Satellite determining dominant sources of particulate organic carbon across different eutrophic waters

Abstract

Particulate organic carbon (POC) plays a vital role in carbon cycling in aquatic ecosystems. A knowledge of POC source dynamics is important for a comprehensive understanding of many biogeochmeical processes in inland and coastal waters. Yet, determining POC sources from remote sensing have not been fully explored. Using bio-optical datasets from 10 cruises in Taihu Lake, Poyang Lake, Daya Bay and the Pearl River Estuary, an optical classification scheme was developed to detect the dominant source of POC from remote sensing, taking into consideration the absorbing feature of phytoplankton pigment in the near-infrared waveband. Following the approach of POC source identification, the study waters were distinguished into two classes, the algae-based origin and detritus-dominance source. POC sources were thus mapped with 2016–2019 VIIRS imagery data, which exhibited significant temporal variability and spatial heterogeneity for the four study waters across different eutrophic states. It was observed that Poyang Lake was mostly terrigenous in all the study years and phytoplankton-related source was dominated in Daya Bay. Taihu Lake showed heterogeneous conditions varying with time and space, whereas most water areas was contributed by the terrestrial origin. Specially, the Pearl River Estuary presented a typical pattern of POC sources dynamics, with an exogenous source in the north-west waters, while endogenous in the south-east open areas. By implication, the methodology of POC source determination in the present study, will be conveniently applied to the common water color satellites and effectively identify the POC origins in time and space in future, which allows for a better understanding the carbon cycling and biogeochemical processes in inland and coastal waters with different eutrophication conditions.