Saline ground waters can also lead to elevated levels of sulfate, dissolved iron and nitrate (Nines et al . 1992). Sulfate has been implicated in the cycling of phosphorus (Carraco et al . 1989). Sulfate-reducing bacteria use the sulfate ion for anaerobic respiration. The respiratory end product from sulfate reduction is hydrogen sulfide, which is a reducing agent that can facilitate the dissolving of iron minerals with a release of phosphorus (Boström et al . 1988). It has also been suggested that sulfide can displace P from insoluble Fe2+ phases (Roden and Edmonds 1997). On the other hand, if a saline groundwater intrusion has a high level of dissolved iron, oxidation and subsequent precipitation of the iron can lead to the removal of phosphorus from solution (Baldwin 1996 b). Similarly, increases in the concentration of calcium can also lead to the loss of phosphorus from solution through precipitation (House 1999).