Abstract

Extract

During the last two years, there have been so many enquiries about algae in farm ponds that it seems appropriate to summarize some of the information about these plants and their toxic strains. Algae are found in nearly all surface waters, irrespective of whether they are fresh, salt or brackish, and are suspended and free-floating or attached to various substrata. Although the free-floating forms are usually invisible to the naked eye, a few of them sometimes multiply rapidly, bring about an obvious change in the appearance of the water and give rise to what is often known as a water-bloom. It is a striking phenomenon which, in medieval times, was regarded with foreboding and as a warning of impending disaster. An event which is interpreted as a water-bloom occurred in Egypt (Exodus, vii, 20–21), similar events in Russia and Babylon were described by Pliny, and in Britain there is a lake in which water-blooms have appeared intermittently for more than 800 years (Griffiths, 1939 Griffiths, B. M. 1939. Early references to water-blooms in the British Isles. Proc. Linn. Soc., (Session, 151), : 12–19.  [Google Scholar]; Brook, 1957 Brook, A. J. 1957. Water-blooms. New Biology, 23: 86–101.  [Google Scholar]).