Biological Effects of Nutrient Nualgi on the Water Ecological Environment in Culture Pond

摘要

In order to study the short-term effects of Nualgi on water quality and phytoplankton in fishpond,we conducted continuous and regular surveys on the phytoplankton community and the water quality indexes in four groups. The four groups were a Nualgi group( M_1 ),a diatom group(M2),a Nualgi and diatom group( M_3 ),and a control group(C). The results showed that there were no significance differences in p H,dissolved oxygen(DO),total nitrogen(TN) and total phosphorus( TP) among the four groups. The IP concentration of groups M_1 and M_3 was significantly lower than that of groups M_2 and C,indicating that Nualgi can reduce the IP concentration of water. The concentrations of NH^+4-N,NO_2^--N and COD_(Mn) of groups M_1 ,M_2 and M_3 were significantly lower than those of group C,suggesting that both Nualgi and dominant diatom species can adjust water quality by reducing the concentrations of NH^+4-N,NO_2^--N and COD_(Mn). In this test,we identified 186 species that belonged to 109 genera of seven phyla. Among them,86 species were Chlorophyta,48 were Bacillariophyta,27 were Cyanophyta,17 were Euglenophyta,three were Dinophyta,three were Cryptophyta and two were Chrysophyta. Both diatom species and Nualgi can promote the growth of Bacillariophyta,restrain the growth of Chlorophyta and Cyanophyta,and thus change phytoplankton community structure. The biomass of Bacillariophyta in groups M_1 ,M_2 and M_3 was larger than that in group C from the 20 ^(th) d of the experiment,while the biomasses of Chlorophyta and Cyanophyta were lower than that in group C. Melosira granulata became the dominant algae species in groups M_1 ,M_2 and M_3 ,while Coelastrum microporum and Crucigenia tetrapedia were the dominant algae species in group Conly. Scenedesmus quadricauda became the dominant algae in groups M_1 ,M_2 and C. There was no remarkable difference in diversity index among the four groups. The Shannon-Wiener index in all the four groups were all above 2. 00,suggesting that the addition of Nualgi or diatom species did not affect the species diversity in this experiment.