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Auteur (down) Saraux, C.; Van Beveren, E.; Brosset, P.; Queiros, Q.; Bourdeix, J.-H.; Dutto, G.; Gasset, E.; Jac, C.; Bonhommeau, S.; Fromentin, J.-M.
Titre Small pelagic fish dynamics: A review of mechanisms in the Gulf of Lions Type Article scientifique
Année 2019 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 159 Numéro Pages 52-61
Mots-Clés Population dynamics; Zooplankton; anchovy; fisheries; history; forage fish; nw mediterranean sea; el-nino; fluctuations; body condition; Bottom-up; Disease; Exploited species; Top-down; sardine sardinops-sagax; southern benguela
Résumé Around 2008, an ecosystem shift occurred in the Gulf of Lions, highlighted by considerable changes in biomass and fish mean weight of its two main small pelagic fish stocks (European anchovy, Engraulis encrasicolus; European sardine, Sardina pilchardus). Surprisingly these changes did not appear to be mediated by a decrease in fish recruitment rates (which remained high) or by a high fishing pressure (exploitation rates being extremely low). Here, we review the current knowledge on the population's dynamics and its potential causes. We used an integrative ecosystem approach exploring alternative hypotheses, ranging from bottom-up to top-down control, not forgetting epizootic diseases. First, the study of multiple population characteristics highlighted a decrease in body condition for both species as well as an important decrease in size resulting from both a slower growth and a progressive disappearance of older sardines. Interestingly, older sardines were more affected by the decrease in condition than younger ones, another sign of an unbalanced population structure. While top-down control by bluefin tuna or dolphins, emigration and disease were mostly discarded as important drivers, bottom-up control mediated by potential changes in the plankton community appeared to play an important role via a decrease in fish energy income and hence growth, condition and size. Isotopic and stomach content analyses indicated a dietary shift pre- and post-2008 and modeled mesozooplankton abundance was directly linked to fish condition. Despite low energy reserves from 2008 onwards, sardines and anchovies maintained if not increased their reproductive investment, likely altering the life-history trade-off between reproduction and survival and resulting in higher natural mortality. The current worrying situation might thus have resulted from changes in plankton availability/diversity, which remains to be thoroughly investigated together with fish phenotypic plasticity.
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ISSN 0967-0645 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2526
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Auteur (down) Ramirez-Romero, E.; Molinero, J.C.; Paulsen, M.; Javidpour, J.; Clemmesen, C.; Sommer, U.
Titre Quantifying top-down control and ecological traits of the scyphozoan Aurelia aurita through a dynamic plankton model Type Article scientifique
Année 2018 Publication Revue Abrégée J. Plankton Res.
Volume 40 Numéro 6 Pages 678-692
Mots-Clés 2 hydromedusae; annual cycle; baltic sea; coastal ecosystem; common jellyfish; ctenophore mnemiopsis-leidyi; jellyfish; kiel-bight; planktonic food web; population modeling; population-dynamics; predation impact; sarsia-tubulosa; stage-resolved model; zooplankton
Résumé Aurelia aurita (Linneaus, 1758) is a cosmopolitan scyphozoan, probably the most investigated jellyfish in temperate and highly productive coastal ecosystems. Despite a prominent top-down control in plankton food webs, a mechanistic understanding of A. aurita population dynamics and trophic interactions has been barely addressed. Here we develop a food web dynamic model to assess A. aurita role in the seasonal plankton dynamics of the Kiel Fjord, southwestern Baltic Sea. The model couples low trophic level dynamics, based on a classical Nutrient Phytoplankton Zooplankton Detritus (NPZD) model, to a stage-resolved copepod model (referencing Pseudocalanus sp.) and a jellyfish model (A. aurita ephyra and medusa) as consumers and predators, respectively. Simulations showed the relevance of high abundances of A. aurita, which appear related with warm winter temperatures, promoting a shift from a copepod-dominated food web to a ciliate and medusa dominated one. The model captured the intraspecific competition triggered by the medusae abundance and characterized by a negative relationship between population density and individual size/weight. Our results provide a mechanistic understanding of an emergent trait such as size shaping the food web functioning, driving predation rates and population dynamics of A. aurita, driving its sexual reproductive strategy at the end of the pelagic phase.
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Volume de collection Numéro de collection Edition
ISSN 0142-7873 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2476
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Auteur (down) Pagano, M.; Sagarra, P.-B.; Champalbert, G.; Bouvy, M.; Dupuy, C.; Thomas, Y.; Charpy, L.
Titre Metazooplankton communities in the Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia): Spatiotemporal variations and trophic relationships Type Article scientifique
Année 2012 Publication Revue Abrégée Marine Pollution Bulletin
Volume 65 Numéro 10–12 Pages 538-548
Mots-Clés Atoll lagoon; French Polynesia; Metazooplankton; Spatio-temporal patterns; Trophic relationships; pearl oyster
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ISSN 0025-326x ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 693
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Auteur (down) Noyon, M.; Rasoloarijao, Z.; Huggett, J.; Ternon, J.-F.; Roberts, M.
Titre Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages 104759
Mots-Clés biomass size spectrum; chlorophyll-a; cyclonic eddy; eddies; leeuwin current; Mesoscale eddies; Normalised biovolume size spectrum (NBSS); north pacific; Oligotrophic environment; patterns; Pelagic ecology; plankton; temperature; Topography; zooplankton distribution
Résumé Seamounts are recognised as hotspots of biodiversity, attracting large numbers of top predators, but the underlying mechanisms are still unclear. We studied mesozooplankton abundance and size distribution at three shallow seamounts (60 m, 240 m and 18 m deep) in the South West Indian Ocean, along a latitudinal gradient (19 degrees S, 27 degrees S and 33 degrees S). Samples were analysed using a ZooScan, allowing the use of a size-based approach. Differences were observed between seamount areas, but overall zooplankton communities did not seem to be affected by the changes in topography. Only in the lee of La Perouse seamount was the zooplankton community slightly more concentrated than upstream, suggesting that zooplankton were flushed downstream of the seamount. The southernmost and shallowest seamount, Walters Shoal, had low abundance and its size spectrum differed greatly from the two other seamounts further north. These differences were attributed to seasonality and mesozooplankton population dynamics, whereas the other two seamounts exhibited a more “typical” oligotrophic pelagic ecosystem, at equilibrium and dominated by small organisms. At the time of sampling, the unnamed seamount south of Madagascar was influenced by a mesoscale dipole that impacted the zooplankton distribution, potentially masking any seamount effect. The normalised biomass size spectrum approach contributed to a better understanding of the ecosystem dynamics (i.e. equilibrium vs. non-steady state) but revealed little variability within a stable oligotrophic environment.
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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 0967-0645 ISBN Médium
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Notes WOS:000556810400008 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2853
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Auteur (down) Melo, D.C.M.; Lira, S.M.A.; Moreira, A.P.B.; Freitas, L.; Lima, C.A.D.; Thompson, F.; Bertrand, A.; Silva, A.C.; Neumann-Leitao, S.
Titre Genetic diversity and connectivity of Flaccisagitta enflata (Chaetognatha: Sagittidae) in the tropical Atlantic ocean (northeastern Brazil) Type Article scientifique
Année 2020 Publication Revue Abrégée PLoS One
Volume 15 Numéro 5 Pages e0231574
Mots-Clés acartia-tonsa; copepod; differentiation; global phylogeography; heterogeneity; marine; mesozooplankton; mitochondrial-dna; pelagic chaetognath; population-structure
Résumé The phylogeography of the holoplanktonic chaetognath Flaccisagitta enflata was investigated in the Tropical Western Atlantic (TWA). Considering the cosmopolitan range of this species and the fact that its entire life cycle is planktonic, the central hypothesis of this study is that F. enflata exhibits connectivity due to its high dispersal capacity, forming a panmictic population among the study sites. The evaluated areas included neritic (Port of Recife-PR, and Tamandare – TA) and oceanic (Fernando de Noronha Archipelago-FN, Rocas Atoll-RA, Guara seamount-GS and Saint Peter and Saint Paul's Archipelago-SPSPA) locations of the Brazilian Blue Amazon. We used COI gene sequences as molecular marker. Partial sequences (425 bp) were obtained for 116 specimens and employed to reconstruct the phylogeny, build an haplotype network, evaluate gene flow through a migration model, and estimate diversity indices, population structuring and demographic history. High levels of haplotype diversity (mean: 0.98) and moderate to high levels of nucleotide diversity (mean: 0.023) were observed. The phylogeny and the haplotype network topologies showed some geographic clustering, indicating local structuring in GS and PR. This finding was supported by the AMOVA high global phi st (0.033, significant) and some pairwise phi st comparisons (7 out of 15 were significantly > 0). Significant differences suggested lower levels of connectivity when GS population was compared to those of FN and SPSPA; as well as when TA was compared to FN. These results might be related to particularities of the oceanic dynamics which rules the TWA, sustaining such dissimilarities. Structuring was also observed between PR and all oceanic locations. We hypothesize that the topography of the port inlet, enclosured by a reef barrier, may constrain the water turnover ratio and thus migration rates of F. enflata in the TWA. Accordingly, Migrate-N yielded a four metapopulations model (PR (sic) TA (sic) SPSPA+FN (sic) GS+RA) as the best (highest probability; similar to 0.90) to represent the structuring of F. enflata in the TWA. Therefore, the null hypothesis of one randomly mating population cannot be accepted. The demographic evaluation demonstrated that the neutral hypothesis of stable populations may not be rejected for most of the locations. This work is the start point to broaden the knowledge on the phylogeography and population genetic structure of a numerically dominant species in the Western Atlantic, with key role in the marine trophic web.
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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 1932-6203 ISBN Médium
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Notes WOS:000537283500009 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2911
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