Abstract
Abstract In spite of the length of the Brazilian coastline, studies of marine phytoplankton species in offshore areas have been largely neglected. Regarding phytoplankton species composition, the aim was to assess biodiversity status, species frequency, and the similarities at different sites along the Vitoria-Trindade Seamount Chain. Phytoplankton net samples were analyzed. One hundred and seventy five infrageneric taxa were identified. They represented four phyla, viz., Cyanobacteria, Bacillariophyta, Dinophyta, and Ochrophyta. Dinophyta was the most diverse, and its genus Tripos the largest contributor. This genus also represented more than half of the most common taxa in the sampled area. Thirty-five new infrageneric taxa were recorded, 12 of which are new reports for Brazil. Neritic stations assemblages were markedly different from those of seamounts and deep offshore. The high species diversity, especially among dinoflagellates can be considered typical of tropical oligotrophic waters. The new records demonstrate the gap in knowledge of phytoplankton biodiversity in Brazil.
Highlights
In spite of the long extent of the Brazilian coastline, the study of phytoplankton in offshore areas is incipient, notwithstanding the important role of this marine community as the source of more than 45% of primary production worldwide (Field 1998)
The Vitória-Trindade Seamount Chain is located off the central coast of Brazil
The 175 identified infrageneric taxa of the micro and mesophytoplankton identified were distributed among four phyla, viz., Bacillariophyta L.S.Dillon, Cyanobacteria Stanier ex Cavalier-Smith, Dinophyta F.E.Round and Ochrophyta Cavalier-Smith in CavalierSmiith & E.E.Chao (Table 1)
Summary
In spite of the long extent of the Brazilian coastline, the study of phytoplankton in offshore areas is incipient, notwithstanding the important role of this marine community as the source of more than 45% of primary production worldwide (Field 1998). The greatest species-diversity is found among diatoms (13.776 species) and dinoflagellates (3.281) (Guiry & Guiry 2015), other groups such as haptophytes, prasinophytes and cyanobacteria, are significant. The Vitória-Trindade Seamount Chain is located off the central coast of Brazil. The chain emerged on the seafloor during the Cenozoic, simultaneously with the westward movement of the South America Plate (Almeida 2006). Trindade Island and Martin Vaz Archipelago are located at the eastern end, the farthest location from the coast (Almeida 2006, Motoki et al 2012). The last 17 submarine banks rise higher than 2.5km from the seafloor, with more than half reaching the euphotic zone (Motoki et al 2012)
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