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Auteur Ben Gharbia, H.; Yahia, O.K.-D.; Cecchi, P.; Masseret, E.; Amzil, Z.; Herve, F.; Rovillon, G.; Nouri, H.; M’Rabet, C.; Couet, D.; Triki, H.Z.; Laabir, M.
Titre New insights on the species-specific allelopathic interactions between macrophytes and marine HAB dinoflagellates Type Article scientifique
Année 2017 Publication (down) Revue Abrégée Plos One
Volume 12 Numéro 11 Pages e0187963
Mots-Clés Dinoflagellates; Lagoons; Leaves; marine ecosystems; Phenols; Photosynthesis; Phytoplankton; Toxins
Résumé Macrophytes are known to release allelochemicals that have the ability to inhibit the proliferation of their competitors. Here, we investigated the effects of the fresh leaves of two magnoliophytes (Zostera noltei and Cymodocea nodosa) and thalli of the macroalgae Ulva rigida on three HAB-forming benthic dinoflagellates (Ostreopsis cf. ovata, Prorocentrum lima, and Coolia monotis). The effects of C. nodosa and U. rigida were also tested against the neurotoxic planktonic dinoflagellate Alexandrium pacificum Litaker sp. nov (former Alexandrium catenella). Co-culture experiments were conducted under controlled laboratory conditions and potential allelopathic effects of the macrophytes on the growth, photosynthesis and toxin production of the targeted dinoflagellates were evaluated. Results showed that U. rigida had the strongest algicidal effect and that the planktonic A. pacificum was the most vulnerable species. Benthic dinoflagellates seemed more tolerant to potential allelochemicals produced by macrophytes. Depending on the dinoflagellate/macrophyte pairs and the weight of leaves/thalli tested, the studied physiological processes were moderately to heavily altered. Our results suggest that the allelopathic activity of the macrophytes could influence the development of HAB species.
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Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1932-6203 ISBN Médium
Région Expédition Conférence
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2242
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Auteur Pagès, R.; Baklouti, M.; Barrier, N.; Richon, C.; Dutay, J.-C.; Moutin, T.
Titre Changes in rivers inputs during the last decades significantly impacted the biogeochemistry of the eastern Mediterranean basin: A modelling study Type Article scientifique
Année 2020 Publication (down) Revue Abrégée Prog. Oceanogr.
Volume 181 Numéro Pages 102242
Mots-Clés Biogeochemistry; Coupled physical-biogeochemical model; ecosystem changes; Flexible stoichiometry model; Mediterranean Sea; nitrogen; Nutrient; nutrients; organic-carbon; phosphate; phosphorus limitation; phytoplankton; primary productivity; River inputs; sea; western
Résumé The Mediterranean Sea (MS) is a semi-enclosed sea characterized by a zonal west-east gradient of oligotrophy, where microbial growth is controlled by phosphate availability in most situations. External inputs of nutrients including Gibraltar inputs, river inputs and atmospheric deposition are therefore of major importance for the biogeochemistry of the MS. The latter has long been considered to be driven mainly by nutrient exchanges at Gibraltar. However, recent studies indicate that river inputs significantly affect nutrients concentrations in the Mediterranean Sea, although their resulting impact on its biogeochemistry remains poorly understood. In this study, our aim was to help fill this knowledge gap by addressing the large-scale and long-term impact of variations in river inputs on the biogeochemistry of the Mediterranean Sea over the last decades, using a coupled physical-biogeochemical 3D model (NEMO-MED12/Eco3M-Med). As a first result, it has been shown by the model that the strong diminution (60%) of phosphate (PO4) in river inputs into the Mediterranean Sea since the end of the 1980s induced a significant lowering of PO4 availability in the sub-surface layer of the Eastern Mediterranean Basin (EMB). One of the main consequences of PO4 diminution is the rise, never previously documented, of dissolved organic carbon (DOC) concentrations in the surface layer (by 20% on average over the EMB). Another main result concerns the gradual deepening of the top of the phosphacline during the period studied, thus generating a shift between the top of the nitracline and the top of the phosphacline in the EMB. This shift has already been observed in situ and documented in literature, but we propose here a new explanation for its occurrence in the EMB. The last main result is the evidence of the decline in abundance and the reduction of size of copepods calculated by the model over the years 1985-2010, that could partially explain the reduction in size of anchovy and sardine recently recorded in the MS. In this study, it is shown for the first time that the variations in river inputs that occurred in the last decades may have significantly altered the biogeochemical cycles of two key elements (P and C), in particular in the EMB. To conclude, the magnitude of the biogeochemical changes induced by river inputs and runoff alone over the last thirty years clearly calls for the use of realistic scenarios of river inputs along with climate scenarios for coupled physical-biogeochemical forecasts in the MS.
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Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0079-6611 ISBN Médium
Région Expédition Conférence
Notes WOS:000512481200014 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2757
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Auteur Pete, R.; Guyondet, T.; Bec, B.; Derolez, V.; Cesmat, L.; Lagarde, F.; Pouvreau, S.; Fiandrino, A.; Richard, M.
Titre A box-model of carrying capacity of the Thau lagoon in the context of ecological status regulations and sustainable shellfish cultures Type Article scientifique
Année 2020 Publication (down) Revue Abrégée Ecological Modelling
Volume 426 Numéro Pages 109049
Mots-Clés Carrying capacity; Coupled biogeochemical-deb model; Ecological indicators; Nitrogen and phosphorus inputs; Phytoplankton depletion; Shellfish farming; Stakeholder implication; Water frame directive
Résumé The decrease of microbial and nutrient inputs from the watershed has long dominated lagoon ecosystem management objectives. Phytoplankton biomass and abundance have drastically decreased for more than a decade and Zostera meadow have gradually recovered, expressing lagoon ecosystem restoration such as Thau lagoon. Do the progressive achievement of the good ecological status of the Thau lagoon possibly threatens the shellfish industry in terms of production and oyster quality, by reducing the carrying capacity? To provide answers about the right balance to be achieved between conservation and exploitation, a new numerical tool was developed to help in decision-making. We hereby propose to incorporate a Dynamic Energy Budget type shellfish production model to an existing lagoon ecosystem box-model. The influence of different scenarios of nutrient inputs (related to projections of population growth or improvement of treatment plants) and shellfish stocks were tested on oyster performances (production, oyster condition index), carrying capacity of the lagoon and ecological status indices used within the EU Water Framework Directive. Model outputs demonstrated that shellfish production was mainly controlled by nutrient inputs, which depend on hydro-meteorological variability, and specifically by phosphorus and N:P ratios of nutrient inputs. Scenarios tested, however, demonstrated smaller differences of oyster production in comparison to inter-annual variability. The overall ecological status of the lagoon remained in a “good” status with acceptable lagoon-scale phytoplankton depletion, regardless of scenarios, setting the carrying capacity of this ecosystem to be sustainable.
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Editeur Lieu de Publication Éditeur
Langue en Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0304-3800 ISBN Médium
Région Expédition Conférence
Notes WOS:000529795300004 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2762
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Auteur Ramirez-Romero, E.; Molinero, J.C.; Sommer, U.; Salhi, N.; Yahia, O.K.-D.; Yahia, M.N.D.
Titre Phytoplankton size changes and diversity loss in the southwestern Mediterranean Sea in relation to long-term hydrographic variability Type Article scientifique
Année 2020 Publication (down) Revue Abrégée Estuar. Coast. Shelf Sci.
Volume 235 Numéro Pages 106574
Mots-Clés bay; climate-change; Diversity loss; dynamics; evolution; jellyfish; marine; Nanophytoplankton; Ocean warming; patterns; Phytoplankton diversity; plankton communities; Size structural changes; Southwestern mediterranean; temperature; time-series
Résumé Structural changes in plankton primary producers have large implications for food web dynamics, energy fluxes and the vertical export of biogenic particulate carbon. Here we examine phytoplankton data spanning the period 1993-2008 from the Bay of Tunis, southwestern Mediterranean Sea, in relation to long term hydroclimate variability. We show a conspicuous shift in the structure of the phytoplankton community characterized by an increase of small-sized species and diversity loss, revealing a dominance of smaller blooming diatoms and cyanobacteria. Such changes were concurrent with marked modifications in hydroclimatic patterns experienced in the Bay of Tunis consisting of a shift towards enhanced winter precipitation together with rising temperatures. This novel study shows an overall rise in the proportion of small phytoplankton cells and a decreasing trend in phytoplankton diversity in the southern Mediterranean area. These findings warn of a potential decline of trophic efficiency and lesser food web stability resulting from mean size reduction and the diversity loss.
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Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0272-7714 ISBN Médium
Région Expédition Conférence
Notes WOS:000527915700034 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2766
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Auteur Gueroun, S.K.M.; Molinero, J.C.; Piraino, S.; Daly Yahia, M.N.
Titre Population dynamics and predatory impact of the alien jellyfish Aurelia solida (Cnidaria, Scyphozoa) in the Bizerte Lagoon (southwestern Mediterranean Sea) Type Article scientifique
Année 2020 Publication (down) Revue Abrégée Mediterr. Mar. Sci.
Volume 21 Numéro 1 Pages 22-35
Mots-Clés abundance; asexual reproduction rates; aurita cnidaria; common jellyfish; cyanea-capillata; gullmar fjord; mesozooplankton; moon jellyfish; predation; prey selection; prince-william-sound; Scyphomedusae; SW Mediterranean; tokyo bay; zooplankton
Résumé Understanding the life cycle strategies and predatory impact of alien jellyfish species is critical to mitigate the impact that these organisms may have on local populations, biodiversity, and ultimately on the functioning of food webs. In the Mediterranean Sea, little is known about the dynamics of alien jellyfish, despite this biodiversity hotspot being one of the most threatened areas by increasing numbers of alien jellyfish. Here, we investigated the population dynamics and predatory impact of a non-indigenous scyphomedusa, Aurelia solida Browne 1905, in the Bizerte Lagoon, Tunisia. The study was based on bimonthly surveys performed over two consecutive years, from November 2012 to August 2014. Field observations showed that the planktonic phase of A. solida occurs from winter to early summer. Prey composition was investigated by means of gut content and field zooplankton analyses. Calanoid copepods, mollusc larvae, and larvaceans represented the main food items of A. solida. To determine the jellyfish feeding rate and their predatory impact on zooplankton populations, the digestion time for zooplankton prey was assessed at three different temperatures: 13, 18, and 23 degrees C in laboratory conditions, corresponding to the average range of temperatures encountered by A. solida in the Bizerte Lagoon. We found that A. solida consumed 0.5-22.5% and 0.02-37.3% of the daily zooplankton standing stock in 2013 and 2014, respectively. These results indicate a non-negligible but restricted seasonal grazing impact on some mesozooplankton groups, explained by the relatively short lifespan of the medusa stage (5-6 months).
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Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1108-393x ISBN Médium
Région Expédition Conférence
Notes WOS:000524248700003 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2773
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