engleski

Effects of a large dam on the structure of macroinvertebrate assemblages in a karst river – case study of the hydropower plant Lešće

Macroinvertebrate community structure in the Gojačka Dobra River was studied two years after the construction of the hydroelectric dam Lešće. Results were compared with previous studies which determined community structure before and one year after the construction of the dam. Sampling was conducted in July 2012 at the station located 460 meters downstream of the hydropower dam Lešće. Altogether, 18 groups of macroinvertebrates were recorded. The community structure significantly differed between two types of studied microhabitats, rocky substrate and moss. Additionally, noticeable changes of macroinvertebrate assemblages structure were established in both microhabitats after two years. One month after the dam was closed, and again a year later, we have recorded a decrease in population densities of major macroinvertebrate groups, such as gammarids, snails, caddisflies, mayflies and beetles. After two years, the assemblages of these groups had recovered, as higher population densities were recorded. On the other hand, population densities of bivalves, stoneflies and oligochaetes remained low. Water fleas and copepods appeared only after the construction of the dam, as they represent the zooplankton from the newly formed reservoir. Higher densities of hydrozoans also appeared in 2012. Additionally, an invasive clam, Dreissena polymorpha, was recorded for the first time in 2012, on the rocky substrate. In conclusion, the results of this study indicate that the construction of hydroelectric power plant Lešće caused significant changes in the structure of macroinvertebrate assemblages in the Gojačka Dobra River.

macroinvertebrates assemblages, dam impact, Dinaric karst, Dobra River, Croatia

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