Variability In Beam Attenuation And The Suspended Particles In The West Philippine Sea

A new proxy of particulate organic material was optically determined in West Philippine Sea, and the optical data was firstly used to examine the suspended particle and POC variability. Using these linear fit equations between beam attenuation coefficients at 660nm (c_p) and POC, continuous and high-resolution POC profiles could be derived. Integrations of POC and chlorophyll a to 150m within transect of WE and SN revealed uniform spatial variations than expected, and POC in the upper water column mainly came from the detrital particulate materials. In West Philippine Sea, the diel changes of mixed layer depth played a significant role in the optical variability and particle export of the upper layer. The sea surface temperature, beam attenuation coefficient due to particles and the mixed layer depth covary with the photosynthetically available radiation (PAR). The standing stocks of POC in the surface waters were controlled by the changes of mixed layer depth. But in the mid- and lower water column, it was speculated that vertical migration, aggregation and sinking contributed to the POC standing stock.The numerical abundances of three microorganisms (Prochlorococcus, Synechococcus and autotrophic eukaryotes) and their optical scattering cross sections were determined. The bulk scattering coefficients of each population (bp) and total scattering coefficients of these three picoplankton populations (bp(Tot)) were calculated and compared with beam c_p. In West Philippine Sea, Prochlorococcus was the most abundant population, and the abundance of autotrophic eukaryotes was the lowest. The autotrophic eukaryotes and Prochlorococcus were the most significant contributors to the beam c_p (2.85% and 2.15% of beam c_p, respectively) via scattering, and only 0.33% of the beam c_p was accounted for by Synechococcus. And the study area could be subdivided into three biohydrographic regimes according to particle scattering.The underwater light field was also observed in the West Philippine Sea, and it...