MINERALIZATION OF INOSITOL HEXAPHOSPHATE IN AEROBIC AND ANAEROBIC MARINE-SEDIMENTS - IMPLICATIONS FOR THE PHOSPHORUS CYCLE

Inositol hexaphosphate (IP6) is a significant carrier of organic P in riverine sediments and suspended matter. Its mineralization in coastal sediments was investigated by laboratory experiments under simulated marine environments. Despite being chemically refractory, IP6 was effectively mineralized to inorganic P by aerobic and anaerobic degradation processes. The extent and rate of IP6 mineralization were found to be strongly regulated by the redox conditions: under anaerobic conditions, IP6 decomposed almost completely within 40 days, whereas about 50% of IP6 remained under aerobic conditions during a 60 days experiment. Most of the IP6 added to sediment/seawater mixtures was bound to the sediment particles in both aerobic and anaerobic samples. The soluble fraction of IP6 in the aqueous phase was, however, depressed under aerobic conditions, which could account for the reduced efficiency of aerobic IP6 mineralization. These results suggest that terrigenous IP6 decomposes rapidly under marine environmental conditions and thus may be an important P source in marine ecosystems.