| |
| |
|
|
|
|
| |
 |
Biogeochemistry in oligotrophic ocean gyres
|
| |
|
|
DOM dynamics in the Low-latitude Western Boundary Current System: insights from optical analyses
P-M2-05-S
Chao Wang* , State Key Laboratory of Marine Environmental Science,Xiamen University
Weidong Guo, State Key Laboratory of Marine Environmental Science, Xiamen University
Presenter Email: marineswang@163.com |
| Despite its potential importance in the global carbon cycle, biogeochemical and hydrological behaviors of dissolved organic matter (DOM) in the low-latitude western boundary current system (LLWBC) remained unclear. We report here for the first time on the observations of carbon concentration (DOC), absorption (CDOM) and fluorescence (FDOM) spectra of DOM associated with these currents, made in the tropical Northwest Pacific Ocean. The results showed that there were significant differences of environmental parameters (nutrients, dissolved oxygen and chlorophyll), DOC, CDOM and FDOM among different currents (t-test, p < 0.05). The highest DOC but lowest CDOM absorption coefficient and fluorescence intensities of FDOM were observed in the North Equatorial Current (NEC), while the lowest DOC but highest CDOM and FDOM abundances appeared in the North Equatorial Counter Current (NECC). Enhanced inventories of DOC, CDOM and FDOM were found in the quasi-stationary cold eddy, the Mindanao Eddy (ME), associated with the elevated productivity and upwelling inside the eddy. In the aphotic zone, there were significant relationships between DOC, CDOM and FDOM with AOU as well as nutrient concentrations, suggested the consumption of labile organic fraction (a254, protein-like component) and the in situ production of bio-refractory DOM (a350, humic-like components) during microbial metabolism coupled to the remineralization of biogenic sinking particles. The in situ production rate of humic-like FDOM in the intermediate layer of LLWBC was overall low compared with other region, which could be associated with the oligotrophic upper ocean and low flux of sinking particles in the LLWBC. Although there was relatively large difference of primary production in the different currents, no significant difference of in situ production rates of bio-refractory DOM below the euphotic zone among different currents were observed, which indicated an important role of the strong subsurface countercurrents on the carbon inventory and transport in the subsurface waters of LLWBC |
|
|
|
|
|
|
|
|