The aim of this paper is to make a comparative analysis of benthic macroinvertebrate compositions in streams and rivers in Croatia with relation to different physical-chemical factors, especially nutrients. Samples were collected according to the AQEM method. At all the sites, 20 taxa were recorded of which Turbellaria, Gastropoda, Bivalvia, Oligochaeta, Hirudinea, Crustacea, Ephemeroptera, Odonata, Plecoptera, Heteroptera, Trichoptera, Coleoptera and Diptera were included in the present study. Water temperature mostly affected the composition of benthic macroinvertebrates to which it was inversely proportional. Nutrient enrichment, i.e., higher concentrations of ammonium, nitrates, nitrites, total nitrogen, orthophosphates and total phosphorus mostly affected Ephemeroptera, Plecoptera, Trichoptera and Diptera, by decreasing their diversity.

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The caddisfly species Cyrnus crenaticornis (Kolenati, 1859) was recorded for the first time in Croatia in the Odra River during August 2015. The record refers to a larval stage which was determined according to morphological characteristics and supported by DNA barcoding.

The subfamily Drusinae (Trichoptera, Limnephilidae) is represented in Croatia with eight (8) species, including Ecclisopteryx asterix Malicky, 1979 recorded for the first time in Croatian fauna. The species was collected on two occasions: March 10th 2015 and March 6th 2021 in the Šumi Spring, at the Ivanščica Mt. in Hrvatsko Zagorje (North Croatia). This new finding considerably extends the distribution of this species, previously considered a microendemic of the Alps. The distribution of the two species, Drusus schmidi Botosaneanu, 1960 and D. croaticus Marinković-Gospodnetić, 1971 has been also enlarged with new findings. Within this study, nine specimens of the aforementioned species have been DNA barcoded and sequences were entered into the BOLD database. The results of this paper contribute to the ecological and faunistic knowledge of caddisflies in Croatia, with an emphasis on the subfamily Drusinae.