Monitoring the Dissipation of the Floating Green Macroalgae Blooms in the Yellow Sea (2007–2020) on the Basis of Satellite Remote Sensing

Deyu An,Qianguo Xing,Xiangyang Zheng,Ling Meng,Yan Zhou,Dingfeng Yu

doi:10.3390/rs13193811

Abstract

Large scale green macroalgae blooms (MABs) caused by Ulva prolifera have occurred regularly in the Yellow Sea since 2007. In the MAB dissipation phase, the landing or sinking and decomposition of U. prolifera would alter the physical-chemical environment of seawater and cause ecological, environmental, and economic problems. To understand MAB dissipation features, we used multiple sensors to analyze the spatiotemporal variation of the MAB dissipation phase in the southern Yellow Sea. The results show the variation in the daily dissipation rate (DR) was inconsistent from year to year. Based on the DR variation, a simple method of estimating MAB dissipation days was proposed for the first time. Verification results of the method, from 2018 to 2020, showed the estimated dissipation days were relatively consistent with the results obtained by remote sensing imagery. From 2007 to 2020, the order in which macroalgae landed in the coastal cities of Shandong Peninsula can be roughly divided into two types. In one type, the macroalgae landed first in Rizhao, followed by Qingdao, Rushan, and Haiyang. In the other type, they landed in the reverse order. The MABs annual distribution density showed significant differences in the southern Yellow Sea. These results provided a basis for evaluating the MABs’ impact on marine ecology and formulating the green-tide prevention and control strategies.

Highlights

Macroalgal blooms (MABs), caused by the outbreak of macroalgae, have increased remarkably in the global oceans in recent years and have become a worldwide marine ecological problem [1,2,3,4]
Every April, when mariculture iculture rafts were recycled after harvesting the seaweed P. yezoensis, U. prolifera rafts were recycled after harvesting the seaweed P. yezoensis, U. prolifera macroalgae atmacroalgae attached to the rafts were scraped off and discarded into sea water [14,22,29]
The unique feature of this study is that multiple sensors were used to study the spatiotemporal variation of macroalgae bloom dissipation in the southern Yellow Sea from four aspects including: (1) variation in the daily dissipation rate, (2) variation in the order in which the macroalgae landed in the coastal region of Shandong Peninsula, and (3) variation in the annual distribution density

Summary

Introduction

Macroalgal blooms (MABs), caused by the outbreak of macroalgae, have increased remarkably in the global oceans in recent years and have become a worldwide marine ecological problem [1,2,3,4]. The remote sensing monitoring methods of the green tide are basically mature and the overall understanding and the early development processes are largely clear: many studies from multiple perspectives including satellite remote sensing, ocean circulation models, and field observations indicate that U. prolifera originates in the Subei. Evidence has indicated that P. yezoensis aquacul(Porphyra yezoensis) in this area [14,22]. Evidence has indicated that P. yezoensis aquaculture ture rafts would be the main source of U. prolifera [13,22,26,27,28]. Every April, when mariculture iculture rafts were recycled after harvesting the seaweed P. yezoensis, U. prolifera rafts were recycled after harvesting the seaweed P. yezoensis, U. prolifera macroalgae atmacroalgae attached to the rafts were scraped off and discarded into sea water [14,22,29]

Methods

Results

Discussion

Conclusion