Key Laboratory of Cultivation and High-value Utilization of Marine Organisms in Fujian Province，National and Local Joint Engineering Research Center of Marine Biological Seed Industry Technology，Fujian Fishery Research Institute，Xiamen 361013，China
Abstract: To investigate the nitrogen removal capacity of different filler-biofilms in mariculture tail water, biofilters were constructed by the addition of oyster shells (M), coral stones (S), suspended ball fillers (F), elastic fillers (T), and without any filler as control (C), respectively. The formation speed and the biomass of biofilms as well as the nitrogen removal capacity of the biofilms at 24 hours were compared, while the changes in microbial community structure of the biofilms on biofilters were analyzed using Illumina Miseq high-throughput sequencing technology during biofilms formation period(20th day, 40th day, and 60th day). The different filler-biofilms were found to required 46-50 days for mature, with most rapid formation of the coral stone filler biofilm. Scanning electron microscopy showed that the biofilms on elastic filler and suspended ball filler had more biomasses than the other two fillers, largely consisting of rod-shape bacteria. The analysis of nitrogen removal capacity at 24 hours showed that there was the maximal removal rate of ammonia nitrogen and nitrate nitrogen by suspended ball fillers, and that the maximal removal rate of nitrite nitrogen by coral stone, which were (68.66%±6.27%), (6.73%±3.41%), and (99.99%±0.00%), respectively. The analysis of microbial community diversity revealed that the abundance of bacteria on elastic filler biofilms was increased, while the diversity of bacteria on oyster shell and coral stone biofilms was decreased significantly with the prolongation of biofilms formation time (P<0.05). The dominant microfloras of biofilms with different fillers were shown to be Proteobacteria and Bacteroidetes at the phylum level. The relative abundances of Nitrospirae and Nitrospinae were increased with the extension of biofilms formation time. Nitrosomonas, Nitrospira, Nitrospina and unclassified_Nitrosomonadaceae were the dominant bacteria with nitrification on different filler-biofilms at the genus level. The descending order of relative abundance of nitrifying bacteria at 60th day was described as: suspended ball fillers (42.53%)> oyster shells (30.50%), elastic fillers (29.30%)> coral stones (11.74%)(P<0.05). The relative abundance of denitrification bacteria, such as Pseudomonas, Ralstonia, Chitinophaga and Herbaspirillum, were higher on the biofilms of coral stone than on other filler-biofilms. The findings indicated that coral stone and suspended ball filler as ideal fillers were favorable to enrichment of nitrogen removal bacteria, and had better denitrification ability for mariculture wastewater.
2024, Vol. 39 
