engleski

Chironomid assemblages in artificial and heavily modified freshwater ecosystems

To implement the EU Water Framework Directive, all member states must develop national classification of good ecological status/potential and to synchronize it through an intercalibration exercise, what includes intercalibration for all Biological Quality Elements (BQE). Man-made or anthropogenically altered water-bodies are also included in the classification process since most water-bodies have been influenced by human activities in one way or another. They have various use and origin, and differ in hydromorphological characteristics and water quality what reflects in the diversity and abundance of present biota. Macrozoobenthos represents a BQE used in the monitoring and bioassessment procedures in suchlike and in natural aquatic ecosystems. Especially important are the representatives of the dipteran family Chironomidae, often representing more than 50% of the invertebrates within the benthos. Quantitative and qualitative composition of chironomid larvaeassemblages can be very indicative of water quality state and changes, considering the presence of indicator taxa. For the purposes of assessment system development of water-bodies in the Pannonian ecoregion in Croatia, samples of macrozoobenthos were taken at two sites in 15 lakes/reservoirs bigger than 0.5 km2, during summer 2016. At each sampling site, a total of ten samples was collected using a benthos hand net (25 cm × 25 cm ; 500 μm). Chironomid larvae made from approx. 1% to over 90% of the macroinvertebrate assemblages. We identified 66 chironomid taxa distributed into five subfamilies: Tanypodinae, Diamesinae, Prodiamesinae, Orthocladiinae and Chironominae. Least abundant and diverse were Diamesinae and Prodiamesinae including one and two taxa, respectively, recorded at three locations. Chironominae larvae were dominant at all localities, except in lake Biljsko where the larvae of subfamily Orthocladiinae were the most abundant and in lake Novo Čiče, where we found the dominance of Tanypodinae larvae. Most abundant, in total, were representatives of Cladotanytarsusspp. (Tanytarsini), often found in shallow waters of reservoirs and lakes. Most abundant Chironomini were Glyptotendipes pallensagg. and Polypedilum nubeculosum ; Orthocladiinae: Cricotopus intersectusand Cricotopusgr. sylvestris, and Tanypodinae Ablabesmyia monilisagg. The indication that microhabitat conditions (e.g. substrate type, available oxygen, nutrient input, organic matter) at the research sites, can significantly influence chironomid assemblages’ structure, can be useful in creating a monitoring system. Implementation of Chironomidae larvae assemblage structure in whole, can help in improving the use of BQE in the water quality assessment.

macrozoobenthos, intercalibration, Chironomidae, artificial water-bodies

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