Studies On The Carbon, Nitrogen, Phosphorus Budgets In The Integrated Aquaculture Of Sea Cucumber Apostichopus Japonicus-jellyfish Rhopilema Esculenta-shrimp Fenneropenaeus Chinensis And Sea Cucumber Monoculture Fed With Benthic Diatom Cylindrotheca Fusif

In order to provide theoretical basis for the high-efficient clean aquaculture of seacucumber and improve the breeding technology, the carbon, nitrogen and phosphorusbudgets were investigated in the integrated aquaculture system of sea cucumber-jellyfish-shrimp and the sea cucumber monoculture system which was fed with freshdiatom. The present study was conducted to explore the utilization ratios of carbon（C）, nitrogen （N） and phosphorus （P） and the purification ability of a ternaryintegration of A. japonicus, R. esculenta and F. chinensis. Some measures andsuggestions were offered to optimize the stocking density of shrimp and sea cucumberaccording to the aquaculture products and the conditions of the sediment. The study ofsea cucumber monoculture fed with benthic diatom was conducted for the naturaldiatom biomass was low and the artificial algae powder may pollute water andsediment. The effect of the benthic diatom on the sea cucumber and water quality wasinvestigated according to measuring the C, N, P budgets in the system. The detailedresults of the study are as follow: 1. Total organic carbon budget of integrated aquaculture system of sea cucumber,jellyfish and shrimpThe total organic carbon （TOC） budget of the integrated aquaculture system of seacucumber Apostichopus japonicus, jellyfish Rhopilema esculenta and shrimpFenneropenaeus chinensis was investigated in a cofferdam （120.2hm2） for13-monthfield study. The results showed that the total input of TOC to the system was498,300kg yr^-1, of which photosynthesis accounted for26.8%of input TOC. The TOCproduction of sea cucumber A. japonicus was3,668kg yr^-1, and that of the jellyfish R.esculenta and shrimp F. chinensis was714kg yr^-1. The TOC utilization rate of theinput TOC by sea cucumber production was7.4‰, and that of the integrated systemincreased by18.9%than that of sea cucumber monoculture model through integrationwith jellyfish and shrimp. The outflow TOC from the system was336,600kg yr^-1,which account for92.7%of the inflow TOC and67.5%of the total input TOC. Theintegrated aquaculture system not only produce aquatic products but also eliminate7.3%of the inflow TOC, therefore, this system was not only a production system ofaquatic products but also an organic matter purification system for the coastalenvironment. The TOC utilization rate of the system can be probably improved bymeans of increasing stocking density of the sea cucumber and/or the shrimp.2. Nitrogen and phosphorus budget of integrated aquaculture system of seacucumber, jellyfish and shrimpThe nitrogen （N） and phosphorus （P） budgets as well as ecological efficiencies of theintegrated aquaculture system of sea cucumber Apostichopus japonicus, jellyfish Rhopilema esculenta and shrimp Fenneropenaeus chinensis were studied in acofferdam （120.2hm2）. The nutrients of the system were supplied by spring tideinflow, and no artificial diet was provided. Totally139,600kg yr^-1N and9,730kg yr^-1P input to the system,118,900kg yr^-1N and2,840kg yr^-1P outflowed from thesystem concurrently, which was85.7%N and29.2%P of the inputs to the system.Furthermore, the N and P productions of the sea cucumber were889.5kg yr^-1and49.28kg yr^-1, and those of the jellyfish and shrimp were204kg yr^-1and18.03kg yr^-1,respectively. The utilization rates of the inflow N and P by aquaculture products were7.8‰and6.9‰, which were21.9%and38%higher than those in the sea cucumbermonoculture model. This study indicates that the integrated aquaculture system is notonly an efficient production system of aquatic products，but also a purification systemfor the coastal environment，considering its elimination of14.3%N and70.8%P fromthe incoming water. The ecological efficiencies of the system will be probablyimproved further by increasing the stocking density and/or the size of sea cucumber.3. The effect of benthic diatom on the growth of the sea cucumber and waterqualityThe growth of sea cucumber and the water quality in the aquaculture system of seacucumber Apostichopus japonicus fed with benthic diatom Cylindrotheca fusiformiswere investigated for13months. The results showed that the special growth rate（SGR） and survival rate of the sea cucumber were higher in the experimental group（feeding diatom） than in the control group. The SGR and mean weight of seacucumber in the experimental ponds were significantly higher than that in the control ponds in June （P<0.05）. The experimental group held a growth advantage until theend of the experiment （p>0.05）. The results indicated the benthic diatom can promotethe growth of sea cucumber in their earlier growth stages. The growth-promotingeffects will weaken as the feed intake increase, but it was better than the control group.The NH4-N content was lower in the experimental ponds than that in control group inOctober （P<0.05）, and the TN and TP contents were lower in the experiment pondsthan that in control group during most of the period （P>0.05）. The results showed thatthe purification function of the benthic diatom would be more remarkable whensplashing more diatoms. According to the profitability analysis,16500￥ha^-1moremoney would be gained in the ponds of sea cucumber fed with benthic diatom.4．The effect of benthic diatom on the fatty acid composition of the sediment andsea cucumberThe fatty acid composition of the sediment and sea cucumber were investigated in thestudy. The results showed that the ratio of C16:1（n-7）/C16:0and the content ofC20:5（n-3） in the sediment were higher in the experimental ponds than that in thecontol group in June （P<0.05）. The content of C16:1（n-7） in the sediment in theexperimental group was19%, and it was higher than that in the control ponds.Meanwhile the C16:1（n-7）/C16:0in the experimental ponds was higher than that inthe control group in November （P>0.05）. The value of C16:1（n-7）/C16:0and theC16:1（n-7） content of sea cucumber in the experimental group was higher than that inthe control group in June. The experimental group has significantly higher fatty acidof diatom-biomarker than the control group in November （P<0.05）. The results indicated that feeding the benthic diatom to the sea cucumber ponds can promote thebiomass of benthic diatom, and it was conductive to the growth of sea cucumber.5. Total organic carbon budget in the system of sea cucumber fed with benthicdiatomThe total organic carbon （TOC） budget as well as utilization efficiency in theaquaculture system of sea cucumber Apostichopus japonicas fed with benthic diatomwere studied for13-month field study. The results showed that the total input of TOCto the control group and experimental groups’（feeding diatom） ponds were248.4kgyr^-1and257.9kg yr^-1respectively. TOC utilization efficiency in the experimentalgroup was7.1‰, it increased by16.8%than that of sea cucumber monoculture. TOCamount fixed according to photosynthesis in the diatom pond was69.34kg yr^-1, and itwas15.9%more than that of the control group. During the suitable period for thebenthic diatom, TOC content of the sediment in the experimental group wassignificantly higher than in the control group （P<0.05）. This study indicated thatadding additional alive diatom to the pond for sea cucumber can promote the growthof sea cucumber and the TOC utilization of the system according to boosting the TOCcontent in the sediment.6. The effect of the benthic diatom on the total nitrogen and phosphorus budgetsin the system of sea cucumber fed with benthic diatomThe total nitrogen （TN） and total phosphorus （TP） budget as well as utilizationefficiency in the system of sea cucumber Apostichopus japonicas polyculture withbenthic diatom were investigated in the sea cucumber ponds for13-month field study. The results showed that there was88.84kg yr^-1N input to the experimental andcontrol group ponds,42.25kg yr^-1N and43.24kg yr^-1N outflowed from theexperimental and control ponds respectively, which was47.6%and48.7%of theinputs to the ponds. The N production of the sea cucumber were0.46kg yr^-1and0.37kg yr^-1in the experimental group and control group respectively, the results indicatedthat the benthic diatom promote the TN removal capability of the sea cucumber.During most of the period, TN contents of the sediment were higher in theexperimental group than in the control group, and the TN contents of sea cucumber inthe experimental group was significantly higher than the sea cucumber monoculturesystem without feeding diatom（P<0.05）. The results indicated that adding additionalalive diatom to the pond for sea cucumber can promote the growth and protein contentof the sea cucumber according to boosting the TN content in the sediment.There was4.3kg yr^-1P input to the experimental and control group ponds,1.42kg yr^-1and1.37kg yr^-1P outflowed from the experimental and control ponds, which was33%and32%of the inputs to the ponds. The P production of the sea cucumber were0.23kg yr^-1and0.21kg yr^-1in the experimental group and control group respectively, theresults indicated that the benthic diatom promote the TP removal capability of the seacucumber. During most of the period, the experimental group had the similar TPcontents in the sediment with the control ponds. TP contents of sea cucumber in theexperimental group was similar with the sea cucumber non-feeding diatom （P>0.05）.The results indicated that adding additional alive diatom to the pond for sea cucumberhas the weak interaction with the TP contents in the sediment and sea cucumber. The TN/TP value had small fluctuations during the whole experiment, it showed that thenutrition content of the sediment was low about the low biomass of phytoplanktonbiomass.