8th International Nannoplankton Association Conference


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Anders Henriksson:
Coccolithophore and dimethylsulfide production variations over the last 200 000 years in the equatorial Atlantic

Dimethylsulfide (DMS) released from phytoplankton produces cloud condensation nuclei in the marine troposphere, thereby providing a climate-regulating mechanism by increasing cloud albedo. A 200 000 year long sedimentary record from the equatorial Atlantic (Meteor core 16772: 121'S, 1158'W, 3912m water-depth) has been investigated. The core is located in the centre of the divergence area of the equatorial Atlantic, where cold, nutrient-rich waters seasonally well up and give rise to high productivity.

To establish an optimal record of 'DMS-coccolithophore' production, coccoliths were converted into coccolithophores by using the known number of coccoliths on each of the coccolithophore species known to produce DMS (Emiliania huxleyi, Gephyrocapsa sp., G. oceanica, Calcidiscus leptoporus). Fluxes of alkenones were calculated and compared to accumulation rates of DMS-coccolithophores.

In a general, but not consistent, trend, data for cold Oxygen Isotope Stages 2, 4, 5b, 5d and 6 reveal that both the fluxes of biomarker compounds derived from DMS producers, and the accumulation rates of DMS-generating coccolithophores, were high when SST was low. The record of DMS-producing coccolithophores suggests that DMS production increased during the glacial stages, thus potentially working to further cool the glacial world. Important factors limiting the operation of this possible feedback mechanism for planetary cooling may be the strength of trade winds increasing upwelling of nutrients and transporting fine, iron-rich dust needed to fertilise the growth of DMS-producing coccolithophores.


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

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