1 and F2). Transcription of the gene encoding DNA methyltransferase (dnmt3ba) was also modified in all generations. Our results lead us to hypothesize that chronic dietary exposure to an environmentally relevant mixture of PCB and PBDE triggers multigenerational and transgenerational molecular and behavioral disruptions in a vertebrate model.
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Anastasiadi, D., Vandeputte, M., Sánchez-Baizán, N., Allal, F., & Piferrer, F. (2018). Dynamic epimarks in sex-related genes predict gonad phenotype in the European sea bass, a fish with mixed genetic and environmental sex determination. Epigenetics, 13(9), 988–1011.
Résumé: The integration of genomic and environmental influences into methylation patterns to bring about a phenotype is of central interest in developmental epigenetics, but many details are still unclear. The sex ratios of the species used here, the European sea bass, are determined by genetic and temperature influences. We created four families from parents known to produce offspring with different sex ratios, exposed larvae to masculinizing temperatures and examined, in juvenile gonads, the DNA methylation of seven genes related to sexual development by a targeted sequencing approach. The genes most affected by both genetics and environment were cyp19a1a and dmrt1, with contrasting sex-specific methylation and temperature responses. The relationship between cyp19a1a methylation and expression is relevant to the epigenetic regulation of vertebrate sex, and we report the evidence of such relationship only below a methylation threshold, 80%, and that it was sex-specific: negatively correlated in females but positively correlated in males. From parents to offspring, the methylation in gonads was midway between oocytes and sperm, with bias towards oocytes for amh-r2, er-β2, fsh-r and cyp19a1a. In contrast, dmrt1 levels resembled those of sperm. The methylation of individual CpGs from foxl2, er-β2 and nr3c1 were conserved from parents to offspring, whereas those of cyp19a1a, dmrt1 and amh-r2 were affected by temperature. Utilizing a machine-learning procedure based on the methylation levels of a selected set of CpGs, we present the first, to our knowledge, system based on epigenetic marks capable of predicting sex in an animal with 90% accuracy and discuss possible applications.
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Auguet, J. C., Montanie, H., Hartmann, H. J., Lebaron, P., Casamayor, E. O., Catala, P., et al. (2009). Potential effect of freshwater virus on the structure and activity of bacterial communities in the Marennes-Oleron Bay (France). Microb Ecol, 57(2), 295–306.
Résumé: Batch culture experiments using viral enrichment were conducted to test the response of a coastal bacterial community to autochthonous (i.e., co-existing) or allochthonous riverine viruses. The effects of viral infections on bacterial dynamics and activity were assessed by epifluorescence microscopy and thymidine incorporation, respectively, whereas the effect of viral infection on bacterial community composition was examined by polymerase chain reaction-single strand conformation polymorphism 16S ribosomal RNA fingerprinting. The percentages of high nucleic acid-containing cells, evaluated by flow cytometry, were significantly correlated (r2=0.91, n=12, p<0.0001) to bacterial production, making this value a good predictor of active cell dynamics along the study. While confinement and temperature were the two principal experimental factors affecting bacterial community composition and dynamics, respectively, additions of freshwater viruses had significant effects on coastal bacterial communities. Thus, foreign viruses significantly reduced net bacterial population increase as compared to the enrichment treated with inactivated virus. Moreover, freshwater viruses recurrently and specifically affected bacterial community composition, as compared to addition of autochthonous viruses. In most cases, the combined treatment viruses and freshwater dissolved organic matter helped to maintain or even enhance species richness in coastal bacterial communities in agreement to the 'killing the winner' hypothesis. Thus, riverine virus input could potentially influence bacterial community composition of the coastal bay albeit with modest modification of bulk bacterial growth.
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Bax, N. J., Miloslavich, P., Muller-Karger, F. E., Allain, V., Appeltans, W., Batten, S. D., et al. (2019). A Response to Scientific and Societal Needs for Marine Biological Observations. Front. Mar. Sci., 6.
Résumé: Development of global ocean observing capacity for the biological EOVs is on the cusp of a step-change. Current capacity to automate data collection and processing and to integrate the resulting data streams with complementary data, openly available as FAIR data, is certain to dramatically increase the amount and quality of information and knowledge available to scientists and decision makers into the future. There is little doubt that scientists will continue to expand their understanding of what lives in the ocean, where it lives and how it is changing. However, whether this expanding information stream will inform policy and management or be incorporated into indicators for national reporting is more uncertain. Coordinated data collection including open sharing of data will help produce the consistent evidence-based messages that are valued by managers. The GOOS Biology and Ecosystems Panel is working with other global initiatives to assist this coordination by defining and implementing Essential Ocean Variables. The biological EOVs have been defined, are being updated following community feedback, and their implementation is underway. In 2019, the coverage and precision of a global ocean observing system capable of addressing key questions for the next decade will be quantified, and its potential to support the goals of the UN Decade of Ocean Science for Sustainable Development identified. Developing a global ocean observing system for biology and ecosystems requires parallel efforts in improving evidence-based monitoring of progress against international agreements and the open data, reporting and governance structures that would facilitate the uptake of improved information by decision makers.
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