engleski

Stream food-web changes along multiple gradients of urban stress

With the aim to enhance our understanding of the structure and functioning of urban stream ecosystems, we investigated two low-order urban streams in Zagreb, Croatia. The headwater (reference) sites of each stream were located in the Nature Park, whereas middle and lower stream sites were aligned along a gradient of urban disturbance within the city center. We measured and analyzed: (i) key water quality parameters and 28 metal/metalloid concentrations ; (ii) composition of periphytic- and meio-fauna ; (iii) distribution of macrozoobenthos and particulate organic matter in benthos and drift ; and (iv) food-web structure of the streams. We found that the urbanization gradient, amounts of nutrients, dissolved organic matter and metals/metalloids in water altered the community structure across the study sites. In comparison to the headwater sites, the more urbanized sites had more abundant and diverse macrozoobenthic-, periphytic- and meio-fauna dominated by eurivalent taxa, but lacking the less tolerant species. Urbanized sites had higher macroinvertebrate drift density and diversity dominated by Amphipoda, Ephemeroptera and Diptera and reduced particulate organic matter in benthos and drift. Using carbon (δ13C) and nitrogen (δ15N) stable isotope analysis we also detected shifts in macroinvertebrate food sourcing, indicating that macrozoobenthic taxa change their feeding habits with increased urbanization. Our findings demonstrate the dynamic nature and sensitivity of low-order stream communities along the gradients of urban influence. These streams require comprehensive further research to enable more effective management strategies.

urban streams, periphyton, macrozoobenthos, meiofauna, stable isotopes, food webs

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