Study on the planktonic algae community in low salinity culture ponds of Litopenaeus vannamei

By investigating in 44 low salinity culture ponds of Litopenaeus vannamei,113 species of algae were identified in all, belonging to 7 phyla and 62 genera,respectively. They included 26 Cyanophyta species, 54 Chlorophyta species, 14 Bacillariophyta species, 11 Euglenophyta species, 3 Cryptophyta species, 4 Pyrrophyta species and 1 Chrysophyta species.Chlorophyta was the first in species variety and next came Cyanophyta. The important dominant species included Spirulina sp., Pseudoanabaena sp., Raphidiopsis curvata, Oscillatoria tenuis and Dactylococcopsis acicularis. The average abundance of Spirulina sp. amounted to 50%. Other dominant species of Chlorophyta and Bacillariophyta included Scenedesmu dimorphus, Chlamydomonas globosa, Chlorella vulgaris and Cyclotella meneghinian. Cryptomonas ovata,C. erosa and Euglena virdis were very common species in the low salinity culture ponds. Thedominant and common species were those that were adapted to the eutrophic aquatic environment. In culture ponds,the average number of algae species was 43±9, biodiversity index was 2.19±0.56 and their densities were 1.45±0.87×10~ 8 cells/L.The species numbers and biomass were low in early culture period and high in post culture period, but the biodiversity was in reversal.The algae composition had a direct impact on the shrimp growth.