Meiofauna constitute a considerable portion of invertebrate drift among moss-rich patches within a karst hydrosystem

Checklist of aquatic Diptera (Insecta) of Plitvice Lakes National Park, Croatia, a UNESCO world heritage site

Studies on aquatic Diptera in the Plitvice Lakes National Park (Croatia) conducted in the last 50 years have produced 157 species and 7 taxa of aquatic Diptera placed in 13 families. Samples were collected at 25 sampling sites representing the four main types of karst aquatic habitats: spring, stream, tufa barriers and lakes. All records of all the aquatic families of Diptera in Plitvice Lakes NP are summarized, including previously unpublished data. Twelve species new for Plitvice Lakes NP are recorded for the first time, belonging to the families: Chironomidae – Labrundinialongipalpis (Goetghebuer, 1921), Nilothaumabrayi (Goetghebuer, 1921), Potthastialongimanus Kieffer, 1922, Polypedilum (Polypedilum) nubeculosum (Meigen, 1804), Tanytarsusbrundini Lindeberg, 1963; Dixidae – Dixellaautumnalis (Meigen, 1838); Scathophagidae – Acanthocnemalatipennis Becker, 1894 and Stratiomyidae – Oxycerapardalina Meigen, 1822, Oxyceralimbata Loew, 1862, Oxyceraturcica Ustuner & Hasbenli, 2004, Nemoteluspantherinus (Linnaeus, 1758), Oplodonthaviridula (Fabricius, 1775). The most species-rich family was the Chironomidae with 62 species (and an additional seven taxa), followed by the Empididae with 22 species and Limoniidae with 19 species. The highest number of species was recorded in springs. The relatively low number of species in certain families and the complete absence of some aquatic families shows that further research into the aquatic Diptera in Plitvice Lakes NP is needed.

The genus Dixa (Diptera, Dixidae) in Croatian lotic habitats, with a checklist of species and relationships with the fauna of neighbouring countries

Invertebrate surveys in Croatia conducted between 2005 and 2018 included 39 sampling sites yielding bycatch samples of Dixidae (Diptera). All records of this family from the territory of Croatia are summarized, including previously unpublished data. Collections contained six species of Dixa Meigen - D. dilatata Strobl, D. maculata Meigen, D. nebulosa Meigen, D. nubilipennis Curtis, D. puberula Loew, and D. submaculata Edwards, with Dixa dilatata reported from Croatia for the first time. Information relating to the ecoregions in which species were found and specific species traits are provided. Compared to neighbouring countries, the Croatian species assemblage is most similar to the fauna of Italy and least similar to that of Serbia and Montenegro.

Benthos-drift relationships as proxies for the detection of the most suitable bioindicator taxa in flowing waters - a pilot-study within a Mediterranean karst river

Mediterranean karst aquifers are sensitive systems vulnerable to contamination, exhibiting high rates of diversity and endemicity. In the present pilot-study, we aimed to detect the most suitable bioindicators of contaminant accumulation and mobilization within a Mediterranean karst river (Krka River, Croatia), whose lowermost sections belong to a designated protection area (national park). To meet our goal, we sampled water, drift and benthos (macroinvertebrates and periphytic microfauna) at the two Krka River sites, located upstream and downstream from town Knin and its urban influences. We compared: 1) environmental conditions (water physico-chemical parameters, trace- and macro-element concentrations); 2) abundance and diversity of periphyton and macroinvertebrate taxa constituting benthos; and 3) macroinvertebrate benthos-drift relationships between the two sites. Despite higher values of all measured physico-chemical parameters, and most trace- and macro-element concentrations at the urban-influenced site, the concentrations of contamination indicators (i.e., COD, nutrients, metals) at both sites were generally low. This is likely a result of specific "self-purification ability" of the Krka River, mediated by relatively high contaminant retention potential of the underlying tufa (i.e., calcareous) and/or macrophyte substrates. Between-site differences in water quality further affected the spatial variation of macrozoobenthos, drift, and periphytic microfauna. We suggest that increased COD and orthophosphate concentration, and macrophyte presence at the urban-influenced site, supported higher densities and diversity of benthic organisms dominated by eurivalent (i.e., contamination-tolerant) taxa. The most numerous macroinvertebrate taxa in benthos were amphipod Gammarus balcanicus and the representatives of the endemic Dinaric karst taxa - gastropods Emmericia patula and Radomaniola curta germari, and another amphipod Echinogammarus acarinatus. Although we expected to observe significantly increased drift at the urban-influenced site due to the degraded environmental conditions, it was not observed. The observed benthos-drift patterns suggest that freshwater amphipods (i.e., gammarids), which were found most numerous in drift, could be considered as the most suitable bioindicators of a contaminant (i.e., metal) accumulation and mobilization within karst aquifers comparable to Krka River.