Epilithic algal communities and their relationship to environmental variables in lakes of the English Lake District

1. The relationship between epilithic algal communities and 17 environmenta l variables from 17 oligo- to eutrophic lakes in the English Lake District was explored using canonical correspondence analysis (CCA). Total phosphoru s (TP) and calcium (Ca) concentration were the most important variables acc ounting for species distribution. 2. Weighted-averaging regression and calibration models with tolerance down weighting and classical deshrinking were developed to infer TP, Ca, dissolv ed inorganic carbon (DIC) and conductivity from the relative abundance of 1 38 epilithic algal taxa. 3. The ranges of the environmental variables covered by the models are 0.8- 49.2 mug L-1 for TP, 2.2-13.0 mg L-1 for Ca, 0.5-8.6 mg L-1 for DIC and 38- 124 muS cm(-1) for conductivity. Within these limits the models can be used to infer chemical properties of lakes from epilithic communities in the En glish Lake District. 4. The major advantages of using transfer functions based on epilithic comm unities are the low logistic requirements and the integrative character of algal samples compared to direct point measurements of chemical parameters of the lakes.