engleski

Effects of increased water level and salinity fluctuations on littoral macroinvertebrate assemblages in the shallow Vrana Lake in Dalmatia (Croatia)

The shallow Vrana Lake (max depth -3, 9 m a.s.l.) is the largest natural lake in Croatia by surface area. It is located in the Dinaric karst in close proximity to the Adriatic Sea to which it is directly connected by the Prosika canal, constructed in the 18th century. Climate change caused increased fluctuations of water level during the last two decades resulted in increased lake water salinity fluctuations from oligohaline (<1-4 ‰) to mesohaline levels during dry years (maximums: 2008 – 11, 3‰ ; 2012 – 18, 2‰) when seawater inflow increased through the Prosika canal and the karst ridge between the Lake and the sea. The aim of this work is to present the effects of increased water level and salinity fluctuations on the macroinvertebrate assemblages in the littoral zone of the Lake. Samples of benthic macroinvertebrates were collected using hand net at four sites along the southern coast of the Lake in the period 2011- 2018. All available physicochemical parameters and hydrological data were also collected and analyzed. The recorded values of water level and salinity in the study period were the lowest/highest extremes in more than 50 years of data records. Macroinvertebrate assemblages showed site-specific and pronounced changes, from brackish water taxa domination during the high salinity and recovery phases to the freshwater (oligohaline) phase. Suitability of different groups as indicators of increased salinity was examined for the purpose of adaptive water level management which should be implemented after the reconstruction of the Prosika canal with movable gate.

shallow lake ; salinity, water level, macroinvertebrate assemblages, climate change

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