What question did this study set out to answer?

The study aims to evaluate the performance of native macroalgae species in integrated multi-trophic aquaculture systems.

February 12, 2026Open Access

Evaluation of native macroalgae species of the Southeast U.S. and Caribbean for use in integrated multi-trophic aquaculture (IMTA)

Key Points

The study aims to evaluate the performance of native macroalgae species in integrated multi-trophic aquaculture systems.
Cultured yellowtail snapper with four candidate macroalgae species in replicated raceways.
Analyzed nutrient levels including temperature, dissolved oxygen, and total ammonia nitrogen.
Evaluated nutritional composition of macroalgae species for protein, fat, fiber, ash, minerals, and metals.
Calculated carbon and nitrogen content and stable isotope ratios.
Agardhiella subulata reduced total ammonia nitrogen levels below detectable limits at a density of 6.73 kg m−3.
Optimal hydraulic retention time for TAN reduction was 54 minutes.
Caulerpa racemosa had the highest protein content at 25.49%, while Ulva lactuca had the highest carbohydrate content at 61.48%.
Ulva lactuca efficiently incorporated carbon based on calculated dissolved CO₂ concentrations.

Abstract

Abstract This study assessed the comparative performance of candidate marine macroalgae species under integrated multi-trophic aquaculture (IMTA) culture conditions in a system culturing yellowtail snapper ( Ocyurus chrysurus ) at a commercial-scale biomass density. The nutrient-rich effluent water from the marine finfish culture tank supplied replicated macroalgae raceways containing four candidate species of macroalgae ( Agardhiella subulata , Caulerpa racemosa , Gracilaria caudata , and Ulva lactuca ) native to the Southeast U.S. and Caribbean regions. Water temperature, dissolved oxygen (DO), salinity, alkalinity, pH, phosphate, and total ammonia nitrogen (TAN) readings were sampled daily, and dissolved CO 2 was calculated over the course of the trials. Each species of macroalgae was analyzed for protein, fat, fiber, ash, minerals, and metals. Additionally, the carbon and nitrogen content and stable isotope ratios of the nutritionally enriched (i.e., “fortified”) macroalgae (“seaweed”) species were analyzed. Results provide novel insights on macroalgae biomass levels under specific hydraulic retention times (HRT) that allow for the reduction of TAN levels in fish effluent water below detectable levels. Specifically, Agardhiella subulata at a density of 6.73 kg m −3 , lowered TAN levels in fish effluent water below detectable limits under a hydraulic residence time (HRT) of 54 min from average starting concentrations of 0.04 mg/L TAN. Compositional analyses indicated Caulerpa racemosa had the highest protein content (25.49%) and Ulva lactuca had the highest carbohydrate content (61.48%) of the macroalgae species tested. Calculated dissolved CO₂ concentrations of effluent water before and after the macroalgae culture tanks and the carbon-to-nitrogen ratio of macroalgae samples indicated that Ulva lactuca up took and incorporated carbon most efficiently. The results of this project provide novel information that will help improve economic and environmental sustainability for existing and prospective marine finfish aquaculture operations throughout the focal regions and allow producers to make well-informed decisions on candidate species of macroalgae for marine IMTA applications.

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