engleski

Spatial distribution of phytoplankton along a Danube floodplain system (Kopački Rit Nature Park)

River-floodplain systems are characterized by a high level of habitat heterogeneity where the hydrological connection with the river has been recognized as the most important environmental parameter. The aim of the present research is to analyze phytoplankton spatial distribution in the different types of aquatic habitats (eupotamal, parapotamal and paleopotamal) in Kopački Rit Nature Park in relation to the hydrological connection with the river (Danube). The study included five floodplain habitats with their different location in the lateral direction: Danube - Channel Hulovo - Lake Kopačko - Channel Čonakut - Lake Sakadaš. Phytoplankton biomass was calculated from the number and volume of phytoplankton individuals and expressed as mg/L fresh mass. During the hydrological connectivity diatoms comprised the largest contribution to the total phytoplankton biomass in all studied sites. According to the redundancy analysis, the development of diatoms is associated with higher water depth, transparency and concentration of nutrients. Relative biomass of diatoms decreased with the distance of the floodplain sites from the river. The highest contribution of diatoms to the total biomass was found in the Danube (up to 96.6%) and Channel Hulovo (up to 82.9%), while in the other sites (Lake Kopačko, Channel Čonakut and Lake Sakadaš) their contribution was up to 51.8%. Besides different diatom species, other groups such as cryptophytes and colonial phytomonads which were well represented during the flood period appeared to indicate altered conditions in the floodplain driven by flooding. During the isolation period, different species of Cyanobacteria were dominant followed by chlorococcal green algae. In that time, high values of total phytoplankton biomass in the floodplain sites were found (up to 185.5 mg/L), with high contribution of Cyanobacterial species (up to 92.9%). In the Danube, diatoms remained dominant species exhibiting a different pattern of species succession. According to the redundancy analysis, the development of phytoplankton during the hydrological isolation was associated with a higher water temperature, lower water depth and transparency. Altogether, the location of the floodplain sites in relation to the river and hydrological connectivity between the river and its floodplain significantly influenced the phytoplankton community structure and the overall ecological condition of floodplain microlocalities.

heterogeneity; flood pulse; biodiversity; algae; floodplain

nije evidentirano