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Morat, F., Letourneur, Y., Blamart, D., Pecheyran, C., Darnaude, A. M., & Harmelin-Vivien, M. (2014). Offshore-onshore linkages in the larval life history of sole in the Gulf of Lions (NW-Mediterranean). Estuarine Coastal and Shelf Science, 149, 194–202.
Résumé: Understanding individual dispersion from offshore natal areas to coastal nurseries during pelagic larval life is especially important for the sustainable management of exploited marine fish species. For several years, the hatching period, the larval life duration, the average growth rate and the otolith chemical composition (delta C-13, delta O-18, Sr:Ca and Ba:Ca) during the larval life were studied for young of the year (YOY) of sole collected in three main nurseries of the Gulf of Lions (GoL) (Thau, Mauguio and Berre). We investigated the spatial variation in the origin of the sole larvae which colonised the nurseries around the GoL, and whether temporal differences in environmental conditions during this life stage affected growth and larval life duration. The hatching period ranges from October to March, depending on year and site. Average ages at metamorphosis varied between 43 and 50 days, with the lowest and highest values consistently found for Mauguio and Berre, respectively. Otolith growth rates ranged between 2.7 and 3.2 mu m d(-1), with the lowest values in Thau and Mauguio and the highest in Berre. Otolith chemical composition during the larval life also varied, suggesting contrasted larval environmental histories in YOY among nurseries. In fishes from Berre and Mauguio, larval life was more influenced by the Rhone River, showing consistently higher larval Ba:Ca ratios (10/23 mu mol mol(-1)) and lower delta C-13 (-6.5/-6.1 parts per thousand) and delta O-18 values (-1.6/0.1 parts per thousand) than for Thau (with Ba:Ca ratios < 8 mu mol mol(-1), delta C-13 similar to-2.3 parts per thousand and delta O-18 similar to 1.5 parts per thousand). Differences in larval otolith composition were observed for 2004, with higher Ba:Ca and lower delta C-13 and delta O-18 values than in the two other years. These differences were explained by changes in composition and chemical signatures of water masses after an exceptional flooding event of the Rhone River in late 2003. (C) 2014 Elsevier Ltd. All rights reserved.
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Blanchet, M., Pringault, O., Panagiotopoulos, C., Lefevre, D., Charriere, B., Ghiglione, J. - F., et al. (2017). When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition. Aquat. Sci., 79(1), 27–43.
Résumé: Heterotrophic bacterial communities in marine environments are exposed to a heterogeneous mixture of dissolved organic compounds with different bioreactivity that may control both their activity and composition. The coastal environment is an example of a mixing area where recalcitrant allochthonous organic matter from rivers can encounter labile organic matter from marine phytoplanktonic blooms. The objective of this study was to explore the effects of mixed qualities of dissolved organic matter (DOM) on bacterial community activity (BCA) and bacterial community composition (BCC) and to test for a priming effect when DOM sources are added in combination. Coastal marine bacterial communities were incubated separately with a mixture of amino acids and with natural riverine DOM or with both sources together for 42 days. Addition of amino acids alone or in combination with riverine DOM led to a similar stimulation of BCA compared to control condition, whereas addition of riverine DOM alone did not modify BCA compared to the control. On the contrary, BCC analyzed by 16S rRNA gene pyrosequencing was not affected by the addition of amino acids alone, but changed dramatically with riverine DOM alone or in combination with amino acids. Our results show that changes in BCA and BCC can be driven by different types of DOM, but that these changes are not necessarily coupled. Moreover, the addition of labile DOM did not modify the microbial decomposition of riverine DOM, nor the BCC, suggesting that a priming effect did not occur under these experimental conditions.
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