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Helgol Mar Res (2014) 68:2735 DOI 10.1007/s10152-013-0366-z
ORIGINAL ARTICLE
Community structure of rhodolith-forming beds on the central Brazilian continental shelf
Alexandre B. Villas-Boas Rafael Riosmena-Rodriguez
Marcia Abreu de Oliveira Figueiredo
Received: 30 November 2012 / Revised: 24 June 2013 / Accepted: 6 July 2013 / Published online: 24 July 2013 Springer-Verlag Berlin Heidelberg and AWI 2013
Abstract The community structure of rhodoliths beds in the central Brazilian continental shelf was studied under the hypothesis that nongeniculate coralline algae are the major contributors of the individual rhodoliths. Samples were collected from ve localities within a single area at 1718 m depth. At each locality, rhodoliths were collected in 10 random quadrat samples along a 20-m transect. Our results show that dead cores of rhodoliths were signicantly composed by nongeniculate coralline red algae rather than bryozoans, corals, or inorganic material. The live outer layers of the rhodoliths are composed mainly of 7 species of nongeniculate red coralline algae (Lithophyllum coralline, L. johansenii, L. depressum, L. stictaeformis, Neogoniolithon brassica-orida, Spongites fruticosus, and Lithothamnion muellerii) associated with other encrusting organisms such as bryozoans, sponges, corals, barnacles, and Peyssonnelia red algae. Signicant differences were found in the proportion of Lithophyllum species in relation to other red coralline algae found in this study. Our results show that on the Brazilian continental shelf, the rhodolith-
forming species are quite higher in size than in any other studied areas in the world. There was no difference in the proportion of live-to-dead rhodolith materials, suggesting an old bed deposit. Also, the amount of calcium carbonate material in the specimens is relevant to take in account in terms of the CO2 balance worldwide.
Keywords Coralline red algae Community structure
Encrusting organisms Rhodolith bed
Introduction
Rhodolith beds support subtidal communities around the world relevant in many ecological processes (Foster 2001). The rhodolith skeleton is composed of carbonate components, commonly encrusted, abraded, and bioeroded (Checconi et al. 2006). Rhodolith sphericity (Bosence 1976; Foster et al. 1997), branch density (Steller and Foster 1995; Basso et al. 2009), and species composition (Steller et al. 2003, 2009) are inuenced by water motion and depth. Substratum stability can be one of the main forces that drive rhodolith community composition, as demonstrated for some other environments (Littler and Littler 1984). Consequently, one...