Y. Collos et al., VARIABILITY IN NITRATE UPTAKE KINETICS OF PHYTOPLANKTON COMMUNITIES IN A MEDITERRANEAN COASTAL LAGOON, Estuarine, coastal and shelf science, 44(3), 1997, pp. 369-375
Nitrate uptake kinetics of different phytoplankton communities exhibit
great variability over a 1-year period. Classical saturation kinetics
accompanied by an induction phase are shown by blooms of Chaetoceros
sp. in low nitrate waters. Biphasic kinetics, with transition points b
etween 10 and 50 mu M, are shown by blooms of Skeletonema costatum and
flagellates, while unsaturated kinetics (up to 100 mu M) are shown by
Thalassiosira blooms and flagellate blooms. The latter also exhibit s
urge uptake of nitrate in situations of negative growth rates and rath
er high ammonium levels. The uptake patterns of the three diatom gener
a are similar to those observed in cultures or consistent with known i
nternal nitrate accumulation characteristics. Based on the kinetic pat
terns presented, it is apparent that, for nitrate concentrations near
50 mu M such as in upwelling areas, nitrate uptake will be underestima
ted in present models of nitrate assimilation by a factor of almost 2
for S. costatum and a factor of about 3 for Thalassiosira sp. (C) 1997
Academic Press Limited.