Composting the Invasive Toxic Seaweed Rugulopteryx okamurae Using Five Invertebrate Species, and a Mini-review on Composting Macroalgae

Abstract

Since 2015, the invasive alga Rugulopteryx okamurae has explosively burst into the waters of the Strait of Gibraltar with serious repercussions on marine biodiversity, tourism and the fishing industry. Its elimination entails an enormous cost for the municipalities in the area and vermicomposting is proposed as a solution, but the anti-food secondary metabolites of the algae make it unfeasible. This work analyzed for the first time the bioremediation of this toxic algae using vermicomposting (Dendrobaena veneta and Eisenia fetida), blatticomposting (Eublaberus spp. “Ivory”), mealworms (Tenebrio molitor) and black soldier fly larvae (BSFL, Hermetia illucens). Both BSFL composting and blatticomposting are viable alternatives, as the toxics in the algae do not affect the long-term survival, growth or reproduction of these invertebrates. All other tested species do not resist consumption of R. okamurae. In parallel, a synthesis of current knowledge on marine macroalgae composting has been carried out. The results of this work will allow the use of insect farms in the upwelling areas that will eliminate algae, providing fertilizers and animal proteins that will be an economic aid to the municipalities in the affected coasts of southern Mediterranean Spain.Graphical