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Auteur Reynolds, P.L.; Stachowicz, J.J.; Hovel, K.; Bostrom, C.; Boyer, K.; Cusson, M.; Eklof, J.S.; Engel, F.G.; Engelen, A.H.; Eriksson, B.K.; Fodrie, F.J.; Griffin, J.N.; Hereu, C.M.; Hori, M.; Hanley, T.C.; Ivanov, M.; Jorgensen, P.; Kruschel, C.; Lee, K.-S.; McGlathery, K.; Moksnes, P.-O.; Nakaoka, M.; O'Connor, M.I.; O'Connor, N.E.; Orth, R.J.; Rossi, F.; Ruesink, J.; Sotka, E.E.; Thormar, J.; Tomas, F.; Unsworth, R.K.F.; Whalen, M.A.; Duffy, J.E.
Titre Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere Type Article scientifique
Année 2018 Publication Revue Abrégée Ecology
Volume 99 Numéro 1 Pages 29-35
Mots-Clés patterns; communities; diversity; ecosystems; temperature; seagrasses; eutrophication; predation; biogeography; prey; top-down control; enrichment; latitude; mesograzer; seagrass; species interactions; water temperature; Zostera
Résumé Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37 degrees of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas insitu water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simply increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in predation intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.
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Auteur Salhi, N.; Zmerli Triki, H.; Molinero, J.C.; Laabir, M.; Sehli, E.; Bellaaj-Zouari, A.; Daly Yahia, N.; Kefi-Daly Yahia, O.
Titre Seasonal variability of picophytoplankton under contrasting environments in northern Tunisian coasts, southwestern Mediterranean Sea Type Article scientifique
Année 2018 Publication Revue Abrégée Marine Pollution Bulletin
Volume 129 Numéro 2 Pages 866-874
Mots-Clés Bay of Bizerte; Eutrophication; Lagoon of Bizerte; Picophytoplankton
Résumé We investigated at the single cell level during 16months (June 2012 to September 2013) the temporal distribution of picophytoplankton (picoeukaryotes, Synechococcus and Prochlorococcus) communities in two contrasted ecosystems: the Bay of Bizerte characterised by an oligotrophic regime typical of the Mediterranean Sea and the Bizerte Lagoon that exhibits a mesotrophic/eutrophic state. We aimed at depicting seasonal variations and quantifying the relationships between the environmental factors and the structure and abundance of picophytoplankton communities. Results showed that picophytoplankton groups were able to grow under a wide range of environmental conditions varying seasonally, although their abundances and contributions to the total chlorophyll biomass significantly varied and showed importance in the Bay of Bizerte. Synechococcus was the most abundant group reaching 225∗103cells·cm−3 in the Bay and 278∗103cells·cm−3 in the lagoon. This group was present all over the year in both ecosystems. Structural equation model results pointed out a different configuration regarding the picophytoplankton environmental drivers. The complexity of the configuration, i.e. number of significant links within the system, decreased under enhanced eutrophication conditions. The less exposure to anthropogenic stress, i.e. in the Bay of Bizerte, highlight a larger role of nutrient and hydrological conditions on the seasonal variations of picophytoplankton, whereas a negative effect of eutrophication on picophytoplankton communities was unveiled in the Bizerte Lagoon. We stress that such influence may be exacerbated under expected scenarios of Mediterranean warming conditions and nutrient release in coastal ecosystems.
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Auteur Triki, H.Z.; Daly-Yahia, O.K.; Malouche, D.; Komiha, Y.; Deidun, A.; Brahim, M.; Laabir, M.
Titre Distribution of resting cysts of the potentially toxic dinoflagellate Alexandrium pseudogonyaulax in recently-deposited sediment within Bizerte Lagoon (Mediterranean coast, Tunisia) Type Article scientifique
Année 2014 Publication Revue Abrégée Marine Pollution Bulletin
Volume 84 Numéro 1-2 Pages 172-181
Mots-Clés Alexandrium pseudogonyaulax; autocorrelation; bay; Benthic; blooms; cysts; dynamics; eutrophication; gonyaulax-excavata; gulf; Harmful algae; Mapping; Mediterranean Lagoon of Bizerte; resting cysts; Sediment characteristics; spatial-distribution; surface sediments
Résumé This study investigated the spatial distribution of Alexandrium pseudogonyaulax resting cysts in recently-deposited sediment of Bizerte lagoon (South-Western Mediterranean, Tunisia). This lagoon is the subject of many anthropogenic impacts, such as holding important fishing and aquaculture activities. A. pseudogonyaulax has been shown to produce Goniodomin A, which is a biologically-active compound. We showed that this dinoflagellate produces two types of resting cysts, which could be distinguished by the presence or the absence of a paratabulate wall. The average cyst density across the whole lagoon was rather high, reaching 639 cysts g(-1) of dry sediment (DS). Cyst densities varied widely among the sampled stations, with the highest density of 1685 cyst g(-1) DS being recorded at station 51 near a mussel farm. With respect to sediment characteristics, the highest cyst densities were found within silty sediments with high water content values. The distribution of A. pseudongoyaulax cysts in Bizerte lagoon appears to be related to hydrodynamic factors. (C) 2014 Elsevier Ltd. All rights reserved.
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Notes <p>ISI Document Delivery No.: AL0GF<br/>Times Cited: 0<br/>Cited Reference Count: 45<br/>Triki, Habiba Zmerli Daly-Yahia, Ons Kefi Malouche, Dhafer Komiha, Yosr Deidun, Alan Brahim, Mouldi Iaabir, Mohamed<br/>JEAI ECO-BIZ (Jeune Equipe Associee, Ecologie de la lagune de Bizerte) program – IRD (Institut Francais pour la Recherche et le Developpement), IRD; TOTAL Foundation<br/>This work benefitted from financial supports from the JEAI ECO-BIZ (Jeune Equipe Associee, Ecologie de la lagune de Bizerte) program funded by IRD (Institut Francais pour la Recherche et le Developpement), IRD also funded 2 months stay of Dr. Mohamed Laabir in Tunis (INAT). Thanks to TOTAL Foundation for funding LAGUNOTOX project which supported financially the stay of Mrs Triki-Zmerli in Montpellier.<br/>Pergamon-elsevier science ltd<br/>Oxford</p> Approuvé pas de
Numéro d'Appel MARBEC @ alain.herve @ collection 1175
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