Analysis Of Phytoplankton Community Structures In Three Drinking Water Source Reserviors In Liaoning Province

This paper conducted a total of seven phytoplankton sampling surveys of Qinghe,Chaihe and Tanghe reservoirs in November 2018,April 2019,July 2019,October 2019,August 2020,December 2020 and April 2021,of which January 2020（winter）could not be sampled due to epidemic reasons.This paper analyzes the species composition,dominant species,cell density and biomass of phytoplankton in Qinghe,Chaihe and Tanghe reservoirs in each sampling time period,analyzes the environmental factors affecting the community structure of phytoplankton,and estimates the fish production potential according to phytoplankton biomass,which provides a reference basis for future conservation of reservoir water quality and rational stocking of fish.The results of this study are as follows:1.A total of 8 phytoplankton 97 genera and 242 species were identified in Qinghe Reservoir,244 species in 8 104 genera and 244 species were identified in Chaihe Reservoir,213 species in 8 102 genera were identified in Tanghe Reservoir,and the species composition of the three reservoirs was mainly green algae and diatoms,followed by cyanobacteria and naked algae,and there were fewer species data on the phyla,cryptoalgae,phylum phylum and phylum.Among them,Qinghe Reservoir:92species in 39 genera of green algae phylum,69 species in 19 genera of diatom phylum,28 species in 8 genera of gymnodisperm phylum,27 species in 16 genera of cyanobacteria phylum;Chaihe Reservoir:103 species in 41 genera of green algae phylum,62 species in 19 genera of phylum diatom,31 species in 19 genera of phylum Cyanobacteria,22 species in 7 genera of phylum gymnoflora,7 species in 7 genera of Phylum Phytophala in Tanghe Reservoir,75 species in 38 genera,59 species in 23genera in 23 genera,29 species in 19 genera,and 23 species in 7 genera of phylum nudibranchus.2.There are obvious spatial and temporal distribution changes in the composition of the dominant species in Qinghe,Chaihe and Tanghe reservoirs,and the blue algae such as pseudo-fishy algae are the mainstay in summer,and the green algae such as chlamydia and fibrous algae are dominant in spring and winter.In the summer,cyanobacteria such as pseudo-fishy algae and spirulina in the Chai He Reservoir are dominant.There are many dominant species in Tanghe Reservoir,and cyanobacteria,green algae,cryptoalgae,and diatom phylums have appeared.The mean Shannon-Wiener diversity indexes of the Qinghe,Chaihe and Tanghe reservoirs were 2.18,2.33and 2.19,respectively,and the overall nutrient level was moderate.3.The distribution of phytoplankton cell density was significant in time and space,and the three reservoirs showed obvious summer and autumn,spring and winter,among which the phytoplankton density of Qinghe Reservoir in July 2019 and August 2020was 9.9×10⁶cells/L and 3.8×10⁷cells/L,respectively,and the density of phytoplankton in November 2018 and December 2020 was 1.51×10⁶cells/L and 1.56×10⁶cells/L,respectively,and the density of phytoplankton increased significantly in summer The density of phytoplankton in July 2019 and August 2020 was 3.5×10⁷cells/L and4.8×10⁷cells/L,respectively,and 3.1×10⁶cells/L and 8.7×10⁶cells/L in November 2018and December 2020,respectively,with a significant increase in phytoplankton density;The phytoplankton density of the Tanghe Reservoir reached the highest in October 2019at 1.7×10⁷cells/L,and the phytoplankton density in November 2018 and December2020 was 1.7×10⁶cells/L and 2.8×10⁶cells/L,respectively.The average annual biomass of Qinghe,Chaihe and Tanghe reservoirs was 4.2 mg/L,5.32 mg/L and 4.31 mg/L,respectively,the Qinghe Reservoir had the highest biomass of 9.63 mg/L in August2020,the Chai River Reservoir reached its highest value of 10.45 mg/L in July 2019,and the highest value of phytoplankton biomass in Tanghe Reservoir was 10.24 mg/L in October 2019.On the whole,the Qinghe and Chaihe reservoirs need to pay close attention to the ecological data of phytoplankton in the water body in order to prevent the outbreak of local cyanobacterial blooms,and the low summer density and biomass of the Tanghe River are caused by the high density of fish stocking and the high intensity of fish feeding.4.WT,pH,TP,NO²-N,SD of Qinghe Reservoir are the main environmental factors affecting the density and distribution of dominant species of phytoplankton,and WT and pH reflect the seasonal changes of phytoplankton:high-temperature cyanobacteria multiply in summer;due to water level fluctuations in Chaihe Reservoir,nutrient salts change greatly,so depth,DO,SD,pH,NO²-N,PO₄³-P,TP,NH₄⁺and WT are environmental factors that affect the density and distribution of dominant species of phytoplankton;WT,DO,NO³-N is the main environmental factor for the density of phytoplankton in Tanghe Reservoir,mainly because the nitrogen salts in upstream farmland will affect the distribution of phytoplankton.The density of phytoplankton in all three reservoirs is affected by water temperature,while the dominant species are more related to N,P nutrient salts and pH.5.From November 2018 to April 2021,the total fish yield potentials available to phytoplankton in the three reservoirs were 533.6 t,265.0 t and 224.8 t,and the average fishing potentials were 125.9 kg/hm²,159.7 kg/hm² and 129.2 kg/hm²,respectively.Combined with the community structure of phytoplankton in the three reservoirs and the catch of silver carp,it is believed that the phytoplankton resources of Qinghe Reservoir are not fully utilized,and the potential for fish production is large,which can appropriately increase the stocking of silver carp.The potential of fish production in the Chai River Reservoir is fully exploited,which can appropriately reduce the stocking of bighead carp,increase the catch of silver carp,strive to control the miniaturization of phytoplankton and provide fish with better quality food organisms.The fish production potential of Tanghe Reservoir is low,and the stocking density of fish is large,which can appropriately reduce the amount of fish stocked,increase the catch of silver carp,and increase the economic benefits by making the fish grow faster and the size is larger.