Contribution of Particulate Phosphorus (> 250 μm) to the Total Phosphorus Pool in Lake Water

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Abstract
Particulate phosphorus (PP) > 250 μm was concentrated in the euphotic zone of 17 lakes in central Alberta. When the euphotic zone extended below the epilimnion, PP >250 μm was concentrated deep in the euphotic zone. PP > 250 μm was a significant but variable portion of the total phosphorus (TP) pool in individual lakes; thus, samples should be collected from the euphotic zone on several dates to estimate the contribution of PP > 250 μm to the TP pool. As well, the contribution of this fraction varied among lakes: average summer values for the euphotic zone ranged from 3 to 19%. Among lakes, the contribution of large particles to the TP pool decreased proportionally as lake productivity (estimated by chlorophyll a (Chl a)) increased. The relative contribution of PP > 250 μm in summer accounted for a significant portion of the residual variation in the spring TP-summer Chl a relationship but not the summer TP-summer Chl a relationship in the study lakes. These apparently contradictory results can be explained by differences between lakes that mixed intermittently throughout the summer and those that remained permanently thermally stratified during this time.