Functionally distinct classes of complex phosphorus compounds in lake water1

Complex phosphorus compounds were classified functionally according to the manner by which orthophosphate was released. Filtrable phosphorus compounds in two eutrophic lakes (East and West Twin lakes) and a humic bog (Crazy Eddie Bog) in northeastern Ohio were fractionated by anion‐exchange and gel‐filtration chromatography. Fractions were analyzed for soluble reactive phosphorus and total dissolved phosphorus; absorbance at 400 nm was used as a measure of filtrable “yellow acids.” The eutrophic lakes contained numerous low molecular weight compounds which were resistant to low‐dose ultraviolet irradiation but readily released orthophosphate upon treatment with alkaline phosphatase. Filtrable phosphorus compounds of the humic bog were predominantly high molecular weight, cochromatographed with the yellow acids in each fractionation procedure, and resisted enzyme hydrolysis, but released orthophosphate upon irradiation with low doses of ultraviolet light.