Dissolved phosphorus concentrations in Cayuga Lake system and differences from two analytical protocols

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© 2016, © Copyright by the North American Lake Management Society. Effler SW, Prestigiacomo AR, Hairston NG, Auer MT, Kuczynski A, Chapra SC. 2016. Dissolved phosphorus concentrations in Cayuga Lake system and differences from two analytical protocols. Lake Reserve Manage. 32:392–401. Differences in the concentrations of dissolved forms of phosphorus (P) measured with 2 widely used spectral protocols were documented and evaluated for Cayuga Lake, New York, and 4 of its primary tributaries. The analysis focuses on 2 operationally defined forms of dissolved P, soluble reactive P (SRP) and soluble unreactive P (SUP), which together constitute dissolved P (TDP). Direct comparisons were based on analysis of the results from the 2 protocols of split samples of year-round deep water representative of the entire water column during turnover and the respective dependencies of tributary concentrations on stream flow. Although the TDP concentrations converged for the 2 protocols, there were systematic differences for the contributions of SRP versus SUP (i.e., one protocol yielding lower SRP but higher SUP). The interpretive implications of the differences in the operationally defined concentrations from the 2 analytical protocols were considered in the context of common limnological and bioavailable paradigms for these forms of P, and the needs and structures of mechanistic P-eutrophication models. The lower SRP analytical protocol was favored because of its greater consistencies with the independent bioavailability results, limnological paradigms for dissolved forms of P, and contemporary mechanistic modeling. The differences between the 2 protocols are particularly problematic where contemporary mechanistic models are to be applied, requiring compensating differences in kinetic representations, and likely structure, for cases of higher SRP datasets attributable to the protocol.

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Lake and Reservoir Management