Add SRP and algal P explicitly in stocks. Flows travel between these two stocks. Links from Umax, kmp into Puptake (SRP to algal P), link from kd into Pmineralization (algal P to SRP)
Puptake = kmax*srp/(kmp+srp)/kmp
NO3 assimilation = puptake*algalN:P (stoichiometric ratio of N:P (=7)) *k1*no3/((k1*no3)+(k2*nh4))