THE INTEGRATED CULTURE OF ROCK WEED Mastocarpus jardinii IN A RECIRCULATING LAND-BASED SYSTEM WITH RED ABALONE Haliotis rufescens

Producing sustainable food to meet the demands of an increasing human population will be a significant challenge in the coming decades. Integrated multi-trophic aquaculture (IMTA) is an efficient, viable and environmentally friendly method to meet these needs. Land-based recirculating systems are an excellent way to optimize food production in a small footprint; however, they do come with large associated costs. A limiting factor for an aquaculturist may be access to the constant and reliable electricity required to maintain airflow for macroalgae tumble culture. To address these limitations we compared intermittent aeration (16h on: 8hr off) with continuous aeration (24hr on) on the productivity of two macroalgae species, Pacific Dulse Palmaria palmata and Rock Weed Mastocarpus jardinii while co-culturing the macroalgae with Red Abalone Haliotis rufescens. This experiment was designed to replicate a commercial marine farm producing high-value species that could offset the associated costs of being land-based. The integrated system consisted of twelve 19L buckets, separated into six replicates per aeration (constant and intermittent) in a gravity-fed vertical system held under 32 W fluorescent lamps, with a 16:8-h light/dark photoperiod. Five Red Abalone Haliotis rufescens were held in a 190L tank, and fed 0.5 kg of bull kelp fronds each week, after a 7-day starvation period. Overflow from the abalone tank flowed into a manifold that distributed water to each of the twelve 19L buckets containing an initial stock density of 2 kg m^-2 of Pacific Dulse Palmaria palmata and Rock Weed Mastocarpus jardinii. Air was injected through 1 mm holes drilled every 2 cm in a 1.3 cm (inside diameter) vinyl tubing that lined the bottom of each bucket in a 5-cm-diameter circle. To compare the nitrogen removal and uptake efficiency, total tissue N and C was determined at the end of the experiment. Following a seven day acclimation period, the biomass of each bucket was removed weekly, spun in a salad spinner for 20 seconds, weighed, and replaced at the initial stocking density of 2 kg m^-2. Water quality parameters (nitrates, nitrites, ammonia, phosphates, oxygen saturation, pH and alkalinity) were measured each week for four weeks. This experiment is ongoing, with Rock Weed Mastocarpus jardinii having a higher yield as of 09/2019. Producing high-value macroalgae in an integrated intermittent tumble culture with abalone may be one alternative for addressing our current and future global food demands.