Fig. 1. Relationship between water-extractable phosphorus (P_w) measured after addition of the molybdate reagent, and absorption measured at 882 nm in a second subsample of the same filtrate without the molybdate reagent. The filled squares represent the P_w values measured in a third subsample, after addition of NaCl and 0.45-µm filtration. The symbol *** indicates significance at the 0.001 probability level.