糖蜜对草鱼混养池塘水质和细菌群落结构的影响

Effects of Molasses Supplementation on Water Quality and Microbial Community Structure in Polyculture Ponds of Grass Carp

为探讨C/N对草鱼混养池塘水体中细菌群落结构的影响,本研究通过泼洒糖蜜将草鱼混养池塘水体中C/N调整为4个不同水平(10∶1、15∶1、20∶1和25∶1)。利用16S rRNA测序技术分析泼洒糖蜜对草鱼混养池塘水体中细菌群落结构的影响,并监测养殖水质指标的变化。试验结果显示,泼洒糖蜜后草鱼混养池塘水体中的生物絮团沉积量和总固体颗粒悬浮物量升高;同时水体中氨氮、亚硝酸盐氮的含量降低,其中C/N 20∶1组降低幅度最大,且与对照组差异显著(P<0.05);但是泼洒糖蜜后,水体的溶解氧含量下降,C/N 25∶1组的溶解氧含量最小,与其他组差异显著(P<0.05)。16S rRNA测序结果显示,泼洒糖蜜后草鱼混养池塘水体中优势菌门蓝细菌门丰度降低,放线菌门丰度显著升高,变形菌门和拟杆菌门丰度基本未变;泼洒糖蜜后水体中主要菌属中聚球藻属和新鞘氨醇杆菌属丰度显著降低,CL500_29_marine_group、hgcI_clade和束缚杆菌属的丰度升高。试验结果表明,泼洒糖蜜调整草鱼混养池塘水体C/N为20∶1时,可显著增加水体的生物絮团沉积量和总固体颗粒悬浮物量,改变水体细菌群落结构并有效降低水体中氨氮、亚硝酸盐氮的含量。

The bacterial community structure and water quality were determined in 12 of each 25 m×25 m×2 m square cement grass carp(Ctenopharyngodon idellus)ponds with C/N levels of 10(group CK),15,20 and 25 adjusted by splashing molasses by 16S rRNA sequencing technique and chemical methods to investigate the effects of molasses on bacterial community structure in grass carp polyculture ponds.The amount of bioflocs and total suspended solids were shown to be increased and the contents of NH 4^+-N and NO 2^--N were found to be decreased in the water of grass carp ponds treated by spraying molasses,the minimum in C/N 20∶1 group,significant difference between group CK and C/N 20∶1 group(P<0.05).Meanwhile,the dissolved oxygen levels(DO)were decreased in the water in grass carp ponds sprayed molasses,the minimum in C/N 25∶1 group(P<0.05).The 16S rRNA sequencing revealed that the abundance were decreased in Cyanobacteria in C/N 20∶1 group,increased in Actinobacteria,and stable in Proteobacteria and Bacteroidetes.The abundance of Synechococcus and Novosphingobium in the C/N 20∶1 group were decreased,while the abundance of CL500_29_marine_group,hgcI_clade and Haliscomenobacter were improved in the main bacterial genera in the water in grass carp ponds treated by spraying molasses.The findings indicate that supplemented with molasses to adjust the C/N ratio of grass carp culture ponds at 20∶1 leads to significant increase in levels of biological flocs and total suspended solids and to so change in bacterial community structure that the contents of NH 4^+-N and NO 2^--N are effectively reduced in the water.