Temporal-spatial Distribution And Countermeasures Study Of Algae Disaster In The Bohai And Yellow Sea Based On Multi-source Data

Marine algae disasters such as green tide in the Yellow Sea and red tide in the Bohai Sea are increasingly affecting the offshore marine environment and the sustainable development of coastal economy in China.Remote sensing technology has become an important means to study with it because of advabtages such as low cost and wide monitoring range.This paper carries out the temporal-spatial monitoring of green tide and red tide based on GOCI to compensate for the problem of insufficient time resolution in traditional satellite imagery.Based on this,the multi-platform datasets including GF-1,VIRRS,Ascat,and research voyages are applied to comprehensively analyze the environmental factors during algae outbreaks,to improve the research shortages in outbreak mechanism and corresponding countermeasures of algae disasters.Therefore,we can provide scientific reference for the prevention of green tide in the Yellow Sea and red tide in the Bohai Sea,the main research conclusions are as follows:(1)The NDVI algorithm has a good detection capability on the ulva prolifera,and band selection of GOCI has a significant effect on the extraction results;GF-1 has better accuracy in green tide extraction than GOCI,but the data availability is weaker;The daily variation area of ulva prolifera showed an "M" curve while the aggregation showed an inverted "U" curve;The best pre-refloatation opportunity is the middle and late of May in the northern sea area of Yancheng.(2)The area of aquaculture rafts in northern Jiangsu showed a positively correlated with the coverage area of green tide,but the significance was weak;SST plays a dominant role in the growth and reproduction of the ulva prolifera disaster;The south-east monsoon in the south Yellow Sea drove the green tide to the northwest direction until geographically blocked by the southern bank of the Shandong Peninsula,and landed to form an ecological disaster.(3)While chlorophyll threshold method has many limitations on the extraction of red tide,the multi-band ratio method has better extraction results;The number of red tide outbreaks is similar in recent years,but the total area is significantly reduced,while summer season has a higher explosion frequency,especially from May to September;The outer sea of Qinhuangdao is a concentrated area of outbreaks,while the Tianjin-Tangshan coast is another hot spot.(4)The kriging method can achieve more accurate spatial interpolation result;The Bohai Sea has already in sub-health state,and the pollution in Laizhou Bay and Bohai Bay is more serious while the central Bohai Sea and the Straits are better;The Laizhou Bay lacks the dominant species of red tide and the Bohai Bay should control the discharge of phosphorus-containing wastewater,the Liaodong Bay may cooperate with the Bohai Bay to rectify runoff and discharge comprehensively,to eliminate the nutritional basis of red tide.The innovations in this thesis are as follows:(1)For the first time,the aggregation degree was used as an indicator to quantify the different levels of green tide,and to optimize the temporal-spatial choice of pre-refloatation area;(2)By constructing an appropriate evaluation models,the ecological health statue in the Bohai Sea is spatialized for the first time,providing a more intuitive reference for the prevention of red tides.