A bioplastic composition may contain certain biodegradable and renewable components. In some examples, the bioplastic composition includes at least one kind of aquatic macrophyte biomass, which may contain a native composition of protein and carbohydrates, in a blend with one or more types of biodegradable or durable thermoplastic polymers. The aquatic macrophyte composition may provide a balance of both polymeric and reinforcing properties to the blended bioplastic not typically exhibited by terrestrial feedstock such as soy meal or corn starch. Such a bioplastic composition may be formed into molded articles using extrusion, injection molding, compression molding, or the like.