Invasive potential of Kappaphycus alvarezii off the south coast of Rio de Janeiro state, Brazil: a contribution to environmentally secure cultivation in the tropics

The carragenophyte Kappaphycus alvarezii has been introduced into tropical regions, including Brazil, for aquaculture purposes. Our study estimated the biomass loss of farmed cuttings, the establishment of cuttings outside the rafts, the occurrence of spores, and evaluated the invasive potential of K. alvarezii at three sites in Rio de Janeiro state. Temperature, salinity, water transparency, wind velocity and direction (hydrodynamic indicator) and solar radiation (irradiance availability indicator) varied spatially. We found no spores in cultivated cuttings and no verified spore recruitment on artificial substrata. Biomass loss of cuttings varied temporally; however, it was restricted to the cultivation management area of one site and was low compared to native algal biomass. The establishment of cuttings was apparently limited by herbivory at Ilha Grande Bay and controlled by water transparency, hydrodynamics and temperature at Sepetiba Bay. The invasive potential of K. alvarezii was considered remote. However, the use of environmental protocols for cultivation activities is necessary to prevent environmental impacts, mainly in tropical regions.