Noelle Maillet

Bio: Noelle Maillet is an academic researcher from University of Bordeaux. The author has contributed to research in topics: Neogene & Corbicula fluminea. The author has an hindex of 8, co-authored 11 publications receiving 413 citations.

Field transplantation of the freshwater bivalve Corbicula fluminea along a polymetallic contamination gradient (river Lot, France): II. Metallothionein response to metal exposure

Abstract: Specimens of the Asiatic clam Corbicula fluminea were transplanted from a clean lacustrine site to four stations along a polymetallic pollution gradient in the river Lot, France, downstream from an old Zn ore treatment facility (see Part I). From April to September 1996, we studied Cd and Zn bioaccumulation and the metallothionein-like metal-binding protein (MT) concentrations by subsampling the cages at t = 0, 21, 49, 85, 120, and 150 d. Marked differences were observed among the four stations. At the most polluted station Riou-Mort, MT concentrations did not increase despite very rapid metal accumulation; all mollusks died between days 49 and 85, suggesting that the metal detoxification mechanisms were overwhelmed at this station. At the next station downstream, the final levels of bioaccumulated metal after 150 d were as high as those at the Riou-Mort station (t = 21 d), but in this case the MT concentrations also increased progressively with positive correlations between MT and metal concentrations; no mortality was observed, but a significant growth inhibition was revealed in comparison to the reference site, with a lack of correlation between MT (as a stress response) and reduced growth. Subcellular metal partitioning, as determined by size-exclusion chromatography, revealed that most of the Cd was sequestered by MT (70% of cytosolic Cd). In contrast, most of the Zn was bound to low molecular weight proteins (70%, ≤ 6.5 kD), the MT fraction representing only 12% of cytosolic Zn. These data show the marked role of MT toward Cd bioaccumulation and toxic effects on this freshwater bivalve species.

Field transplantation of the freshwater bivalve Corbicula fluminea along a polymetallic contamination gradient (river Lot, France): I. Geochemical characteristics of the sampling sites and cadmium and zinc bioaccumulation kinetics

Abstract: Specimens of the Asiatic clam Corbicula fluminea were transplanted from a clean lacustrine site to four stations along a polymetallic gradient in the river Lot (France), downstream from an old Zn ore treatment facility. The bivalves were held in benthic cages for a 5-month exposure period, April to September 1996; mollusk growth and metal bioaccumulation kinetics (Cd, Zn) were followed by subsampling the cages at t = 0, 21, 49, 85, 120, and 150 d. Rates of Cd bioaccumulation in the whole soft bodies and in individual organs were greater at the upstream stations located close to the pollution source, but there was no direct proportionality between Cd in the bivalves and in the unfiltered or filtered river water samples. Unlike the case for Cd, rates of Zn bioaccumulation did not reflect the contamination gradient. Marked growth differences were measured among the four stations, reflecting both nutritional differences and changes in the degree of metal contamination; these growth differences produced markedly different trends when metal bioaccumulation was expressed in terms of burdens rather than concentrations.

Mediterranean outflow through the Strait of Gibraltar since 18,000 Years B.P.: Mineralogical and geochemical arguments

Abstract: Data obtained from mineralogical and geochemical analyses of piston and gravity cores, recovered from an area off Lisbon (Portugal) to the Alboran Sea (Mediterranean), serve as a basis for better understanding the past 18,000 years of hydrological exchanges at Gibraltar. Tracers used in this study are smectite, kaolinite, Ta, Th, La. One of the primary sources of particles both into and out of the Mediterranean is the Guadalquivir River. These particles are transported back into the Atlantic in the Mediterranean outflow water, and deposited along the Iberian slope. No evidence for reversal of this outflow current was found in those cores, since 18,000 years B.P.

Flux de matières en suspension et de cadmium dans le Lot

Abstract: La contamination en cadmium, observee dans les huitres de l'estuaire de la Gironde, provient, principalement par l'intermediaire du Lot, d'une ancienne usine de traitement du minerai de zinc et des metaux qui lui sont associes. Les flux de cadmium principalement expulse sous la forme particulaire sont suivis annuellement depuis 1990. Un des facteurs repose sur la strategie et la methodologie d'echantillonnage. L'important echantillonnage recueilli au niveau des turbidites a permis non seulement d'etablir et de comparer deux methodes de calcul des flux de MES mais aussi de montrer l'importance du regime hydrologique de la riviere en particulier du role des crues quant a la remobilisation des sediments de fonds. Le bilan suffisamment precis des flux de MES a permis d'etablir les flux de cadmium particulaire emis avec une approximation suffisante pour permettre de juger des efforts de rehabilitation du site pollueur.

Variability of the western Mediterranean Sea surface temperature during the last 25,000 years and its connection with the Northern Hemisphere climatic changes

Abstract: Sea surface temperature (SST) profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a W-E latitudinal transect encompassing the Gulf of Cadiz (Atlantic Ocean), the Alboran Sea, and the southern Tyrrhenian Sea (western Mediterranean). The results document the sensitivity of the Mediterranean region to the short climatic changes of the North Atlantic Ocean, particularly those involving the latitudinal position of the polar front. The amplitude of the SST oscillations increases toward the Tyrrhenian Sea, indicating an amplification effect of the Atlantic signal by the climatic regime of the Mediterranean region. All studied cores show a shorter cooling phase (700 years) for the Younger Dryas (YD) than that observed in the North Atlantic region (1200 years). This time diachroneity is related to an intra-YD climatic change documented in the European continent. Minor oscillations in the southward displacement of the North Atlantic polar front may also have driven this early warming in the studied area. During the Holocene a regional diachroneity propagating west to east is observed for the SST maxima, 11.5–10.2 kyr B.P. in the Gulf of Cadiz, 10–9 kyr B.P. in the Alboran Sea, and 8.9–8.4 kyr B.P. in the Thyrrenian Sea. A general cooling trend from these SST maxima to present day is observed during this stage, which is marked by short cooling oscillations with a periodicity of 730±40 years and its harmonics.