Rhodolith bed structure along a depth gradient on the northern coast of bahia state, brazil

Abstract

A B S T R A C TThe aim of this study was to determine the structure of a rhodolith bed along a depth gradient of 5 to 25 m in the shelf in front of Salvador City, a region of northeastern Brazil. The dimensions, morphology and coralline algae composition of the rhodoliths were analyzed, as well as the vitality, density, and associated flora of the bed at three depths: 5, 15 and 25 m. Samples were obtained by SCUBA divers in summer 2007. Five rhodolith-forming taxa were identified: Sporolithon episporum, Lithothamnion brasiliense, Lithothamnion superpositum, Mesophyllum erubescens, and Lithophyllum sp. The encrusting growth form and the spherical shape were predominant at all depths. Rhodolith dimensions and vitality decreased and the density increased from the shallow to the deepest zones. Fifty-six macroalgal species were found as rhodolith-associated flora. The shallower depth presented higher values for macroalgal biomass and number of species. These results associated with other recent rhodolith bed descriptions indicate that the pattern of Brazilian rhodolith bed structure along depth gradients may be related to a combination of the extent and slope of the continental shelf. R E S U M OO objetivo deste estudo foi determinar a estrutura de um banco de rodolitos ao longo de um gradiente de profundidade na plataforma em frente à cidade de Salvador, nordeste brasileiro. Foram analisadas as dimensões, a forma e composição das algas calcárias dos rodolitos, bem como a vitalidade, densidade e flora associada ao banco, em três profundidades: 5, 15 e 25 m. As amostras foram obtidas por meio de mergulho autônomo no verão de 2007. Cinco espécies de algas calcárias formadoras de rodolito foram identificadas: Sporolithon episporum, Lithothamnion brasiliense, Lithothamnion superpositum, Mesophyllum erubescens e Lithophyllum sp. A forma de crescimento incrustante e a forma esférica foram predominantes em todas as profundidades. Houve uma redução da dimensão e vitalidade dos rodolitos e um aumento da densidade com a profundidade. Cinqüenta e seis espécies de macroalgas foram encontradas como flora associada aos rodolitos. A profundidade mais rasa apresentou os maiores valores de biomassa e número de espécies de macroalgas. Esses resultados, associados com outras descrições recentes de bancos de rodolitos, indicam que o padrão estrutural desses bancos no Brasil, ao longo de gradientes de profundidade, pode estar relacionado a uma combinação da extensão e da inclinação da plataforma continental.

Taxonomic study of crustose coralline algae off the northeastern Brazilian coast

“…The characteristics observed in the examined material correspond to those already identified by Foslie (1900b), Taylor (1960), Horta (2000), and Bahia et al (2010) (Table 8). The specimens collected by Horta (2000) occurred between 12 and 22 meters and those collected by Bahia et al (2010) between 5 and 15 meters. The specimens in this study were collected in the midlittoral zone, and between 22 and 25 m in the subtidal zone, thereby expanding the known range of depths at which this species occur.…”

“…Keats et al (2000), Harvey et al (2003), Bahia et al (2010), Farias et al (2010), and Basso et al (2011) have set the following criteria for species identification in the genus Lithothamnion: the size of the tetrasporangial conceptacle, the number of cell layers that constitute the roof of tetrasporangial conceptacles, and the presence or absence of depressions around the pores of tetrasporangial conceptacles (Table 7). The presence of this latter characteristic has been considered decisive in identifying specimens of Lithothamnion as L. crispatum.…”

DNA barcoding allows the accurate assessment of European maerl diversity: a Proof-of-Concept study

“…On the other hand, we observed that largest maerl was linked to deep sites in Brittany (Trevignon, P. calcareum and L. corallioides) and S Portugal (Algarve2, Phymatolithon sp.3). Other authors have reported cases where rhodolith size either increases (Amado-Filho et al 2007, Gagnon et al 2012 or decreases (Steller & Foster 1995, Bahía et al 2010 with depth. However, in our study, the relationship between size and depth is far from clear because other deep sites (San Francisco, Ons) did not follow the pattern and contained small rhodoliths.…”

Filling a Knowledge Gap on the Biodiversity of Rhodolith-Associated Echinodermata from Northeastern Brazil

“…Furthermore, the rhodoliths tend to decrease in diameter with increasing depth [39]. All these factors, combined with others still unknown, may affect the richness and abundance of the associated fauna.…”