Infection dynamics of Marteilia refringens in flat oyster Ostrea edulis and copepod Paracartia grani in a claire pond of Marennes-Oléron Bay
The protozoan parasite Marteilia refringens has been partly responsible for the severe decrease in the production of the European flat oyster Ostrea edulis Linnaeus in France since the 1970s. The calanoid copepod Paracartia grani Sars was recently found to be a host for M. refringens in French shallow-water oyster ponds (Œclaires¹). This study reconsidered M. refringens transmission dynamics in the light of this finding, taking into account not only oyster infection dynamics and environmental factors but also data concerning the copepod host. P. grani population dynamics in the claire under study revealed that this species is the dominant planktonic copepod in this confined ecosystem. During winter, M. refringens overwintered in O. edulis, with P. grani existing only as resting eggs in the sediment. The increase in temperature in spring controlled and synchronized both the release of M. refringens sporangia in the oyster feces, and the hatching of the benthic resting eggs of the copepod. Infection of oysters by M. refringens was limited to June, July and August, coinciding with (1) the highest temperature recorded in the claire, and (2) the highest abundance of P. grani. PCR detection of M. refringens in P. grani during the summer period was linked to the release of parasite sporangia by the oyster. Our results are supported by previous results on the effective transmission of this parasite from the oyster to the copepod.
(Diseases of Aquatic Organisms. vol. 61, n° 0177-5103, pp. 103 - 111, 21/10/2004)
IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Heterogeneity of macrozoobenthic assemblages within a Zostera noltii seagrass bed: diversity, abundance, biomass and structuring factors
The macrobenthic fauna community of a 70-km2 Zostera noltii seagrass bed (Arcachon bay, France) was studied by sampling 49 stations systematically. A total of 126 taxa were identified. Cluster Analysis based on χ2 distance showed that in this apparently homogeneous habitat, four distinct macrobenthic communities could be identified. Multiple Discriminant Analysis highlighted the major contribution of the overlying water mass as a forcing variable, and, to a lesser extent, of tidal level and Z. noltii's below-ground parts. Seven stations did not constitute any conspicuous group, and were characterized by a low biomass of leaf (<28 g DW m−2), considered as the lowest value to constitute a Z. noltii community. Less than 24% of the seagrass bed was situated in more oceanic waters and at a quite low tidal level. In this relatively stable environment, the macrofauna community was characterized by a high species richness (mean = 39) and a moderate density and high biomass (12 638 individuals m−2 and 25 g AFDW m−2, respectively). Annelids dominated, particularly the oligochaetes. When physical constraints increased (emersion or brackish water conditions), diversity decreased, abundance and biomass increased. The seagrass bed (55%) was flooded with highly fluctuating waters in term of temperature and salinity, here species richness was low (mean = 27) but abundance and biomass were high (24 384 individuals m−2 and 28 g AFDW m−2, respectively), with a dominance of molluscs. The meadow (7%) was in external waters but at a higher tidal level (2.4 m vs 1.8 m above medium low tide level). This community was characterized by the particularly high density (41 826 individuals m−2) and dominance of oligochaetes (79% of total abundance). Species richness was high (mean = 37) here. A fourth community, extending over 12% of the meadow was dominated by the gastropod Hydrobia ulvae but could not be linked to a specific forcing variable. This study confirmed the almost complete replacement of the native clam Ruditapes decussatus by the Manila clam Ruditapes philippinarum since its introduction in the 1980s.
(Estuarine, Coastal and Shelf Science. vol. 61, n° 0272-7714, pp. 111-123, 01/09/2004)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Invasion of the eastern Bay of Biscay by the nassariid gastropod Cyclope neritea: origin and effects on resident fauna
The distribution area of the nassariid gastropod Cyclope neritea (L.) includes the Mediterranean and the Black Sea, as well as the Atlantic coasts of the southern Iberian Peninsula. The species has spread north to the eastern Bay of Biscay (Arcachon Bay in 1976, Marennes-Oléron area and Morbihan Gulf in 1983-84). This spread might be explained either by (1) a natural spread favoured by environmental changes (e.g. an increase of temperature) or (2) a sudden range expansion due to the introduction of individuals from distant native populations. Molecular genetic analyses based on mitochondrial markers suggest that the present C. neritea population in Arcachon Bay has been introduced, probably unintentionally with oyster transfers, from several source populations, genetically similar to the populations analysed in this study, i.e. those in the western Mediterranean and in south Portugal. Within its new distribution area, C. neritea could potentially compete with the autochthonous nassariid Nassarius reticulatus, both species being scavengers. Although C. neritea tends to occur mainly in relatively clean sands in the intertidal and N. reticulatus in subtidal, organic rich sediments, the habitats of both species partially overlap. Laboratory experiments showed that in still water conditions C. neritea was more active and reached carrion faster than N. reticulatus, thereby having a competitive advantage over the latter; flow conditions ( ~1 cm s-1) appeared to stimulate the activity of N. reticulatus. Analysis of parasite load in both species in Arcachon Bay indicated that N. reticulatus was more heavily parasitized by digenean trematodes than C. neritea. This suggests that the spread and population dynamics of C. neritea along the French Atlantic coast has been favoured by the lack of parasites. Altogether, recurrent introduction, competitive ability and lack of heavy parasitic load might explain the successful settlement of C. neritea along the French Atlantic coast.
(Marine Ecology Progress Series. vol. 276, n° 0171-8630, pp. 147 - 159, 02/08/2004)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, LBEM, ULR, CREMA, IFREMER, CNRS, SBR, UPMC, CNRS
Climatic "pause" during Termination II identified in shallow and intermediate waters off the Iberian margin
The sequence of Termination II, from the end of marine isotopic stage 6 (MIS 6) to MIS 5e, is observed through an isotopic study (δ18O) of planktic and benthic foraminifera in core MD99-2331 (42°09′N; 09°41′W), collected in the North Atlantic, on the Iberian margin. First, to build an approximate time scale, a record of the planktic δ18O signal is achieved from the top of the core (Holocene) to MIS 6. The remarkable similarity of this planktic record to the Greenland Ice Core Project ice core δ18O record allows a rough dating of our core. A focus on Termination II reveals one "standstill" in the benthic record. This "pause" can be linked either to a perturbation of North Atlantic oceanic circulation pattern, as a slowing down of the North Atlantic Deep Water formation, or to an interruption in polar ice sheet melting, which could be a more global phenomenon. © 2004 Elsevier Ltd. All rights reserved.
(Quaternary Science Reviews. vol. 23, n° 0277-3791, pp. 1523-1528, 01/07/2004)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, IRSN/PSE-ENV/SRTE/LRC, IRSN/PSE-ENV/SRTE, IRSN
Etude sédimentologique de la Grande Vasière.
(10/06/2004)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER
The distribution of heavy metals in the Sidi Moussa lagoon sediments (Atlantic Moroccan Coast)
The superficial and cored sediments of the Sidi Moussa lagoon (Atlantic Moroccan coast) have been analysed in order to determine their main characteristics and their heavy metals contents. Two groups of metals can be distinguished: Al, Fe and Cu whose distribution is mainly governed by the intra-lagoonal dynamics. These contents are near of those of the natural geochemical background noise that underlines their natural origin. Zn, Cr and Ni have relatively more elevated contents than the natural geochemical background noise indicating human-made pollution. The geo-accumulation indicator shows that the Sidi Moussa lagoon is moderately polluted. The totality of results in this context compared to the standard values suggested by the Agency of Protection of the Environment of United States leads to the conclusion that the sediments of Sidi Moussa lagoon would rank as slightly polluted for, Cu, Zn, Cr and Ni.
(Journal of African Earth Sciences, n° 1464-343X, pp. 473-483, 01/06/2004)
LETG - Nantes, UNICAEN, NU, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Comparing the Epica and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods
(Earth-Science Reviews. vol. 66, n° 0012-8252, pp. 63 - 87, 01/06/2004)
CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, LGGE, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNRS, GEOAZUR 6526, IRD, UPMC, UNS, INSU - CNRS, UniCA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A massive dissolved inorganic carbon release at spring tide in a highly turbid estuary
[1] In September 2003, the highly turbid Loire estuary (France) showed drastic oxygen depletions (down to 11% of saturation), high pCO 2 (up to 3740 matm) and high CO 2 fluxes (280 ± 100 mmol.m À2 .d À1). A rapid rise in Dissolved Inorganic Carbon (DIC) was observed when the tidal amplitude increased from 3.8 m to 5.8 m. In two days, average concentrations in the 0.1-25 salinity range increased by 106 ± 17 mmol.kg À1 for DIC, by 80 ± 14 meq.kg À1 for Total Alkalinity (TA) and by 684 ± 142 matm for pCO 2. In parallel, oxygen decreased by 65 ± 12 mmol.kg À1. These changes in concentrations were attributed in majority to a massive fluid mud resuspension in the estuarine turbidity maximum. At spring tide, this DIC input was 30% higher than the river input. When averaged over the neap-spring period, resuspension contributed to only 10% of the atmospheric CO 2 flux from the estuary, but to 60% to the net TA production in the estuary.
(Geophysical Research Letters. vol. 31, n° 0094-8276, pp. n/a-n/a, 16/05/2004)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN/PSE-ENV/SRTE/LRC, IRSN/PSE-ENV/SRTE, IRSN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Intense summer Si-recycling in the surface Southern Ocean
(Geophysical Research Letters. vol. 31, n° 0094-8276, pp. L09305, 01/05/2004)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, LBCM, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Copper detection in the Asiatic clam Corbicula fluminea: optimum valve closure response
When exposed to a contaminant, bivalves close their shell as a protective strategy. The aim of the present study was to estimate the maximum expected dissolved copper sensitivity in the freshwater bivalve Corbicula fluminea using a new approach to determine their potential and limit to detect contaminants. To take into account the rate of spontaneous closures, we integrated stress problems associated with fixation by a valve in usual valvometers and the spontaneous rhythm associated with nycthemeral activity, to optimize the response in conditions where the probability of spontaneous closing was lowest. Moreover, we used an original system with impedance valvometry, using lightweight impedance electrodes, to study free-ranging animals in low stress conditions combined with an analytical approach describing dose-response curves by logistic regression, with valve closure reaction as a function of response time and concentration of contaminant. In C. fluminea, we estimated that copper concentrations >4 μg/l (95% confidence interval (CI95%), 2.3–8.8 μg/l) must be detected within 5 h after Cu addition. Lower values could not be distinguished from background noise. The threshold values were 2.5 times lower than the values reported in the literature.
(Aquatic Toxicology. vol. 66, n° 0166-445X, pp. 333-342, 25/02/2004)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN/DPRE/SERLAB/LRE, IRSN/DPRE/SERLAB, IRSN, LMBA, UBS, UBO EPE, CNRS