Comparative Analysis of Total and Size-Fractionated Chlorophyll in the Yellow Sea and Western Pacific.

Measurements of different size-fractionated chlorophyll concentrations (Chl ) of phytoplankton assemblages are vital for advancing our understanding of the phytoplankton size structure and thus the marine biogeochemical cycle. In the present study, we thus made a comparative analysis of total and size-fractionated Chl in the Yellow Sea (YS) and Western Pacific (WP). Our results suggest that the total Chl was highly variable in the YS (averaging ~1.02 μg L) and was generally 3-4-fold more than that in the WP (averaging ~0.30 μg L). The pico-sized Chl had a significant contribution to total Chl in the WP (range 75-88%), while the average contributions of the nano-sized and pico-sized Chl to total Chl in the YS were 47 and 38%, respectively, suggesting that a majority of the total Chl in the YS was associated with nano- and picophytoplankton. Moreover, we applied the generalized additive models (GAMs) to explore the relationships between the total Chl and that contained in each of the three size classes. These GAMs relationships suggested a continuum from picophytoplankton dominated waters to large phytoplankton (cells> 2 μm) domination with increasing Chl . Finally, we made a comparison of the total Chl obtained with GF/F filters and that measured from size-fractionated filtration and revealed that their corresponding concentrations are in good agreement, indicating the size-fractionated filtration had no effect on total Chl determination.