Pendant temperature data logger

The following physical and chemical properties of the water were measured at each sampling site: water temperature and oxygen saturation (using a WTW Oxi 330/SET oximeter, Wissenschaftlich-Technische Werkstätten GmbH, Weilheim, Germany)), pH (using a WTW pH 340i, Wissenschaftlich-Technische Werkstätten GmbH, Weilheim, Germany), conductivity (using a WTW Cond 340i, Wissenschaftlich-Technische Werkstätten GmbH, Weilheim, Germany) and alkalinity (through titration with 0.1 M HCl). Daily average discharge values were provided by the Croatian Meteorological and Hydrological Service. The data on ammonia, orthophosphate and nitrogen were provided by the Plitvice Lakes National Park Public Institution. The current velocity and water temperature were measured at each microhabitat, where emergence traps were placed using a current velocity meter (a P-670-M series, Dostmann electronic, Wertheim, Germany)and a HOBO Pendant Temperature Data Logger (#Part UA-001-XX, Bourne, MA, USA), respectively. Depth was measured using a hand meter on a metal stick.

Dipteran individuals were collected on a monthly basis over a 13-year period from March 2007 to December 2019 (154 months) using six pyramid-type emergence traps at each site (154 months × 3 sites × 6 traps = 2772 samples). Each trap was a four-sided pyramid with a base of 45 × 45 cm and a height of 50 cm, covered with 1 mm mesh netting. Emergence traps were fastened to the streambed, with an unnetted gap of approximately 4 cm proximal to the streambed enabling the free movement of larvae both into and out of the sampling area. On top of each emergence trap was a collecting container filled with a preservative (2% formaldehyde with detergent as a surface-tension-reducing agent [26 (link)]). Traps were positioned in different representative microhabitats at each site, although the microhabitat structure is very dynamic and changeable over time (Table 1). After sampling, all specimens were counted and preserved in 80% ethanol. Taxonomic identification to the family level was based on [27 ,28 ].
Daily mean discharge data was obtained from the Croatian Meteorological and Hydrological Service from their three gauging stations located near the three sampling sites in the PLNP. Water temperature data were measured daily with the HOBO Pendant temperature data logger (#Part UA-001-XX, Bourne, MA, USA).