engleski

Chironomid community response to climate driven changes in a tufa barrier in Plitvice Lakes National Park (Croatia)

Chironomids are the most diverse and usually most abundant macroinvertebrates in freshwater ecosystems. Plitvice Lakes National Park is located in the Dinaric Western Balkan Ecoregion of Croatia and it consists of 16 oligotrophic, dimictic and fluvial lakes divided by tufa barriers. The goal of this study is to evaluate effects of climate change on the chironomid composition of tufa barrier Kozjak- Milanovac. The study was conducted in Plitvice Lakes NP due to minimal anthropogenic impact on the system. Adult chironomids were collected monthly from 2007 to 2020 using emergence traps. Traps were pyramid- shaped with a 45x45 cm base and 50 cm height, with 1 mm mesh walls A collection container was placed on top of each trap, filled with a 2 % formaldehyde solution. The larvae were free to enter and exit the base of the trap. Water temperature was recorded 2 times a day with data loggers. Current velocity was measured monthly during collection of the animals. Discharge values were provided by Croatian Meteorological and Hydrological Service and data on organic material by Plitvice Lakes NP. In 14 years more than 13, 000 adults were collected belonging to more than 80 taxa. In this time span, water temperature, velocity, discharge and amount of organic material increased, while chironomid abundance and number of species did not change significantly. On the other hand, community structure changed. Specifically, decreasing abundance of active filter feeders and detritivores like Polypedilum scalaenum and Tanytarsus signatus and increasing abundance of rheophilic passive filter feeders like Rheotanytarsus reissi and R. curtistylus was observed. Overall abundance of predators decreased but abundance of Rheopelopia maculipennis, a predatory species that is usually found among tubes of Rheotanytarsus genus, increased in these new conditions characterized by increase in frequency and strength of spates. Number of species and abundance did not indicate any change over the years however community structure did, directing us towards high-level taxonomy and its impact on fine resolution of community response.

Chironomidae, climate change, water temperature, discharge, long-term study

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