Identifying suitable zones for Kappaphycus alvarezii (Doty) L.M.Liao farming in a densely developed portion of the South Atlantic

Due to the growing demand for bioproducts, mariculture can have an important sustainable role in the cultivation of marine macroalgae. While the southern coast of Rio de Janeiro State, Brazil, currently has dozens of aquaculture structures installed, we sought to identify additional suitable sites for marine macroalgae enterprises as well as to estimate current production levels along its densely developed southern coast (Ilha Grande and Sepetiba bays). High resolution satellite images were used to generate 31maps related to the criteria and constraints that could influence aquaculture productivity. Individual weights were assigned to those criteria and constraints based on the judgments of technicians, researchers, and other stakeholders using a pairwise comparison method. Those factors were combined using multicriteria decision rules, and a suitability map was derived from their reclassifications. Of the total area calculated, 12.88% was determined to be unsuitable for cultivation, and 87.12% was considered suitable. We identified 91 K. alvarezii cultivation structures, and their annual biomass production was estimated to be between 400 and 1,500kg/year. Our analyses calculated the cultivation potential of the entire region, although the presence of heavy metals in Sepetiba Bay removes from consideration its production of algae for human consumption (although their biomasses could be used for other purposes). The results are designed to contribute to marine spatial planning and assist producers, decision makers, and social actors in promoting the sustainable development of seaweed farming.