Coccolithophore export production, species composition, and coccolith-CaCO3 fluxes in the NE Atlantic (34 degrees N 21 degrees W and 48 degrees N 21 degrees W)

Coccolithophores were examined in two sediment traps, deployed for one year (April 1989 to April 1990) at approximately 1 km water depth, in the subtr opical NE Atlantic at 34 degrees N 21 degrees W (station NABE-34) and in th e temperate NE Atlantic 48 degrees N 21 degrees W (station NABE-48) as part of the JGOFS North Atlantic Bloom Experiment (NABE). At both stations, max imum coccolith and coccosphere fluxes were recorded during local spring blo om periods. The average coccolith and coccosphere fluxes at NABE-34 were 1. 12 x 10(9) m(-2) d(-1) and 4.90 x 10(6) m(-2)d(-1), respectively. At this s tation coccoliths from 51 taxa were identified. A marked seasonal change wa s noticed in relative abundances of Emiliania huxleyi and deep photic zone species: E. huxleyi dominated during spring, while in late autumn the cocco lith assemblage was dominated by Florisphaera profunda and the coccosphere assemblage by G. flabellatus and Algirosphaera spp., Emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assembla ges with 69% and 64%, respectively. At NABE-48, the average daily fluxes we re significantly lower, with 3.88 x 10(8) coccoliths m(-2) d(-1) and 8.45 x 10(5) coccospheres m(-2) d(-1), and only 36 taxa were recorded in the trap samples. Emiliania huxleyi was the dominant species in the coccolith assem blage throughout the year with 72%, and showed maximum fluxes during spring 1990. Coccolithus pelagicus exhibited a distinct seasonal pattern, with ma ximum fluxes in early June 1989, probably related to the development of a m esoscale cyclonic eddy in the vicinity of the trap site. Holococcolithophor e fluxes were highest during maximum sea surface temperatures in summer. Th e coccosphere assemblage was dominated by Gephyrocapsa spp., Syracosphaera spp., and E. huxleyi. Estimated CaCO3 fluxes of coccoliths, coccospheres, a nd calcareous dinophytes were compared with the CaCO3 content in the fine(< 32 mu m) fraction. The annual mass estimated CaCO3 flux of coccoliths and c occospheres was 5.1 g m(-2) yr(-1) at NABE-34 and 2.7 g m(-2) yr(-1) at NAB E-48, and that of calcareous dinophytes 0.9 and 0.1 g m(-2) yr(-1), respect ively. These summed mass estimated values contributed on average only 55% a t NABE-34 and 60% at NABE-48 to the fine fraction CaCO3. (C) 2000 Elsevier Science Ltd. All rights reserved.