engleski

Influence of nutrient addition on macrozoobenthos in tufa depositing system (Plitvice Lakes)

The freshwater ecosystem of the Plitvice Lakes National Park represents a unique cascading system of 16 lakes separated by tufa barriers. This study was conducted on the tufa barriers of the outlet of one of the upper lakes (Gradinsko jezero lake - GJ) and one of the lower lakes (Novakovića brod lake - NB) at two microlocations on each barrier: with and without macrovegetation. Experimental treatments included: control, N, P and N+P treatments. Replicated nutrient diffusing substrates (NDS) remained in the water for 6 weeks during each season in 2015. The NDS were colonised by 13 macrozoobenthic groups, with 83 taxa determined. The highest abundance was recorded for Diptera (mean 94.5 ind. dm-2) and Oligochaeta (mean 22.5 ind. dm-2). Statistically significant differences were found between barriers and microlocations with increased abundance and taxa numbers at GJ barrier compared to NB barrier and at microlocations without macrovegetation compared to microlocations with macrovegetation. Seasonal dynamics were observed with increased abundance and taxa numbers in spring and decreased abundance in winter. Statistically significant differences were observed between treatments with higher mean abundance for the P treatment and the N+P treatment compared to other treatments. The proportion of functional feeding groups of grazers and detritivore-collectors was increased in the above treatments. Following the distinct positive response of phytobenthos, macrozoobenthos weakly responded to the addition of nutrients. Spatial and temporal changes in the abundance of macrozoobenthos could be related to water velocity, phenology, tufa deposition processes and food availability.

tufa barriers, macrozoobenthos, nutrients

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