AUTHOR=Shih Yung-Yen , Shiah Fuh-Kwo , Lai Chao-Chen , Chou Wen-Chen , Tai Jen-Hua , Wu Yu-Shun , Lai Cheng-Yang , Ko Chia-Ying , Hung Chin-Chang 

TITLE=Comparison of Primary Production Using in situ and Satellite-Derived Values at the SEATS Station in the South China Sea

JOURNAL=Frontiers in Marine Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.747763

DOI=10.3389/fmars.2021.747763

ISSN=2296-7745

ABSTRACT=<p>Satellite-based observations of primary production (PP) are broadly used to assess carbon fixation rate of phytoplankton in the global ocean with small spatiotemporal limitations. However, the remote sensing can only reach the ocean surface, the assumption of a PP vertically exponential decrease with increasing depth from the surface to the bottom of euphotic zone may cause a substantial and potential discrepancy between <italic>in situ</italic> measurements and satellite-based observations of PP. This study compared euphotic zone integrated PP derived from measurements based on ship-based <italic>in situ</italic> incubation (i.e., PP<sub><italic>in situ</italic></sub>) and those derived from the satellite-based vertically generalized production model (VGPM; PP<sub>VGPM</sub>) for the period 2003∼2016 at the South East Asian Time-series Study (SEATS) station. PP values obtained during the NE-monsoon (NEM: Nov∼Mar; PP<sub><italic>in situ</italic></sub> = 323 ± 134; PP<sub>VGPM</sub> = 443 ± 142 mg-C m<sup>–2</sup> d<sup>–1</sup>) were ∼2-fold higher than those recorded during the SW-monsoon (SWM: Apr∼Oct; PP<sub><italic>in situ</italic></sub> = 159 ± 58; PP<sub>VGPM</sub> = 250 ± 36 mg-C m<sup>–2</sup> d<sup>–1</sup>), regardless of the method used for derivation. The main reason for the higher PP values during the NEM appears to have been a greater abundance of inorganic nutrients were made available by vertical advection. Note that on average, PP<sub><italic>in situ</italic></sub> estimates were ∼50% lower than PP<sub>VGPM</sub> estimates, regardless of the monsoon. These discrepancies can be mainly attributed to differences from the euphotic zone depth between satellite-based and <italic>in situ</italic> measurements. The significantly negative relationship between PP measurements obtained <italic>in situ</italic> and sea surface temperatures observed throughout this study demonstrates that both methods are effective indicators in estimating PP. Overall, our PP<sub><italic>in situ</italic></sub> analysis indicates that a warming climate is unfavorable for primary production in low-latitude open ocean ecosystems.</p>