Abstract
Rising global demand for seafood and declining catches have resulted in the volume of mariculture doubling each decade. The FAO (Food and Agriculture Organization of the United Nations) expects such a growth to persist in the years to come. This exponential growth has created a subsequent need to find alternative solutions to wastewater generation. The use of marine algae as bio-filters for aquaculture wastewater treatment has been shown to be an efficient and cost effective strategy. For this study, I selected Caulerpa racemosa (commonly known as sea grape algae) as a potential bio-filtration candidate for the mitigation of aquaculture effluent. Sea grapes are highly valued in Asian and South-Pacific cuisine, where they are referred to as green caviar. They are also high in omega-3 fatty acids and antioxidants, representing a possible new marketing angle as a “super food.” This alga has been largely excluded from western markets, as the Pacific varieties are known invasives in the Atlantic basin. For this reason, I decided to utilize the native Floridian variety, which is poorly researched, despite being present throughout the Caribbean and parts of South America. For my study, I conducted laboratory growth trials to determine optimal conditions for both irradiance and nutrient concentrations. Floridian C. racemosa was found to be highly adaptable to a wide range of irradiance and nutrient regimes, with nutrient uptake efficiency greater than 90%. A clear set of optimal parameters could not be defined, however, as the treatment results were not significantly different. This finding demonstrates the high adaptability and resilience of this species. For the final trials, I constructed a 1500-L outdoor recirculating aquaculture system, raising juvenile pinfish (Lagodon rhomboides). The setup was designed to serve as a proof of concept, to test how good C. racemosa performed outside of the laboratory. The study produced mixed results, but found that a 4:1 fish to seaweed wet weight ratio was ideal in maintaining stable nutrient levels. Overall, the results designate C. racemosa as a strong candidate for commercial bio-filtration, and as a possible cash crop for the domestic sushi and algal supplement industries.