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<p>The phytoplankton light absorption coefficient (<i>a</i><sub>ph</sub>) is crucial for understanding growth, composition, size classes, photo-acclimation, and carbon cycling processes of phytoplankton. However, the existing estimation methods suffer from low estimation accuracy and limited applicability due to insufficient theoretical support. Sun-induced chlorophyll-<i>a</i> fluorescence (SIF) serves as an optical indicator of phytoplankton photosynthesis activity and holds potential to estimate <i>a</i><sub>ph</sub>. The factors affecting the relationship between SIF and phytoplankton absorption were explored. A new algorithm for estimating the phytoplankton absorption coefficient at 665 nm (<i>a</i><sub>ph</sub> (665)) incorporating the diffuse attenuation coefficient of photosynthetically active radiation (<i>K</i><sub><i>d</i></sub> (PAR)) was developed to classify water types and SIF and estimate <i>a</i><sub>ph</sub> (665) for each water type. Validation datasets collected from eight inland waters in China were used to assess the accuracy of the new method. Results demonstrate that the new algorithm outperforms two classical approaches with overall win rate (OWR) of 50.89%, unbiased mean absolute percentage error (UMAPE) of 30.73%, and root mean square error (RMSE) of 0.24/m. Furthermore, the robustness and applicability of the developed algorithm were confirmed through successful application in Belgian inland and coastal waters. Finally, the algorithm was applied to map the spatiotemporal distribution of <i>a</i><sub>ph</sub> (665) in Taihu Lake for year 2022 using Sentinel-3 Ocean and Land Color Instrument (OLCI) imagery. The advantages of this method can be further expanded with the launch of the Plankton, Clouds, Aerosols, and Ecosystems (PACE) satellite with higher spectral resolution.</p>

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A novel method of estimating phytoplankton absorption coefficient for inland waters based on OLCI using Sun-induced chlorophyll-a fluorescence

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Wenyu Liu,
  • Yiling Zheng,
  • Jie Lin,
  • Yunmei Li,
  • Honglei Guo,
  • Huaiqing Liu,
  • Yuxin Zhu,
  • Fangfang Chen,
  • Heng Lü,
  • Song Miao

摘要

The phytoplankton light absorption coefficient (aph) is crucial for understanding growth, composition, size classes, photo-acclimation, and carbon cycling processes of phytoplankton. However, the existing estimation methods suffer from low estimation accuracy and limited applicability due to insufficient theoretical support. Sun-induced chlorophyll-a fluorescence (SIF) serves as an optical indicator of phytoplankton photosynthesis activity and holds potential to estimate aph. The factors affecting the relationship between SIF and phytoplankton absorption were explored. A new algorithm for estimating the phytoplankton absorption coefficient at 665 nm (aph (665)) incorporating the diffuse attenuation coefficient of photosynthetically active radiation (Kd (PAR)) was developed to classify water types and SIF and estimate aph (665) for each water type. Validation datasets collected from eight inland waters in China were used to assess the accuracy of the new method. Results demonstrate that the new algorithm outperforms two classical approaches with overall win rate (OWR) of 50.89%, unbiased mean absolute percentage error (UMAPE) of 30.73%, and root mean square error (RMSE) of 0.24/m. Furthermore, the robustness and applicability of the developed algorithm were confirmed through successful application in Belgian inland and coastal waters. Finally, the algorithm was applied to map the spatiotemporal distribution of aph (665) in Taihu Lake for year 2022 using Sentinel-3 Ocean and Land Color Instrument (OLCI) imagery. The advantages of this method can be further expanded with the launch of the Plankton, Clouds, Aerosols, and Ecosystems (PACE) satellite with higher spectral resolution.