Palmaria palmata was integrated with Atlantic halibut Hippoglossus hippoglossus on a commercial farm for one year starting in November, with a temperature range of 0.4 to 19.1°C. The seaweed was grown in nine plastic mesh cages (each 1.25 m 3 volume) suspended in a concrete sump tank (46 m 3 ) in each of three recirculating systems. Two tanks received effluent water from tanks stocked with halibut, and the third received ambient seawater serving as a control. Thalli were tumbled by continuous aeration, and held under a constant photoperiod of 16 : 8 (L : D). Palmaria stocking density was 2.95 kg m -3 initially, increasing to 9.85 kg m -3 after a year. Specific growth rate was highest from April to June (8.0 to 9.0°C), 1.1% d -1 in the halibut effluent and 0.8% d -1 in the control, but declined to zero or less than zero above 14°C. Total tissue nitrogen of Palmaria in effluent water was 4.2 to 4.4% DW from January to October, whereas tissue N in the control system declined to 3.0-3.6% DW from April to October. Tissue carbon was independent of seawater source at 39.9% DW. Estimated tank space required by Palmaria for 50% removal of the nitrogen excreted by 100 t of halibut during winter is about 29,000 to 38,000 m 2 , ten times the area required for halibut culture. Fifty percent removal of carbon from the same system requires 7,200 to 9,800 m 2 cultivation area. Integration of P. palmata with Atlantic halibut is feasible below 10°C, but is impractical during summer months due to disintegration of thalli associated with reproductive maturation.Key Words: bioremediation; IMTA; integrated multi-trophic aquaculture; nutrient removal; Palmaria
INTRODUCTIONMany aquaculture businesses are intent not only on maximizing productivity and profitability, but also accomplishing this using environmentally responsible practices. Efficient use of energy (e.g., pumping of water) and natural resources (surrounding environment, ambient water supply, and waste streams) are key elements in this approach. Land-based recirculating aquaculture systems facilitate greater control over culture water and waste discharge than flow-through systems (Blancheton et al. 2009). Though the surrounding environment may be enhanced by moderate volumes of aquaculture discharge (White et al. 2011), the trend toward larger land-based facilities (e.g., 1,000 metric tons finfish production per year) and the associated effluent waste may pose a risk of local eutrophication. Alternatively, integration of seaweed and land-based marine finfish culture can convert these nutrients to a usable product. Previous investigations into land-based seaweed integration have included Gracilaria For this study, integration of Palmaria palmata and Atlantic halibut was established within a land-based recirculating aquaculture facility for one year to evaluate the growth and nutrient uptake characteristics of the seaweed in a commercial application. This study was essential to compare the bioremediation capacity of P. palmata under both lab and small-scale applied conditions...