Bivalves represent one of the most important components of freshwater zoobenthos, and their shells provide a substrate for many organisms to create epibiotic communities of predominantly facultative nature. Thus far, information regarding colonization of Unio tumidus by microorganism assemblages has been almost absent. Moreover, data on the functioning of trophic networks created by epibionts are also unavailable. Therefore, the present study aimed to examine the assemblage of epibiotic microorganisms inhabiting live and dead bivalves with regard to the physicochemical properties of the habitat and determine whether stable isotope levels in primary producers and consumers colonizing bivalve shells exhibit significant seasonal variability. The substrate characteristic and physicochemical properties of water – primarily biogenic compounds and total organic carbon clearly modified the taxonomic composition of microorganisms and the function of the trophic network. This was reflected by the increased diversity of microorganisms (phycoflora, ciliates and rotifers) on live bivalves and the increase in their abundance on dead bivalves. The level of stable isotopes exhibited clear seasonal variability in individual components of the epibiotic trophic network, whereas food preferences of the potential consumers (protozoans and rotifers) depended significantly on the availability and abundance of food.

双壳类代表淡水游动底栖动物的最重要组成部分之一，它们的壳为许多生物提供了建立主要兼性性质的表生生物群落的基础。到目前为止，有关Unio tumidus定殖的信息几乎没有微生物聚集。此外，还没有关于表兽的营养网络功能的数据。因此，本研究旨在就栖息地的理化特性检查居住在活生生和死的双壳类动物中的表观生物微生物的组合，并确定在定居于双壳类动物壳的初级生产者和消费者中稳定的同位素水平是否表现出明显的季节性变化。水的底物特性和理化特性（主要是生物化合物和总有机碳）明显改变了微生物的分类学组成和营养网络的功能。这反映在微生物（藻类，活的双壳类动物的纤毛和轮虫）和死的双壳类动物的丰富度增加。稳定同位素的水平在表观生物营养网络的各个组成部分中表现出明显的季节性变化，而潜在消费者（原生动物和轮虫）的食物偏好在很大程度上取决于食物的可获得性和丰度。