Abstract
The main objective of this study was to quantify the relationship between taxonomic and functional parameters of macroinvertebrate assemblages and reach/landscape attributes of agricultural catchment. We aimed to analyse the relation between landscape patchiness and land-water ecotone structure, and their influence on benthic fauna composition, biomass and functional organization. A variety of catchment characteristics: land use patterns, surface geology (e. g. type of soils), elevation, hydrology database were incorporated into a geographical information system (GIS) to evaluate anthropogenic impact on landscape properties. The scenarios of potential transfer of nitrogen load along the gradient of the river valley were elaborated. The assessment of nutrient export focused on identifying the most effective nutrient barriers across spatial scales. The analysis of landscape and reach units demonstrated significant, negative correlations between the rate of nutrient transfer to surface/groundwaters and (i) the length of riparian ecotones, (ii) river width, and (iii) the areas of wetland and forested patches in the catchment. The trophic base (primary producers; CPOM; FPOM) in the stream channel was analysed as a factor modifying the structural and functional organization of macrobenthos. Canopy cover, and the consequent amount of solar input reaching the stream bed, significantly influenced food-related variables: leaf input and algal biomass. The factor that significantly affected food availability, retention and transport of benthic paniculate organic matter (BPOM) and amount of chlorophyll a was stream discharge. Higher discharge contributed to low retention of BPOM. To obtain more information about environmental variability (56 variables) and macroinvertebrate functional organization, the entire data matrix was analysed using Principal Component Analysis. A significant correlation was shown in the case of shredder abundance (i) in the low-order station S1. (ii) high canopy cover complexity, and (iii) retention of benthic organic matter. Filtering collectors were significantly associated with the presence of suspended organic matter. Other faunal assemblages, highly related to stream hydraulics factors, were alternative gathering collectors/scrapers, much retained at fourth-order station S3. Stream discharge, depth and chlorophyll a significantly affected the presence of these organisms. This indicated the crucial role of habitat heterogeneity, which was attributable to local conditions (detrital inputs, hydraulics, morphological characteristics), and significantly influenced the trophic structure of biocommunities. In the regulated section of the river (S2) without overhanging vegetation, the abundance of scrapers was significantly correlated with open canopy. Domestic and agricultural impact, evidenced by high nutrient concentrations, significantly reduced species richness (stations S4/S4a). Macroinvertebrate communities were used to detect environmental stress in the river system. Assessment of water quality with biological indices directly revealed human-induced alterations (e. g. land use, lack of riparian vegetation, channelization).
Published Version
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