Physiological Processes, Nutrient Availability, and the Concept of Relative Growth Rate in Marine Phytoplankton Ecology

After more than thirty years of intensive research in phytoplankton ecology, our knowledge of how to measure accurately growth rates of photosynthetic organisms in nature is still very limited (1–3). Difficulties in extrapolating results from in situ bottle tests involving standard rate-measuring incubation methods (such as the 14C-labelling technique) are becoming increasingly evident (3–6); hence, we now are faced with conflicting opinions regarding the magnitude of phytoplankton growth rates in the marine environment (5,7–10).