| Enregistrements |
| Auteur |
Brochier, T.; Ecoutin, J.M.; de Morais, L.T.; Kaplan, D.M.; Lae, R. |
Titre  |
A multi-agent ecosystem model for studying changes in a tropical estuarine fish assemblage within a marine protected area |
Type |
Article scientifique |
| Année |
2013 |
Publication |
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Revue Abrégée |
Aquatic Living Resources |
| Volume |
26 |
Numéro |
02 |
Pages |
147-158 |
| Mots-Clés |
ecosystem model; Life history; marine protected area; Spill-over; trophic level; Tropical estuarine fish assemblage; West Africa |
| Résumé |
As marine protected areas (MPAs) are increasingly being utilised as a tool for fishery management, their impact on the food web needs to be fully understood. However, little is known about the effect of MPAs on fish assemblages, especially in the presence of different life history and ecological traits. Modelling the observed changes in fish population structures may provide a mechanistic understanding of fish assemblage dynamics. In addition, modelling allows a quantitative estimate of MPA spill-over. To achieve this purpose, we adapted an existing ecosystem model, OSMOSE (Object-oriented simulator of marine biodiversity exploitation), to the specific case of the presence of fish with multiple life histories. The adapted model can manage 4 main categories of life history identified in an estuary MPA: fish that (1) spend their entire life cycle locally, (2) are present only as juveniles, (3) enter the area as juveniles and stay permanently except during reproduction periods, which occur outside the estuary, and (4) are present occasionally and for a short time for foraging purposes. To take into account these specific life-history traits, the OSMOSE code was modified. This modelling approach was developed in the context of the Bamboung Bolong MPA, located in a mangrove area in the Sine-Saloum Delta, Senegal. This was the ideal case to develop our approach as there has been scientific monitoring of the fish population structure inside the MPA before fishery closure, providing a reference state, and continuous monitoring since the closure. Ecologically similar species were pooled by trophic traits into 15 groups that represented 97% of the total biomass. Lower trophic levels (LTL) were represented by 6 compartments. The biomass of the model species was calibrated to reproduce the reference situation before fishery closure. Model predictions of fish assemblage changes after fishery closure corresponding to the Bamboung MPA creation scenario were compared to field observations; in most cases the model reproduces observed changes in biomass (at least in direction). We suggest the existence of a “sanctuary effect”, that was not taken into account in the model, this could explain the observed increase in biomass of top predators not reproduced by the model. Finally, the annual MPA fish spill-over was estimated at 11 tons (~33% of the fish biomass) from the model output, mainly due to diffusive effects. |
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LL @ pixluser @ |
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298 |
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Meddeb, M.; Niquil, N.; Grami, B.; Mejri, K.; Haraldsson, M.; Chaalali, A.; Pringault, O.; Hlaili, A.S. |
| Titre |
A new type of plankton food web functioning in coastal waters revealed by coupling Monte Carlo Markov chain linear inverse method and ecological network analysis |
Type |
Article scientifique |
| Année |
2019 |
Publication |
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Revue Abrégée |
Ecol. Indic. |
| Volume |
104 |
Numéro |
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Pages |
67-85 |
| Mots-Clés |
Bacterial multivorous food web; biogenic carbon; Coastal waters; continental-shelf; Ecology; ecosystem attributes; flow networks; Food web modeling; grazing impact; gulf; mediterranean sea; model analysis; Network analysis; Seasonal variations; seasonal-dynamics; trophic network; Trophic structure |
| Résumé |
Plankton food webs (PFW) typology is based on different categories of functioning, according to the dominant processes and the role played by heterotrophic bacteria, small vs large phytoplankton, and small vs large zooplankton. Investigating the structure and the function of planktonic food webs in two SW Mediterranean waters (inshore and marine sites) at four seasons, using inverse (LIM-MCMC) and ecological network (ENA) analyses, we identified a new type of food web, called the “bacterial multivorous food web”. This food web adds to the conventional trophic continuum as previously reported. The “bacterial multivorous food web” present in winter showed the lowest primary production among seasons, but highest bacterial production. Several food web ratios characterized this new typology e.g. picophytoplankton net primary production to total primary production varied from 0.20 to 0.28; bacterial to primary production ratio is higher than values reported in global scale (congruent to 1); bacterial net production to the potential protozoan prey net production was high (>0.2). In this special food web, carbon was mostly recycled, with a moderate fraction channeled to deep waters, which lead to a higher retention of carbon inside the ecosystem. This winter PFW also seemed to be the most organized, specialized, stable and mature, as related to common interpretations of ENA. The spring was characterized by herbivorous food web, with highest activity coinciding with low stability. Although less usual, the herbivorous pathway was also observed during summer, in inshore waters. The autumn food webs, which functioned as multivorous or microbial food webs, appeared to be stable and mature. Finally, our study demonstrates the usefulness of food web models derived ratios combined with ecological network analysis indices to conduct evaluation of the structure and functioning of ecosystems and potentially to support management decisions in marine environment. |
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English |
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1470-160x |
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pas de |
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MARBEC @ isabelle.vidal-ayouba @ |
collection |
2596 |
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Olokotum, M.; Mitroi, V.; Troussellier, M.; Semyalo, R.; Bernard, C.; Montuelle, B.; Okello, W.; Quiblier, C.; Humbert, J.-F. |
| Titre |
A review of the socioecological causes and consequences of cyanobacterial blooms in Lake Victoria |
Type |
Article scientifique |
| Année |
2020 |
Publication |
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Revue Abrégée |
Harmful Algae |
| Volume |
96 |
Numéro |
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Pages |
101829 |
| Mots-Clés |
climate-change; Consequences of cyanobacterial blooms; Cyanobacteria; East Africa; Eutrophication; harmful algal blooms; introduced nile perch; Lake Victoria; land-use; lates-niloticus; microcystin concentrations; murchison bay; nutrient concentrations; nyanza gulf; oreochromis-niloticus; Potential toxicity; Socioecological analysis |
| Résumé |
Africa is experiencing high annual population growth in its major river basins. This growth has resulted in significant land use change and pollution pressures on the freshwater ecosystems. Among them, the Lake Victoria basin, with more than 42 million people, is a unique and vital resource that provides food and drinking water in East Africa. However, Lake Victoria (LV) has experienced a progressive eutrophication and substantial changes in the fish community leading to recurrent proliferation of water hyacinth and cyanobacteria. Based on an extensive literature review, we show that cyanobacterial biomasses and microcystin concentrations are higher in the bays and gulfs (B&Gs) than in the open lake (OL), with Microcystis and Dolichospermum as the dominant genera. These differences between the B&Gs and the OL are due to differences in their hydrological conditions and in the origins, type and quantities of nutrients. Using data from the literature, we describe the multiple ways in which the human population growth in the LV watershed is connected to the increasing occurrence of cyanobacterial blooms in the OL and B&Gs. We also described the consequences of cyanobacterial blooms on food resources and fishing and on direct water use and water supply of local populations, with their potential consequences on the human health. Finally, we discuss the actions that have been taken for the protection of LV. Although many projects have been implemented in the past years in order to improve the management of waste waters or to reduce deforestation and erosion, the huge challenge of the reduction of cyanobacterial blooms in LV by the control of eutrophication seems far from being achieved. |
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English |
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1568-9883 |
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WOS:000541912700007 |
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pas de |
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MARBEC @ isabelle.vidal-ayouba @ |
collection |
2822 |
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Roques, C.; Grousset, E.; Troussellier, M.; Hermet, S.; Le Carrer, J.; Sar, C.; Caro, A. |
| Titre |
A trade-off between mucocytes and bacteriocytes inLoripes orbiculatusgills (Bivalvia, Lucinidae): a mixotrophic adaptation to seasonality and reproductive status in a symbiotic species? |
Type |
Article scientifique |
| Année |
2020 |
Publication |
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Revue Abrégée |
Mar. Biol. |
| Volume |
167 |
Numéro |
10 |
Pages |
154 |
| Mots-Clés |
bacterial endosymbionts; carbon; chemoautotrophic symbionts; codakia-orbicularis; crassostrea-virginica; life-cycle; loripes-lucinalis; lucinoma-aequizonata; mytilus-edulis; particle processing mechanisms |
| Résumé |
In this study, we investigated the composition of the gill tissue relative to the reproductive status of the lucinid clamLoripes orbiculatus(sensus Poli, 1791) according to seasonal as well as biological parameters to provide insights into the physiological variability of this symbiotic bivalve. Temporal variation in population density was also studied. The species was investigated inZostera noltiiseagrass beds in the Thau lagoon (43 degrees 26 ' 52.27 '' N, 3 degrees 39 ' 6.25 '' E) in the south of France in a monthly sampling study from May 2013 to July 2015. A total of 257 individual adults of different sizes were analysed according to water temperature and salinity variations. The findings revealed a very stableLoripesdensity over time, with one single reproductive period during late spring/early summer. We also found that bacteriocytes and mucocytes in the gills were negatively correlated and highly variable in their respective proportions. Bacteriocytes remained dominant during cold periods, whereas mucocytes appeared mainly in the gills of large individuals when the water temperature increased in the spring. As mucocytes were also related with gonadal maturation, we hypothesize that these may allow the host to increase the proportion of heterotrophy in its nutrition during spring primary production to face the metabolic demands required for reproduction. It is possible that mucocytes may also be involved in host immunity. |
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0025-3162 |
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WOS:000576898400001 |
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pas de |
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MARBEC @ isabelle.vidal-ayouba @ |
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2895 |
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Lassalle, G.; Gascuel, D.; Loc'h, F.L.; Lobry, J.; Pierce, G.J.; Ridoux, V.; Santos, M.B.; Spitz, J.; Niquil, N. |
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An ecosystem approach for the assessment of fisheries impacts on marine top predators : the Bay of Biscay case study |
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Article scientifique |
| Année |
2012 |
Publication |
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Revue Abrégée |
Ices Journal of Marine Science |
| Volume |
69 |
Numéro |
6 |
Pages |
925-938 |
| Mots-Clés |
Ecopath; Ecosystem modelling; EcoTroph; fisheries impacts; Marine mammals; trophic level |
| Résumé |
A number of marine mammal populations is currently threatened by their interactions with fisheries. The present study aimed to provide insights into the severity of potential impacts of operational and biological interactions between top predators and fisheries, in the Bay of Biscay region. Our approach was to modify an Ecopath with Ecosim (EwE) model describing the overall structure and function of the ecosystem by including landings and discards of exploited stocks and estimations of the bycatch of non-target compartments. Second, a set of ecological indices and a trophic level (TL)-based model (EcoTroph, ET) were derived from the EwE model. ET was used to simulate the effects of increasing fishing pressure on the ecosystem and, more particularly, on top predators. The Bay of Biscay was demonstrated to be not far from overexploitation at the current fishing rate, this phenomenon being particularly noticeable for the highest TLs. Within the toothed cetacean community, bottlenose dolphins appeared the most sensitive to resource depletion, whereas common dolphins and harbour porpoises were most impacted by their incidental captures in fishing gears. This study provides a methodological framework to assess the impacts of fisheries on ecosystems for which EwE, or other ecosystem models, already exist. |
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1054-3139 |
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LL @ pixluser @ |
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201 |
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