Identifying suitable zones to Kappaphycus alvarezii (Doty) L.M.Liao farming in densely portion of Atlantic South

Abstract

Algae aquaculture rapidly expanded into what currently represents approximately half of global marine aquaculture production landings (51%). In Brazil, seaweed aquaculture is more concentrated on the exotic species K. alvarezii, and the rearing areas are restricted to the southern coast of Rio de Janeiro State, northern São Paulo State, and central Santa Catarina State. The southern coast of Rio de Janeiro State, which comprises two socio-economical and geographically important bays: Ilha Grande and Sepetiba, is densely populated with multiple economic activities using coastal environments, where recently algae farming is considered strategic to its socioeconomic development, an alternative to oil-based economy. This study serves as a tool to identify suitable areas for Kappaphycus farming in this densely urbanized portion of southern Atlantic. We formulated suitability maps, as a marine spatial planning tool to facilitates decision making, for civil society, managers and investors while providing resources for algae farming sustainable development. Thirty-one maps were generated related to the criteria and constraints that influence their productivity. Individual weights were obtained through the judgment of technicians, researchers, and other stakeholders using the pairwise comparison method. The criteria and weights were combined using the multicriteria decision rules and the suitability map was created derived from reclassifications. Of the total area calculated, 12,88% are areas restricted for cultivation and 87,12% were considered suitable areas. The analyses indicated aquaculture potential for the entire region. Sepetiba Bay has more most suitable areas than Ilha Grande bay. However, the presence of heavy metals in Sepetiba Bay should be taken account when the biomass is for human consump even if it can be used for other purposes. The results contribute to the construction of a marine spatial planning, which assists producers, decision makers, and social actors in the sustainable development of seaweed farming.