North Atlantic Ocean

Carbon concentrations in suspended particulate material; Chlorophyll pigment concentrations in water bodies; Dissolved organic carbon concentration in the water column; Nitrate concentration parameters in the water column; Salinity of the water column; Temperature of the water column

Fluorometers; radiometers; CTD; expendable CTDs

The inverse gradients of light and nutrients (nitrogen) with depth have resulted in a unique phytoplankton distribution and primary production in oligotrophic stratified (tropical) oceans. These gradients can only partly explain why a Deep Chlorophyll Maximum (DCM) is found here world-wide at depths of 80 or 150 m. The microbial composition of this layer is remarkably constant in spite of the high activity of the photosynthetic, microbial and heterotrophic components which indicate a highly dynamic system. The phytoplankton composition is dominated by picoplankton (< 2 micron in diameter) and consists of a mixture of prokaryotic (Synechococcus and Prochlorococcus) and various (unknown) eukaryotic species of which various subpopulations dominate at different depths. By modelling the production processes and trophic interaction the contribution of the DCM to the sedimentation of particulate carbon will be studied. The expedition on board Hr. Ms. Tydeman focuses on the factors which prevent (major) fluctuations in structures and organisation of microbial populations present near the Deep Chlorophyll Maximum.

Royal Netherlands Institute for Sea Research
Landsdiep 4 P.O. Box 59
Den Burg/Texel

1790 AB
Netherlands