The present invention provides methods and systems for the production of macroalgae in a manner to provide a sustained, economical source of biomass that may be used in various end-use processes, including energy production. The invention provides specific combinations of macroalgae types, saltwater growth medium compositions, and open pond water containers that results in biomass production beyond what may occur naturally without the required manipulation. Specifically, macroalgae that produce an exoskeleton in the presence of brackish water (e.g., stoneworts) have been found to provide excellent biomass production under the conditions of the invention.