Retrieval of Phytoplankton Carbon Concentration in Fishponds in the Pearl River Delta Using Sentinel-3 OLCI imagery

The Pearl River Delta (PRD) is one of China's most ecologically diverse regions, characterized by extensive aquaculture activities, particularly in fish ponds. These aquaculture systems play a vital role in the region's carbon cycling; however, their contribution to the overall carbon balance remains poorly quantified. This study aimed to estimate phytoplankton carbon concentration in fishponds within the PRD using Sentinel-3's Ocean and Land Color Instrument (OLCI) data. To enhance the accuracy of reflectance values, atmospheric correction was performed using the SeaDas software, thereby ensuring more reliable data for subsequent carbon retrieval. An algorithm based on key OLCI bands (Oa08, Oa09, and Oa017) was applied to predict phytoplankton carbon concentration from 2016 to 2024.

The study investigated spatiotemporal variations in phytoplankton carbon contributions to the regional carbon cycle. Preliminary results revealed notable differences in phytoplankton carbon concentration across different fishponds, with higher concentrations observed in regions with elevated chlorophyll-a levels. In particular, the phytoplankton carbon concentration is substantially higher in summer than in winter, a pattern that could drive local carbon flux variations and influence regional carbon sequestration dynamics, especially during algal bloom events.

This study underscored the potential of satellites, particularly Sentinel-3 OLCI, for estimating carbon fluxes in aquaculture areas. The findings provided valuable insights into the carbon cycle dynamics of the PRD and enhanced our understanding of carbon sequestration in small fishpond ecosystems. These results are valuable for improving local environmental management practices, and applicable for future study on carbon dynamics in similar aquaculture systems, and can.