Lili-Mei Judd: Nitrogen cycling in a crab-polychaete-macroalgae IMTA system: implications for waste recycling and water quality

Lili-Mei Judd (MSci Marine Biology) joins us to discuss whether a simplified crab–polychaete–macroalgae integrated multi-trophic aquaculture (IMTA) system could reduce nitrogen accumulation to biologically safer levels than crab monoculture through internal waste recycling.  Within fed aquaculture, including crustacean culture, crabs excrete nitrogenous waste as a direct result of protein catabolism, this accumulates within the water system with direct welfare consequences for the cultured species and if discharged to local water bodies can exceed the assimilative capacity and drive algal proliferation and eutrophication. In this system I designed, fed crab species were co-cultured with extractive organisms from complementary trophic levels so that organic and inorganic nitrogen waste from crab component became feed inputs for the polychaete worms and macroalgae compartments, being recycled within the system rather than discharged as pollution. This project addressed SDG 12: Responsible consumption and production and SDG 14: Life below water to ensure that we sustainably use marine resources in aquaculture to ensure resilient and nature-based food systems. Three sequential 10-day tank experiments were conducted using native UK species of triplicate crab monoculture tanks and triplicate integrated systems containing European shore crab (Carcinus maenas), common ragworm (Hediste diversicolor), and serrated wrack seaweed (Fucus serratus) and daily water-column dissolved inorganic nitrogen and nitrogen speciation were measured. Here IMTA was shown to reduce waste release and its associated environmental impacts compared to crab monoculture. This project has given me hope that when you observe natures processes and interactions within an ecosystem and then manipulate through science into our food systems, you will get a most productive system- it is a time to bring more circularity to how we produce our food. If you would like to learn more about this project, please follow the link here to the PDF: Nitrogen cycling in a crab-polychaete-macroalgae IMTA system implications for waste recycling and water qualityEpisode guest: Lili-Mei Judd, MSci Marine BiologyEpisode host: Prof Simon KempEpisode producer and editor: Ellie HowellThe Meliora Podcast Student Research Symposium is part of the 2026 Student Takeover Season where we celebrate the fantastic sustainability research work of our Undergraduate Students.