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Escalas, A., Troussellier, M., Yuan, T., Bouvier, T., Bouvier, C., Mouchet, M. A., et al. (2017). Functional diversity and redundancy across fish gut, sediment and water bacterial communities. Environ. Microbiol., 19(8), 3268–3282.
Résumé: This article explores the functional diversity and redundancy in a bacterial metacommunity constituted of three habitats (sediment, water column and fish gut) in a coastal lagoon under anthropogenic pressure. Comprehensive functional gene arrays covering a wide range of ecological processes and stress resistance genes to estimate the functional potential of bacterial communities were used. Then, diversity partitioning was used to characterize functional diversity and redundancy within (), between () and across () habitats. It was showed that all local communities exhibit a highly diversified potential for the realization of key ecological processes and resistance to various environmental conditions, supporting the growing evidence that macro-organisms microbiomes harbour a high functional potential and are integral components of functional gene dynamics in aquatic bacterial metacommunities. Several levels of functional redundancy at different scales of the bacterial metacommunity were observed (within local communities, within habitats and at the metacommunity level). The results suggested a high potential for the realization of spatial ecological insurance within this ecosystem, that is, the functional compensation among microorganisms for the realization and maintenance of key ecological processes, within and across habitats. Finally, the role of macro-organisms as dispersal vectors of microbes and their potential influence on marine metacommunity dynamics were discussed.
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Sirot, C., Gronkjaer, P., Pedersen, J. B., Panfili, J., Zetina-Rejon, M., Tripp-Valdez, A., et al. (2017). Using otolith organic matter to detect diet shifts in Bardiella chrysoura, during a period of environmental changes. Mar. Ecol.-Prog. Ser., 575, 137–152.
Résumé: Accurate knowledge on fish trophic ecology and its modifications is crucial for understanding the impact of global change on ecosystems. In this context, we investigated the value of the delta C-13 and delta N-15 of otolith soluble organic matter (SOM) for identifying temporal diet shifts in American silver perch Bairdiella chrysoura over a 30-yr period characterized by strong changes in its population size and habitats within the Terminos Lagoon (Mexico). We first compared the otolith SOM isotopic signatures from present-clay adults to those of muscle and the main local prey. Our results suggest that otolith SOM can be confidently extracted and analyzed for both present and past otoliths of this species. The mean otolith SOM signatures obtained (-15.92 +/- 1.35%, for delta C-13 and 9.38 +/- 0.93%, for delta N-15) were consistent with those of the diet as 85% of the individual signatures were included within the prey isotopic niche area. Moreover, this study supports a trophic enrichment factor between diet and otolith (TEFdiet-otolith) close to 0 for delta N-15, while for delta C-13, the TEFololith-muscle of +0.02% warrants further investigation. Then, we compared past and contemporary otolith SOM signatures to investigate temporal diet shifts in B. chrysoura. This showed that 613C and delta N-15 differed significantly between the past and present period even if the temporal shift remained relatively small (respectively +1.17%, and 0.55%). The present study substantiates the use of otolith SOM delta C-13 and delta N-15 as a proxy of fish present and past trophic position, opening the possibility for major progress in studies of temporal changes in food web ecology.
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