engleski

Ecological valorisation of Gornjogradsko lake, Osijek, with a special emphasis on the functional role of brown hydra, Hydra oligactis (Pallas, 1776)

Based on the analysis of limnological parameters during the spring and summer of 2010, and calculated trophic state indices, eutrophy with a tendency to hypertrophy was found for the small artificial lake Gornjogradsko inOsijek. Eight taxonomic groups of invertebrates were determined: brown hydra (Hydra oligactis), chironomid larvae (Chironomidae), beetles larvae (Coleoptera), other insect larvae, cladocerans (Cladocera), copepods (Copepoda) and snail juveniles (Gastropoda). The most abundant representative during the sampling period was brown hydra. They accounted for 30% of total invertebrate fauna while nematodes and chironomid larvae accounted for 25%. Cladocerans represented 12%. These four taxa groups were eudominant and euconstant. A statistically important positive correlation was found between brown hydra and air temperature. Pearson coefficient of correlation between length of rigid hornwort and hydra abundance as well as hornwort biomass and epiphyton biomass indicated a positive correlation but was not statistically significant. Significant negative correlation was found between predatory brown hydra and its favoured prey - cladocerans.

ecological valorisation; eutrophication; invertebrate fauna; Hydra oligactis; Euroasian watermilfoil; Myriophyllum spicatum; Gornjogradsko Lake in Osijek

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