This volume gives an insight into what a group of contemporary plankton biologists think about the utility, virtues, strengths and theoretical and practical weaknesses of J.H. Connell's Intermediate Disturbance Hypothesis within the context of phytoplankton ecology. The sequence of papers in this volume moves from particular case studies to more general and finally theoretical approaches.

The question "Why are there so many species?" has puzzled ecologist for a long time. Initially, an academic question, it has gained practical interest by the recent awareness of global biodiversity loss. Species diversity in local ecosystems has always been discussed in relation to the problem of competi tive exclusion and the apparent contradiction between the competitive exclu sion principle and the overwhelming richness of species found in nature. Competition as a mechanism structuring ecological communities has never been uncontroversial. Not only its importance but even its existence have been debated. On the one extreme, some ecologists have taken competi tion for granted and have used it as an explanation by default if the distribu tion of a species was more restricted than could be explained by physiology and dispersal history. For decades, competition has been a core mechanism behind popular concepts like ecological niche, succession, limiting similarity, and character displacement, among others. For some, competition has almost become synonymous with the Darwinian "struggle for existence", although simple plausibility should tell us that organisms have to struggle against much more than competitors, e.g. predators, parasites, pathogens, and envi ronmental harshness.

These proceedings deal with the relationship between species composition of freshwater phytoplankton and the trophic gradient. Particular regard is paid to the composite question, what lives where and why? Overview papers report the state of the art and suggest that the trophic spectrum appears to be a probabilistic outcome of several dimensions of variability that impinge upon phytoplankton species selection. Studies on community structure span all latitudes from those of Antarctica to equatorial Brazil, and also include reports on light and nutrient gradients, pH and fish-stock effects on species composition. Seasonal and longterm phytoplankton dynamics in lakes of varying trophic status are also considered. Finally, studies on the taxonomy and autoecology of some groups (e.g. Volvocales, Chrysophytes and Euglenophytes) living at the extremes of the trophic spectrum contribute to our knowledge of this usually neglected phytoplankton. This is the first time that a book covers such a topic, and it will prove an excellent source of information to anyone working on phytoplankton ecology and ecological indicators. Limnologists in general, algologists and the technical staff at water authorities will all benefit by reading this book.

This volume summarises the outcome of the 13th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP) on if, and if so under what conditions phytoplankton assemblages reach equilibrium in natural environments. Quite a number of ecological concepts use terms such as: ecological equilibrium, stability, steady-state, climax, stable state, etc. However, these ecological concepts often have been "translations" of scientific theories developed in physics or chemistry but they almost always lack scientific corroboration, the problem being that often these concepts remain vague and they are not formally defined. Here an attempt to formally recognize what "equilibrium" is in phytoplankton ecology is traced. The book also contains papers by leading scientists on the taxonomy of two selected key groups: cryptomonads and filamentous cyanoprokaryotes. This volume is addressed to all those involved in phytoplankton taxonomy and ecology and in ecology itself.