Coccolithophores in the Nordic Seas: comparison of living communities with surface sediment assemblages

Coccolithophores were investigated in both numerous plankton samples and surface sediments from across the entire Nordic Seas. Cell numbers of living coccolithophore communities are consistently higher during the high-production period (summer) than during the low-production period (fall–early summer). Particularly high cell numbers are found far to the west during the high-production period. High cell densities in general are mainly caused by Emiliania huxleyi, which often dominates the communities in the eastern Norwegian Sea. In contrast, during the low-production period, many of the collected samples contain no coccolithophores. The original composition of the living communities is obscured in the surface sediment assemblages. Samples from surface sediments contain significantly fewer coccolithophore species than the living communities of the same area. The most frequently occurring species are Emiliania huxleyi and Coccolithus pelagicus. In addition, Calcidiscus leptoporus and Gephyrocapsa muellerae are regularly found in small amounts. This is remarkable since these species are rarely found in living communities. Based on the diversity and concentration of the preserved species and on the ratio change between E. huxleyi and C. pelagicus, distinct surface water masses in this area are clearly reflected.