4:15 PM - 4:30 PM
[ACG46-04] Spatio-temporal distribution and biological processes of Transparent exopolymer particles (TEP) in the western North Pacific during the winter and spring seasons
Keywords:biological organic particles, biological carbon pump, phytoplankton community composition
Transparent exopolymer particles (TEP) are primary organic particles composed of polysaccharide polymers derived from marine biological activities and are a type of gel-like particles that are abundant in the marine environment. TEPs play an important role in the efficiency of the carbon cycle by promoting particle aggregation. However, the spatial distribution of TEP has not been clarified due to the limited observation opportunities. On the other hand, organic matter originating from marine organisms are released into the atmosphere as aerosols which may act as cloud condensation nuclei (CCN) and ice-nucleating particles (INP), but the whole of this process is not yet completely understood. In this study, we collected seawater samples over the western North Pacific from winter to spring, and then the relationship with primary producers and environmental factors were investigated based on the results of horizontal and vertical distributions of TEP.
The samples were collected from February to March 2021 during the MR21-01 cruise of the R/V Mirai. To investigate the differences in TEP concentrations due to marine environments, such as sea surface temperature and nutrients, water samples were taken from multiple layers from the surface to 5000 m depth at 15 sampling stations, including K2 (47N,160E) and KNOT (44N,155E) in the subarctic western North Pacific as well as at stations KEO (32N,142E) and KEOS (25N,145E) in the subtropical western North Pacific. The horizontal distribution of TEP at the sea surface layer showed a latitudinal gradient between 14.3 µg xanthan gum equivalent L−1 (XGeq L-1) for station KNOT as compared to 8.7±1.4 µg XGeq L-1 for stations KEO and KEOS, which were responsive to changes in the variability of Chl-a concentrations. The vertical distribution of TEP showed almost constant concentrations from the surface to 5000m at stations K2 and KNOT. On the other hand, the vertical distribution of TEP concentration at stations KEO and KEOS showed a tendency to be lower below 50m. According to the analysis of size-fractionated chlorophyll-a and phytoplankton community composition, a high fraction of coarse particles with a diameter of larger than 10 μm were found at stations K2 and KNOT, and Diatoms were dominant. On the contrary, at stations KEO and KEOS, a high fraction of fine particles with a diameter of less than 1μm were found and cyanobacteria (Prochlorococcus) were dominant.
We will also discuss the spatio-temporal analysis including the results obtained in the subtropical to central Pacific.
The samples were collected from February to March 2021 during the MR21-01 cruise of the R/V Mirai. To investigate the differences in TEP concentrations due to marine environments, such as sea surface temperature and nutrients, water samples were taken from multiple layers from the surface to 5000 m depth at 15 sampling stations, including K2 (47N,160E) and KNOT (44N,155E) in the subarctic western North Pacific as well as at stations KEO (32N,142E) and KEOS (25N,145E) in the subtropical western North Pacific. The horizontal distribution of TEP at the sea surface layer showed a latitudinal gradient between 14.3 µg xanthan gum equivalent L−1 (XGeq L-1) for station KNOT as compared to 8.7±1.4 µg XGeq L-1 for stations KEO and KEOS, which were responsive to changes in the variability of Chl-a concentrations. The vertical distribution of TEP showed almost constant concentrations from the surface to 5000m at stations K2 and KNOT. On the other hand, the vertical distribution of TEP concentration at stations KEO and KEOS showed a tendency to be lower below 50m. According to the analysis of size-fractionated chlorophyll-a and phytoplankton community composition, a high fraction of coarse particles with a diameter of larger than 10 μm were found at stations K2 and KNOT, and Diatoms were dominant. On the contrary, at stations KEO and KEOS, a high fraction of fine particles with a diameter of less than 1μm were found and cyanobacteria (Prochlorococcus) were dominant.
We will also discuss the spatio-temporal analysis including the results obtained in the subtropical to central Pacific.