Tropical macroalgae culture potential is constrained by the oligotrophic nature of most tropical oceanic waters. Our trials tested the addition of Deep Sea Water (DSW) and an IMTA model using fish tank effluent to provide nutrients for culture of macroalgae. This presentation reports on the cultivation of three red macroalgae (Halymenia hawaiiana, Gracilaria parvispora and Agardhiella subulata) in our land-based system at NELHA (Natural Energy Laboratory of Hawaii Authority) in Kailua-Kona, HI (Figure 1). For the marine finfish effluent, we co-cultured with the following two marine finfish; Seriola rivoliana, aka Kampachi or amberjack, and the herbivorous reef-fish Kyphosis vaigiensis, aka chubs or nenue.
Research focused on optimizing production and yield based on DSW and finfish effluent concentrations, stocking density and irradiation rates. Nutrient levels (total nitrogen, total phosphorus, ammonia/ammonium nitrate/nitrite, and ortho-phosphate) at the inflow and outflow of the macroalgae tanks gave measures of nutrient uptake rates by macroalgae. Macroalgal tissue composition, including % tissue ash, carbohydrate, and nitrogen will be presented.
Red macroalgae cultivation in conjunction with fish culture could mitigate nutrient loading of effluent waters, as well as provide increased productivity of commercially valuable macroalgae. The addition of DSW has the potential to drive macroalgal yields and Specific Growth Rates (SGR). This research is setting a baseline foundation for growing tropical macroalgae offshore for food, feed, and biofuels.