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Riverine influence on nitrogen fixation in the upwelling region off Vietnam, South China Sea
Author(s) -
Voss Maren,
Bombar Deniz,
Loick Natalie,
Dippner Joachim W.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl025569
Subject(s) - trichodesmium , upwelling , subtropics , nitrogen fixation , oceanography , monsoon , environmental science , plume , diatom , cyanobacteria , water column , amazon rainforest , nitrogen , geology , geography , ecology , diazotroph , biology , chemistry , paleontology , organic chemistry , meteorology , bacteria
Nitrogen fixation is assumed to be most important in oligotrophic subtropical regions of the oceans. Here we show that nitrogen fixation can also be pronounced in the upwelling region off Vietnam. We compare nitrogen fixation rates and other hydro‐chemical variables from the monsoon season with the intermonsoon season and find that nitrogen fixation rates are app. 10 times higher during the monsoon season. However, this was not the case in the actual upwelling region – a 40–50 km wide strip along the coast – but further offshore, where the Mekong plume was noticeable. Therefore, we hypothesize that the stability of the water column, micronutrients and/or trace metals in the Mekong river plume may be responsible for enhanced cyanobacterial growth. These cyanobacteria may be either Trichodesmium , unicellular, or diatom‐associated symbionts, the latter are known from other river plumes like the Amazon.