engleski

Rotifer fauna of the flooded area of the nature park Kopački rit (Croatia) during treatment with Bacillus thuingiensis israelensis

Natural Park Kopački rit is flooded area of the rivers Drava and Danube. It is situated at the north-east part of Croatia and is one of the most preserved swamps in the Europe. During the high water-levels in Danube river water from the upper areas overflow lower area where many small ponds occur and retain water for the next 45 to 90 days. Mosquito larvae’ s which develop in these ponds each year are treated with the Bacillus thuingiensis israelensis (B.t.i.). We aimed to test if B.t.i. has any impact on zooplankton community in these ponds as well. Samples of zooplankton and benthos community were collected before and after treatment with B.t.i. by standard methods on four sites in April, May and June. All standard physical, chemical and bacteriological parameters were measured. Most numerous groups in zooplankton community were Rotifer fauna represented by 20 species, followed by three species of Cladocera while Copepoda were represented only by immature forms and developmental stages. Before treatment number of Rotifer individuals were small, less than 30 ind./L. It was probably resulting from competition for food with the mosquito larvae’ s and the short time of water presence in the ponds. During that short period microfiltrators Brachionus angularis, B. qudridentatus, Filinia longiseta, Kellicottia longispina, Keratella cochlearis and K. quadrata were dominant. After treatment with the B.t.i. in April the number of Rotifer individuals was smaller then before treatment. It was probably consequence of the successions which depended on water retention rather then effect of B.t.i. because it degrades very quickly. Numbers of Rotifer individuals increased again in May and June but as a result of the organic matter inflow dominant species were Keratella cochlearis and its form tecta and K. quadrata, as well as representatives of higher trophic levels.

flooded area; Danube River; Bacillus thuingiensis israelensis; Rotifer fauna

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