Seaweed, or macroalgae, refers to several species of macroscopic, multicellular, marine algae. The term includes some types of Rhodophyta (red), Phaeophyta (brown) and Chlorophyta (green) macroalgae. Seaweed species such as kelps provide essential nursery habitat for fisheries and other marine species and thus protect food sources other species, such as planktonic algae, play a vital role in capturing carbon, producing up to 90 percent of earth's oxygen. Understanding these roles offers principles for conservation and sustainable use. Mechanical dredging of kelp, for instance, destroys the resource and dependent fisheries. Seaweed are a source of biologically active compounds including proteins and polysaccharides with promising uses in nutrition, biomedicine, bioremediation and other uses.