Some Aspects of the Ecology of Fresh-Water Algae: (With Special Reference to Static Waters)

Abstract

IN the following I propose to give a general account of the present position of our knowledge as regards the algal ecology of static fresh-waters. A good deal of attention is now being paid to flowing waters in this country in relation to pollution and, since it became necessary to narrow down the field of these considerations, it appeared most suitable to omit flowing waters and to confine my attention to standing water. This may be the more appropriate, since it is to be hoped that the present year will see the establishment of a fresh-water biological station on Lake Windermere. One of the earliest attempts to classify fresh-water algal communities as a whole was made by G. S. West in 1916 (161) in the Cambridge Botanical Handbooks2. West had enjoyed unrivalled opportunities of becoming acquainted with the fresh-water algal flora of many parts of the world and this, combined with his extensive investigations on British Algae, afforded him a general view of algal habitats such as few others possessed. With few exceptions, however, he did not succeed in establishing a classification that could serve as a foundation for further investigations. As will be familiar, his main classification was into subaerial associations, associations of irrorated (or dripping) rocks, and aquatic associations, the last being further subdivided into those of swiftly running water, those of bogs and swamps, those of ponds and ditches, and those of pools and lakes. A perusal of these aquatic associations leaves one with very few tangible data for their separation or for the distinction of individual communities among them. The data provided are essentially floristic, and this is true also of a large number of so-called ecological accounts of the algal flora of various districts that have been published in the last two decades. West and his father, howeveri, made one very noteworthy contribution in the direction of a further elucidation of algal habitats. As a result of their extensive studies of British phytoplankton they arrived at the conclusion that the rich Desmid floras, comprising a large number of types in this country exclusively confined to the western region, corresponded geographically with