Community Characteristics and Influencing Factors of Phytoplankton in Desalination Culture Ponds of Pacific White Leg Shrimp Litopenaeus vannamei
The structural characteristics,temporal and spatial changes in phytoplankton community composition and their main ecological influencing factors were investigated in a 6 667 m2 pond with a water depth of about 1.6 m in Senmiao Fishery Professional Cooperative where desalinated for 12 d to salinity of 0.8 post larval Pacific white leg shrimp Penaeus vannameii were reared at stocking density of about 45 ind./m3.The water sample was first collected in the test ponds using the standard method on the day of seedlings once a week,a total of 12 times,by multivariate analysis methods.The results showed that a total of 103 species were identified,with 8 dominant species.Chlorophyta was represented by the most species with 39 species,followed by Bacillariophyta with 29 species,Cyanphyta with 23 species and others less than 4 species.Densities of phytoplankton were found to be varied from 4.58×106 ind./L to 9.66×108 ind./L,with an average of(2.05±2.93)×108 ind./L,and biomass from 0.80 mg/L to 101.47 mg/L with an average of(30.49±33.81)mg/L.Multivariate analysis indicated that the correlations between Cyclotella and ammonium and between Cyclotella and active phosphate were very insignificant;Chlorella pyrenoidosa,Selenastrum bibraianum and Chlamydomonas spp.became more prone to be dominant taxa in high concentration ammonia water;the increases in content active phosphate became an important incentive for the Cyanophyta bloom;Grazing behavior of herbivorous zooplankton had an effect on phytoplankton community succession,which preferred to transform phytoplankton from small edible species into larger or inedible species.The understanding of temporal and spatial changes in phytoplankton community composition and their main ecological influencing factors in desalinated Pacific white leg shrimp culture ponds helps to provide scientific basis for further researches on manipulating for aquaculture pond of penaeid shrimp.
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