The Aquatic Ecology in Litopenaeus vannamai Desalination Culture Health Ponds

In June 2002 to October 2003, the investigation was conducted in 20 Litopenaeus vannamai desalination culture health ponds in Doumen, Zhuhai City, Guangdong Province. The areas of the health ponds were (0.48±0.19) hm~2 with water depth (145±13) cm, its culture density of L.vannamai was (148±30)×10~4 individuals/hm~2.The water temperature was (30.6±3.3) ℃, the value of water pH was (8.5±0.7), salinity of cultural water (2±2)‰ and the water transparency (19±5) cm; ammonia_nitrogen(0.65±0.76) mg/L, nitrite_nitrogen (0.15±0.17) mg/L,chemical oxygen demand(COD) (21.52±5.45) mg/L. The numbers of algae species were 43±8 in health ponds, algae density (1.51±0.76)×10~8 individals/L and its biodiversity index 2.15±0.49. There were 12 algae dominant species identified which included Cyanophyta 6 species, Chlorophyta 3 species, Bacillariophyta 2 species, Cryptophyta 1 species. The Spirulina sp. was common and important dominant species in health ponds, its abundance was very high and populations were stable. The numbers of protozoan species were 14±3 in health culture ponds, its density were (2.71±1.79)×10~5 cell/L and biodiversity index 2.01±0.47. 9 dominant species of Protozoa were identified, in which Tintinnopsis cylindrata, Coleps hirtus and Pleuronema marinum were common appearance,they live mainly on bacteria and organic fragment. The sum of heterotrophic bacteria was( 2.37±1.83)×10~7 cfu/L and Vibrio were (11.77±13.86)×10~5 cfu/L in cultural water, but in sediment surface the heterotrophic bacteria were (7.90±29.08)×10~8 cfu/L, the Vibrio (1.18±3.27)×10~7 cfu/L.