Potential Influencing Factors For The Resource Variation Of Zostera Marina L. In Sanggou Bay And Seed Selection Techniques

Seagrass is a common name for higher flowering plants living in the ocean.It is a typical marine ecosystem with coral reefs and mangroves.It plays an important ecological role in shallow sea ecosystems.However,since the 20 th century,seagrass beds have been degraded due to various natural factors and human disturbances.This paper selects three factors that may affect seagrass resources: petroleum hydrocarbon pollution,the resources of Ruditapes philippinarum in seagrass beds,seawater acidification.the experiment of petroleum hydrocarbon pollution to explore the chlorophyll fluorescence parameters of zostera marina L.which is exposed to different concentrations and different times.the R.philippinarum is abundant around seagrass meadow at Chudao in the Sanggou Bay.In order to determine the interactions between the R.philippinarum and Z.marina,the amount of R.philippinarum was evaluated in the seagrass meadow at Chudao from May to July,2016.The feeding and metabolic physiology of R.philippinarum were determined based on the individual experiment with flowing water.The benefit between the R.philippinarum and Z.marina was invested in an enclosure experiment in the field.The experiment of seawater acidification is to research the effect of acidification on the transcriptome of Z.marina.Moreover,seeds selection experiment was done by a sieve with a pore size of 1.8 mm and a 2.19 mol/L sucrose solution,then seed germination experiment was done by using 1(seawater): 5.2(fresh water).All of these dexperiments will provide data support for the restoration of seagrass resources.Main results were as follows: 1.during the experimental period when the Z.marina were exposed to different concentrations of petroleum hydrocarbons(0,0.5,2.5,5,10,20 mg/L)for 8 days,decreased after being stressed,the end of the experiment was significantly lower than the beginning of the experiment(p<0.05).The chlorophyll fluorescence parameters NPQ did not change significantly from 0 to 3 days,at the end of the experiment,when the concentrations of petroleum hydrocarbons was 5,10,20mg/L,The chlorophyll fluorescence parameters NPQ,Yield,q P values were significantly lower(P<0.05),photosynthesis inhibition was significant at 5,10,20 mg/L(P<0.05),when the concentrations of petroleum hydrocarbons was 0.5,2.5 mg/L,the increase trend of the light curve was comparable to that of the control group,and the increase tendency was significantly slower at 5,10,and 20 mg/L.2.The results showed that the biomass of R.philippinarum was 572 ± 20.23 ind·m-2,which included 9.01% large(Shell length 3.50-4.10 cm),43.60% medium(Shell length 3.00-3.50 cm),and 47.38% small(Shell length 2.00-3.00 cm)clams.The ammonia nitrogen excretion rate,oxygen consumption rate,clearance rate a were from 0.44 ± 0.15 to 1.40 ± 0.35 ?mol·ind-1·h-1,0.21 ± 0.02 to 0.33 ± 0.08 mg·ind-1· h-1,0.69 ± 0.38 to 0.83 ± 0.66 L· ind-1 ·h-1 respectively.There were four groups(R.philippinarum group,R.philippinarum + Z.marina group,Z.marina group and the control)with three replications each in the enclosure experiment which was run for four hours.The results showed that there were significant difference in dissolved oxygen concentration among R.philippinarum group,R.philippinarum + Z.marina group and Z.marina group(P<0.05).The ammonia nitrogen concentration in R.philippinarum group was significantly higher than those in the other three groups(P<0.05).The R.philippinarum group and R.philippinarum + Z.marina group were significantly lower than the control in the total particles(P<0.05),while no significant difference was found between the Z.marina group and the control(P>0.05).The habitat of R.philippinarum is about 0.5 km2 around Chudao in Sanggou Bay.About 5 square meters clam can meet the ammonia nitrogen requirement of 1 square meter the Z.marina meadow.The present study is good for the supplementation of the knowledge about the ecological roles of R.philippinarum in the Z.marina meadow area.3.The transcriptomic changes of Z.marina by response to seawater acidificationThrough the transcriptome sequencing analysis of the control group and the acidification treatment group,the results showed that 1834 differentially expressed unigenes were screened,of which 1090 were up-regulated and 744 were down-regulated.GO enrichment analysis showed that the unigenes involved in photosynthesis(photosystem,GO: 0009521;photosystem II,GO: 0009523;photosynthetic membrane,GO: 0034357)were20,17,20,up-regulation3,3,3,down-regulation 17,14,17 in the cell component category.Carbon fixation in photosynthetic organisms found that 13 unigenes were involved in the metabolic pathway of photosynthetic organisms(C3)(3.1.3.11,5.1.31)down 5,up 2.C4 down 1,up 3.CAM pathway was one up-regulated and one down-regulated.The N metabolic pathway(Nitrogen metabolism)found that carbonic anhydrase(Carbonic Anhydrase,CA,EC: 4.2.1.1)down regulated expression.The photosynthesis pathway enriched 21 differentially expressed genes and all expressions down-regulated.The PSII light-harvesting protein genes Lhcb5 and Lhcb7 were down-regulated in photosynthetic-antenna protein pathways(photosynthesis.antenna proteins).4.Seed selection technology of Z.marinaThe results showed that the germination rate of seeds in the control group(E)was only 16% after germination at 30 days,and the germination rate of the seeds was D> B> E> A> C.The seedlings in the next step were selected mainly for D and B seeds.