Nitrogen uptake characteristics of Chordaria flagelliformis (Phaeophyta) in batch mode and continuous mode experiments

The uptake of NH super(+)d4 and urea by C. flagelliformis) was measured in a perturbed system (batch mode) and in an apparent steady-state system (continuous mode). The maximum uptake rates (V sub(max)) measured in short-term depletion experiments greatly exceeded those determined under a steady nutrient supply. C. flagelliformis briefly exposed to high nutrient concentrations has an impressive capacity for rapid uptake (high V sub(max)) which is uncoupled from growth. In contrast, under continuous, homogenous low N concentrations the alga appears well equipped (low half-saturation constant, K sub(m)) to take up the available N. The results show that previous work based on batch mode uptake experiments probably overestimated the N requirements for the growth of many seaweeds.