engleski

Long-term variation in stream physico-chemical attributes within a low-order urban stream (Veliki potok, Zagreb, Croatia)

The interplay of environmental changes brought by the various climate change and urbanisation scenarios can severely alter physical, chemical and biological attributes of streams. Intense anthropogenic activities and/or high discharge events in urban zones often result in higher in-stream loads of phosphorous and nitrogen compounds. We gathered and compared a stream physicochemical data from three independent annual studies conducted during 1992, 1998/1999 and 2016 within a low-order urban stream (Veliki potok) located in the Medvednica Nature Park (Zagreb, Croatia). The data were collected monthly during the three study periods. The following physicochemical parameters were compared: water discharge (obtained from Croatian Meteorological and Hydrological Service), water temperature and oxygen concentration, COD (chemical oxygen demand, i.e., a proxy for dissolved organic matter in water), and in-stream concentrations of nitrites, nitrates and orhophosphates. The data revealed a pronounced seasonality of water temperature and oxygen concentration with maximal temperatures in summer and minimum in winter, and the opposite oxygen seasonal trend. Significant inter-annual differences were observed only for in-stream COD and nitrate concentrations. In 1998/1999, COD levels were in average up to twofold higher than in 1992 and 2016, whereas 2016 was observed as a year of peaking nitrate concentrations, which were in average eightfold higher than in 1992 and 1998/1999. None of the water chemistry parameters was found to be correlated to the water discharge. It might suggest an increasing anthropogenic influence (beyond the natural variability) on the long-term variations of the investigated stream attributes within the Medvednica Nature Park.

urban streams ; urban ecology ; temporal variability ; stream discharge

nije evidentirano