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- Characterization of the coccolithophore community off Cabo Verde archipelago, including the Senghor Seamount (Eastern North Atlantic)Publication . Narciso, Áurea; Javidpour, Jamileh; Chi, Xupeng; Cachão, Mário; Kaufmann, ManfredA systematic investigation of the extant coccolithophore community around Cabo Verde archipelago was per formed during the cruise MSM49 of RV Maria S. Merian, which took place in the late fall of 2015. The description of the spatial and vertical distributions of coccolithophores was based on a survey performed to the north, east and south of Cabo Verde archipelago, between the surface and 150 m water depth. The total cell densities ob tained for the studied region were relatively low, reaching to a maximum of 30 × 103 cell L− 1 in the upper 50 m over the southeastern slope of the Senghor seamount. Emiliania huxleyi and Gephyrocapsa oceanica were the dominant species, followed by Florisphaera profunda. The coccolithophore distribution off Cabo Verde was essentially explained by relatively warm and nutrient-depleted waters in the region during the surveyed interval, in result of the weaker NE trade winds and the northward migration of the Intertropical Convergence Zone. In these conditions, a notable zonation of coccolithophores along depth was depicted, in consequence of the inferred general well-stratified water column. Four typical depth-related groups were identified: (i) a Shallow oligotrophic (10–30 m), represented by Discosphaera tubifera and Umbellosphaera spp.; (ii) an Intermediate (40–50 m), formed by the three placolith-bearing species E. huxleyi, G. ericsonii and G. oceanica, and by Algir osphaera robusta, Helicosphaera spp., Michaelsarsia spp., Syracosphaera spp. and Umbilicosphaera spp.; (iii) a Deep (60–75 m) with F. profunda, Ophiaster spp., Oolithotus spp. and Reticulofenestra sessilis as typical members; (iv) and The Deepest (>80 m), composed by Gladiolithus flabellatus and Syracosphaera lamina. In addition, high abun dances of G. oceanica related with the Eddy station were attributed to the transport and thriving of the coastal coccolithophore community, dominated by this species, from the African coast towards Cabo Verde.
- The effect of a transient frontal zone on the spatial distribution of extant coccolithophores around the Madeira archipelago (Northeast Atlantic)Publication . Narciso, Áurea; Caldeira, Rui; Reis, Jesus; Hoppenrath, Mona; Cachão, Mário; Kaufmann, ManfredIn order to characterize the coccolithophore community around the Madeira archipelago and to understand the effect of a transient frontal zone on its distribution, 149 seawater samples from the first 150 m were collected in 37 stations, during the research cruise POS466 of RV Poseidon. The present study revealed the occurrence of two biogeographic domains, NE and SW, during the late winter of 2014, with distinct physical-chemical and cal careous nannoplankton characteristics. The NE sector was characterized by higher coccolithophore cell densities (mean of 56 × 103 cell L−1) and a slightly lower diversity (Margalef diversity index of 1.80) when compared with the SW sector (mean of 47 × 103 cell L−1; Md index of 1.86). The more productive sector, NE, was asso ciated with colder, less saline and higher nutrient content water masses, linked to the injection of a westerly flow with origin in the Azores frontal system. Total cell densities ranged between 12 × 103 and 112 × 103 cell L−1, being Emiliana huxleyi the dominant species followed by small Gephyrocapsa. The most common and subordinate taxa, in order of decreasing abundance, were: Gephyrocapsa oceanica, Michaelsarsia spp., Syracosphaera spp., Umbilicosphaera spp. and Algirosphaera robusta. Relationships between environmental conditions and spatial and vertical variability in coccosphere abundance, associated E. huxleyi and small Gephyrocapsa with the more productive water mass conditions, linked to the thermohaline transient front. G. oceanica distribution indicated its preference for warmer and less turbulent coastal waters, when compared to E. huxleyi and small Gephyrocapsa. Michaelsarsia spp. and A. robusta revealed preference for the northwest coast of Madeira, associated with mesotrophic con ditions of the water column. Syracosphaera spp. and Umbilicosphaera spp. were well distributed throughout the archipelago and along the sampled depths, from the coast to open ocean conditions, as well as from lower to higher productive zones, displaying affinities for the meso to oligotrophic conditions, typical of these subtropical waters. The broad depth range of several taxa and the nonexistence of the coccolithophore vertical succession were the result of homogeneous and generalized well-mixed surface layer during the present survey.