Biological strategy to improve decomposition of organic matter in tilapia pond

The increment of decomposition of organic matter in sediment samples from Nile tilapia farms was evaluated with the introduction of Bacillus subtilis and B. licheniformis bacteria.

Methods

Sediment samples placed in 18L plastic boxes received single dose inoculum with the following concentrations: 1.21 x 10⁶ CFU g^-1 (equivalent to 75 g ha^-1), 2.41 x 10⁶ CFU g^-1 (equivalent to 150 g ha^-1), 4.82 x 10⁶ CFU g^-1 (equivalent to 300 g ha^-1) and 1.61 x 10⁷ CFU g^-1 (equivalent to 1000 g ha^-1), in addition to a control treatment with saline solution only. Organic matter content, total organic carbon (TOC) and oxidizable (OOC), total nitrogen (TN), ratios (TOC: N and OOC: N), clay content, pH in water, Shoemaker, McLean, Pratt index (SMP Index), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) contents, potential acidity (H + Al), cation exchange capacity (CEC) at pH 7.0, base saturation (V) and sum of bases (S).

Results

The values of OM showed significant difference, between the lowest values (treatments 75, 150 and 300 g ha^-1) and the highest value, (control treatment). TOC, OOC, NT and their relationships (TOC: N and OOC: N) showed significant differences between the mean values of the control treatment and the other treatments.

Conclusions

The addition of Bacillus subtilis and B. licheniformis bacteria increased the decomposition rate of organic matter in sediments samples from Nile tilapia farms.

Keywords:
aquaculture; bioremediation; Bacillus subtilis; Bacillus licheniformis; sediment

Treatment	0 g ha^-1		75 g ha^-1		150 g ha^-1		300 g ha^-1		1000 g ha^-1		P value
Treatment	Mean	S.D.	Mean	S.D.	Mean	S.D.	Mean	S.D.	Mean	S.D.	P value
OM g kg^-1	45.33^a	1.53	41.00^bc	1.73	37.00^c	2.00	40.00^bc	1.73	42.00^b	2.00	0.003
TOC g kg^-1	23.09^a	0.78	20.88^bc	0.88	18.84^c	1.02	20.37^bc	0.88	21.39^b	1.02	0.003
OOC g kg^-1	19.02^a	0.78	16.81^bc	0.88	14.77^c	1.02	16.30^bc	0.88	17.32^b	1.02	0.003
TN g kg^-1	1.16^a	0.05	1.32^b	0.00	1.29^b	0.05	1.29^b	0.05	1.23^ab	0.00	0.007
TOC:N	19.88^a	1.47	15.81^bc	0.67	14.63^c	1.00	15.84^bc	1.39	17.44^b	0.83	0.002
OOC:N	16.39^a	1.32	12.73^bc	0.67	11.47^c	0.92	12.68^bc	1.25	14.12^b	0.83	0.002
Clay g kg^-1	30.67	0.58	29.67	2.08	28.67	2.08	28.67	1.53	28.67	1.53	0.511
pH-Water 1:1	6.77	0.06	6.80	0.00	6.73	0.06	6.77	0.06	6.77	0.06	0.655
SMP Index	6.57	0.12	6.53	0.06	6.50	0.00	6.60	0.10	6.57	0.06	0.596
P mg dm^-3	390.20	13.36	381.10	2.13	379.40	3.30	368.10	7.07	377.50	9.27	0.082
K mg dm^-3	324.80^ab	15.80	312.67^b	7.57	318.27^b	3.52	345.93^a	12.07	323.67^ab	6.91	0.022
Ca cmolc dm^-3	7.27	0.21	7.50	0.40	6.63	0.50	6.93	0.12	6.67	0.47	0.067
Mg cmolc dm^-3	3.23	0.45	3.07	0.06	3.03	0.12	2.97	0.21	2.77	0.21	0.302
Potential acidity H + Al cmolc dm^-3	2.33	0.29	2.33	0.06	2.40	0.00	2.20	0.10	2.33	0.15	0.630
CEC pH7.0 cmolc dm^-3	13.64	0.41	13.71	0.39	12.87	0.61	13.01	0.39	12.63	0.61	0.083
Base saturation - V	82.89	2.10	82.99	0.63	81.30	0.89	83.10	0.36	81.47	1.83	0.337
Sum of bases - S	11.31	0.45	11.38	0.39	10.47	0.61	10.81	0.30	10.30	0.71	0.096

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