Biological Availability of Low Versus High Molecular Weight Reactive Phosphorus

When equivalent concentrations of reactive high molecular weight phosphorus (RHMW-P > 5000) and free orthophosphate (PO 4 -P) from Lake Tutaeinanga, New Zealand, were added to P-starved Chlorella cultures, free PO 4 showed a faster growth response within 48 h than RHMW-P. Algal preference for PO 4 over RHMW-P could also be shown by ( 32 P)PO 4 turnover experiments. After 96 h both fractions showed good growth yields. Analyses on culture filtrates indicated that all forms of reactive P had been removed. This demonstrates that RHMW-P, which reacts with "reactive P" reagents, can eventually be utilized.