8th International Nannoplankton Association Conference


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Mário Cachão, Áurea Narciso, Alexandra Silva, CODENET team, Richard Jordan, Kozo Takahashi:
The morphometric response of Coccolithus pelagicus to glacial-interglacial couplets during the last 4my

Coccolithus pelagicus was defined as one of the key species for the CODENET (European Community Training & Mobility of Researchers Programme) research network. Included in CODENET's work area 3 (Coccolithophorid Ecology), subdivided into the research tasks RT13 (Holocene Sample Set) and 14 (Geological Sample Set), the morphometry of C. pelagicus was analysed with three main foci: (1) in cultures; (2) in Holocene samples world wide; and (3) during glacial and interglacial maxima, in the last 4my.

Culture experiments, varying temperature and light conditions, performed at The Natural History Museum (London) provided specimens, which were subsequently measured by an automatic digitalised procedure. Due to the small number of specimens found in some of the Holocene and ODP samples, rippled smear-slides were prepared and observed with optical petrographic microscopy to increase the probability of finding C. pelagicus coccoliths. Coccoliths were subsequently measured by eye estimation using an eyepiece graticule. Twenty-five Holocene samples from the EC Pacific, WC Pacific, N Pacific, Indian, N Atlantic, C Atlantic and S Atlantic oceans were studied. From each ODP site - 81-522A (N Atlantic), 108-659A (C Atlantic), 114-704A (S Atlantic), 115-709C (Indian), 130-806B (WC Pacific), 138-849B (EC Pacific) - 10 samples were previously selected, two (maximum glacial and maximum interglacial isotopic stage) for each of the 0-1Ma, 1-2Ma, 2-3Ma, 3-4Ma and 4-5Ma time-intervals.

For each specimen, maximum and minimum diameter was measured together with a simple characterisation of the central-area (with or without bridge). Measurements were tabulated and, for each set of 100 measurements, the mean, standard deviation, skewness and kurtosis of the curves were determined. The results were compared to available mean SST values for Holocene samples and d18O values for ODP samples. Results were further compared with data from cultures.


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

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