Contribution of phytoliths to the suspended load of biogenic silica in the Nyong basin rivers (Cameroon)

Lise Cary (1, 2) , Anne Alexandre (1) , Jean-Dominique Meunier (1) , Jean-Loup Boeglin (3) , Jean-Jacques Braun (3)

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
2 INRA - Institut National de la Recherche Agronomique
3 LMTG - Laboratoire des Mécanismes et Transfert en Géologie

Particulate biogenic silica (BSi) carried by rivers to estuaries and marine sediments is generally assumed to be primarily composed of diatoms. Phytoliths-biogenic opal formed in plants-are found in some marine sediments where they are interpreted to be the result of atmospheric and river inputs. In this study, we evaluate the contribution of phytoliths to the suspended load of rivers of the Nyong basin (Cameroon). BSi (2 lm to 2 mm fraction) in the soils and the rivers range respectively, from 0.9 to 3.9 wt% and from 1.3 to 4 wt%. About 90% of the BSi pool in both soils and river suspended load are composed of phytoliths. Thecamoebians and fresh water diatoms are minor components. The concentrations of BSi and the phytolith assemblages show great similarities between the waters and the soil samples. This result implies that the erosion of top soils is the major source of the suspended load, in good agreement with the transport limited weathering regime of the study basin.

Mots clés: erosion; weathering; phytolith; biogenic silica; Cameroon

Domaines: Sciences de l'environnement

Lise Cary, Anne Alexandre, Jean-Dominique Meunier, Jean-Loup Boeglin, Jean-Jacques Braun. Contribution of phytoliths to the suspended load of biogenic silica in the Nyong basin rivers (Cameroon). Biogeochemistry, 2005, 74 (1), pp.101 - 114. ⟨10.1007/s10533-004-2945-1⟩. ⟨hal-01909688⟩