The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment

Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.A contribution to the GRIL (Groupe de Recherche Interuniversitaire de Limnologie)