engleski

Hydrology driven changes in the rotifer trophic structure and implications for food web interactions

Rotifers display r-strategy life-histories and are adaptable to environmental disturbances.Although rotifers constitute a large proportion of zooplankton in river-floodplain systems, the influence of hydrology on their assemblage has been poorly studied. We postulated that rotifer assemblage and grazing activities were controlled by mechanisms associated with hydrological conditions. We conducted a 5-year study (Kopački Rit Nature Park, NE Croatia) to assess the influence of hydrology on (i) rotifer assemblage during different hydrological phases, (ii) the vertical distribution of rotifer abundance, functional feeding guilds and grazing intensity, and (iii) the main drivers affecting rotifer assemblage in the floodplain lake. The results indicated that (i) during isolation, longer residence time and high phytoplankton biomass microfilter-feeders (mIff) and macrofilter-feeders (mAff) grazing rates were similar while predators (Pr) were the most efficient consumers, (ii) during high flow pulses, high conductivity and variable water level governed rotifer grazing rates of mIff and mAff at a retion of 1:2, and a decline of Pr grazing activity and (iii) during the flood pulse, reduced phytoplankton biomasss still resulted in mAff and Pr domination of the community while mIff grazing activity remained at the same level. Under stable hydrological conditions algivorous species co-dominated with bacterivores and predators, suggesting an increased biodiversity and food web interactions. In contrast, throughout the inundation period algivorous species predominated. However, differences in rotifer assemblage between normal flow and flood pulses indicated the importance of hydrology in shaping rotifer trophic structure through modifying lower trophic levels and the availability of food sources.

grazing activity ; functional feeding guilds ; floodplain lake ; protected area

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