Recent Vertebrate and Invertebrate Burrows in Lowland and Mountain Fluvial Environments (SE Poland)

Abstract

Over geological time, fauna inhabiting alluvial environment developed numerous traces of life, called bioturbation structures. However, present literature rarely offers comprehensive and comparative analyses of recent bioturbation structures between different types of environments. In this paper, the distribution of recent animal life traces in two different fluvial environments (lowland and mountain watercourse) was examined. An analysis of a set of vertical cross-sections of river bank enabled to determine physical and environmental features of the burrows, as well as degree of bioturbation in individual sections. Most of the burrows were assigned to their tracemakers and compared between two studied reaches in relation to the geomorphic zones of a stream channel. A mesocosm was conducted using glass terraria filled with river bank sediment and specimens of Lumbricus terrestris. The experiment confirmed field observations on the ability of earthworms to migrate into deep sediment layers along plant roots. The impact of floods on fauna survival was assessed on the basis of observations of large floods in 2016, 2018 and 2019. The abundance, distribution and activity of fauna in the sediment are mainly controlled by the occurrence of high and low flows (droughts and floods), which was particularly visible in lowland river reach.