Farming Macroalgae Seaweed Integration Boosts Efficiency and Cuts Waste in Aquaculture

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Seaweed could become a practical tool for cleaner and more efficient fish farming. A study shows that selected macroalgae species can absorb nutrient-rich effluent from marine finfish aquaculture, reducing waste while creating an additional crop with commercial potential.

A new study found that cultivating seaweed species alongside marine finfish in integrated multi-trophic aquaculture (Imta) operations, where seaweeds receive nutrient-rich effluent from fish production, can significantly reduce — and even eliminate — key waste products from marine finfish farming.

Led by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, the study offers new insights into how aquaculture producers can improve sustainability by farming macroalgae species in a complementary system alongside finfish.

“With the significant interest in the development of marine aquaculture throughout the Southeast U.S. and Caribbean, these findings can be used to guide the selection of extractive macroalgae species in operations culturing marine finfish,” said study lead author Haley Lasco, a marine biology graduate student at the Rosenstiel School and currently a scientist at the South Carolina Department of Natural Resources.

To conduct the study, the researchers established a pilot-scale Integrated Multi-Trophic Aquaculture (Imta) system at the Rosenstiel School’s Experimental Hatchery facility on Virginia Key, Florida, to evaluate the performance of four candidate macroalgae (seaweed) species under consistent marine finfish effluent conditions.

The flow-through Imta system used a consistent source of nutrient-rich effluent from a yellowtail snapper (Ocyurus chrysurus) grow-out tank maintained at commercial-scale density and feeding rates. Each macroalgae species was grown in three replicate tanks receiving the same effluent, enabling controlled comparisons of nutrient removal, nutritional composition, and market potential under conditions representative of commercial aquaculture.

At the end of each two-week trial, macroalgae were evaluated for growth and analyzed for protein, fat, fiber, ash, minerals, metals, and carbon and nitrogen content, including stable isotope ratios. Results provide new insights into macroalgae performance under real-world conditions and demonstrate the potential to reduce total ammonia nitrogen (TAN) in marine finfish aquaculture effluent to below detectable levels.

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“This work shows how integrating macroalgae into marine finfish aquaculture systems can reduce waste while producing a valuable secondary crop. It provides a practical framework for selecting species based on specific production goals, improving environmental performance while creating opportunities for better production economics and more diversified products using an Imta approach,” said John D. Stieglitz, Ph.D., a research associate professor in the Department of Marine Biology and Ecology, who led the project as principal investigator.

Imta is a production system where different species from different trophic levels are farmed together in a complementary system with a goal to mimic natural ecosystems, thus improving sustainability, reducing waste, and increasing overall productivity. This form of aquaculture allows for the waste of one organism to be utilized by another organism across trophic levels, creating a system with less waste and therefore a lower environmental impact.

The primary aim of this study was to provide an understanding of which macroalgae species from the Southeast U.S. and Caribbean regions perform the best in these different categories, providing stakeholders with a guide to select a desirable species of macroalgae to utilize and implement in their operations.

The results demonstrate the potential of Imta in these regions and offers potential mitigation solutions for many of the most prominent sustainability concerns regarding the development of marine aquaculture operations for fed-species such as marine finfish.

“Our findings support more sustainable aquaculture operations and help producers make smarter choices about macroalgae for Imta,” said Lasco.

Original Article: Evaluation of native macroalgae species of the Southeast U.S. and Caribbean for use in integrated multi-trophic aquaculture (Imta); Aquaculture International; DOI:10.1007/s10499-026-02441-1

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