Seaweed
Seaweed or macroalgae refers to several species of macroscopic, multicellular, marine algae. The term includes some types of red, brown, and green macroalgae. Marine algae species such as kelps provide essential nursery habitat for fisheries and other marine species and thus protect food sources; ocean algae species from seaweeds to planktons play a vital role in carbon capture, producing up to 90 percent of the planet's oxygen. Understanding these roles provides guiding principles for conservation and sustainable use of seaweeds to take precedence over industrial exploitation. Mechanical dredging of kelp, for instance, destroys the resource and dependent fisheries. Certain species of seaweed are valuable for nutrition, biomedicine, bioremediation, and other uses.
Herbivore
Herbivorous fish and marine animals are an indispensable part of the coral reef ecosystem. Since algae and seaweeds grow much faster than corals they can occupy spaces where corals could have settled. They can outgrow and thus outcompete corals on bare surfaces. In the absence of plant-eating fish, seaweeds deprive corals of sunlight. They can also physically damage corals with scrapes.