Modelling Asparagopsis nitrogen bioremediation efficiency in Australian coastal environments

Coastal nitrogen enrichment poses a growing threat to marine ecosystems, and macroalgae cultivation has been identified as a promising bioremediation strategy in Australian coastal waters. Recent interest in cultivating Asparagopsis species as additives to livestock feeds presents an opportunity to leverage a commercial industry for ecosystem-based management goals, but the bioremediative potential of these species remain largely uncharacterised. An existing nitrogen-based macroalgae growth model is here adapted and parameterised for Asparagopsis armata and Asparagopsis taxiformis, and growth and nitrogen removal are modelled in coastal waters around Australia in both natural and supplemented conditions. Despite their low uptake rate of nitrogen, particularly nitrate, both Asparagopsis species effectively remove nitrogen in constantly supplemented conditions due to their high internal tissue concentration. These results offer a spatially explicit, adaptable, and freely available framework for assessing Asparagopsis cultivation sites for dual commercial and bioremediation purposes across Australian coastal waters while highlighting key physiological knowledge gaps that can be addressed to refine future bioremediation predictions.