engleski

Rotifer community composition along the increasing salinity gradient - a pilot-study in a brackish marsh (Palud, Croatia)

Palud is a natural depression in the southwest of the Istrian peninsula (N Adriatic Sea, Croatia), situated by the sea and transformed into a marsh by the inflow of water from the adjacent hills. At the beginning of the 20th century, the marsh was connected to the sea by an artificially dug channel to control mosquitoes (vectors of malaria). This led to the brackish conditions in the marsh. The objective of this pilot-study was to investigate the rotifer community composition in Palud Marsh during the summer of 2021. Zooplankton samples were collected at two-week intervals during July 2021 at the four sampling sites that extend along the Palud salinity gradient. Water physicochemical factors analysis showed a significant trend along the salinity gradient indicating a decrease in plankton productivity in July, likely caused by a decrease in Palud water depth due to runoff from the marsh to the sea. Only a very small number of taxa (6) were found in the plankton. Rotifers were represented by three taxa (Brachionus plicatilis, Encentrum sp., Lecane lunaris). Of all individuals recorded, 97.3% belonged to B. plicatilis, a cosmopolitan eurythermal species and a halobiont (i.e., it prefers saline shallow waters and lagoons). This pilot-study was the first step in assessing the ecological conditions of Palud Marsh. Further studies are necessary to develop effective conservation measures for this protected habitat, which was declared a special ornithological reserve in 2001.

Brachionus, halobiont, zooplankton, ecological conditions

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