FURTHER OPTIMIZATION OF Isochrysis sp. (CLONE C-ISO) CULTURE FOR A LAND-BASED INTEGRATED MULTI-TROPHIC AQUACULTURE SYSTEM  

Harbor Branch Oceanographic Institute at Florida Atlantic University has been for more than four years operating a prototype Land-Based Integrated Multi-Trophic Aquaculture (LB-IMTA) system, which uses recirculating water system design concepts.  It was found that LB-IMTA derived fine particulates did not support growth of oysters, but providing a supplement of microalgae stimulated growth.  Therefore, determining a method for culturing microalgae as an integral part of the LB-IMTA system is required.  

An earlier experiment examining Isochrysis sp. (clone C-ISO) growth in beakers found the addition of nutrients did not increase cell density above LB-IMTA water alone, but maximum cell density was ~28% less than the control (well saltwater + f/2).  However, this experiment was performed without CO₂-enriched air.  Therefore, an experiment was performed to compare the effect of CO₂-enriched air on Isochrysis sp. (clone C-ISO) growth in LB-IMTA derived water. Triplicate 8-L beakers with 4L of LB-IMTA water (no nutrients, ~1/3 f/2, or only metals added) were compared to well saltwater with complete f/2; all aerated with air or CO₂-enriched air.

Cell density (Figure) was greatest in the IMTA water with 1/3 f/2 and CO₂ enrichment; maximum density of 16 million cells/mL. The next highest maximum density was in the IMTA water + metals and CO₂ at 4.56 million cells/mL.  All other cultures were below this density.  

Cultures that received only air reached a pH of ~9 by day 3 and ~9.5 by day 4 and remained at that level. Cultures receiving CO₂-enriched air did not exceed pH 9.  The addition of CO₂ to all treatments, except for control (no nutrients added), increased cell density.  Integration of CO₂ addition and control is necessary for microalgae production as an integral part of an LB-IMTA. Supported by HBOI Aquaculture Specialty License Plate program.