engleski

Chironomid community responses to environmental drivers in man-made lakes of the Dinaric karst

Reservoirs are man-made water bodies that are usually created by using a dam or lock to store water that can be used for the production of electric energy, irrigation or flood control. The family Chironomidae is widely distributed and often among the most abundant taxa in benthic macroinvertebrate communities of reservoirs, and they are frequently used in the ecological quality assessment of these habitats. Littoral macroinvertebrate samples were collected from May to October 2016/2017 in 21 reservoirs of the Dinaric region in Croatia. With regard to the surface area of the reservoir, from 2 to 6 sampling locations were chosen in analysed man-made lakes. A sampling site covered the length of 25 m lakeshore and a distance of 10 m towards the open water – or alternatively, to the point at which the water depth exceeded 1 m. At each sampling site, a total of ten samples was collected using a benthos hand net (25 cm × 25 cm ; 500 μm). In the littoral microhabitat type, the strata are defined as a combination of a depth class and a substrate category proportionate to their coverage in the sampling site. Four waterdepth classes were defined: 0–0.25 m, 0.25–0.5 m, 0.5–0.75 m and 0.75–1 m. A total of 490 samples were analysed. Totally 112 358 chironomid larvae were found, belonging to 5 subfamilies and 61 taxa. Bray-Curtis based non-metric multidimensional scaling analysis based on chironomid assemblages clearly separated reservoirs with a very short water retention time. These reservoirs were characterised with the presence of lotic faunal elements, and species such as Paratendipes albimanus and Micropsectra contracta were present only in these reservoirs. In general, species richness was found to decrease with higher values of pH and water temperature (p<0.05), which is in agreement with previous research. On the other hand, species richness was found to increase with higher values of variables associated with eutrophication (chl a, orthophosphate and nitrate concentrations ; p<0.05). When compared to lowland reservoirs with organogenic geology, the reservoirs from the Dinaric region are characterised by a low nutrient input. This means that relatively higher concentrations of these elements in the Dinaric karst region represent optimal conditions for most taxa of the chironomid assemblages. Even though benthic macroinvertebrates usually are good indicators of hydromorphological changes there were no significant patterns observed in chironomid larval substrate preference between natural and man-made substrates. There were no observed differences in chironomid assemblage composition regarding depth classes as well.

reservoir ecology ; Chironomidae

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