Diversidade e estoque de carbono em cianobactérias na costa e nos arquipélagos da porção oeste do giro Equatorial Atlântico

Abstract

The South Equatorial - SEC and North Brazillian - NBC surface currents are directly connected to the Atlantic Equatorial Gyre. These currents influence water movement and contribution on the surface water in the brazilian oceanic archipelagos and the border of Brazil’s northeast continental platform. The carbon stock of the cyanobacterias follow a coast oceanic archipelagos longitudinal gradient: PP>PA=IC>AC>FN>AS. The carbonstock alongcoast corresponds to 1,04mg C m-3, with relative stock of 2,69% Synechococcus and 0,48% of the POC in Prochlorococcus. On the oceanic archipelagos, only 0,15mg C m-3 are stocked in the cyanobacterias, with a relative stock of 0,38% in Synechococcus and 0,10% of the POC in Prochlorococcus on surface waters. Although equatorial waters are considered poor when it comes to carbon stock, the carbon stocked on the surface keeps its levels throughout the year, sustaining the primary productivity. The Saint Peter and Saint Paul Archipelago - AS shows bigger POC oscillations due to its geographic position, being directly influenced by the SEC’s seansonality. Altogether, 1.158.901 sequences have been represented in 56 taxons, within 48 belonging to cyanobacterias. Out of amount of taxons, 37 have been common among nano and picophytoplanktonics fractions. Isolating the phytoplankton fractions by the longitudinal gradient, coasts and islands, 4 distinct cenarios are built, in which only 20 taxons are common among each other. The cenario with taxonomic exclusivity has been represented on the archipelagos, on the nanophytoplanktonic, with 9 exclusive taxons. The genuses Prochlorococcus and Synechococcus have been dominants, accumulating 98% of the total of sequences in both phytoplanktonic fractions. The coastal replicates correlate more with Synechococcus, while insular replicates have been dominated by Prochlorococcus. It hasn’t been possible to establish a cyanobacterias’diversity coastilsand gradiente through 16S rRNA sequences, because the sampled archipelagos are very distinct among each other. FN locations showed bigger diversity levels and several rare taxons, even with average sequence abundance, as far as AS locations showed fully opposite patterns. The environmental parameters that have mostly dominated the cyanobacterias distribuition on the coast-island surface gradiente was the temperature. The hydrodinamic variables and kind of substract revealed bigger picophytoplanktonic diversity on the surfaces on exposed conditions. For the nanophytoplanktonic fraction, these conditions represented the smallest biodiversity.