Paul Sabatier University

About: Paul Sabatier University is a education organization based out in Toulouse, France. It is known for research contribution in the topics: Population & Adipose tissue. The organization has 15431 authors who have published 23386 publications receiving 858364 citations.

Exportation of organic carbon from the Amazon River and its main tributaries

Abstract: As part of a joint Brazilian–French project, entitled ‘Hydrology and Geochemistry of the Amazon Basin’, we carried out a seven-year study (1994–2000) on the distribution, behaviour and flux of particulate and dissolved organic carbon in the Amazon River and its main tributaries (the Negro, Solimoes, Branco, Madeira, Tapajos, Xingu and Trombetas rivers). The concentrations of particulate and dissolved organic carbon varied from one river to another and according to the season, but dissolved organic carbon (DOC) always accounted for about 70% of the total organic carbon (TOC). The mean concentration of dissolved organic carbon was 6·1 mg l−1 in the Madeira River, 5·83 mg l−1 in the Solimoes River and 12·7 mg l−1 in the Negro River. The percentage in weight of the particulate organic carbon decreased as the concentration of suspended matter increased. The Solimoes River contributed the most carbon to the Amazon River: about 500 kg C s−1 during the high water period and about 300 kg C s−1 during the low water period. However, the temporal variations in organic carbon in the Amazon River (i.e. downstream of Manaus) are basically controlled by inputs from the Negro River and its variations. The Negro River does not produce a simple dilution effect. During the high water period (between March and August) the TOC flux, calculated as the sum of the Solimoes, Negro and Madeira tributaries, was about 5·7 × 1013 g C yr−1, whereas during the low water period (between September and February) the TOC flux was about 2·6 × 1013 g C yr−1. The mean annual flux of TOC at Obidos (the final gauging station upstream of the estuary) was about 3·27 × 1013 g C yr−1 (i.e. 32·7 ± 3·3 Tg yr−1). Of this, the flux of DOC represents about 2·7 × 1013 g C yr−1 and the flux of particulate organic carbon (POC) represents about 0·5 × 1013 g C yr−1. The mean annual input of TOC by all tributaries (Negro, Solimoes, Madeira, Trombetas, Tapajos and Xingu) was about 2·8 × 1013 g C yr−1. When we compared this input with the output recorded at Obidos (3·27 × 1013 g C yr−1), we found that the amount of organic carbon increased (about 0·4 × 1013 g C yr−1). This shows that other important sources of organic carbon exist in the lower reaches of the Amazon River. These inputs can be attributed to the adjacent floodplain lake system, called ‘varzea’. Copyright © 2003 John Wiley & Sons, Ltd.

Genotyping, Orientalis-like Yersinia pestis, and Plague Pandemics

Abstract: Three pandemics have been attributed to plague in the last 1,500 years. Yersinia pestis caused the third, and its DNA was found in human remains from the second. The Antiqua biovar of Y. pestis may have caused the first pandemic; the other two biovars, Medievalis and Orientalis, may have caused the second and third pandemics, respectively. To test this hypothesis, we designed an original genotyping system based on intergenic spacer sequencing called multiple spacer typing (MST). We found that MST differentiated every biovar in a collection of 36 Y. pestis isolates representative of the three biovars. When MST was applied to dental pulp collected from remains of eight persons who likely died in the first and second pandemics, this system identified original sequences that matched those of Y. pestis Orientalis. These data indicate that Y. pestis caused cases of Justinian plague. The two historical plague pandemics were likely caused by Orientalis-like strains.