Abstract

Satellite images with different spatial resolutions are widely used in the observations of floating macroalgae booms in sea surface. In this study, semi-synchronous satellite images with different resolutions (10 m, 16 m, 30 m, 50 m, 100 m, 250 m and 500 m) acquired over the Yellow Sea, are used to quantitatively assess the effects of spatial resolution on the observation of floating macroalgae blooms of Ulva prolifera. Results indicate that the covering area of macroalgae-mixing pixels (MM-CA) detected from high resolution images is smaller than that from low resolution images; however, the area affected by macroalgae blooms (AA) is larger in high resolution images than in low resolution ones. The omission rates in the MM-CA and the AA increase with the decrease of spatial resolution. These results indicate that satellite remote sensing on the basis of low resolution images (especially, 100 m, 250 m, 500 m), would overestimate the covering area of macroalgae while omit the small patches in the affected zones. To reduce the impacts of overestimation and omission, high resolution satellite images are used to show the seasonal changes of macroalgae blooms in 2018 and 2019 in the Yellow Sea.

Highlights

  • Macroalgal blooms (MABs) caused by fast growth and accumulation of floating macroalgae have been increasing in global oceans in recent years [1,2,3,4]

  • The coverages of MM-CA, pure macroalgae (PM-CA) and area by macroalgae blooms (AA) of macroalgae obtained by multi-source remote sensing images are compared, and the effects of satellite image spatial resolution on monitoring of floating macroalgae and the corresponding spatial and temporal characteristics are intensively investigated for promoting the quantitative assessment of floating macroalgae by satellite remote sensing

  • The results show that, both the number of macroalgae patches and the total area of macroalgae pixels (MM-CA) tend to decrease with the increase in the patch size; and the total number of macroalgae patches decreases with the increase of image spatial resolution

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Summary

Introduction

Macroalgal blooms (MABs) caused by fast growth and accumulation of floating macroalgae have been increasing in global oceans in recent years [1,2,3,4]. These blooms can bring economic loss to human society as well as the changes in the marine ecosystem [5,6,7,8]. The coverages of floating macroalgae monitored by multi-source images are significantly different, which is mainly caused by the mixed pixels of images with different spatial resolutions [32]. The coverages of MM-CA, PM-CA and AA of macroalgae obtained by multi-source remote sensing images are compared, and the effects of satellite image spatial resolution on monitoring of floating macroalgae and the corresponding spatial and temporal characteristics are intensively investigated for promoting the quantitative assessment of floating macroalgae by satellite remote sensing

The Study Area
Satellite Images and Data Processing
June 2018 11:10:00
Estimation of the Area of Floating Macroalgae
Results and Analysis
Conclusions and Prospect
Full Text
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