Diatoms are important in life of all kinds of water. Benthic species are widely used for water quality evaluation. However in many cases species identification, on which water quality evaluation relies, is difficult as there are no unambiguous morphological criteria defining species limits. For solving this problem the 1st European Workshop on Diatom Taxonomy (1st EWDT) was held in November 2009 where researchers and students from twelve countries, mainly, but not only from Europe participated. This special issue of the journal Algological Studies dedicated to the genus Achnanthidium Kützing contains the main results of participants of the 1st EWDT and additional publications on this genus.

Members of Achnanthidium are common and abundant in all types of freshwater therefore that increases their bioindication relevance. Nevertheless, taxonomy and identification of these monoraphid diatoms are problematic; their small size makes distinguishing characters difficult to observe under light microscope.

This volume includes ten articles on describing not only morphological characteristics but in many cases distribution, ecological preferences of several Achnanthidium species living in different parts of Europe, Africa, Asia and South America. Diatoms belonging to this genus are presented from Nepal and India, Bolivia as well as southern Poland. Exploration of streams in the Himalayas is based on the observation of A. pyrenaicum and related species. The authors, Jüttner et al. also analysed the response of these species to gradients in altitude, water chemistry, habitat characteristics and geographical distribution.

The taxonomic position of some new and some described Achnanthidium species is determinated based on light and scanning electron microscopical features. Among these A. ennediense is intriguing because this species was originally described as a Navicula.

Hlúbiková et al. examined five species within the Achnanthidium minutissimum complex. Their work is interesting because this group considered to live in all freshwater habitats is one of the most difficult to distinguish. Van de Vijver et al. reviewed European populations of A. lineare revealing two additional species.

The real value of this book lies in the exact morphological descriptions and the good quality light and scanning electron microscopical images providing features that could distinguish species that were until now difficult to distinguish. This volume could be recommended not only to diatom taxonomists but ecologists dealing with diatoms and their role in water quality evaluation.

M. DULEBA

Acta Botanica Hungarica 53 (3-4), 2011, p. 444-445