Uptake and Release of Dissolved Organic Phosphorus by Representatives of a Coastal Marine Ecosystem1,2

A benthic diatom, a benthic amphipod, and mixed species of marine bacteria were used in studies of the uptake and release of dissolved organic phosphorus (DOP) using the radionuclide P 32 . Over one‐third of the soluble phosphorus released by the amphipod was in organic form (0.79 µ g‐at. DOP/g of animal per hr). Marine bacteria utilized 80% of this DOP. Thirty per cent was hydrolyzed in sterile media, possibly by alkaline phosphatase released by the amphipods. Bacteria‐free diatoms released little DOP during growth, but released 20% of their total phosphorus as DOP after growth had ceased. Growing diatoms could reabsorb 40% of this DOP. Marine bacteria were able to absorb 92% of it. No regeneration of dissolved inorganic phosphate (DIP) from DOP in the presence of bacteria was observed. Marine bacteria, living or dead, released very little DOP.