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Nutrients removed by Kappaphycus alvarezii (Rhodophyta, Solieriaceae) in integrated cultivation with fishes in re-circulating water |
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| Authors: | Leila Hayashi Nair S Yokoya Srgio Ostini Ricardo TL Pereira Elisabete S Braga Eurico C Oliveira |
| Institution: | aDepartamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Caixa Postal 11.461, 05422-970, São Paulo, Brazil bInstituto de Botânica, Seção de Ficologia, Caixa Postal 3005, 01061-970, São Paulo, Brazil cNúcleo de Pesquisa do Litoral Norte, APTA da Secretaria de Agricultura e Abastecimento do Estado de São Paulo, Caixa Postal 28, 11680-970, Ubatuba, São Paulo, Brazil dDepartamento de Oceanografia Física, Química e Geológica, Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico, 191, 05508-120, São Paulo, Brazil |
| Abstract: | The potential of the red alga Kappaphycus alvarezii to remove nutrients was tested to treat effluents of Trachinotus carolinus fish cultivation, and the production of carrageenan in this condition was analyzed. Experiments were conducted in four tanks of 8000 L with approximately 1200 fishes of 30 g each integrated with three tanks of 100 L with 700 g of K. alvarezii, as initial biomass per tank. Seawater was re-circulated between tanks with seaweed and with fish. As a control, three tanks with seawater circulating in an open system were utilized. Seawater samples were collected daily for 10 days and concentrations of nitrate, nitrite, ammonium and phosphate were determined in the inflow and outflow water of the tanks. Significant differences between both collecting points were considered as nutrient removal by the seaweed. Growth rates and carrageenan yields were also analyzed in seaweed cultivated in seawater and in effluents. Growth rates of seaweed cultivated in tanks were lower than those obtained in open sea and in laboratory cultivation. Effluents had concentrations of nitrate and nitrite ca. 100 times higher than in the control. Maximum values of nutrient removal on effluents were: nitrate = 18.2%; nitrite = 50.8%; ammonium = 70.5% and phosphate = 26.8%. All plants survived throughout the experimental period, but some developed “ice–ice”, a disease associated with physiological stress. After the experimental period, some plants selected and cultivated in open sea presented higher growth rates in 40 days, indicating nutrient storage. No significant differences between carrageenan yields of K. alvarezii cultivated in seawater and in the effluents were observed. Our results show that K. alvarezii can be utilized as a biofilter for fish cultivation effluents, reducing the eutrophication process and can also be processed for carrageenan production, which provides an additional benefit to the fisheries. |
| Keywords: | Biofilter Carrageenan Integrated cultivation Kappaphycus alvarezii Trachinotus carolinus |
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