Marine macroalgae are a diverse group of multicellular, plantâ€like protists that can be classified into brown (Phaeophyta), green (Chlorophyta) and red (Rhodophyta) algae. ... The chemical composition of macroalgae varies considerably between species and with season of harvest, growth habitat, and environmental conditions.Marine macroalgae are considered as promising sustainable alternatives to conventional terrestrial animal feed resources. The advantages include high growth rate, potential cultivation in saltwater, and no occupation of arable land. Macroalgae are broadly classified as brown (Phaeophyta), red (Rhodophyta) and green (Chlorophyta) algae, and are a diverse group of marine organisms. The nutritional value of macroalgae is highly variable. The protein and essential amino acid content can be low, especially in brown species, and indigestible polysaccharides adversely affect the energy value.