| Planktonic ciliates are unicellular,eukaryotic protists with cilium around its body which belong to Protozoan-Ciliophora-Oligotrichea-Oligotrichina and Tintinnina,including aloricate ciliates and tintinnids.Planktonic ciliate are small size(size range of 10-200 ?m),living with planktonic life and ubiquitous in various marine habitats.Planktonic ciliates are primary consumers of pico-(0.2-2 ?m)and nano-(2-20 ?m)sized producers,and are important food sources for metazoan and fish larvae.As the dominant component of the microzooplankton,the marine planktonic ciliate is a key medium through microbial food web to classical food chain,which plays an important role in material circulation and energy flow of marine ecosystem.Therefore,it's very important to understand ecology roles of planktonic ciliates.Fundamental research about the vertical distribution and community structure variation of planktonic ciliates in different seas were rare.In this dissertation,we studied planktonic ciliates vertical distribution and community structure in the tropical oceanic area(the Yap,Mariana and Caroline seamounts),shelf area(the northern South China Sea(nSCS)),the oceanic to shelf area(the tropical western Pacific and the nSCS)and the tropical to cold area(the tropical western Pacific,the Bering Sea and the Arctic Ocean).The community structure including aloricate ciliate size-fraction,proportion of tintinnid abundance to total ciliate,lorica oral diameter(LOD)size-class and redundancy of tintinnid species and so on.Eventually,we carried out a preliminary study about the relationship between the ciliate abundance and temperature,salinity and the chlorophyll a in different seas.The vertical distribution and community structure of planktonic ciliates were investigated in the Yap(depths 300-5000 m),Mariana(depths 30-5000 m)and Caroline seamounts(depths 50-5000 m)of the tropical western Pacific from December 2014 to January 2015,March to April 2016 and July to August 2017,respectively.In the Yap,Mariana and Caroline seamounts,vertical distribution pattern of planktonic ciliates abundance and biomass both showed “bimodal-peak”,with high anundance and biomass value appeared in the surface and DCM(Deep Chlorophyll a Maximum)layers.Planktonic ciliate abundance ranged from 0-331 ind./L,0-405 ind./L and 0-405 ind./L,respectively.Biomass ranged from 0.0-0.6 ?g C/L,0.0-0.9 ?g C/L and 0.0-1.1 ?g C/L,respectively.For planktonic ciliate community structure,the aloricate ciliates were the dominant groups in three seamounts,and the abundance proportion of the above 50 ?m size-fraction to total aloricate ciliate decreased from surface to the bottom.The proportion of tintinnid abundance to total ciliate was less than 10%.According to the inhabited depth,tintinnid could be divided into four groups: I: 0-100 m depth;II: 50-200 m depth;III: > 100 m depth and V: occured in each depth.Group I and V were the dominant tintinnid groups.The 28-32 ?m LOD size-class had the top species richness while the 22-28 ?m LOD size-class had the top abundance proportion of tintinnids in three seamounts.The redundancy in the Yap,Mariana and Caroline seamounts were 79.0%,79.5% and 78.9%,respectively.In the Yap,Mariana and Caroline seamounts,89 tintinnid species of 33 genera were identified.Among them,Cosmopolitan and warm water were the main genera in three seamounts which occupied 93.5%,93.2% and 94.7% in total tintinnids species richness,respectively.No neritic species were found in three seamounts.Relationshilp between ciliate abundance and temperature showed positive correlation.The vertical distribution and community structure of planktonic ciliates were investigated in the northern South China Sea(nSCS,depths 110-2000 m)from March 2017.We found a meso-scale anti-cyclonic warm eddy in the survey stations.Combined the satellite data and the hydrography during the survey stations,we classified the nSCS into the reference stations and the warm eddy center areas.In the reference stations and the warm eddy center areas,vertical distribution pattern of planktonic ciliates abundance and biomass showed “surface-peak” and “bimodal-peak”.In the reference stations and warm eddy center,ciliate abundance ranged from 2-767 ind./L and 14-458 ind./L,respectively.Ciliate biomass ranged from 0.0-2.7 ?g C/L and 0.0-1.3 ?g C/L,respectively.At the reference stations,the surface abundance was higher than in the warm eddy center.For planktonic ciliate community structure,the 10-20 ?m sizefraction of aloricate ciliate was less abundant from surface to DCM layers in the reference stations than in the eddy center,and the average ratio of tintinnid to total ciliate abundance in the reference stations was about 2% lower than in the eddy center.The vertical distribution of tintinnid species groups I and V had higher abundances in the reference stations than in the warm eddy center showed surface and DCM peaks,respectively.But the difference value between the groups I and V of the surface layer in the reference stations was 31% lower than in the warm eddy center.In the reference stations,the number of lorica oral diameter(LOD)size-classes,species richness,and ratio of redundant species were also larger than in the warm eddy center.In the time series station,ciliate vertical distribution pattern was bimodal-peak in both the day and night time.But ciliate average abundance of each depth in the night time was higher than in the day time.Planktonic ciliate may conduct diel vertical migration.The vertical distribution and community structure of planktonic ciliates were investigated in the nSCS(depths 110-2000 m)and the tropical western Pacific(depths above 2000 m)from June 2015 and November to December 2015,respectively.In the tropical western Pacific and the nSCS,vertical distribution pattern of planktonic ciliates abundance and biomass showed “bimodal-peak” and “surface-peak”,respectively.Ciliate abundance ranged from 2-767 ind./L and 14-458 ind./L,and biomass ranged from 0.0-2.7 ?g C/L and 0.0-1.3 ?g C/L,respectively.At stations influenced by shelf water,the surface abundance was much greater than in slope waters.For planktonic ciliate community structure,the aloricate ciliates were the dominant groups,tintinnid abundance to total ciliate of the surface layer in the shelf water(1.5%)was less than in the slope water(6.4%)and tropical western Pacific(5.9%).Both the tintinnid species number,LOD size-classes number and the redundancy in the tropical western Pacific were higher than in the nSCS.Within the ciliates,the vertical distribution of tintinnid species groups I and V had higher abundances overall and showed surface and DCM peaks,respectively.There was no tintinnid species below 500 m depth in our study.We speculate that aloricate ciliates might also have surface peak and DCM peak groups.The overall vertical distribution patterns showed that the planktonic food web may function differently within the surface waters and the DCM layer.The vertical distribution and community structure of planktonic ciliates were investigated in the the tropical western Pacific(water depths above 2000 m),the Bering Sea(water depths above 500 m)and the Arctic Ocean(water depths above 200 m)from November to December 2015,July to August 2016,respectively.In the tropical western Pacific,the Bering Sea and the Arctic Ocean,vertical distribution pattern of planktonic ciliates abundance and biomass showed “bimodal-peak”,“surface-peak” and “DCMpeak”,respectively.Ciliate abundance ranged from 35-443 ind./L,152-3267 ind./L and 12-1615 ind./L,respectively.Ciliate biomass ranged from 0.0-0.7 ?g C/L,0.3-11.6 ?g C/L and 0.0-4.5 ?g C/L,respectively.For planktonic ciliate community structure,the abundance proportion of tintinnid to total ciliate in the Bering Sea(42.6%)was higher than both the tropical western Pacific(7.8%)and the Arctic Ocean(2.0%).The abundance proportion of 10-20 ?m size-fraction aloricate ciliates in the tropical western Pacific was highest in these three seas,while abundance proportion of aloricate ciliate above 30 ?m size-fraction in each depth in the Bering Sea and the Arctic Ocean were larger than the tropical western Pacific.In the Bering Sea and the Arctic Ocean,abundance and abundance proportion of mixotrophic ciliate to total aloricate ciliate were higher than in the tropical western Pacific.The tropical western Pacific had higher abundance proportion of tintinnids in smaller LOD(lorica oral diameter,12-16 ?m)size-class,while the Arctic Ocean had higher abundance proportion of tintinnids in larger LOD(60-64 ?m)size-class.Proportion of redundant species increased from the Arctic Ocean to the tropical western Pacific.Relationship between the aloricate ciliate abundance and temperature,Chl a concentration showed strong positive correlation.In this dissertation,we compared planktonic ciliates vertical distribution and community structure variation in different seas.From oceanic to shelf seas,vertical distribution pattern of planktonic ciliates changed from “bimodal-peak” into “surfacepeak”,and both the tintinnid species number and redundancy decreased.From tropical to cold areas,tintinnid species number,LOD size-class number and redundancy decreased,while aloricate ciliate size-fraction and dominant tintinnid LOD size-class become larger.Temeperature maybe the main influence factor of ciliate abundance. |
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