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Yuichiro Tanaka:
Coccolith fluxes in the NW Pacific Ocean
(Poster)

Coccolith fluxes and assemblages were investigated by time-series sediment-trap experiments at different areas in the NW Pacific: W Caroline Basin (Site 1), C equatorial Pacific (Site 3), E China Sea (Sites 2, 4) and the Hess Rise (Sites 5, 6, 7, 8), in order to evaluate seasonal change in both fluxes and the species composition of coccoliths in relation to water-masses. The annual calculated flux of coccoliths was significantly different at these sites. At Site 3, the annual flux was low, with 3.1x10¹⁰ coccolith/m²/year. The highest coccolith flux was recorded in the Hess Rise trap, with 37.8x10¹⁰ coccolith/m²/year, which was about 10 times higher than in the central equatorial area.

Two seasonal maxima of coccolith fluxes were observed in the low- to middle-latitude sites (Site 1: September-October, December-January; Site 3: June, September-November; Site 2: March, November; Sites 6, 7: March-April, July), whereas only one maximum occurred in the middle- to high-latitude sites (Site 8: September). An increase of the coccolith flux was recorded in spring in the middle latitudes and is delayed towards higher latitudes. These seasonal patterns of coccolith fluxes were correlated with the organic matter fluxes at all sites.

In the E China Sea and Hess Rise area, the dominant species was Emiliania huxleyi. E. huxleyi dominated the community during March to May at Site 2, and during June to July at Site 7. High fluxes of this species were probably corresponding to the spring bloom in the middle- to high-latitude areas. On the contrary, at Sites 1 and 3, E. huxleyi occurs in low abundance, and the predominant species are Gephyrocapsa oceanica and Umbilicosphaera sibogae. The abundance of Florisphaera profunda correlates with low-nutrient water-conditions and high temperature.

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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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