A substantial nitrate pool is stored within living cells in various benthic marine environments. The fate of this bioavailable nitrogen differs according to the organisms managing the intracellular nitrate (ICN). While some light has been shed on the nitrate carried by diatoms and foraminiferans, no study has so far followed the nitrate kept by gromiids. Gromiids are large protists and their IC...

The size of tissue amino acid pools in plants may indicate nitrogen status and provide a signal that can regulate nitrate uptake and assimilation. The effects of treating barley roots with glutamine have been examined, first to identify the transport system for the uptake of the amino acid and then to measure root NR activity and cellular pools of nitrate. Treating N replete roots with glutamin...

Ammonium and nitrate uptake was measured in 6 European tidal estuaries (Ems. Rhine, Scheldt, Loire, Gironde and Douro) using I5N-tracer techniques. Uptake rates of ammonium and nitrate ranged from 0.005 to 1.56 pmol N 1-' h-I and 0.00025 to 0.25 pmol N 1-' h-I, respectively, and differed significantly between and within estuaries. Analysis of nitrogen uptake using the relative preferential inde...

The ability to model ‘‘new’’ (nitrate-based) production is crucial to predicting the ocean’s role in the global carbon cycle. The ability to model the distribution of high-nutrient/low-chlorophyll (HNLC) areas is particularly important in this regard. Here I draw together three elements that appear to be necessary for constructing the required model: (1) iron limitation of algal growth rates as...