Relationship between Tmax N-status (N:C) and cell size (ESD).
This is shown for cells as protists or diatoms of different size (as equivalent spherical diameter, ESD), defined using Eqs 5, 6 and 7 with KTcon = 0.1. The green layer shows the transport need to support growth; the difference between this green layer and the potential transport rate Tmax indicates the potential over-capacity for transport (see S2 Fig). The maximum growth rate was assumed as 0.693 d-1; at higher Gmax the green layer is elevated there thus being less difference between Tmax and the transport required to meet demand. Maximum and minimum N:C were assumed at 0.18 and 0.05 gN gC-1, respectively; the cellular carbon density was set via the allometric relationships for Cprot and Cdiat ; the maximum transporter rate density was set at TRDmax = 0.4 pgN μm-2 d-1.