engleski

The use of pupal exuviae in the research of chironomid (Chironomidae, Diptera) biodiversity in freshwater reservoirs

Reservoirs and anthropogenically altered water-bodies have features common to both lacustrine and riverine ecosystems, but morphology and water movement are what makes them distinct. Croatian reservoirs include water-bodies of variable physicochemical parameters, depth and different types of substrate, which influence the diversity and abundance of organisms living there. Moreover, there is a limited number of published data on macroinvertebrate diversity in this kind of water-bodies. One of the most important taxonomic groups of aquatic macroinvertebrates are Chironomidae, with essential role in the food webs, energy flow and ecosystem functioning. Due to their considerable diversity, high share in the biomass of total macrozoobenthos, they can also be used as water quality indicators in the bioassessment. We collected chironomid pupal exuviae from 29 reservoirs throughout Croatia, in both Dinaric and Pannonian ecoregion (16 and 13 respectably), during summer 2016 and spring and summer 2017, using the chironomid pupal exuviae technique (CPET). Pupal exuviae were collected using the exuvial net with 300 μm mesh, by skimming the water surface in the areas of the shore with the highest density of accumulated debris. After the separation of exuviae and preparation of the microscopic slides, we identify 116 species, i.e. 166 taxa in total. Identified taxa belonged to five subfamilies: Tanypodinae, Buchonomyiinae, Diamesinae, Orthocladiinae and Chironominae. Most frequent taxon, recorded in 13 reservoirs, was Procladius choreus, a specieswhich prefers stagnant and slow flowing, productive waters. Also frequently found taxa, recorded in more than one third of thereservoirs were: Ablabesmyia monilis/longistyla, Zavrelimyia(Paramerina) sp., Cricotopusspp., Dicrotendipes nervosus, Paratanytarsus bituberculatus, Tanytarsus brundini, Tanytarsus ejuncidusand Tanytarsus spp. A substantial biodiversity was established in the reservoirs Čakovec and Gusić Polje, with more than 30 chironomid taxa recorded. However, these reservoirs had only seven species in common, most likely since they are situated in different ecoregions. We found a higher taxonomic diversity in the water-bodies from the Dinaric ecoregion. The localities with the lowest diversity were: Popovac, Sabljaci, Jošava, Lake Bilje and Lake Sakadaš, with no more than five taxa recorded, all located in the Pannonian ecoregion, except Sabljaci. Although athropogenically altered water-bodies, reservoirs represent specific aquatic ecosystems with various microhabitats, which can support a development of very diverse chironomid communities, and as such, it is vital to include them in the ecological studies. CPET has proven to be a very useful tool in studying chironomids, their ecology, distribution or for bioassessment and monitoring purposes.

Chironomidae pupae, bioassessment, anthropogenic impact

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