8th International Nannoplankton Association Conference


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Mário Cachão, Jeremy Young, Hanno Kinkel, Anabela Oliveira, Maria T. Moita, Kees van Lenning, Alexandra Duarte, Markus Geisen, Patrizia Ziveri, Christine Klaas, Ian Probert, Ana S. Palma, Annelies Kleijne, LluÏsa Cros, José C. Mendes:
The distribution of the coccolithophore community off Lisbon (Portugal), during June 1999 (CODENET II Cruise): ecological interpretation

CODENET is a research network of eight European geological and marine biological teams, funded by the EC Training and Mobility of Researchers Programme to carry out an integrated, multidisciplinary study of six coccolithophore key taxa. The research strategy focuses on different types of studies on these taxa (Calcidiscus leptoporus, Coccolithus pelagicus, Gephyrocapsa spp., Helicosphaera carteri, Syracosphaera pulchra, Umbilicosphaera sibogae), following and developing the strategy that had already proved successful with the Global Emiliania Modelling (GEM) initiative and the MAST-funded EC project, EHUX, centred only on the species Emiliania huxleyi. One of the main research task subjects of the CODENET is based on studies of coccolithophore assemblages collected during oceanographic cruises, the sample sets being used by different research teams, each studying particular taxa (e.g. for culture studies), or specific studies based on coccolithophores, such as marine biomarkers (alkenones, pigment analysis), coccolith Ca-Sr ratios, or molecular genetic analysis (see further details at In the present work, the coccolithophore community component of the data obtained during the CODENET II cruise, held during June, 1999, will be described.

The shelf off western Portugal is relatively narrow and, during the summer, northerly coast-parallel winds promote upwelling along it. As a result, there is a sharp productivity gradient from inshore eutrophic water to offshore oligotrophic conditions. Previous phytoplankton studies in the area have shown that coccolithophores form a significant part of the phytoplankton and that all the CODENET key taxa occur in the area. These provided excellent conditions for a detailed analysis of their autecology along a eutrophic-oligotrophic transect.

To meet the operational objectives, we carried out a transect across the shelf (Figure 1) collecting samples with two sampling protocols: (a) multi-cast stations - at five stations we stayed for a prolonged period (1-2 hours) collecting all the sample types. This included: (1) use of the deck pump for bulk sampling from approx. 5m depth; (2) two rosette casts from the top of the thermocline (10-30m) for bulk sampling; and (3) one or two rosette casts to sample from four depths for phytoplankton, nutrients, chlorophyll and coccolithophore samples; and (b) single cast samples - at six stations we stayed for a short period only (15-20 minutes) conducting a single CTD-rosette cast in order top collect samples for four depths for phytoplankton, nutrients, chlorophyll and coccolithophore samples. In addition, the deck pump was used to collect samples for these analyses from 5m water-depth.

The data was subdivided in two data matrixes, one with the biological counts of the phytoplankton main groups (diatoms, dinoflagellates and coccolithophores) together with nutrient and pigment data, and the second gathering the coccolithophore individual taxa counts together with physical parameters such as temperature, salinity and nephelometry. The Factorial Analysis performed in these two data matrices allowed us to confirm the upwelling as the main controlling factor of the phytoplankton distribution in general, and of the coccolithophores in particular.


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

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