Abstract: By using Smith’s and Pianka’s indices, this paper studied the niche breadths and overlaps of four common microalgae populations in shrimp ponds along radients of light intensity, temperature and salinity. The results showed that he niche breadth of Nitzschia closterium andChlorella pyrenoidosa was higher than that of Cryptomonas erosa and Nannichloropsis oculata.N. oculata and C. pyrenoidosahad the highest niche overlap in all different resources imensions, but C. erosa appeared with the lowest niche overlap, compared to other icroalgae in all the different resources dimensions. Nitzschia closterium and Chlorella pyrenoidosa grew well in wide range of light intensity. When the emperature reached 16.9 ℃ and 25 ℃, N. closterium and C. erosa would be breeding in the ponds, respectively. When the temperature reached 30 ℃, N. closterium, N. oculata and C. pyrenoidosa were suitable for breeding. N. oculata and C. pyrenoidosa were suitable for breeding in the ponds with a salinity anging from 9 to 26, Cryptomonas erosa was suitable with the salinity ranging from 9 to 17.5, while Nitzschia closterium was better with higher salinity. N. oculata and C. pyrenoidosa would not be breeding at the same time in the same ponds, because they have the highest overlap in all resources dimensions.

Key words: Community structure, Environmental factors, Spatial factors, Mowing, Grazing