Efekat višestrukih stresora na multitrofički biodiverzitet barskih ekosistema

Abstract

This study deals with the effects of multiple anthropogenic activities (i.e. stressors) on the richness and abundance of phytoplankton, macrophytes, zooplankton, benthic and epiphytic macroinvertebrates, and fishes, and their trophic groups. Multiple anthropogenic stressors were integrated in one measure by calculating anthropogenic stress index. The aim was to compare the responses of different pond communities to anthropogenic impact, disentangle the potential mechanisms responsible for variations in pond biodiversity (direct, water-chemistry mediated, and cascading effects), and to quantify pond net-community response to anthropogenic impact. In addition, the importance of pond natural variability on the variations of biodiversity of pond hydrobiocenoses was analysed. All communities were sampled in September 2016, from the 18 study sites distributed across the six permanent ponds that differ in origin, connectedness, the intensity of a river impact, and the level of pond coverage in surrounding area. The effects of anthropogenic stressors varied across the distinct pond communities, from negative effects on the richness and abundance of macrophytes and on the richness of epiphytic macroinvertebrates, via neutral effects on benthic macroinvertebrates, to positive effects on fish abundance through predominance of the invasive species. The natural pond variability affected the pond communities and water chemistry in the majority of cases and it is expected to alter the effects of anthropogenic stressors on pond communities. The underlying mechanisms of anthropogenic stressors clearly differed among different trophic levels. Direct effects were mainly detected witihin primary producers, while the consumers were mainly affected indirectly: the increase of nutrient concentrations in water affected abundance and richness of invertebrate trophic groups, while cascading effects were the most influential drivers of multitrophic diversity in the fish community. Despite the variable responses of different communities and their trophic groups, the total netcommunity effect of the anthropogenic stressors was negative.