Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.

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The Ecology of Phytoplankton

Stichochrysis immobilis E. Pringsheim was described as a new genus and species of the Chrysophyceae (Pringsheim 1955) on the basis of a pure culture grown on agar. There is now con­ vincing evidence that the organism in culture was in fact a clone of the diatom Cyclotella meneghiniana Kiitzing. The clone upon which Stichochrysis immobilis is based was isolated by Dr Jack Myers from plates of agar enriched with Chu # 1 0 medium (Chu 1942), a freshwater medium lacking added vitamins. The sample from which the isolation was made was collected in February 1949 from a waste-water clar­ ification pond receiving discharge from the city of Alamo, Texas. The water, for which no chemical data were given, was golden-brown in colour because of a dense algal population. The cells of this clone at first appeared square, but later became more rectangular. An axenic culture on agar was furnished to Dr Pringsheim in June 1949. The organism was described (Pringsheim 1955) as consisting of cylindrical cells, mostly twice as long as broad, 7-10 J.Lm in length and 5 J.Lm in diameter, forming chains under certain circumstances. It was considered to represent an undescribed genus and was assigned to the Chrysophyceae on the basis of colour and storage products as deduced by Pringsheim from light microscope examination. Pringsheim's culture from Myers, considered to be the type clone, was deposited with CCAP (Cambridge, UK) as clone number 956/1. Some difficulties with the taxonomy of the genus developed fairly quickly. In 1957, one of us (RRLG) isolated (from agar) several strains of small euryhaline mi­ croalgae from brackish ponds and coastal waters near Milford, Connecticut (USA). These algae grew in chains and were first thought to be clones of Stichochrysis. Drawings of the 'Milford clones' were remarkably like Pringsheim's figures (Pringsheim 1955, figs I-I to 1-8) except that cells or chains were often narrower. However, suspicion was aroused by observations of rows of small 'protuberances' on chains of liquid-grown cells supplied with high levels of silicon. That nominally unicellular

Stichochrysis immobilis is a diatom, not a chrysophyte

Cylindrospermopsis raciborskii, a tropical blooming species of cyanobacterium (blue-green alga), was isolated from the domestic water supply reservoir on Palm Island, a continental island off the tropical northeast coast of Australia. This species, not previously known to be toxic, was shown to be severely hepatotoxic for mice. The 50% lethal dose at 24 h after injection was found to be 64 +/- 5 mg of freeze-dried culture per kg of mouse. The principal lesion produced was centrilobular to massive hepatocyte necrosis, but various degrees of injury were also seen in the kidneys, adrenal glands, lungs, and intestine. The possible implication of this finding in relation to an incident of hepatoenteritis in humans living on the island is discussed.

Severe hepatotoxicity caused by the tropical cyanobacterium (blue-green alga) Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju isolated from a domestic water supply reservoir.

has constituted an obstacle to the causal analysis of many aspects of phytoplankton ecology. Most measurements on photosynthetic rates of phytoplankton have been carried out under field conditions in which the relevant physical variables (notably light intensity) were inadequately known. Moreover, such experiments have generally utilized mixed natural populations whose history was little understood. This paper is concerned with information on the photosynthetic characteristics of three freshwater planlkton diatoms derived from experiments in the English Lakes. Photosynethtic behaviour of the diatoms, recorded from exposures at varying depths in the lakes, is analysed in terms of the photosynthetic characteristics of the species and the environmental conditions of underwater radiation and temperature. In certain aspects, the interpretation has been aided by supplementary data from laboratory experiments. Cultured populations of one species, Asterionella formosa Hass., have been used as the standard material in this work. With the photosynthetic characteristics of this material the photosynthetic behaviour of various natural populations of the same species, of known history, have been compared. A further, inter-specific, comparison has been made with the photosynthetic characteristics derived for the diatoms Fragilaria crotonensis Kitton (cultured population) and Melosira italica (Ehr.) Kiitz. subsp. subarctica 0. MUll. (natural population).

Photosynthetic characteristics of some freshwater plankton diatoms in relation to underwater radiation

Features of cyanobacteria are introduced for non-specialists by highlighting topics in the various chapters. Aspects where much more is known now than a decade ago are pointed out, such as the importance of cyanobacterial nitrogen fixation in the oceans. This is followed by an account of the recent molecular studies most relevant for ecologists, especially topics not mentioned elsewhere in the book. Several ecological subjects of current interest are discussed, including research which seems important, but has sometimes been overlooked. Topics mentioned include sensing the environment and other organisms and signalling between cyanobacterial cells and between cyanobacteria and other organisms, and methods for studying N and P. The authors air their views on past and present matters concerning cyanobacterial taxonomy and nomenclature. Finally, comments are made on practical topics such as the use of cyanobacteria for inoculating soils, barley straw to control blooms and the likely contribution of cyanobacteria to developments in algal biotechnology during the coming decade.

S. P. Chu

Papers

The Influence of the Mineral Composition of the Medium on the Growth of Planktonic Algae: Part I. Methods and Culture Media