Species Diversity And Ecology Of Benthic Ciliates In Dongtan Wetland Of Chongming Island,Shanghai

Ciliated protozoa is an important part of the benthic microbial food web and plays an important role in the material circulation and energy flow of the benthic ecosystem.Wetland ecosystem,called "kidney of the earth",plays a key role in maintaining species diversity and ecological balance.As a national nature reserve,Shanghai Chongming Dongtan wetland has abundant biological and natural resources,and the research on its species diversity is of great significance to the conservation of biodiversity and the ecological construction of Chongming Island or even Shanghai.However,the study on species diversity and ecology of benthic ciliates in Dongtan wetland is very scarce so far.Therefore,we use the Ludox density centrifugation combining the quantitative protargol staining techniques to take sample at three sites of different salinity in Dongtan wetland of Chongming in the spring,summer,autumn and winter of 2015,and carry out ecological studies on species diversity and community structure of benthic ciliates and their relationship with environment.From the perspective of ciliated protozoa,this paper provides a new historical file for the study of biodiversity in the Dongtan wetland of Chongming Island,and also provides a reference for the study of the relationship between the community structure of benthic ciliates and the environment.The main results are as follows:The detection results of 10 environmental factors in Dongtan wetland of Chongming Island show that the temporal and spatial changes of 5 nutrients(nitrate,nitrite,phosphate,silicate,ammonium)are obvious,but the regular patterns are different.The contents of TOC and TN are the lowest in site 1,and higher in site 2and 3.At the same time,compared with previous studies,it is found that the grain size of the sediments will change with time due to the influence of the Yangtze River and the sea current to Dongtan wetland of Chongming Island.The salinity is the highest in the site 3 and the lowest in the site 1,and the lower salinity of the three sites insummer may be related to the high discharge of the Yangtze River and the increase of precipitation.123 species of benthic ciliates belonging to 69 genera,52 families,26 orders and11 classes are identified.The difference of the average abundance,frequency of occurrence and contribution to the average Bray-Curtis similarity of each site is big.From the class level,three species are abundant: 34 species of Oligohymenophorea,32 species of Litostomatea,and 20 species of Spirotrichea,accounting for 27.64%,26.02% and 16.26% of the total species,respectively.From the order level,Pleurostomatida(28.32%)and Pleuronematida(21.10%)are dominant groups;Haptorida(13.22%)and Stichotrichida(11.16%)are secondary dominant groups.There are 8 dominant species,which are Amphileptus lanceolatus,Chaenea minor,Deviata estevesi,Kentrophyllum setigerum,Phialina sp1,Protocyclidium sp1,Pseudocyclidium marylandi,Spelaeophrya polypoides.The temporal and spatial distribution characteristics of each dominant species are different.The results of canonical analysis of principal coordinates(CAP)show that the community structure of benthic ciliates in Dongtan wetland of Chongming Island have obvious temporal and spatial differences.The variation of 3 community structure parameters is that the species evenness(J')has little change in the whole year,while the species richness(d)and species diversity(H')showed a similar change pattern.Both of them have obvious changes in time and space.Spearman correlation analysis show that the species richness index(d)and species diversity index(H')of benthic ciliates in Dongtan wetland of Chongming Island are positively correlated with phosphate concentration and negatively correlated with salinity.Besides,species evenness index(J')are positively correlated with salinity.Compared with previous studies,it is found that the species composition and diversity of ciliates are greatly affected by the habitat,and a higher species numberare often found in studying region with higher habitat heterogeneity.The studying area of this experiment is estuary,the range of salinity variation is larger than that of fresh water and marine habitat,so some groups with large tolerance to salinity are the dominant groups in the community such as Oligohymenophorea,Litostomatea and Spirotrichea.There are some differences in the dominant groups between this study and those in the intertidal zone,the Yellow Sea or the East China Sea,where the abundance of the typical marine sandy species—Karyorelictea and algophagous Nassophorea is higher.Because of the wide range of salinity variation,the study of intertidal zone and estuary all present that there is a distinct correlation between ciliates community structure parameter and salinity.Previous studies have shown that,in addition to the case of eutrophication,the benthic ciliate community structure parameter has a negative correlation with nutrient,and the coastal zone area will not limit the ciliate community because of its ample nutrients.However,in our study area,compared with the high concentration of nitrate from the diluted water of the Yangtze River,the concentration of phosphate from the diluted water of the Yangtze River and the warm current of Taiwan is much lower,so it would affect the benthic ciliates community.This paper provides the basic data of annual variation of ciliate community for the study of species diversity in Dongtan wetland of Chongming,and also reveals the close relationship between the parameters of ciliate community structure and environmental factors,besides,provides an important basis for the use of ciliates to monitor environmental changes.