Spatiotemporal Variation in Particulate Organic Carbon Based on Long-Term MODIS Observations in Taihu Lake, China

Changchun Huang,Hao Yang,Ling Yao,Mingli Zhang,Tao Huang,Yunmei Li,Quanliang Jiang

doi:10.3390/rs9060624

Abstract

In situ measured values of particulate organic carbon (POC) in Taihu Lake and remote sensing reflectance observed by three satellite courses from 2014 to 2015 were used to develop an near infrared-red (NIR-Red) empirical algorithm of POC for the Moderate Resolution Imaging Spectroradiometer (MODIS-Aqua) satellite image. The performance of the POC algorithm is highly consistent with the in situ measured POC, with root mean square error percentage (RMSPs) of 38.9% and 31.5% for two independent validations, respectively. The MODIS-derived POC also shows an acceptable result, with RMSPs of 53.6% and 61.0% for two periods of match-up data. POC from 2005 to 2007 is much higher than it is from 2002 to 2004 and 2008 to 2013, due to a large area of algal bloom. Riverine flux is an important source of POC in Taihu Lake, especially in the lake’s bank and bays. The influence of a terrigenous source of POC can reach the center lake during periods of heavy precipitation. Sediment resuspension is also a source of POC in the lake due to the area’s high dynamic ratio (25.4) and wind speed. The source of POC in an inland shallow lake is particularly complex, and additional research on POC is needed to more clearly reveal its variation in inland water.

Highlights

Inland freshwater has an important role in the regional and global carbon cycle despite its small fraction of the earth’s surface relative to the land and ocean [1,2,3,4,5,6,7]
A detailed understanding of the distribution and long-term patterns of particulate organic carbon (POC) in inland water is important to understanding the carbon cycle in inland water and its effect on the global carbon cycle [15,16,17,18]
This study develops an near infrared-red (NIR-Red) band ratio empirical algorithm of POC, based on the in situ POC

Summary

Introduction

Inland freshwater has an important role in the regional and global carbon cycle despite its small fraction of the earth’s surface relative to the land and ocean [1,2,3,4,5,6,7]. In the global carbon cycle, inland freshwater is a pivotal point for carbon transport between terrestrial and marine (about 0.9 Pg C y−1 ) locations, but it serves to bury terrestrially derived carbon (about 0.98 Pg C y−1 ). This buried carbon will be emitted to the atmosphere as CO2 (0.75 Pg C y−1 ). Particulate organic carbon (POC) in inland waters is an important carbon pool that has a clear effect. A detailed understanding of the distribution and long-term patterns of POC in inland water is important to understanding the carbon cycle in inland water and its effect on the global carbon cycle [15,16,17,18]

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Discussion

Conclusion