Biological Availability of Low Versus High Molecular Weight Reactive Phosphorus

Abstract

When equivalent concentrations of reactive high molecular weight phosphorus (RHMW-P > 5000) and free orthophosphate (PO₄-P) from Lake Tutaeinanga, New Zealand, were added to P-starved Chlorella cultures, free PO₄ showed a faster growth response within 48 h than RHMW-P. Algal preference for PO₄ over RHMW-P could also be shown by (³²P)PO₄ 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. Key words: reactive phosphorus, orthophosphate, algae, Chlorella, growth, bioassay