page_title: Seaweed
section_title: Ecology
hierarchical_section_title: Seaweed / Ecology
caption_attribution_description: English: Seabed in the Royal National Park, NSW
context_page_description: Seaweed, or macroalgae, refers to several species of macroscopic, multicellular, marine algae. The term includes some types of Rhodophyta, Phaeophyta and Chlorophyta 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% 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.
context_section_description: Two environmental requirements dominate seaweed ecology. These are seawater (or at least brackish water) and light sufficient to support photosynthesis. Another common requirement is an attachment point, although genera such as Sargassum and Gracilaria have species that float freely. Seaweed most commonly inhabits the littoral zone (nearshore waters) and, within that zone, on rocky shores more than on sand or shingle.
  Seaweed occupies various ecological niches. At the surface, they are only wetted by the tops of sea spray, while some species may attach to a substrate several meters deep. In some areas, littoral seaweed colonies can extend miles out to sea. The deepest living seaweed are some species of red algae.
  Others have adapted to live in tidal rock pools. In this habitat, seaweed must withstand rapidly changing temperature and salinity and occasional drying.
caption: Seaweed covers this rocky seabed on the east coast of Australia
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