| Qingcaosha Reservoir of Shanghai has a special geographical location.It is located on Changxing Island in Chongming County and adjacent to the Yangtze River Estuary.It is a semi-natural and semi-artificial reservoir.Qingcaosha Reservoir supplies daily drinking water to the vast majority of citizens in Shanghai.At present,there are many reports that the pollution of lakes or reservoirs is getting more and more attention.As the important source of drinking water,Qingcaosha Reservoir is particularly important for the stability of its water ecosystem and good water quality.Metazoan zooplankton as an important part of the biological community in the water body,its community structure characteristics interact with the water environment,the metazoan zooplankton community structure can reflect the water environment.This article mainly investigated the composition characteristics of the metazoan zooplankton in the Qingcaosha Reservoir and its surrounding waters from 2016 to2017.The results are as follows:1 Within two years,110 species of metazoan zooplankton wereidentified in the Qingcaosha Reservoir,belonging to 32 families and 59 genera,of which 62 were in 2016 and 97 in 2017,accounting for 56.36%and 88.18% of the total species within two years respectively.In 2016,the total biological densities of rotifers,cladocerans,and copepods accounted for 95.97%,1.35%,and 1.72% of zooplankton biological densitiy,respectively,and the biomass percentages were 24.68%,18.95%,and 56.37%,respectively.In 2017,the total biological density of rotifers,cladocera and copepods accounted for 97.97%,1.03%,and 0.99% of the total zooplankton densities,respectively.The proportions of biomass were 49.68%,11.67%,and 38.64%,respectively.2 60 species of rotifers were identified,belonging to 17 genera and30 genera.There were 40 species of pollution indicator species and 10 species of oligo saprobic.In 2017,there were 19 species of rotifers more than in 2016.The rotifer species similarity index for two years was Sj =0.45,which is not similar in the middle.The main dominant species are:Polyarthra trigla,Keratella cochleari,Brachionus calyciflorus,Asplanchna priodonta,Trichocerca pusilla,Diurella tenuior,Rotaria reptunia,etc.In 2016,the average annual biological density of rotifers was(274.20±313.38)ind/L,and the average annual biomass was(0.2081±0.2139)mg/L.The average annual biological density of rotifers in 2017 was(363.29±446.29)ind/L.The average annual biomass was(0.6478±0.9417)mg/L.In general,the biological density and biomass ofrotifers in 2017 was higher than that of rotifers in 2016.The average biological density of rotifers in summer and autumn was higher than that in winter and autumn in the two years of the season,and the change in biomass was not uniform.In 2017,it was the highest in spring,and in2016 it was the highest in summer.In terms of horizontal distribution,the rotifer biological density and biomass in the river area was the lowest in2017,the highest in the lake area,and the intermediate level in the transition area.In 2016,the transition area was the highest area of rotifer biological density and biomass.The Shannon-Wiener species diversity index H',the Pielou species evenness index J,and the Margalef species richness index D of rotifers did not change significantly,and the overall trend was stable.RDA analysis showed that the effects of water temperature,pH,electrical conductivity and nutrient on rotifer abundance were significant.3 24 species of Cladocera were identified in Qingcaosha Reservoir,belonging to 5 genera and 12 genera.In 2016,13 species of Cladocera were identified.There are 8 more species in 2017 than in 2016.The species similarity index of Cladocera within two years is Sj=0.42,which is not moderately similar.The main dominant species are: Bosmina longirostris,Moina rectirostris,Daphnia cristata,Diaphanosoma leuchtenbergianum,and Ceriodaphnia laticaudata.In 2016,the average annual densities and biomass of Cladocera were(4.6±4.1)ind/L and(0.1527±0.2456)mg/L,respectively,and the average densities and biomass of Cladocera in the reservoir in 2017 were(3.7±5.4)ind/L,(0.1344±0.2008)mg/L.In 2017,the standing crop cladocera was slightly reduced.Within two years,the average biological density and biomass of Cladocera was higher in summer and autumn than in winter and spring.In the horizontal distribution,the existing amount of Cladocera was in the river area <transition area <lake area.The species diversity index,species richness index and species evenness index of Cladocera didn't show obvious rules.Through the redundancy analysis,the water environmental factors affecting the horn type abundance are: water temperature,dissolved oxygen,total nitrogen,and pH.4 A total of 26 species of copepods were detected,belonging to 10 genera and 17 genera.In 2017,the number of species(23)was 8 more than 2016(15).The copepod species are not similar in the two years(Sj=0.46).The main dominant species in two years were: Sinocalanus dorrii,Mesocyclops leuckarti,Eucyclops macruroides,Limnoithona sinensis,Schmackeria inopinus,Eucyclops serrulatus.In 2016,the average annual biological density and biomass of Copepoda in the Qingcaosha Reservoir were(5.08±5.02)ind/L and(0.4654±0.5581)mg/L,respectively,and the average biological density and biomass of Copepoda in 2017 was(3.71±4.40)ind/L and(0.4542±0.5916)mg/L,The trend of the existing quantity of copepods in 2016 was higher in spring andsummer than that in autumn and winter.In 2017,the mean biological density and biomass of copepods were higher in summer and autumn than in winter and spring.The distribution pattern of copepods was the same as the distribution of cladocera in horizontal distribution.The species diversity,richness,and evenness index of copepods peaked in summer and autumn,and they were lower in autumn and winter.The environmental factors affecting the abundance of copepod species are water temperature,dissolved oxygen,water depth and electrical conductivity.5 Eighty-eight species(29 genera and 47 genera)and 53 species(25families and 41 genera)of metazoan zooplankton were detected in central sand and Yangtze River estuary waters,with the largest proportion of rotifers,58.54% and 50.94%,respectively.In 2016,the metazoan zooplankton density was(139.17±286.70)ind/L,and that of the Yangtze River estuary was(18.32±41.36)ind/L.In 2017,the metazoan zooplankton density was(411.29±809.46)ind/L,and the average zooplankton density in the Yangtze River Estuary was(288.40±1682.11)ind/L.Within two years,metazoan zooplankton species similarity indexes between Qingcaosha Reservoir and central sand were 0.52,0.62,respectively,between Qingcaosha Reservoir and the Yangtze River estuary species similarity index were 0.46,0.38,respectively,which was more and more similar to the central sand,there is a growing trend ofdissimilar types between Qingcaosha Reservoir and the Yangtze River estuary.Combined with the changes in the similarity index and the existing amount,it was concluded that the evolutionary success of the metazoan zooplankton community in Qingcaosha Reservoir was slightly greater than that of the external water. |
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