No abstract

The research of zooplankton diversity, abundance and trophic structure was conducted during the summer period in pelagial zone on the longitudinal profile of the Sutla River Backwater. Investigated site consists of two interconnected basins: transparent Upper Basin with submerged macrophytes and turbid Lower Basin without macrophytes in the littoral zone. In the Upper Basin, abundance and diversity of zooplankton in the pelagial was higher in comparison to the Lower Basin, with prevailing species of genus Keratella as microfilter-feeder, and genera of Polyartha and Trihocerca as macrofilter-feeder rotifers. On the contrary, in the Lower Basin, crustaceans dominated in abundance. Microfilter-feeder cladoceran (Bosmina longirostris) and larval and adult stages of macrofilter-feeder copepod (Macrocyclops albidus) prevailed in the Lower Basin. Fish predation pressure was more pronounced in the pelagial of the Upper Basin, indicated by low cladoceran abundance in the surface layer. Although the studied basins were interconnected, results indicate significant (Mann-Whitney U test, p < 0.05) differences in the zooplankton structure as a potential result of the macrophyte impact on environmental conditions and fish predation pressure.

Elucidation of food web interactions provides a better understanding of ecosystem functioning, indicates anthropogenic impacts which often cause alterations in environmental conditions and deterioration in feeding networks in terrestrial and aquatic ecosystems. The importance of microfauna and macroinvertebrates in the littoral zones of shallow waters has been poorly studied regarding their trophic interactions. This study compares invertebrate assemblage and food web interactions among epiphyton, zooplankton and benthic macroinvertebrates across structural heterogeneity in the littoral zone of three temperate shallow water bodies. Submerged and structurally-complex stands of Ceratophyllum demersum inhabited a higher abundance of cladocerans and supported a higher diversity and biomass of epiphytic protozoans and invertebrates than floating-leaved Nuphar lutea stands. Analysis of the ecosystem functioning illustrated the increased biomass of macroinvertebrate predators and a preference of predation over planktonic crustaceans in more complex macrophyte stands. Food webs displayed higher complexity and size with habitat heterogeneity, while epiphyton and zooplankton shared an important fraction in food resources among the invertebrate trophic network. Results of food web modelling indicated zooplankton and epiphyton as more vulnerable to invertebrate predation in the complex submerged macrophytes than in the floating-leaved macrophyte stands. Integrated approaches to community, ecosystem and food webs in explanation of complex trophic interactions in the littoral zones confirmed an increase in diversity and food-web functional complexity with structural heterogeneity of microhabitats. Razjašnjenje interakcija u hranidbenoj mreži omogućuje bolje razumijevanje funkcioniranja ekosustava te indikaciju antropogenih učinaka koji često uzrokuju promjene uvjeta okoliša i narušavanje hranidbene mreže kopnenih i vodenih ekosustava. Trofičke interakcije mikrofaune i makrozoobentosa slabo su proučavane u priobalnim (litoralnim) zonama plitkih vodenih tijela. Cilj ovog rada je usporediti interakcije beskralježnjaka i izvora hrane, uključujući epifiton, zooplankton i makrozoobentos u strukturno heterogenim litoralnim zonama triju plikih jezera umjerenog pojasa. U submerznim i strukturno složenim makrofitskim sastojinama vrste Ceratophyllum demersum NAT. CROAT. VOL. 26 No 2 145-166 ZAGREB DECEMBER 31, 2017146 Špoljar, M. et al.: Disentangling food webs interactions in the littoral of temperate shallow lakes rašljoticalci su razvili populacije velike brojnosti, a također je u njima zbilježena veća raznolikost i biomasa epifitskih protozoa i beskralježnjaka u usporedbi sa sastojinama plutajuće vrste Nuphar lutea. Analiza funkcioniranja ekosustava ukazivala je na to da je u heterogenim makrofitskim sastojinama povećana biomasa makrozoobentoskih predatora i izraženija je njihova predacija nad planktonskim rakovima. Hranidbene mreže bile su složenije u heterogenima staništima, a epifiton i zooplankton imali su važan udio u hranidbe...

-This study investigated the structure of the epiphytic metazoans on emerged macrophytes in the littoral zone of two oxbow lakes with different trophic levels. Differences in the diversity and density of the epiphytic metazoans were analyzed in relation to plant architecture (simple or complex stems), food resources (algae and detritus) and water characteristics (transparency and derived trophic state index). A significant negative correlation was found between detritus on plants as food resource, and diversity and density of epiphytic metazoans, indicating grazing of microphagous species. Rotifers dominated in diversity and density in the epiphyton on all habitats. Total density of metazoans, rotifers and copepods in epiphyton were significantly higher on Mentha in mesotrophic lake than on Iris in a eutrophic lake. We presume that macrophyte belt width and trophic state governed biotic interactions and consequently epiphytic assemblages more strongly than macrophyte architecture. However, a Mentha habitat showed a slightly higher density and diversity of epiphytic metazoans in relation to Iris at the same site, but these differences were not significant.

No abstract