Some Observations on the Algae of Llyn Ogwen, North Wales

The nutrient conditions in the oligotrophic lake Llyn Ogwen were compared with algal populations over a period of 27 months. Oedogonium suecicum (Wittr.) Hirn and a Mougeotia sp. (sterile) both showed some measure of correlation of their proportions in the net plankton with the level of phosphate. A succession of the desmids Hyalotheca mucosa (Mert) Ehr., H. neglecta Racb. and Gymnozyga moniliformis Ehr. could not be correlated with any growth factor. Falling phosphate level was correlated with growth of Dinobryon sertularia Ehr. and a comparison made of the populations on the sediment and in the water. The growth of Tabellaria flocculosa (Roth) Ktz. was correlated with the silicate level and the general nutrient conditions.