Species Identification Technology And Molecular Phylogenetic Analysis Of Green Tides In The Yellow Sea

The periodic large-scale outbreak of green tide has brought huge economic losses to coastal citiessince the green tide has been breaking out in Yellow Sea sea area for ten yearsfrom 2008 to 2017.The species composition and main cause of green algae,the occurrence and development process of green tide,the drift path of green tide,ecological adaptability of green tide algae,early warning and forecast of green tide and prevention and control of green tide have all become the focus of research.The identification of algae species caused by green tide is the basis of a series of in-depth research on green tide and the most direct way to investigate the occurrence and development of green tide is field investigation.In this paper,the identification method of green tide induced algal species by simultaneous PCR gel electrophoresis was put forward for the first time,which provided an effective method for the field investigation and identification of early floating green tide species caused by southern Yellow Sea.Then it carried outthe species identification and population composition analysis of green tide algae and early floating green algae of South Yellow Sea in the Porphyra aquaculture rafts area along Jiangsu coast from 2016 to 2017.Combinedthe results of monitoring from 2009 to 2015,it discussesthe succession of early floating green algae species in South Yellow Sea from 2009-2017.Finally,it studied the 5S rDNA spacer region of Ulva prolifera,a major cause of the large green tide outbreak of Yellow Sea,and found that there were three different subtypes of them and discussed them.The main findings are as follows:1.A method for identification of the cause of green tide algae by agarose gel electrophoresis(PCR)was proposed for the first time,which was compared with the traditional morphological classification method.It avoids the problem that the morphological plasticity of green algae causes the traditional morphological taxonomy to be difficult to identify.Compared with the molecular identification technology based on the amplification of characteristic fragments of green tide algae,itavoidsthe problems of high cost,long time consuming period and inconvenient operation of equipment caused by sequencing.The identification method of green tide algal species by PCR gel electrophoresis provides an effective method for the field investigation of early floating green tide causing species by Yellow Sea.2.It carried outspecies identification and species composition analysis of green tide algae in Laver Culture Shelf area of Rudong,Dafeng and Lvsi coastal areas of Jiangsu Province from 2016 to 2017.Among them,the Porphyra aquaculture rafts area of Rudong was divided into three regions of Rudong Neisha,Rudong Zhongsha and Rudong Waisha.The results showed that the green algae in the Porphyra aquaculture rafts area of Lvsi,Rudong and Dafeng in 2016 were mainly composed of Ulva flexuosa and Ulva linza.Among which,the number of Ulva linza detected in Dafeng Porphyra aquaculture rafts area increased gradually from January to April and the number of attached Ulva flexuosa detected in Lvsi area was larger than that of Ulva linza when the number of attached Ulva linza was more than that of Ulva flexuosa in Rudong Waisha and Rudong Zhongsha.The number of Ulva linza detected in January was the least in Rudong Neisha and the highest in February.From November 2016 to May 2017,the green algae in the Dafeng Porphyra aquaculture rafts area was mainly composed of Ulva flexuosa,while Ulva linza was detected only in April.In Lvsi Porphyra aquaculture rafts area,only Ulva flexuosa was detected from November 2016 to February 2017.The quantity of Ulva flexuosa detected in the Rudong Waisha and Rudong Zhongsha was more than that of Ulva linza,and the species composition of the green tide algae in Rudong Neisha in 2017 was the same as that in 2016.In conclusion,the number of Ulva flexuosa detected in 2017 was significantly higher than that in 2016.In addition,the 5S rDNA spacer region detected in 2016-2017 was almost identical to the HM031152.1 sequence of Ulva prolifera published on GeneBank.The number of attached Ulva prolifera detected in 2017 was more than that in 2016 and most of them were distributed in the Rudong Zhongsha from March to May.3.The reserach investigated and analyzed the species composition and succession of early floating green algae in South Yellow Sea from 2016 to 2017.The succession trend of early floating green algae in South Yellow Sea from 2009 to 2017 was discussed based on the monitoring results from 2009 to 2015.The results showed that Ulva compressa was the first algae species to appear in the early stage of green tides in South Yellow Sea from 2009 to 2011,followed by Ulva flexuosa and Ulva linza,and then Ulva prolifera.The biomass of Ulva prolifera which increased continuously and became the main dominant algae species that floated to Qingdao on a large scale in breaking out of the green tide.From 2012 to 2017,the number of Ulva compressa and Ulva linza decreased and even completely disappeared in the early stage of green tides in South Yellow Sea from 2013 to 2014.Since 2012,Ulva prolifera was not only the first species to appear on the sea surface but also the dominant species during the whole early stage of green tides.4.It studied and analyzed the sequence subtypes of 5S rDNA spacer region of three species of Ulva prolifera caused by green tide of South Yellow Sea.The results showed that the early stage of green tides in South Yellow Sea was of 5S-I type and 5S-II type and the quantity ratio showed a certain change trend.From 2008 to2015,the number of type 5S-I of Ulva prolifera decreased from 100% to 0% and the number of type 5S-II of Ulva prolifera showed a rising trend whichincreased from 0% to 100%.From 2016 to 2017,it showed the opposite trend with the increase of 5S-I and the reduction of type 5S-II of Ulva prolifera.Only a small amount of 5S-III type Ulva prolifera was detected in the early stage of green tides in Dafeng in 2010.From 2016 to 2017,the surveillance and investigation of the Porphyra aquaculture rafts area in Jiangsu coastal area and the early stage of green tides in South Yellow Sea showed that the algae detected in the Porphyra aquaculture rafts area were all 5S-III type Ulva prolefera.The number of 5S-III attached Ulva prolifera in 2017 was more than that in previous years.Except Dafeng,Lvsi,Rudong Neisha,Rudong Zhongsha and Rudong Waisha,5S-III type Ulva prolifera was detected.Especially in Rudong Zhongsha,all of Ulva prolifera were III type from March to May of 2017.However,5S-III type Ulva prolifera was not found in the early stage of green tides in South Yellow Sea from 2016 to 2017.