Bioindication on the basis of benthic diatoms: Advantages and disadvantages of the Polish phytobenthos lake assessment method (IOJ – the Diatom Index for Lakes) / Bioindykacja na podstawie okrzemek bentosowych: Mocne i słabe strony polskiej metody oceny jezior na podstawie fitobentosu (IOJ – Indeks Okrzemkowy Jezior)

Diatoms are widely used for bioindication because of their sensitivity to anthropogenic pressures (e.g. eutrophication or acidity of waters). In many countries in the world, work has been undertaken to develop and implement diatom indices. Since 2000, in the Member States of the European Union, this has been done as part of the implementation of the Water Framework Directive. The results of lake assessment obtained using the Polish method based on epiphytic diatoms (IOJ - Indeks Okrzemkowy Jezior = the Diatom Index for Lakes) are greatly different from those provided by the other ecological status assessment methods. The purpose of this article is to review the scientific literature on the use of phytobenthos for bioindication in order to identify the advantages and disadvantages of the Polish IOJ method and to indicate the possible directions of improvements in this method. The literature evidencing the variability of phytobenthos related to its habitat, the spatial variability at the scale of a lake and the variability in the growing season was reviewed. The cited writings indicate that the further specification of guidelines for the sampling procedure and an increase in the number of survey sites could enhance the functionality of the Polish lake assessment method. It has also been suggested that it may be useful to test the effect of the seasonal variability of a phytobenthos assemblage on its bioindicator value.