How Can the Freshwater Outflow from the Amazon Increase the Salinity of the Guianan Shore?
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Open Archive Toulouse Archive Ouverte The Guianese paradox: How can the freshwater outflow from the Amazon increase the salinity of the Guianan shore? Luc Lambs *, Etienne Muller, F. Fromard EcoLab – Laboratoire d’e´cologie fonctionnelle, UMR 5245 (CNRS-UPS-INPT), 29 rue Jeanne Marvig, 31055 Toulouse cedex, France KEYWORDS Summary French Guiana is notable for the extent of its rain forests, which occupy 97% of French Guiana rivers; the country, and the influence of the Amazon along its shores. In fact, the shores and estu- Stable isotopes; aries support a mangrove forest typical of saline conditions. This paper reports the chem- Oxygen-18; ical characteristics, conductivity and salinity and the stable isotopes (oxygen and Deuterium; deuterium) of the rivers and shores between the Cayenne area and the border with Suri- Salinity nam. The results show a quite homogenous freshwater pool over the country. However, the low slope of the coast, a result of the wide mud banks deposited by the Amazonian plume, have turned the mouths of the smaller rivers to the northwest, creating large salty areas where mangroves grow several kilometers inland. Despite the large amount of Ama- zonian water, the Guianan coast exhibits high salinity. In fact, the freshwater itself remains far from the shore, following the north Brazilian current, while only the mud plume arrives at the coast, creating this paradox. Introduction lens. The interaction of Amazon water and seawater, in front of the Amazonian estuary, were studied during the The discharge from many large rivers, because of the lower Amaseds program between 1989 and 1991 (Karr and Show- density of freshwater relative to seawater, can be detected ers, 2002).
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