engleski

Medium-term alteration of rotifers assemblage in the flow-through system (Papuk Nature Park, NE Croatia)

Diverse but moderate macrophytes coverage supports species and habitat diversity, likewise maintain sustainable ecosystem heterogeneity which is particularly important in protected karst areas. Results of our previous study confirmed that inshore and macrophytes covered zone enable development of plankton community and in interaction with biotic relationships governed zooplankton assemblage in the flow-through system. Sustention or reestablishment of submerged macrophytes stands is overall accepted method in lake restoration. Contrary, overwhelming of macrophytes coverage indicating on ecosystem decay and requires improving treatment. Rotifers and crustacean assemblage, macrophytes coverage and environmental conditions were assessed in flow-through system within the medium-term scale in two artificial reservoirs. By comparison of results recorded during the summer 2008 and 2014 years we established few significant alterations: (i) increase of macrophyte coverage from 50  60% up to 98% with prevalence of uniform species composition of Hippuris vulgaris and Potamogeton natans ; (ii) hypoxia and reduction processes in sediment due to the macrophytes and leaf litter degradation from the surrounding deciduous forest ; (iii) decrease of rotifers and total diversity ; (iv) rotifers and crustacean spatial distribution were remarkably changed considering ratio between vegetated and nonvegetated habitats. Results of our study point out that even on medium-term scale rotifers assemblage may confirm ecosystem major changes. Moreover, we suggested that excessive macrophytes coverage requests simultaneous analyses of water and sediment as well as applying the most suitable method in the lake restoration.

karst; zooplankton; macrophytes

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