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Auteur Dhurmeea, Z.; Pethybridge, H.; Langlais, C.; Somes, C.J.; Nikolic, N.; Bourjea, J.; Appadoo, C.; Bodin, N.
Titre Spatial variation in stable isotopes and fatty acid trophic markers in albacore tuna (Thunnus alalunga) from the western Indian Ocean Type Article scientifique
Année 2020 Publication Revue Abrégée Deep Sea Research Part I: Oceanographic Research Papers
Volume Numéro Pages 103286
Mots-Clés Climate change; Environmental parameters; Phytoplankton; Trophodynamics
Résumé Albacore tuna (Thunnus alalunga) is a highly economically important species in the western Indian Ocean. However, knowledge of its ecological and nutritional characteristics, essential for proper management of the species, is lacking in the region. The trophodynamics of the Indian Ocean albacore was thus examined using known fatty acid trophic markers (FATMs) of primary producers, nutritional condition indices (NCIs) (omega-3/omega-6 ratio and total fatty acid content (TFA)), and baseline and lipid corrected stable isotope of carbon (δ13Ccorr) and nitrogen (δ15Ncorr), measured in the muscle tissue. We applied generalized additive mixed models to understand the spatiotemporal patterns and drivers of these tracers, taking into consideration several intrinsic and extrinsic variables: fish size, fishing position, month, chlorophyll-a and sea surface temperature (SST). Both chlorophyll-a and SST were significant as single explanatory variables for all tracers with SST being the best predictor for docosahexaenoic acid/eicosapentaenoic acid ratio, the omega-6 protists FATM, omega-3/omega-6 ratio, δ13Ccorr and δ15Ncorr. TFA was best predicted by fish size only. Higher primary productivity, as inferred by high δ13Ccorr values and diatom contribution, nutritional condition and trophic position, as inferred by high δ15Ncorr values, were observed in albacore from the temperate southern waters than in the northern tropical regions. Relationships between environmental variables and corrected stable isotopes, FATMs confirm that ocean warming and changes in primary productivity will impact nutrient flow and energy transfer in the marine food web which may have negative nutritional outcomes for albacore. This knowledge is particularly crucial in areas where oceanographic conditions and seawater temperatures are changing at a fast rate and should also be taken into consideration by fisheries managers.
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Volume de collection Numéro de collection Edition
ISSN 0967-0637 ISBN Médium
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Auteur Derolez, V.; Soudant, D.; Malet, N.; Chiantella, C.; Richard, M.; Abadie, E.; Aliaume, C.; Bec, B.
Titre Two decades of oligotrophication: Evidence for a phytoplankton community shift in the coastal lagoon of Thau (Mediterranean Sea, France) Type Article scientifique
Année 2020 Publication Revue Abrégée Estuarine, Coastal and Shelf Science
Volume Numéro Pages 106810
Mots-Clés Eutrophication; Mediterranean coastal lagoon; Nutrients; Oligotrophication; Phytoplankton community shift; Recovery
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Volume de collection Numéro de collection Edition
ISSN 0272-7714 ISBN Médium
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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 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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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
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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 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 (down) 2766
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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 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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Langue en Langue du Résumé Titre Original
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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 (down) 2762
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