engleski

Hydra oligactis (Pallas, 1766) in submerged Myriophyllum spicatum L. stands in Lake Gornjogradsko in Osijek

The study on qualitative composition of invertebrates with special overview on the abundance of brown hydra, in association with submerged species of eurasian water milfoil was conducted in Lake Gornjogradsko in Osijek during spring 2007. Recorded physical and chemical water parameters (conductivity, pH, dissolved oxygen concentration and saturation) within M. spicatum stands corresponded with the sampling period and indicated eutrophication. The following groups of invertebrates were recorded: Ciliata, Cladocera, Copepoda, Chironomidae larvae and Nematoda. The relationship between the density of brown hydra and the size of macrophyte stems, macrophyte biomass, periphyton biomass and total biomass (macrophyte + periphyton biomass) was analyzed. The highest statistical correlation was found between the density of brown hydra and the size of macropyte stems: r=0.75, df=33, p<0.001. Smaller correlation was recorded between the density of brown hydra and total biomass (r=0.66, df=33, p<0.001). Between brown hydra density and macrophyte biomass statistically significant correlation (r=0.62, df=33, p<0.001) was also found. The lowest but still significant correlation was found between the density of brown hydra and the periphyton biomass (r=0.32, df=33, p=0.05). M. spicatum with its dissected leaves serve as a favourable microhabitat for hydras because it provides shelter against predators and at the same time periphyton as available food resource. The presented water body the Lake Gornjogradsko in Osijek being located in the city itself and easily approachable and favourable place for a “ natural classroom” where pupils and the students of the Faculty of Teacher Education can observe, investigate, study and teach science. Paying a visit to this Lake can serve as an ideal place for cross-curricular activities and a great possibility for future teachers and pupils to perform a joint creative work since they are together involved in preparation and performance of tuition in natural environment. The handouts on interaction between environmental parameters of the water body, plants and animal for different age groups, from preschool children to future teachers, have already been made, although new handouts are continuously under preparation by applying new methodological and scientific achievements.

Hydra oligactis; Myriophyllum spicatum; macrophyte-invertebrate correlation; educational methodology

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