title: Rhodolith beds are major CaCO3 bio-factories in the tropical South West Atlantic.
abstract: Rhodoliths are nodules of non-geniculate coralline algae that occur in shallow waters (<150 m depth) subjected to episodic disturbance. Rhodolith beds stand with kelp beds, seagrass meadows, and coralline algal reefs as one of the world's four largest macrophyte-dominated benthic communities. Geographic distribution of rhodolith beds is discontinuous, with large concentrations off Japan, Australia and the Gulf of California, as well as in the Mediterranean, North Atlantic, eastern Caribbean and Brazil. Although there are major gaps in terms of seabed habitat mapping, the largest rhodolith beds are purported to occur off Brazil, where these communities are recorded across a wide latitudinal range (2°N-27°S). To quantify their extent, we carried out an inter-reefal seabed habitat survey on the Abrolhos Shelf (16°50'-19°45'S) off eastern Brazil, and confirmed the most expansive and contiguous rhodolith bed in the world, covering about 20,900 km(2). Distribution, extent, composition and structure of this bed were assessed with side scan sonar, remotely operated vehicles, and SCUBA. The mean rate of CaCO(3) production was estimated from in situ growth assays at 1.07 kg m(-2) yr(-1), with a total production rate of 0.025 Gt yr(-1), comparable to those of the world's largest biogenic CaCO(3) deposits. These gigantic rhodolith beds, of areal extent equivalent to the Great Barrier Reef, Australia, are a critical, yet poorly understood component of the tropical South Atlantic Ocean. Based on the relatively high vulnerability of coralline algae to ocean acidification, these beds are likely to experience a profound restructuring in the coming decades.
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Gilberto M
authors.initials: GM
authors.lastname: Amado-Filho
authors.forename: Rodrigo L
authors.initials: RL
authors.lastname: Moura
authors.forename: Alex C
authors.initials: AC
authors.lastname: Bastos
authors.forename: Leonardo T
authors.initials: LT
authors.lastname: Salgado
authors.forename: Paulo Y
authors.initials: PY
authors.lastname: Sumida
authors.forename: Arthur Z
authors.initials: AZ
authors.lastname: Guth
authors.forename: Ronaldo B
authors.initials: RB
authors.lastname: Francini-Filho
authors.forename: Guilherme H
authors.initials: GH
authors.lastname: Pereira-Filho
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Abrantes
authors.forename: Poliana S
authors.initials: PS
authors.lastname: Brasileiro
authors.forename: Ricardo G
authors.initials: RG
authors.lastname: Bahia
authors.forename: Rachel N
authors.initials: RN
authors.lastname: Leal
authors.forename: Les
authors.initials: L
authors.lastname: Kaufman
authors.forename: Joanie A
authors.initials: JA
authors.lastname: Kleypas
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
authors.forename: Fabiano L
authors.initials: FL
authors.lastname: Thompson
mesh_terms: D059001:Aquatic Organisms / Q000254:growth & development / Q000378:metabolism*; D001267:Atlantic Ocean; D002119:Calcium Carbonate / Q000378:metabolism*; D057894:Coral Reefs; D055110:Radiometric Dating; D000461:Rhodophyta / Q000254:growth & development / Q000378:metabolism*; D013020:South America; D014329:Tropical Climate
chemical_list: D002119:Calcium Carbonate