Investigations of the speciation of phosphorus in coastal and estuarine waters of the Great Barrier Reef, using iron strips and colorimetry

A new method of determining phosphorus in sea water, using iron-impregnated strips of filter paper, was investigated and compared with standard colorimetric methods of phosphorus analysis. Laboratory experiments were undertaken to determine the number of iron strips required to extract phosphorus from sea water, the length of time a strip needed to adsorb all P from solution, the reproducibility of the method, and whether the strips could measure P adsorbed to different particles. Field studies were carried out with iron strips in Cleveland Bay and the Herbert estuary, and comparisons were made with concentrations of dissolved, particulate and organic phosphorus determined by standard techniques. The iron-strip method was shown to work well under laboratory conditions, but the field studies showed varying results for the different environments tested. Generally, most of the dissolved inorganic phosphorus present in sea water was taken up by the strips. The iron strips also took up a proportion of other phosphorus fractions in sea water, but the nature of this uptake appears to vary with environmental conditions.