On the relationship between carbon-to-nitrogen composition ratios of the particulate matter and growth rate of marine phytoplankton from the Northwest African upwelling area

Carbon-to-nitrogen composition ratios of particulate matter ranged between 3.7 and 9.6. High ratios (7.8–9.6) were found at inshore stations located in cold (< 16°C) and nutrient-rich waters, while low ratios (3.7 to 6.6) were observed at offshore stations located mostly in warmer waters. This ratio is inversely related to growth in terms of inorganic carbon and nitrogen (ammonium, nitrate). Such a relationship is similar to those found in steady-state chemostat cultures of various species of marine algae, even though the carbon-to-nitrogen ratio of particulate matter collected in the field can rarely be considered characteristic of phytoplankton only. Correlations between carbon-to-nitrogen composition and carbon-to-nitrogen assimilation ratios were significant. The latter ratios were, however, about an order of magnitude higher than the former.