A Primary Study On The Structure Of Key Food Web In Haizhou Bay

Haizhou Bay is one of the most important fishing grounds in the Yellow Sea of China.It has abundant biological resources and fish resources.Due to overfishing,some fish species can no longer form fishing poles.As an important indicator for evaluating the dynamic changes of biodiversity,the key food network can reflect the transmission and flow of matter and energy at various levels of nutrition reflect the nutritional structure of the entire marine ecosystem.However,few studies have reported on the nutritional structure of Haizhou Bay Food Network.The fatty acid analysis is an important scientific method for the study of marine food webs.Therefore,this paper mainly focuses on the suspended organic matter(POM),phytoplankton,and plankton through the fatty acid labeling method.Animals,benthos,cephalopods,and fishes are the primary food network structures in Haizhou Bay.Samples obtained in the sea areas of Haizhou Bay in September 2016 and May 2017 included zooplankton such as POM,phytoplankton,Sagitta,and Calanus sinicus,Oratosquilla oratoria,Trachypenaeus curvirostris,Parapenaeopsis tenella,Portunus trituberculatus,Scapharca subcrenata,benthic organism,Loligo beka Sasaki,The main cephalopods such as Sepilella maindroni and Octopus variabilis,Argyrosomus argentatus,Thryssa kammalensis,Tridentiger barbatus,and Mugil cephalus.Mainly analyzed the fatty acid characteristics of POM and plankton in Haizhou Bay,the composition characteristics of different trophic fatty acids,the feeding relationship of main organisms,the nutritional status,the changes of fatty acids and food habits in May and September,and The effect of body length on fatty acid content were discussed.The main results were as follows:(1)The nutrients in POM were planktonic bacteria,diatoms,seagrass,land plants,n-6>n-3(paired t-test,p<0.05),C16 : 1n7,C18: 1n9,C18: 2n6,C20: 4n6,C20: 5n3,C22: 6n3,SFA,MUFA,PUFA,n-3,n-6 fatty acid content have significant seasonal differences.The contributions of nutrients from planktonic bacteria,diatoms,seagrasses,and terrestrial plants in POM were higher in May than in September.(2)SFA> PUFA> MUFA(paired t-test,p<0.05),n-6>n-3(paired t-test,p<0.05),consistent with POM fatty acid composition trends.Seasonal differences in phytoplankton fatty acid content were observed.In May,SFA had the highest saturated fatty acid content.In September,the polyunsaturated fatty acid content was the highest,which was n-6>n-3 in either May or September(p<0.05).There was no significant change in C16:1n7.Both C20:5n3 and C22:6n3 were significantly higher in September than in May.(3)Planktonic bacteria,phytoplankton,benthic algae shellfish,and terrestrial nutrition are all sources of plankton nutrition.Copepods mainly ingested planktonic bacteria and phytoplankton;Calanus sinicus mainly ingested planktonic bacteria,planktonic bacteria,and herbivorous copepods;the nutritional level of Sagitta was higher than that of Calanus sinicus and copepods,mainly feeding on planktonic bacteria.,phytoplankton,copepods;(4)Benthic benthic organisms have higher levels of fatty acids(DHA,EPA,C20:4n6)than plankton.There was no significant difference in diatom feed intake between May and September in Oratosquilla oratoria.The meat diet in May was higher than in September;the feeding of diatoms,benthic algae,and shellfish was higher in in September than in May.The carnivorousness of Charybdis japonica in September is higher than May.(5)With the increase of trophic level,the contents of C16: 1n7 in the squid of the Loligo beka Sasaki and Sepiella maindroni are significantly lower than those of zooplankton and benthos,and the content of DHA is significantly increased.(6)According to the similarity of nearly 80,they can be divided into four major groups.The first group is the Zebrias zebra?,the second group is the Sebastes schlegelii,the third group is the Johnius belangerii,and most of the fish belong to the fourth group.There was no significant difference in the composition of fatty acids between May and September except for MUFAs in Larimichthys polyactis.The conption intensity of benthic foods in May was greater than that in September.The conption intensity of benthic food in September was greater than May.(7)The crude fat content in Exopalaemon carinicauda increased with body length,and as the body length increased,the increase rate of crude fat content also increased,There was a significant positive correlation between C18:1n9c and body length(p<0.05),and a linear regression equation with body length as an independent variable with C18:1n9c as the dependent variable was obtained: y = 0.433 x + 0.4851(p<0.05).