Meistertzheim, A. - L., Lartaud, F., Arnaud-Haond, S., Kalenitchenko, D., Bessalam, M., Le Bris, N., et al. (2016). Patterns of bacteria-host associations suggest different ecological strategies between two reef building cold-water coral species. Deep Sea Research Part I: Oceanographic Research Papers, 114, 12–22.
Résumé: Cold-water corals (CWC) are main ecosystem engineers of the deep sea, and their reefs constitute hot-spots of biodiversity. However, their ecology remains poorly understood, particularly, the nature of the holobiont formed by corals with their associated bacterial communities. Here, we analyzed Madrepora oculata and Lophelia pertusa samples, collected from one location in a Mediterranean canyon in two different seasons (autumn and spring), in order to test for species specificity and temporal stability of the host-bacteria associations. The 16S rRNA sequencing revealed host-specific patterns of bacterial communities associated with L. pertusa and M. oculata, both in terms of community composition and diversity. All analyzed M. oculata polyps exhibited temporally and spatially similar bacterial communities dominated by haplotypes homologous to the known cnidarians-associated genus Endozoicomonas. In contrast, the bacterial communities associated with L. pertusa varied among polyps from the same colony, as well as among distinct colonies and between seasons. While the resilient consortium formed by M. oculata and its bacterial community fit the definition of holobiont, the versatility of the L. pertusa microbiome suggests that this association is more influenced by the environmental conditions or nutritional status. Our results thus highlight distinct host/microbes association strategies for these two closely related Scleractinians sharing the same habitat, suggesting distinct sensitivity to environmental change.
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Minguez, L., Farcy, E., Ballandonne, C., Lepailleur, A., Serpentini, A., Lebel, J. M., et al. (2014). Acute toxicity of 8 antidepressants: What are their modes of action? Chemosphere, 108, 314–319.
Résumé: Currently, the hazard posed by pharmaceutical residues is a major concern of ecotoxicology. Most of the antidepressants belong to a family named the Cationic Amphipathic Drugs known to have specific interactions with cell membranes. The present study assessed the impact of eight antidepressants belonging to selective serotonin reuptake inhibitors or serotonin norepinephrine reuptake inhibitors by the combination of multi-approaches (in vivo, in vitro, in silico) and gives some insights on the mode of action for these molecules. Antidepressants were from the most to the least toxic compound for Daphnia magna: Sertraline (EC50 = 1.15 mg L-1) > Clomipramine (2.74 mg L-1)> Amitriptyline (4.82 mg L-1)> Fluoxetine (5.91 mg L-1) > Paroxetine (6.24 mg L-1) > Mianserine (7.81 mg L-1) > Citalopram (30.14 mg L-1) and Venlafaxine (141.28 mg L-1). These acute toxicities were found correlated to Log K, coefficients (R = 0.93, p < 0.001) and to cytotoxicity assessed on abalone hemocytes through the neutral red uptake assay (R = 0.96, p < 0.001). If narcosis as mode of action is typically expected during acute ecotoxicity bioassays, we showed by molecular modeling that particular interactions can exist between antidepressants and phosphatidylcholine, a major component of cell membranes, leading to a more specific mode of action corresponding to a potential acidic hydrolysis of ester functions. (C) 2014 Elsevier Ltd. All rights reserved.
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Mostajir, B., Amblard, C., Buffan-Dubau, E., De Wit, R., Lensi, R., & Sime-Ngando, T. (2015). Microbial Food Webs in Aquatic and Terrestrial Ecosystems. In J. - C. Bertrand, P. Caumette, P. Lebaron, R. Matheron, P. Normand, & T. Sime-Ngando (Eds.), (pp. 485–509). Environmental Microbiology: Fundamentals and Applications. Springer Netherlands.
Résumé: In microbial food webs, different types of interactions occur between microorganisms themselves and with meio- and macroorganisms. After an historical and general introduction, the biological components of the microbial food webs in the pelagic and benthic marine and lake ecosystems, as well as in the terrestrial ecosystems, are presented. The functioning of the microbial food webs in different ecosystems is illustrated and explained, including the trophic pathways and transfer of matter from microbial food webs toward meio- and macroorganisms of the superior trophic levels, the nutrient recycling in the aquatic environments, and the decomposition of organic matter in soils. Finally, the factors regulating microbial food webs, primarily “top-down” and “bottom-up” controls, are described with a special focus on the role of viruses in the aquatic microbial food webs.
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Olson, R. J., Young, J. W., Menard, F., Potier, M., Allain, V., Goni, N., et al. (2016). Bioenergetics, Trophic Ecology, and Niche Separation of Tunas. In B. E. Curry (Ed.), (pp. 199–344). Advances in Marine Biology, Vol 74, 74. San Diego: Elsevier Academic Press Inc.
Résumé: Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts.
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PLANQUE, B., FROMENTIN, J. - M., CURY, P., DRINKWATER, K. F., JENNINGS, S., PERRY, R. I., et al. (2010). How does fishing alter marine populations and ecosystems sensitivity to climate? Journal of Marine Systems, 79(3-4), 403–417.
Résumé: Evidence has accumulated that climate variability influences the state and functioning of marine ecosystems. At the same time increasing pressure from exploitation and other human activities has been shown to impact exploited and non-exploited species and potentially modify ecosystem structure. There has been a tendency among marine scientists to pose the question as a dichotomy, i.e., whether (1) “natural” climate variability or (2) fishery exploitation bears the primary responsibility for population declines in fish populations and the associated ecosystem changes. However, effects of both climate and exploitation are probably substantially involved in most cases. More importantly, climate and exploitation interact in their effects, such that climate may cause failure in a fishery management scheme but that fishery exploitation may also disrupt the ability of a resource population to withstand, or adjust to, climate changes. Here, we review how exploitation, by altering the structure of populations and ecosystems, can modify their ability to respond to climate. The demographic effects of fishing (removal of large-old individuals) can have substantial consequences on the capacity of populations to buffer climate variability through various pathways (direct demographic effects, effects on migration, parental effects). In a similar way, selection of population sub-units within metapopulations may also lead to a reduction in the capacity of populations to withstand climate variability and change. At the ecosystem level, reduced complexity by elimination of species, such as might occur by fishing, may be destabilizing and could lead to reduced resilience to perturbations. Differential exploitation of marine resources could also promote increased turnover rates in marine ecosystems, which would exacerbate the effects of environmental changes. Overall (and despite the specificities of local situations) reduction in marine diversity at the individual, population and ecosystem levels will likely lead to a reduction in the resilience and an increase in the response of populations and ecosystems to future climate variability and change. Future management schemes will have to consider the structure and functioning of populations and ecosystems in a wider sense in order to maximise the ability of marine fauna to adapt to future climates. (C) 2009 Elsevier B.V. All rights reserved.
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