A new study has found that cultivating seaweed alongside marine finfish in integrated multi-trophic aquaculture (IMTA) systems can significantly reduce, and even eliminate, key waste products from fish farming.
The research by the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science highlights how macroalgae species can utilise nutrient-rich effluent from fish production, offering aquaculture producers a practical pathway to improve environmental performance while generating an additional crop.
“With the significant interest in the development of marine aquaculture throughout the south-east US 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.
The team established a pilot-scale IMTA system at the Rosenstiel School’s Experimental Hatchery on Virginia Key, Florida. Using effluent from commercially representative stocks of yellowtail snapper, researchers tested four native macroalgae species under controlled conditions.
Each species was cultivated in replicate tanks receiving identical effluent flows, allowing direct comparison of nutrient removal efficiency, growth rates and biochemical composition. At the end of two-week trials, samples were analysed for protein, fat, fibre, mineral content, and nitrogen and carbon levels.
Results showed that macroalgae could reduce total ammonia nitrogen in fish farm effluent to below detectable levels, demonstrating strong potential to mitigate one of aquaculture’s key environmental challenges.
“This work shows how integrating macroalgae into marine finfish aquaculture systems can reduce waste while producing a valuable secondary crop,” said principal investigator John D. Stieglitz, Ph.D.
“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.”
IMTA systems are designed to mimic natural ecosystems by combining species from different trophic levels, allowing waste from one organism to serve as nutrients for another.
“Our findings support more sustainable aquaculture operations and help producers make smarter choices about macroalgae for IMTA,” Lasco added.
The study was published on 10 February 2026 in Aquaculture International and funded through the Gulf States Marine Fisheries Commission in cooperation with NOAA Fisheries Service.
