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Hattab, T., Albouy, C., Lasram, F. B., Le Loc'h, F., Guilhaumon, F., & Leprieur, F. (2015). A biogeographical regionalization of coastal Mediterranean fishes. Journal of Biogeography, 42(7), 1336–1348.
Résumé: AimTo delineate the biogeographical regions of the continental shelf of the Mediterranean Sea based on the spatial distributions of coastal marine fishes and their evolutionary relationships, with a view to furthering our capacity to answer basic and applied biogeographical, ecological and evolutionary questions. LocationMediterranean Sea. MethodsWe used a dataset summarizing the occurrences of 203 coastal Mediterranean fishes (0.1 degrees resolution grid system) and a molecular phylogenetic tree to quantify both compositional and phylogenetic dissimilarity (or beta diversity) between cells. We then applied multivariate analyses to delineate biogeographical regions and to evaluate how they related to broad-scale environmental gradients. We also assessed the differences between the biogeographical regions identified using phylogenetic beta diversity versus those obtained using compositional beta diversity. ResultsThe bioregionalization schemes based on phylogenetic and compositional beta diversity identified broadly similar regions, each consisting of six distinct pools of coastal fishes. Clear separations between northern and southern regions were observed, as well as a disjunct between inshore and offshore areas. These beta diversity patterns were mainly related to a north-south gradient in sea-surface temperature and bathymetric constraints. Main conclusionsIncorporating phylogenetic information into the measurement of beta diversity did not offer further insights to the bioregionalization scheme based solely on compositional beta diversity. This suggests that evolutionary and historical processes played only a minor role in shaping the contemporary patterns of beta diversity in the Mediterranean coastal fish fauna. However, our results support the view that contemporary environmental conditions play a major role in determining the distribution of these species.
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Elleouet, J., Albouy, C., Ben Rais Lasram, F., Mouillot, D., & Leprieur, F. (2014). A trait-based approach for assessing and mapping niche overlap between native and exotic species: the Mediterranean coastal fish fauna as a case study. Diversity and Distributions, 20(11), 1333–1344.
Résumé: Aim We propose a trait-based approach for assessing and mapping potential niche overlap between native and exotic species at large spatial scales. Location The Mediterranean Sea. Methods We developed two complementary indices based on ecological, biological and ecomorphological similarities between native and exotic species. The first index (FNNr) allows identifying areas where native species are the most at risk in terms of potential ecological interactions with exotic species. The second index (FGO) is species-specific and allows identifying native species that display the broadest functional niche overlap and range overlap with exotic species. We illustrated our approach using the Mediterranean coastal fish fauna as a case study. Results We found that endemic and exotic fishes had a similar global functional niche at the Mediterranean scale, that is, they filled the same functional space defined by trait axes. FNNr hotspots were found to be moderately congruent with exotic species richness hotspots. Higher values of FNNr were observed along the coasts of the Levantine Sea. The computation of the FGO index showed that the geographical range of a given endemic species overlapped in average with 52 exotic species. Species showing the highest FGO values displayed localized and/or fragmented distributions in the eastern Mediterranean basin. Main conclusions Our findings suggest that the number of exotic species alone cannot be used as a broad-scale indicator of potential impact because this metric does not account for functional relatedness between native and exotic species. The trait-based indices developed in this study can be used for other taxa in both aquatic and terrestrial ecosystems and should help environmental managers to set up local-scale studies on areas where the potential impact of exotic species on native biodiversity is the highest.
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McKenzie, D. J., Steffensen, J. F., Taylor, E. W., & Abe, A. S. (2012). The contribution of air breathing to aerobic scope and exercise performance in the banded knifefish Gymnotus carapo L. J. Exp. Biol., 215(8), 1323–1330.
Résumé: The contribution of air breathing to aerobic metabolic scope and exercise performance was investigated in a teleost with bimodal respiration, the banded knifefish, submitted to a critical swimming speed (U-crit) protocol at 30 degrees C. Seven individuals (mean +/- s.e.m. mass 89 +/- 7. g, total length 230 +/- 4. mm) achieved a U-crit of 2.1 +/- 1. body. lengths. (BL). s(-1) and an active metabolic rate (AMR) of 350 +/- 21. mg. kg(-1). h(-1), with 38 +/- 6% derived from air breathing. All of the knifefish exhibited a significant increase in air-breathing frequency (f(AB)) with swimming speed. If denied access to air in normoxia, these individuals achieved a U-crit of 2.0 +/- 0.2. BL. s(-1) and an AMR of 368 +/- 24. mg. kg(-1). h(-1) by gill ventilation alone. In normoxia, therefore, the contribution of air breathing to scope and exercise was entirely facultative. In aquatic hypoxia (P-O2=4. kPa) with access to normoxic air, the knifefish achieved a U-crit of 2.0 +/- 0.1. BL. s(-1) and an AMR of 338 +/- 29. mg. kg(-1). h(-1), similar to aquatic normoxia, but with 55 +/- 5% of AMR derived from air breathing. Indeed, f(AB) was higher than in normoxia at all swimming speeds, with a profound exponential increase during exercise. If the knifefish were denied access to air in hypoxia, U-crit declined to 1.2 +/- 0.1. BL. s(-1) and AMR declined to 199 +/- 29. mg. kg(-1). h(-1). Therefore, air breathing allowed the knifefish to avoid limitations to aerobic scope and exercise performance in aquatic hypoxia.
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Jeanbille, M., Gury, J., Duran, R., Tronczynski, J., Ghiglione, J. - F., Agogué, H., et al. (2016). Chronic Polyaromatic Hydrocarbon (PAH) Contamination Is a Marginal Driver for Community Diversity and Prokaryotic Predicted Functioning in Coastal Sediments. Front. Microbiol., 7, Unsp-1303.
Résumé: Benthic microorganisms are key players in the recycling of organic matter and recalcitrant compounds such as polyaromatic hydrocarbons (PAHs) in coastal sediments. Despite their ecological importance, the response of microbial communities to chronic PAH pollution, one of the major threats to coastal ecosystems, has received very little attention. In one of the largest surveys performed so far on coastal sediments, the diversity and composition of microbial communities inhabiting both chronically contaminated and non-contaminated coastal sediments were investigated using high throughput sequencing on the 18S and 16S rRNA genes. Prokaryotic alpha-diversity showed significant association with salinity, temperature, and organic carbon content. The effect of particle size distribution was strong on eukaryotic diversity. Similarly to alpha-diversity, beta diversity patterns were strongly influenced by the environmental filter, while PAHs had no influence on the prokaryotic community structure and a weak impact on the eukaryotic community structure at the continental scale. However, at the regional scale, PAHs became the main driver shaping the structure of bacterial and eukaryotic communities. These patterns were not found for PICRUSt predicted prokaryotic functions, thus indicating some degree of functional redundancy. Eukaryotes presented a greater potential for their use as PAH contamination biomarkers, owing to their stronger response at both regional and continental scales.
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Li, X., Blancheton, J. - P., Liu, Y., Triplet, S., & Michaud, L. (2014). Effect of oxidation-reduction potential on performance of European sea bass (Dicentrarchus labrax) in recirculating aquaculture systems. Aquaculture International, 22(4), 1263–1282.
Résumé: The direct impact of oxidation-reduction potential (ORP) on fish welfare and water quality in marine recirculating aquaculture systems (RAS) is poorly documented. In this study, the effects of the fish size (S-1, S-2, S-3) and ORP level (normal, four successive levels) on the performance of European sea bass (Dicentrarchus labrax) were investigated. Three size fish were distributed into two RAS (RAS and RAS O-3). Ozone was injected into RAS O-3 to increase the ORP level. The ORP was stabilized to four successive levels: 260-300, 300-320, 320-350, and 300-320 mV in fish tanks during four periods (P1-4). At the last day of each period, the hematological parameters, plasma protein and mortality of sea bass were analyzed. Two-way ANOVA revealed that several hematological parameters, including pH, hematocrit, concentrations of oxygen, carbon dioxide, glucose (Glu), ionized calcium, kalium, and hemoglobin, were significantly influenced by the increased ORP levels over the experimental period. The alteration in blood Glu and plasma protein concentration showed that ORP around 300-320 mV started to stress sea bass. Once the ORP exceeded 320 mV in the tanks during the P-3 period, mortality occurred even when total residual oxidants/ozone-produced oxidants was only 0.03-0.05 mg L-1 in the fish tanks. At the same time, plasma protein decreased notably due to appetite depression. After the decrease in ORP during the P-4 period, mortality continued. In conclusion, the results strongly suggest that for European sea bass in RAS, the ORP should not exceed 320 mV in the tanks. Once ozonation damaged fish, the effect seemed to be irreversible. However, how ORP affected related hematological parameters still need the further investigations.
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