Daily mass balance of phosphorus and nitrogen in effluents of production sectors of trout farming system

Moraes, Munique de Almeida Bispo; Carmo, Clovis Ferreira do; Ishikawa, Carlos Massatoshi; Tabata, Yara Aiko; Mercante, Cacilda Thais Janson

doi:10.1590/S2179-975X1415

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Articles • Acta Limnol. Bras. 27 (3) • Jul-Sep 2015 • https://doi.org/10.1590/S2179-975X1415 copy

Daily mass balance of phosphorus and nitrogen in effluents of production sectors of trout farming system

Balanço de massa diário de fósforo e nitrogênio em efluentes de setores de criação em truticultura

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Aim: The mass balance has recently been applied in Brazilian aquaculture. In relation to trout farming, few studies have used this methodology as environmental indicator, especially when considering each development stage of fish. The daily mass balance allows an estimate of nutrients discharge, because the sampling effort over 24 hours enables to monitor the variations throughout the day. This study aimed to identify the breeding sector (fingerlings, juveniles and adults) in trout farming contributes with the great discharge of phosphorus and nitrogen in the effluent.

Methods

The concentrations of total phosphorus (TP), orthophosphate (PO₄-P), total nitrogen (TN) and ammonium (NH₄-N) were determined in affluent and effluents of the production system. The environmental indicators were calculated based on the values of nutrients loads and by quantifying the daily discharge of nutrients from the mass balance method.

Results

Over the 24 hours, the trout farming exported an average of 0.26 kg TP, 0.11 kg PO₄-P, 3.11 kg TN and 0.18 kg NH₄-N. The discharge of phosphorus and nitrogen in the effluent was higher at night associated to feeding management (hours and feeding frequency) and the nocturnal habits of trout. The juvenile and adult sectors accounted for the greatest contribution of these nutrients, related the largest fish biomass and metabolism, supported by the feed conversion ratio of 1.95:1 and 2.01:1, respectively.

Conclusion

In order to reduce exports of phosphorus and nitrogen there is a need to adequate the feeding management (feeding frequency from two to four times per day according to the trout development stage; carry out feeding in times close at twilight due to the nocturnal habits of this specie; reduce excess of ration offered and use good quality ration considering the distinct nutritional requirements of each trout stage of development). Besides the mass balance, the feed conversion ratio is also an efficient tool to detect the efficiency of feed utilization; therefore, it is proposed its use as environmental indicator, aiming the aquaculture environmental sustainability.

Keywords:
nutrients loads; mass balance; fingerlings; juveniles; adults

Variables	Sites				Reference values
Variables	A_S	E_F	E_J	E_A	Reference values
pH	6.83^a±0.33	6.88^a±0.23	6.61^a±0.13	6.71^a ±0.25	6.00-9.00^* * FAO (2011);
% Sat DO	129.82^a±2.82	124.58^b±2.00	121.13^c±1.69	122.22^bc±1.83	≥ 80.00^* * FAO (2011);
T (°C)	14.35^a±0.42	13.82^ac±0.21	13.67^bc±0.17	13.66^bc±0.16	≤ 20.00^* * FAO (2011);
TP (µg L^–1)	13.66^a±2.30	34.05^b±5.40	78.95^c±11.54	109.80^c±11.21	≤ 100.00^ Brasil (2005).
PO₄-P (µg L^–1)	4.49^a±1.31	8.26^a±3.83	31.80^b±4.50	46.16^b±4.72	-
TN (mg L^–1)	2.05^a±0.24	2.53^b±0.24	3.02^c±0.19	3.00^c±0.31	≤ 2.18^ Brasil (2005).
NH₄-N (µg L^–1)	115.37^a±6.73	134.74^b±9.51	182.87^c±27.01	161.31^c±13.85	≤ 3,700.00 se pH ≤ 7.5^ Brasil (2005).

Variables	Abbreviations	Principal components
Variables	Abbreviations	Axis 1	Axis 2
pH	pH	-0.087	0.772
Dissolved oxygen	%DO	-0.663	-0.651
Water temperature	Temp	-0.467	0.760
Total phosphorus	TP	0.953	-0.077
Orthophosphate	PO₄-P	0.924	0.125
Total nitrogen	TN	0.764	0.187
Ammonium	NH₄-N	0.796	-0.245
	Explicability	52.12%	24.52%

		DO (kg dia^–1)	TP (kg dia^–1)	PO₄–P (kg dia^–1)	TN (kg dia^–1)	NH₄–N (kg dia^–1)
Fingerlings	Affluent	4.13	0.011	0.002	0.75	0.04
	Effluent	4.04	0,012	0.003	0.90	0.05
	D_MB	– 0.09	0.001	0.001	0.15	0.01
Juveniles	Affluent	16.79	0.060	0.007	3.16	0.17
	Effluent	15.94	0.116	0.046	4.39	0.27
	D_MB	– 0.85	0.056	0.039	1.23	0.10
Adults	Affluent	18.99	0.098	0.008	3.71	0.19
	Effluent	18.28	0,181	0.076	4.96	0.27
	D_MB	– 0.71	0.083	0.068	1.25	0.08
Trout farming	D_MB	– 1.65	0.140	0.108	2.63	0.18

Associação Brasileira de Limnologia Av. 24 A, 1515, 13506-900 Rio Claro-SP/Brasil, Tel.:(55 19)3526 4227 - Rio Claro - SP - Brazil
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[1] A_S = affluent of the production system; E_F = effluent of the fingerlings sector; E_J = effluent of the juveniles; E_A = effluent of the adults sector; % Sat OD = saturation percentage of oxygen dissolved; T = water temperature; TP = total phosphorus; PO₄-P = orthophosphate; TN = total nitrogen; NH₄-N = ammonium. Means followed by the same letter in the line do not differ by the SNK test (0.05). Reference values in the last column.

[TFN1] ^*
FAO (2011)FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATION – FAO. Small-scale rainbow trout farming. Rome: FAO, 2011, 92 p.;

[TFN2] ^**
Brasil (2005)BRASIL. Ministério do Desenvolvimento Urbano e Meio Ambiente. Conselho Nacional do Meio Ambiente – CONAMA. Resolução nº 357, de 17 de março de 2005. Diário Oficial da República Federativa do Brasil, Brasília, DF, 18 mar. 2005..