Carbon,Nitrogen And Phosphorus Stoichiometric Ratios Of Laminaria Japonica In Xiangshan Harbor

Laminaria japonica is a kind of common large economic brown algae,is an important primary producer of Marine ecosystem,and is also the main cultured seaweed in China.As we all know,kelp has great potential in economic benefit,ecological regulation and carbon sequestration.We selected Laminaria japonicaculture of Xiangshan Harbor as the study area and common economic seaweed Laminaria japonica as the target species.Using the basic method of field investigation to study the growth parameters of cultured kelp and environmental factors,the growth characteristics of cultured kelp and its relationship with environmental factors can be effectively discussed,and provide theory support for the seaweed cultivation management and provide data support further physiological characteristics research;The nutrient content in the sea area of Xiangshan Harbor was studied by using an automatic nutrient analyzer,and to provide guidance and scientific basis for breeding production and ecological restoration;The contents of C,N,P and their ecostometrics of kelp cultured in Xiangshan Harbor was studied by using the method of ecostometrics,in order to explore the dynamic change rules of the contents of C,N,P and ecostometrics of kelp,and the main influencing factors of the differences in the ecostometrics of kelp,so as to kelp response to environmental changes and adaptive strategy to provide data support,at the same time for mariculture in the ecological regulation and control function of ecological system to provide theoretical basis and seaweed farming in west port of Shanghai to offer reference to improve water quality.The research results are as follows:1)The growth of kelp has obvious monthly changes.The growth is fastest in the concave and convex phase,and the average daily growth can reach 1.51±0.58cm/d.In April,with the increase of temperature,the algae began to decompose and fall off.Kelp reached the thickening stage in mid-february,and the growth rate of kelp plant growth slowed down gradually,and the daily weight gain reached 4.63±0.84g/d.In April,the maximum fresh weight of kelp reached 258.12±86.76g on average.2)The monthly changes of environmental factors were significant（p<0.05）,but the changes in the breeding area and the control area were not significant,and the changes in the surface layer and the bottom layer were not significant.Kelp growth is closely related to environmental factors,temperature and salinity can affect the growth rate of kelp,kelp culture can also adjust pH,DO,turbidity and so on.3)The surface nitrate（NO₃-N）in the kelp area showed a dynamic change rule of first increasing,then decreasing and then increasing.The surface nitrite（NO₂-N）in the kelp area showed a dynamic change of first increasing,then decreasing,then increasing and then decreasing.In the kelp area,the ammonium salt（NH₄-N）increases first,then decreases and then increases.The phosphate（PO₄-P）in the kelp increased first and then decreased.The silicate in the kelp（SiO₃-Si）decreased first,then increased and then decreased.There were significant differences in surface nitrate,nitrite,ammonium salt,phosphate and silicate between each month in the kelp area（p<0.05）.The contents of nitrate,nitrite and silicate in the surface layer were in the kelp area<control area（p<0.05）,and there was no significant difference between the ammonium salt and phosphate in the kelp area and the control area.Overall,nitrate,ammonium salt and phosphate in the kelp area showed a surface layer<bottom layer（p<0.05）,while there was no significant difference between the surface layer and the bottom layer of nitrite and silicate in the kelp area.NO₃/DIN showed a decreasing trend in general;DIN/P showed a trend of first increasing,then decreasing and then increasing.Si/DIN showed a trend of decrease,then increase and then decrease.4)The content of C in kelp showed little change on the whole.The content of N and P in kelp was higher in the early stage and lower in the mature stage.The overall trend of N/P of kelp was basically unchanged,and C/N and C/P of kelp presented a relatively low trend in the early stage and a relatively high trend in the mature stage.The absorption and utilization ability of nutrients in kelp is mainly influenced by environmental factors such as temperature,salinity,pH,DO,chlorophyll a,seawater TN,and seawater TP.5)The annual production of cultured kelp continues to increase,and the distribution range continues to increase,with huge economic benefits,ecological regulation and carbon sequestration.According to a 2017 kelp production calculation,2017 kelp capacity of 563100 tons of carbon sequestration,absorption of N,P nutrient34600 tons and 2200 tons respectively.