The use of flood debris in malacological research: a case study from the Loděnice, a stream in the Czech Republic

Abstract

Flood-debris samples provide mollusc assemblages that are commonly used for faunistic studies of river floodplains. But do the contents of flood debris actually correspond to floodplain mollusc assemblages of that particular water course? We collected 15 flood-debris samples along the stream Lodenice (Central Bohemia) and compared them with the mollusc fauna of the floodplain and adjacent slopes of the stream valley. We found that flood-debris assemblages did not match the floodplain mollusc fauna. The species composition of flood debris depended on the type of flood that created the flood debris (slow vs sudden) and on the geomorphological character of the stream valley. Such factors should be taken into consideration when evaluating flood-debris mollusc assemblages. Despite this, flood debris can help in detecting hidden living and rare species scattered in the landscape in small patches that are difficult to find. Over longer time scales, river flood debris can be used to assess landscape changes.