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| Dauvin, Jean-claude; Dewarumez, Jean-marie; Elkaim, B; Bernardo, D; Fromentin, Jean-marc; Ibanez, F. |
| Populations of Abra alba (Wood) (Mollusca : Bivalvia) were studied over a fifteen-years period at three sites: the southern part of the North Sea (Gravelines area), the Bay of Seine, and the Bay of Morlaix in the western English Channel. These surveys provide an example of long-term changes in a species considered as ''opportunistic'' and as a ''biological indicator'' of disturbance. A summed cumulated function was used to compare the changes of the Abra alba populations and of mean air temperature in each area. The graph of this function shows the timing and duration of changes. Four or five main periods were identified at each site, with a succession of periods of abundance, stability, and decrease. The abundance periods were separated by ten years in... |
| Tipo: Text |
Palavras-chave: ABRA-ALBA; LONG-TERM CHANGES; CYCLES; CLIMATIC STRESS. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/00099/21066/18692.pdf |
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| Desprez, M; Ducrotoy, J; Elkaim, B. |
| In this paper, the results collected since 1978 on the cockle (Cerastoderma edule) in the Bay of Somme have been recapitulated. A synthesis is brought up about causes of the bivalve population collapse which was portended as early as 1982 from the animal cinetics study. In order to back up the discussion, the main results dealing with the biology and ecology of the species are recalled in illustrated form. A review of the international literature leads to a comment upon the diagrams. A comparison with data from European estuaries tends to take climatic and oceanic disturbances into account as well as local pollution such as eutrophication which is probable on the littoral of Picardy. |
| Tipo: Text |
Palavras-chave: Clam fisheries; Stock assessment; Recruitment; Population dynamics; Marine mollusks. |
| Ano: 1985 |
URL: http://archimer.ifremer.fr/doc/1985/publication-1783.pdf |
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| Ducrotoy, J; Desprez, M; Elkaim, B. |
| The recent collapse in the landings of cockles (Cerastoderma edule) from the Bay of Somme (France) required to investigate if a change in the environmental factors was liable for the drop of the bivalve populations. This project has led to a preliminary assessment of the situation and has been drawn up from the data collected by the Groupe d'Etude des Milieux Estuariens et Littoraux since 1978. It relies on the survey of the spatio-temporal changes of bio-facies. it is suggested that the impact of changes in sediment characteristics is important as well as competition with species as Pygospio elegans (Polychaeta). The above parameters are assessed as essential in the fluctuations of the cockle numbers but they do not explain entirely the collapse in the... |
| Tipo: Text |
Palavras-chave: Landing statistics; Clam fisheries; Stock assessment; Population dynamics; Marine mollusks. |
| Ano: 1985 |
URL: http://archimer.ifremer.fr/doc/1985/publication-1784.pdf |
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| Loquet, N; Rybarczyk, H; Elkaim, B. |
| The Bay of Somme is the second ranked estuarine system, after the Seine estuary, on the French coasts of the Eastern Channel. The nutrient retention and regeneration capacities of this estuary have been calculated from continental and coastal hydrological data and from estimation of the residence time. Measurements at the mouths of the main rivers over a one-year period (from October 1994 to November 1995) were used to construct a budget of continental inputs which showed that the smaller rivers could, at times, be important contributors. The annual budget shows continental inputs of nitrogen, phosphorus, silicon and suspended particulate matter of 9 000 t . y(-1), 380 t . y(-1), 5 400 t y(-1) and 67 800 t . y(-1). Estimation of coastal inputs to the... |
| Tipo: Text |
Palavras-chave: Manche; Baie de Somme; Flux de nutriments; Production primaire; English Channel; Bay of Somme; Nutrient fluxes; Primary production. |
| Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/00325/43577/44045.pdf |
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| Rybarczyk, H; Elkaim, B; Wilson, Jg; Loquet, N. |
| Massive mortalities of the benthic fauna, notably the cockle Cerastoderma edule, a commercially exploited species, were observed in the Pale de Somme in 1982, 1983, 1985, 1989 and 1990. Measurements of oxygen saturation levels of the surface water provided evidence of oxygen depletion (65% in 1989 and 62% in 1990). Oxygen saturation was inversely related to phaeopigment a concentrations due to eutrophication, leading to the depletion of oxygen or anoxia and initiating the mortalities, which were important and localized in areas where water persisted at low tide: intertidal pools, films of water on the sediment surface. From laboratory and field experiments, a simple model of the anoxia in intertidal water pools was constructed, based on the oxygen... |
| Tipo: Text |
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| Ano: 1996 |
URL: http://archimer.ifremer.fr/doc/00093/20474/18144.pdf |
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| Fromentin, Jean-marc; Dauvin, Jean-claude; Ibanez, F; Dewarumez, Jean-marie; Elkaim, B. |
| This study examines whether meso-scale meteorological events, in particular the alternation of cold and mild periods, influenced the structure of four Abi cr alba communities, sampled from 1977 to 1992 on the northwest French coast. We propose a new numerical procedure to describe temporal variations in the structure of each assemblage, using some niche-oriented models recently developed by Tokeshi (1993). The description of the temporal changes in the structure of each community was summarized into a 2D-plot of an ordination, performed on observed and simulated patterns. Results showed that important changes occurred in these four assemblages, which were not directly related to the meso-scale climatic events, but mainly to the local environmental factors... |
| Tipo: Text |
Palavras-chave: Macrobenthos community structure species abundance model long-term survey English Channel; North Sea. |
| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00093/20407/18074.pdf |
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