RESUMO

Seaweeds have many uses in industry and agriculture and many species have potential for integrated multi-trophic aquaculture (IMTA), since they are efficient in removing nutrients from water. The efficiency of Ulva flexuosa, U. fasciata and Gracilaria birdiae in removing nutrients from enriched water and their productive performance in outdoor tanks were quantified. These seaweeds (50 g; n = 5) were grown in tanks containing 50 L of eutrophic seawater, with a salinity of 30, a temperature of 28.5 ± 2.8 C, an irradiance of 547 ± 458 mol photons m-2 s-1 and aeration. The nutrients levels were recorded daily and when total nitrogen removal was detected, the biomass was measured. After five days of cultivation, more than 98% of NH3 (H = 1.1; P = 0.56) and NO3- (H = 2.7; P = 0.25) and 62.1% of PO43- (H = 0.0; P = 0.90) had been removed from the tanks. However, the mean daily growth rate (4.5 ± 2.5% day-1) and productivity (3.5 ± 1.9 g m-2 day-1) of U. fasciata and G. birdiae were higher than U. flexuosa (-13.6 ± 7.7% day-1; -6.24 ± 2.8 g m-2 day-1; P 0.01), demonstrating that microalga contamination by this species promoted high removal efficiency in the tanks, but a low productive performance. Based on these results, U. fasciata and G. birdiae show a greater potential for use in IMTA to improve water quality and produce biomass.

As macroalgas são utilizadas em diversos setores industriais e agrícolas. Além disso, muitas espécies apresentam potencial para aquicultura multitrófica integrada (AMTI), pois são eficientes na remoção de nutrientes da água. A eficiência biofiltradora e desempenho produtivo das macroalgas Ulva flexuosa, U. fasciata e Gracilaria birdiae e foram quantificados em tanques outdoor. As algas (50 g; n = 5) foram cultivadas em tanques de 50 L, com água eutrofizada, salinidade 30 e temperatura média 28,3 C. Os nutrientes foram monitorados diariamente e a biomassa foi mensurada assim que detectada a extinção do nitrogênio. Após cinco dias de cultivo, mais de 98% de NH3 (H = 1,1; P = 0,56) e de NO3- (H = 2,7; P = 0,25) e 62,1% de PO43- (H = 0,0; P = 0,9) foram removidos dos tanques. Contudo, a taxa de crescimento (% dia-1) e a produtividade (g m-2 dia-1) de U. fasciata e de G. birdiae (4,5 ± 2,5% dia-1; 3,5 ± 1,9 g m-2 dia-1) foram superiores às de U. flexuosa (13,6 ± 7,7% dia-1; 6,2 ± 2,8; P 0,01), cuja contaminação por microalgas contribuiu para elevada eficiência de retirada nos tanques desta espécie, mas baixo desempenho produtivo. Desta forma, U. fasciata e G. birdiae foram indicadas para AMTI tanto para a manutenção da qualidade da água quanto para aproveitamento de biomassa.

Assuntos

RESUMO

Seaweeds have many uses in industry and agriculture and many species have potential for integrated multi-trophic aquaculture (IMTA), since they are efficient in removing nutrients from water. The efficiency of Ulva flexuosa, U. fasciata and Gracilaria birdiae in removing nutrients from enriched water and their productive performance in outdoor tanks were quantified. These seaweeds (50 g; n = 5) were grown in tanks containing 50 L of eutrophic seawater, with a salinity of 30, a temperature of 28.5 ± 2.8 C, an irradiance of 547 ± 458 mol photons m-2 s-1 and aeration. The nutrients levels were recorded daily and when total nitrogen removal was detected, the biomass was measured. After five days of cultivation, more than 98% of NH3 (H = 1.1; P = 0.56) and NO3- (H = 2.7; P = 0.25) and 62.1% of PO43- (H = 0.0; P = 0.90) had been removed from the tanks. However, the mean daily growth rate (4.5 ± 2.5% day-1) and productivity (3.5 ± 1.9 g m-2 day-1) of U. fasciata and G. birdiae were higher than U. flexuosa (-13.6 ± 7.7% day-1; -6.24 ± 2.8 g m-2 day-1; P 0.01), demonstrating that microalga contamination by this species promoted high removal efficiency in the tanks, but a low productive performance. Based on these results, U. fasciata and G. birdiae show a greater potential for use in IMTA to improve water quality and produce biomass.(AU)

As macroalgas são utilizadas em diversos setores industriais e agrícolas. Além disso, muitas espécies apresentam potencial para aquicultura multitrófica integrada (AMTI), pois são eficientes na remoção de nutrientes da água. A eficiência biofiltradora e desempenho produtivo das macroalgas Ulva flexuosa, U. fasciata e Gracilaria birdiae e foram quantificados em tanques outdoor. As algas (50 g; n = 5) foram cultivadas em tanques de 50 L, com água eutrofizada, salinidade 30 e temperatura média 28,3 C. Os nutrientes foram monitorados diariamente e a biomassa foi mensurada assim que detectada a extinção do nitrogênio. Após cinco dias de cultivo, mais de 98% de NH3 (H = 1,1; P = 0,56) e de NO3- (H = 2,7; P = 0,25) e 62,1% de PO43- (H = 0,0; P = 0,9) foram removidos dos tanques. Contudo, a taxa de crescimento (% dia-1) e a produtividade (g m-2 dia-1) de U. fasciata e de G. birdiae (4,5 ± 2,5% dia-1; 3,5 ± 1,9 g m-2 dia-1) foram superiores às de U. flexuosa (13,6 ± 7,7% dia-1; 6,2 ± 2,8; P 0,01), cuja contaminação por microalgas contribuiu para elevada eficiência de retirada nos tanques desta espécie, mas baixo desempenho produtivo. Desta forma, U. fasciata e G. birdiae foram indicadas para AMTI tanto para a manutenção da qualidade da água quanto para aproveitamento de biomassa.(AU)

Assuntos

RESUMO

Seaweeds are used directly as food or applied indirectly as texturing agents with gelling and thickening properties (carrageenan, agar and alginates) in many industries. They can also be used as fertilizers, animal feed, biomass for fuel, cosmetics and a source of pharmaceuticals, among other applications. The aquaculture of macroalgae is an alternative for producing raw material. Brazil has a coastline with numerous locations suitable for this endeavor. However, despite the known economical and social relevance of seaweed cultivation, Brazilians do not have tradition of using edible seaweeds. In general, the raw material for indirect use (e.g., as a texturing agent) is imported. Consequently, seaweed aquaculture is still incipient in Brazil. This contribution presents data and information about macroalgae cultivation on commercial and experimental scales performed on the Southern and Southeastern Brazilian Coastline, as well as a brief overview of research related to some species cultivated in the last decade.