Interactions between NH4+ and NO3- uptake and assimilation: comparison of diatoms and dinoflagellates at several growth temperatures

The inhibition of NH4+ by NO3- uptake was investigated in estuarine diatoms and dinoflagellates. This was done by growing four species of phytoplankton on NO3- at several different temperatures. The impact of NH4+ additions were then assessed for all species. Results showed that in both diatoms and flagellates, NO3- uptake was reduced with increasing NH4+ concentrations. It was also shown that estimated half-inhibition concentrations were higher in diatoms than in dinoflagellates. Analysis indicates that the mechanism for NO3- inhibition may be similar across species.