Phosphorus Cycle and Phosphorite Formation in Marine Sediments of High Productive Areas

After a recent study, the pore water and high-resolution solid phase analyses as well as microbial investigations on the Namibian shelf indicate that sharp phosphate peaks, observed in 2-3 cm sediment depth, correspond to the depth where great sulfur bacteria are most abundant (Schulz and Schulz, 2005). Beside the well known connection between the benthic cycles of iron and phosphorus it could be shown that under anoxic conditions these bacteria consuming acetate and simultaneously release tremendous amounts of phosphate to interstitial waters, which lead to the formation of hydroxyapatite, a preliminary phase of phosphorites.