Description:
experimental sample treatment defined as follows: CTRL = no nutrient additions; +Si = addition of 320 uL of 20 mM Na2SiO3 to increase ambient dissolved silicon by 20uM (measured total Fe in 20nM Si stock indicates that increasing dissolved Si by 20uM increases total dissolved Fe by 0.05nM); +Fe = addition of 32uL of 10uM FeCl3 for a total concentration of 1nM; +Si+Fe = addition of both above.