| Planktonic microalgae in shrimp ponds play the role of primary producers. In the process of shrimp culture, the community structure of planktonic microalgae in shrimp ponds is closely related to the culture health of shrimp, some beneficial planktonic microalgae can regulate DO, pH of water, assimilate ammonia nitrogen, nitrite nitrogen and other harmful substances, and effecttively improve the culture environment, but some planktonic microalgae which can produce toxin will harm the health of shrimp. So ,there is a great significance to clear the community characteristics of microalgae and its relationship with water quality. Litopenaeus vannamei, Penaeus monodon, Tilapia's semi-intensive aquaculture in south china are widespread, but now the report about the study on the community characteristics of microalgae and its relationship with water quality in three aquatic's semi-intensive culture ponds was less. This article is the study on the relationship between community characteristics and water quality factors in the Litopenaeus vannamei, Penaeus monodon, Tilapia's semi-intensive clture ponds, including the species composition of microalgae, the succession of dominant species, the change of microalgae number and biamss, the change of microalgae diversity, combinated the depth analysis about dynamic of water quality factors ,and the shrimp farming conditions, the results are as follows:1. Study on the community characteristics of planktonic microalgae and its relationship with water quality factors in Litopenaeus vannamei's semi-intensive culture pondsThe continual and regular surveys on the planktonic microalgae community were conducted in four Litopenaeus vannamai's semi-intensive culture ponds of Guanlida bio-technology corporation in Dianbai, Maoming, Guangdong province from May 19 to Augest 25, 2009. Moreover, the community compositions of microalgae in shrimp ponds and their characteristics were analyzed. The results showed that a total of 91 microalgae species were identified during the culture period. Among them, 30 species were Cyanophyta, 15 were Chlorophyta, 37 were Bacillariophyta, 5 were Pyrrophyta, 2 were Euglenophyta, and 2 were Chrysophyceae. During the early culture period, the range of the quantities of microalgae, the biomass and the diversity cellsex averages were 5.12×104～95.41×104 cells·L-1, 1.95～1.18×102μg·L-1, and 0.84～2.16, respectively, Chlorophyta and Bacillariophyta often appeared. However, in the middle and final phase, the planktonic microalgae density, the biomass and the diversity cellsex averages ranged from 66.11×104～1.28×109 cells·L-1, 13.3～11.87×103μg·L-1, and 1.64～2.87, Oscillatoria gradually became to be the dominant species. The present study demonstrated that the microalgae density , biomass and diversity cellsex all showed the same trend that they were generally low at the initial phase of the culture period and became high at the final phase. The dominant species were Chlorella pyrenoidosa, Kirchneriella microscopica, peridinium pusillum, Nitzschia closterium, Lyngbya gardnari, Oscillatoria chlorina, Oscillatoria salina, Oscillatoria neglecta and so on. During the culture, the level of water temperature, TN, TP, IN, COD were gradually increased, but salinity, transparency of water decreased. And the microalgae density, biomass in every pond basically all showed significant positive correlation with TN and TP. Oscillatoria biomass appeared significant positive correlation with TN and TP, but negative correlation with salinity and transparency.2. Study on the community characteristics of planktonic microalgae and its relationship with water quality factors in Penaeus monodon's semi-intensive culture pondsThe continual and regular surveys on the planktonic microalgae community were conducted in four Penaeus monodon's semi-intensive culture ponds of Guanlida bio-technology corporation in Dianbai, Maoming, Guangdong province from May 19 to September 22, 2009. The results showed that a total of 93 planktonic microalgae species were identified during the culture period. Among them, 26 species were Cyanophyta, 33 were Chlorophyta, 32 were Bacillariophyta, one was Dinophyta, one was Cryptophyta. During the early culture period, the range of the quantities of microalgae, the biomass and the diversity cellsex averages were 3.5×104～356.8×104 cells·L-1, 0.02×102～1.83×102μg·L-1, and 1.57～2.12, respectively. However, in the middle and final phase, the planktonic microalgae density, the biomass and the diversity cellsex averages ranged from 1.73×108～2.34×109 cells·L-1, 5.23×103～57.01×103μg·L-1, and 1.64～2.26. The present study demonstrated that the planktonic microalgae density , biomass and diversity cellsex all showed the same trend that they were generally low at the initial phase of the culture period and became high at the final phase. The dominant species were Navicula simples, Chlorella pyrenoidosa, Oscillatoria chlorina, Cylcellsrospermum musiccola, Kirchneriella microscopica, Microcystis flos-aquae, Microcystis firma, Oscillatoria willei and so on. During the culture, the level of water temperature, TN, TP, were gradually increased, but DO, transparency of water decreased. the microalgae density, biomass mostly appeared highly significant negative correlation with transparence, but positive correlation with water temperature, TN, TP. Especially, the microalgae density, biomass in pond 1 and pond 2 showed highly significant positive correlation with TN, TP. and in the final phase, microcystis bloom appeared in them, microalgae density was more than 109 cells·L-1.3. Study on the community characteristics of planktonic microalgae and its relationship with water quality factors in Tilapia's semi-intensive culture pondsThe continual and regular surveys on the planktonic microalgae community were conducted in six Tilapia's semi-intensive culture ponds of Shabei breeding plant in Panyu, Guangzhou from May to November, 2009. The results showed that a total of 157 planktonic microalgae species were identified during the culture period. Among them, 34 species were Cyanophyta, 67 were Chlorophyta, 18 were Bacillariophyta, 5 were Dinophyta, 3 were Cryptophyta, 28 were Euglenophyta, 2 were Chrysophyta. The dominant species in every ponds were prolific but composition was complex, the dominant species belonged to different categories have a large difference among their cell volume. The dominant species which just take the advantage of the microalgae's density were Oscillatoria willei, Merismopedia punctata, Nostoc fuscescens, Gomphosphaeria aponina, Microcystis firma, Microcystis incerta, Chlorella pyrenoidosa, Ankistrodesmus falcatus, Coelastrum sphaericum and so on. Moreover, The dominant species which just take the advantage of the microalgae's biomass were Euglena pisciformis, Lepocinclis autumnalis, Phacus platalea, Phacus tortus, Strombomonas schauinslandii, Peridinium gatunense, Gonyaulax polygramma, Cryptomonas ovata, Chroomonas caudata and so on. Spirulina spirulinoides was not only the number dominant specie but also the biomass dominant specie. During the early and middle culture period, the range of the quantities of microalgae, the biomass and the diversity cellsex average were 0.5972.85×107 cells·L-1, 1.12114.14 mg·L-1, and 2.98, respectively. However, in the final phase, the microalgae density, the biomass and the diversity cellsex average ranged from 16.2967.37×107 cells·L-1, 6.5767.76 mg·L-1, and 2.78. In the the early and middle term, the microalgae density , biomass grew rapidly, the microalgae diversity was rich ,the community's stability was strong. But in the latter, the microalgae density, biomass and diversity cellsex were lower. And the microalgae density, biomass in every pond bacically appeared significant positive correlation with some nutritional factors,such as COD, NH4-N, NO2-N, NO3-N and so on.There were some differences about community structure of microalgae in three types of semi-intensive ponds, that was primarily caused by the differences between their culture environment and mangemant. But there were also some common feature in them. Including that the planktonic microalgae density, biomass in ponds mostly appeared significant correlation with some nutritional factors. Cyanophyta always became the dominant species in ponds, and their dominance was high. The number of Chlorophyta species that usually became the dominant species and common species was abundant, which was the important part of microalgae's diversity. And the community structure's changes of microalgae in ponds had a major impact on water environment. |
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