World Aquaculture March 2019

WWW.WA S.ORG • WORLD AQUACULTURE • MARCH 2019 33 from the Marine Botany Cultivation Facility at HBOI, which is flow-through tank system that uses Indian River Lagoon seawater. Seaweed was stocked into the IMTA outdoor tank system and grown for two weeks prior to the start of the study to acclimate and stabilize in the high-nutrient IMTA system water. The six tanks (2.05 m 2 in surface area) were each stocked with 4.1 kg wet weight (WW) of Gracilaria , based on a stocking density of 2 kg WW/m 2 (Hanisak 1987). Water quality was tested regularly. Salinity, pH, dissolved oxygen concentration and temperature were measured daily in the morning and afternoon. Three times each week, total ammonia- nitrogen, nitrite-nitrogen, and nitrate-nitrogen concentrations were measured in the morning and alkalinity was measured in the afternoon. Water quality parameters were within acceptable limits for Gracilaria tikvahiae production (Table 1). Photosynthetically Active Radiation (PAR; µmol/m 2 sec) data from the nearby IRL-LP station at the Indian River Lagoon Observatory of Environmental Sensors ( fau.loboviz.com ) were used as a measure of ambient light. Full sunlight PAR ranged from 608 to 792 µmol/m 2 secduring the study. Seaweed Growth Gracilaria was harvested weekly from each tank and placed into individual plastic baskets. Each basket of seaweed was placed on a hanging scale and the WWwas recorded after approximately 10 - 15 min, when there was very little water dripping from the seaweed (Fig. 5). As the seaweed was weighed, each tank was scrubbed to remove as much fouling (e.g. epiphytic green seaweed and diatoms) as possible before restocking with 4.1 kg of the same seaweed treatment and replicate. Weekly a 250-300 g WW sample of Gracilaria was collected LEFT, FIGURE 2. Seaweed tanks of the IMTA outdoor component (Photo: Brian Cousin, FAU HBOI). RIGHT, FIGURE 3. Tyler Bianchine, HBOI summer intern, placing shade cloth on a seaweed tank (Photo: Brian Cousin, FAU HBOI). ( C O N T I N U E D O N P A G E 3 4 ) LEFT, FIGURE 4. The six IMTA seaweed tanks used for the study (Photo: Brian Cousin, FAU HBOI). RIGHT, FIGURE 5. Weighing seaweed harvested from one of the treatment tanks (Photo: Brian Cousin, FAU HBOI).