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Carbon cycling in the Amazon River: Implications from the 13C compositions of particles and solutes
Author(s) -
Quay Paul D.,
Wilbur David .,
Richey Jefrey E.,
Hedges John I.,
Devol Allan H.,
Victoria Reynaldo
Publication year - 1992
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1992.37.4.0857
Subject(s) - tributary , amazon rainforest , floodplain , dissolved organic carbon , δ13c , hydrology (agriculture) , environmental science , carbon cycle , organic matter , drainage basin , total organic carbon , particulates , surface runoff , environmental chemistry , geology , ecosystem , chemistry , ecology , stable isotope ratio , geography , biology , physics , cartography , geotechnical engineering , quantum mechanics
The 13 C: 1 2 C of suspended particu‐late organic C (POC), dissolved organic C (DOC), and dissolved inorganic C (DIC) were measured during 1982–1984 at 11 main‐channel and 7 tributary stations over an 1,800 km reach of the Amazon River between Vargem Grande and Obidos, Brazil. The measured δ 13 C range vs. marine carbonate (PDB) was –32 to −26‰ for suspended POC, −30 to −28‰ for DOC, and −26 to −12% for DIC. The δ 13 C of the fine particulate organic C (FPOC) decreased downriver from Vargem Grande, with values lowest during the falling‐water portion of the runoff cycle; these trends were the result primarily of input of 13 C‐depleted FPOC from tributaries draining the lowland regions of the Amazon basin and floodplain soils. The δ 13 C of the FPOC at Obidos implies that at least 35% of the POC exported by the Amazon River is derived from the lowland portion of the Amazon basin. The δ 13 C of DIC decreased downriver with the lowest values measured during falling water; these trends were due primarily to within‐river respiration and tributary input. The δ 13 C of the DIC suggests that ∼40% of the organic matter being respired in the river is C 4 plant material derived from floodplain grasses.