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Espinoza J.C.,Instituto Geofisico Del Peru | Espinoza J.C.,University Agraria la Molina | Ronchail J.,University Paris Diderot | Guyot J.L.,Laboratoire des Mecanismes et Transferts en Geologie | And 13 more authors.
Environmental Research Letters | Year: 2012

In this work we document and analyze the hydrological annual cycles characterized by a rapid transition between low and high flows in the Amazonas River (Peruvian Amazon) and we show how these events, which may impact vulnerable riverside residents, are related to regional climate variability. Our analysis is based on comprehensive discharge, rainfall and average suspended sediment data sets. Particular attention is paid to the 201011 hydrological year, when an unprecedented abrupt transition from the extreme September 2010 drought (8300m3s1) to one of the four highest discharges in April 2011 (49500m3s1) was recorded at Tamshiyacu (Amazonas River). This unusual transition is also observed in average suspended sediments. Years with a rapid increase in discharge are characterized by negative sea surface temperature anomalies in the central equatorial Pacific during austral summer, corresponding to a LaNiña-like mode. It originates a geopotential height wave train over the subtropical South Pacific and southeastern South America, with a negative anomaly along the southern Amazon and the southeastern South Atlantic convergence zone region. As a consequence, the monsoon flux is retained over the Amazon and a strong convergence of humidity occurs in the Peruvian Amazon basin, favoring high rainfall and discharge. These features are also reported during the 201011 austral summer, when an intense La Niña event characterized the equatorial Pacific. © 2012 IOP Publishing Ltd.

Morat F.,Aix - Marseille University | Blamart D.,French Climate and Environment Sciences Laboratory | Candaudap F.,Laboratoire des Mecanismes et Transferts en Geologie | Letourneur Y.,Aix - Marseille University | Letourneur Y.,University of New Caledonia
Vie et Milieu | Year: 2013

To test the hypothesis that both otoliths (left and right sagittae) of a flatfish, Solea solea (Linnaeus, 1758), display the same elemental fingerprint information, we analyzed whole-otolith preparations from coastal lagoons and marine sites in the NW Mediterranean for the presence of 15 elements ( 7Li, 24Mg, 27Al, 44Ca 52Cr, 55Mn,56Fe, 59Co, 60Ni, 63Cu, 68Zn, 86Sr, 111Cd, 137Ba and 208Pb), their ratio to Ca and for carbon and oxygen stable isotope ratios. We found significant concentration differences between the two otoliths for two elements, i.e. 7Li (right > left) and 86Sr (right > left) all sites pooled together. However, this general trend differed between sites, with coastal lagoons showing significant differences for additional elements between the two otoliths, such as 44Ca and 137Ba in coastal lagoons for small juveniles, 55Mn and 68Zn in coastal lagoons for larger juveniles, and for 55Mn/44Ca for adults in marine sites. Both δ18O and δ13C isotopic ratios were higher in the right than in the left otolith (a difference of ∼16% between otoliths in both cases) but these trends were not statistically significant and showed no spatial pattern. The left otolith was significantly heavier than the right otolith, a difference which decreased significantly with increasing fish size. Otolith mass was shown to correlate significantly with the δ18O and δ13C ratios, as well as for concentration in some elements and their ratio to Ca for both otoliths ( 55Mn,68Zn, 86Sr and 137Ba) and for 27Al on the left otolith only. Our results imply that the two otoliths are not interchangeable for fingerprint analysis. The right vs. left difference for 44Ca, 86Sr and 137Ba decreases with increasing fish size, which suggests that differences in element concentrations may be at least partly driven by fish size. Thus, fish physiology and inner ear functioning may differ between otoliths in intensity and/or type of process as a function of increasing fish size and so possibly explain left vs. right differences in the otoliths of S. solea.

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