engleski

Revealing the secrets of the largest Pannonian Danube floodplain

Kopački Rit Nature Park, one of the Danube’s largest conserved floodplains in Europe, included on the list of Important Bird Areas and on the RAMSAR List of Wetlands of International Importance, is situated in the north-east of Croatia, between the Drava River and the Danube (1, 383 to 1, 410 rkm). This area is a part of the Pannonian biogeographic region and has a typical continental climate with wide annual fluctuations of air temperatures and precipitation distribution, as well as four distinctive seasons. The Danube, as the parent river, and its hydrologic regime has the prime influence on the floodplain ecosystem. The dominant wetland types are permanent freshwater marshes/pools, ponds, marshes, and swamps on organic soils, with emergent vegetation waterlogged during most of the growing season. In the last decade, we have been studying the influence of flow- and flood-pulse on different algal and invertebrate communities. Changes in the composition and abundance of plankton communities are being followed within a standard monthly monitoring, whiles the research of periphyton included several in situ experiments on both natural and artificial substrates. The dynamics and duration of the flooding influences the horizontal and vertical distribution of phytoplankton in general, as well as the appearance and blooms of cyanobacteria. Also, the long-term flooding can have a positive influence of the development of the metazooplankton. The conditions within the floodplain water bodies are favourable for the fast and substantial development of the periphytic communities. Autotrophic component (especially diatoms and green algae) provide food and suitable substrate for the invertebrates. We found very diverse invertebrate fauna, including several species of sponges and Bryozoa, which increase substrate heterogeneity and provide shelter for other invertebrates. Chironomidae larvae, Oligochaeta, Dreissena polymorpha and Nematoda were especially abundant. Periphytic communities – structure, composition, abundance ; can also significantly change during different phases of the floodplain’s hydrological connectivity to the Danube. The significant connection of periphyton to the higher trophic levels, such as fish, represents one of the important roles of this complex community in the floodplain water bodies.

Kopački Rit; flooding; periphyton; biodiversity

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