Relationships between benthic diatom assemblages’ structure and selected environmental parameters in Slovak water reservoirs (Slovakia, Europe)

The main objective of the present study is to describe the structure of benthic diatom communities in 23 water reservoirs in Slovakia classified as heavily modified water bodies. Environmental variables together with biological data obtained during the routine biomonitoring of water reservoirs in Slovakia were explored and analysed to understand variability of benthic diatom communities and their relationships with environmental variables in order to obtain an integrated knowledge about their relevance as bioindicators for the Water Framework Directive-compliant ecological potential assessment. This study summarizes results from a four-year monitoring programme of water reservoirs surveyed during the period of 2011–2014. The performed survey and statistical analyses revealed the following: (i) two main groups of reservoirs could be distinguished based on the purpose of their main use (multipurpose or drinking water-supply use); (ii) multipurpose and drinking water-supply reservoirs differed in benthic diatom community structure, diatom water quality indices as well as in the principal environmental gradients structuring the diatom communities; (iii) 5 distinct sub-groups of reservoirs could be identified differing in terms of diatom species composition and several environmental parameters; (iv) the most significant environmental variables in explaining differences in diatom species composition in multipurpose reservoirs were mean depth and mean annual flow; in drinking water-supply reservoirs conductivity and water transparency