Low Dose Formaldehyde Effect On Recirculating Aquaculture System And Sea Bass

The purpose of the present study was to investigate the effect of low dose formaldehyde on sea bass and recirculating aquaculture system. The impact of formaldehyde concentration on the water treatment efficiency of biological aerated filter (BAF) were studied ,the relationship between the number of microorganism in BAF and water treatment was investigated, the impact of different doses formaldehyde on sea bass, the residual of formaldehyde in fish tanks and fish muscle were also studied. The main results were as follows:1. The impact of different doses of formaldehyde on recirculating aquaculture system (RAS) were evaluated. RAS with concentration of 31.59ppm formaldehyde was suffered seriously influence: nitrite concentration in water rose, and the remove rate of nitrite decreased, the impact on ammonium delayed compared with the nitrite's change.2. The number of heterotrophic microbe in BAF rose at the beginning of the experiment and finally declined to normal level with experiment carried out; the number of Ammonium-oxidation bacteria (AOB) and Nitrite-oxidizing bacteria (NOB) in the group of 31.59ppm declined in the later period of the experiment, and NOB number of 10.53ppm and 21.06ppm group also declined at later period of the experiment, however, the number in 10.53ppm group declined more moderate. The number of vibrio in tank water increased in 10.53ppm group during the experiment, while in tank water the number of vibrio in group 21.06ppm and 31.59ppm declined during the experiment.3. 10.53ppm was a special concentration, the relative fatness was just lower than the group of 10.53ppm, spleen weight rate was 0.16% which was the highest rate among groups. Survival rate declined with the raise of formaldehyde concentration, the groups of 31.59 and 21.06ppm had a survival rate below 98%, while 10.53ppm group with 98% survival rate was closed to the control group's survival rate. Fish in 10.53ppm group had higher weight gain and lowest feed coefficient among all the groups. As to biochemical indexes, the activity of amylase (AMS) in intestinal and trypsin in stomach had significantly increased compared with control group, therefore protein and starch utilization ratio increased. The 21.06ppm group's GOT activity in serum increased significantly compared with the other two tried groups, and also the activity of GPT in this group had significantly increased compared with the other groups,the liver of sea bass in 21.06ppm group was damaged to some extent. The SOD activity in serum of 31.59ppm group and 21.06ppm group were significantly higher than the other groups,sea bass in these two groups suffered mild adversity stress.4. Formaldehyde in fish tanks presented linear degradation at the beginning of the experiment, however, at the last test of the experiment formaldehyde in fish tanks showed logarithmic degradation. The remnant of formaldehyde in muscle had out of test scope at the forth day after adding formaldehyde.