AUTHOR=Zhao Hongwuyi , Cao Wenxi , Deng Lin , Liao Jianzu , Zeng Kai , Zheng Wendi , Zhang Yuanfang , Xu Jie , Zhou Wen TITLE=Estimation of primary production from the light absorption of phytoplankton and photosynthetically active radiation in the South China Sea JOURNAL=Frontiers in Marine Science VOLUME=10 YEAR=2023 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1249802 DOI=10.3389/fmars.2023.1249802 ISSN=2296-7745 ABSTRACT=

A model was constructed to estimate Primary production (PP) and examine the effect of the dominant phytoplankton group on PP, using a dataset collected in 2019 in the South China Sea (SCS) based on phytoplankton absorption coefficient at 443nm [a_ph(443)] and photosynthetically active radiation (PAR). There was a significant log-log linear correlation between PP and the product of a_ph(443) and PAR (a_ph(443)×PAR), with an adjusted R² of 0.64. The model was validated using K-fold cross-validation and an in situ dataset collected in 2018 in the SCS basin. The results showed that the model had good generalisability and was suitable across marine environments, including basin, coastal, and offshore areas. The model was more sensitive to changes in PAR than changes in a_ph(443). Phytoplankton in the diatom-dominant and haptophyte-dominant clusters were in the light-limited stage, and their PP values increased with increasing a_ph(443)×PAR. However, Prochlorococcus-dominant samples exhibited photoinhibition, and the PP values decreased with increasing a_ph(443)×PAR, likely due to their bio-optical characteristics. The model’s predictive power was related to the photo-physiological state of dominant phytoplankton, which performs well in light-limited conditions but not in cases of massive photoinhibition. This study provides insight into the development of phytoplankton-specific a_ph-based PP models.