engleski

Seasonal dynamics of periphyton along urban streams in the city of Zagreb

Urban streams are characterised by altered hydromorphology, high fluctuations in water chemistry and energy flux, thus posing challenges for biota. In this study, we investigated periphyton along two urban streams (Bliznec, B and Veliki potok, VP) in Zagreb (Croatian capital) showing a strong gradient of hydromorphological degradation. Both streams were sampled near the source (exhibiting pristine conditions, located within the Medvednica Nature Park), in the middle reach (impaired by channelization and agricultural and urban influences), and in the lower reach (channelized and impaired by agriculture and dense population). Periphyton was sampled on 8 occasions in 2016 from stones, soft sediments and macrovegetation, accompanied by measurements of physicochemical parameters and chlorophyll a analyses. Both B and VP showed high fluctuations in discharge, with occasional drying of the lower reaches in summer. Nutrient concentration, conductivity, COD and chlorophyll a displayed a trend of increasing values from upper to lower sites, reflecting the influence of urbanization. The number of periphytic taxa and their abundance correlated positively with the increasing urbanization gradient, probably due to the increased food sources. Periphyton contained mainly ubiquitous taxa, with 55 phagotrophic protist and 10 micro-invertebrate taxa belonging to 11 higher taxonomic categories. Ciliates dominated both in diversity (44 taxa) and abundance (more than 90% share in mean abundance). Periphyton showed seasonal dynamics, with occasionally high similarity between two urban streams studied. This community exhibited the potential to withstand frequent disturbance and environmental variability in urban streams.

chlorophyll a ; phagotrophic protists

nije evidentirano