Program

Abstract: Transparent exopolymer particles (TEP) are ubiquitous gel particles present in the ocean, which exhibit gel-like properties such as stickiness and surface-active nature. Several studies revealed that their sedimentation might represent an important pathway of carbon export in the ocean, while their role played in the estuary zone remained unclear. Thus, abundance and sinking rates of TEP was studied in the outer Changjiang (Yangtze River) estuary during two cruises in spring and summer of 2011, and a crude estimation of carbon export was carried, with the goal of providing good insight into the biological pump related study in this area. The concentrations of TEP ranged from 0 to 1500 µg Xeq. L^-1 in the study area, and high values appeared at the stations where phytoplankton bloomed. A significant positive correlation was observed between TEP concentration and phytoplankton abundance, which was consistent with other studies around the world. Vertically, the TEP concentration was higher in the upper layers than that in the deeper layers, which was consistent with the Chl a distribution pattern. The SETCOL-determined sinking rates of TEP were below 1.5 m d^-1, which were lower than that of phytoplankton cells. The carbon flux of TEP to bottom water ranged from 9.2~56.0 mg C m^-2 d^-1 in spring (average = 20.56±17.83 mg C m^-2 d^-1) and 21.5~73.8 mg C m^-2 d^-1 in summer (average = 44.58±22.83 mg C m^-2 d^-1), which accounted for more than 30% of carbon flux of phytoplankton cells during both seasons. This study revealed that TEP sedimentation played an important role in the carbon export in the Changjiang (Yangtze River) estuary, and should be taken into account when carry out biological pump related study in this area.