Estimation of the Particulate Organic Carbon to Chlorophyll-<i>a</i> Ratio Using MODIS-Aqua in the East/Japan Sea, South Korea

• Main Authors: Dabin Lee, SeungHyun Son, HuiTae Joo, Kwanwoo Kim, Myung Joon Kim, Hyo Keun Jang, Mi Sun Yun, Chang-Keun Kang, Sang Heon Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Remote Sensing
• Subjects: particulate organic carbon; chlorophyll-<i>a</i>; phytoplankton; ocean color; east/japan sea
• Online Access: https://www.mdpi.com/2072-4292/12/5/840

In recent years, the change of marine environment due to climate change and declining primary productivity have been big concerns in the East/Japan Sea, Korea. However, the main causes for the recent changes are still not revealed clearly. The particulate organic carbon (POC) to chlorophyll-<i>a</i> (chl-<i>a</i>) ratio (POC:chl-<i>a</i>) could be a useful indicator for ecological and physiological conditions of phytoplankton communities and thus help us to understand the recent reduction of primary productivity in the East/Japan Sea. To derive the POC in the East/Japan Sea from a satellite dataset, the new regional POC algorithm was empirically derived with in-situ measured POC concentrations. A strong positive linear relationship (R² = 0.6579) was observed between the estimated and in-situ measured POC concentrations. Our new POC algorithm proved a better performance in the East/Japan Sea compared to the previous one for the global ocean. Based on the new algorithm, long-term POC:chl-<i>a</i> ratios were obtained in the entire East/Japan Sea from 2003 to 2018. The POC:chl-<i>a</i> showed a strong seasonal variability in the East/Japan Sea. The spring and fall blooms of phytoplankton mainly driven by the growth of large diatoms seem to be a major factor for the seasonal variability in the POC:chl-<i>a</i>. Our new regional POC algorithm modified for the East/Japan Sea could potentially contribute to long-term monitoring for the climate-associated ecosystem changes in the East/Japan Sea. Although the new regional POC algorithm shows a good correspondence with in-situ observed POC concentrations, the algorithm should be further improved with continuous field surveys.