A Study of the Distribution and Periodicity of Some Algae in a Bog Pool

A feature of the mountainous areas of North Wales is the abundance of bogs, bog pools and bog lakes, especially in the cwms (corries) of vanished glaciers. Cwm Bochlwyd, in Snowdonia National Park, contains several small Sphagnum bogs at the periphery of the lake, Llyn Bochlwyd; the bog selected for study lies at 550 m at the west shore of the lake and under a ridge of the mountain Glyder Fach (994 m). The cwm receives a well distributed rainfall of about 254 cm/annum, and the bog is supplied by a small stream flowing off the mountainside and drains directly into Llyn Bochlwyd. At the time of the investigation the total area of the bog was about 900 m2, mostly Sphagnum spp., but near the centre this was replaced by an area of open water of about 200 m2 and varying from 5 cm to 30 cm deep. A third of the pool was free of vegetation save for a few shoots of Menyanthes trifoliata, but the remainder contained a variety of species among which Potamogeton natans, Carex nigra and Juncus bulbosus were the most noticeable. Since the investigations of West (1890) the Bochlwyd area has been known to possess a rich algal flora. Woodhead & Tweed (1954-55) recorded over 100 species of desmids in the cwm and over 600 species of algae in the cwm and surrounding area. The principal algal habitat, especially for desmids, was found by the investigator to be the pools in the Sphagnum bogs and their sediments, a few ml of which often yielded over fifty species. The aim of the investigation was two-fold; to determine the periodicity of algae in the pool water and on the sediment, and to investigate the micro-distribution of algae on the sediment. The latter was necessary for a quantitative and representative sampling procedure on the sediment, without which any comparison of algal populations of the pool plankton and the sediment would have been unjustified.