Epilithic diatoms as indicators of stream total N and total P concentration

Patterns of diatom species distribution in relation to total N (TN), total P (TP), and other environmental variables from riffle sites on 2 streams in southern Ontario, Canada, were determined using canonical correspondence analysis (CCA). Relationships with TN and TP were sufficiently strong to develop weighted-averaging (WA) regression-calibration models for inferring stream water concentrations of these nutrients. The models were accurate within +/-2.4 mu g/L for TP (apparent r(2) = 0.52) and +/-2 mg/L for TN (apparent r(2) = 0.53). An evaluation of the goodness of fit of these models with and without bootstrapping indicated that they performed better (bootstrapped r(2) = 0.44 for TP and bootstrapped r(2) = 0.42 for TN) than published TN and TP inference models for which similar assessments were made. Based on Organisation for Economic Cooperation and Development eutrophication ratings, the TP model predicted 76% of the mesotrophic and 57% of the eutrophic samples correctly. The model correctly predicted only 20% and 33%, respectively of oligotrophic and hypereutrophic samples. WA inference models were improved when seasonal variation was removed by using mean summer water quality and diatom data (apparent r(2) = 0.76 and bootstrapped r(2) = 0.61 for TP; apparent r(2) = 0.82 and bootstrapped r(2) = 0.70 for TN). Overall, rye conclude that epilithic diatoms can be related to TN and TF using these methods, and that WA inference models have utility for indicating eutrophication in southern Ontario lowland streams.