Seaweed Cultivation Region Remote Sensing And Analysis On The Dynamics In Seaweed-facility Recycling In Northern Jiangsu Shoal

The world's largest green tide caused by the green macroalge blooms of Ulva prolifera has occurred in the Yellow Sea every summer since 2007.From remote sensing monitoring,field investigation and biological studies,it is found that the green tides in the Yellow Sea originated from seaweed cultivation areas in the northern Jiangsu shoal.Based on the high-resolution optical remote sensing satellite images of GF-1,Sentinel-2A,HJ-1A/B,Landsat series and Sentinel-1A microwave data,the seaweed cultivation areas in the northern Jiangsu shoal were extracted.And the characteristics of seaweed cultivation activities in the northern Jiangsu shoal,mainly in the process of seaweed facility-recycling,were analyzed.The main conclusions in this paper are listed as follows:(1)The extraction results based on the microwave images in the period of algae growing by threshold method has consistent space distribution with that based on optical images.The spectral varies in the process of seaweed facility-recycling.(2)Based on the area of seaweed cultivation areas extracted from different resolution remote sensing images,the conversion relationships were established.(3)From the area results of seaweed cultivation areas in the northern Jiangsu shoal from 2012 to 2018,it was found that the areas of the seaweed cultivation regions in the northern Jiangsu shoal were relatively stable and didn't expand significantly in the past seven years.(4)From the extraction results of seaweed cultivation areas in North Jiangsu Shoal from the late April to the early June in 2012-2018,it was found that the areas of the seaweed cultivation regions varied differently in the process of seaweed facility-recycling.In 2015 and 2016,the recovery of farming facilites was earlier.In 2017 and 2018,the recoveries of farming facilites were relatively late.(5)Combining the green tide information between 2012 and 2018,it is found that the scales of early green tide in 2017 and 2018 in which year the recoveries of farming facilities were late were significantly were smaller than that in 2014,2015 and 2016 when the recoveries of farming facilities were earlier.The maximum daily coverage areas of green tide in 2017 and 2018 are much smaller than that in 2015 and 2016.The result shows that the scale of the green tide could be reduced to some extent by adjusting the seaweed facility-recycling in northern Jiangsu shoal.The extraction results of seaweed cultivation areas and the characteristics of seaweed cultivation activities in the northern Jiangsu shoal could be a reference for decision-making of reducing green tide scale in the Yellow Sea.