Lateral connectivity of a fragmented large river system: Assessment on a macroscale by dragonfly surveys (Insecta: Odonata)

1. The ecological status of floodplain areas along the Austrian section of the Danube was assessed by an approach based on dragonfly surveys. Although this river section contains a relatively high portion of the river-type-specific alluvial floodplain areas, most of them are influenced by river regulation and damming. 2. A key element of the assessment procedure, which is oriented towards the new EC Water Framework Directive, is the Odonate Habitat Index. 3. Classification of ecological status is based on the comparison between the status quo and reference conditions derived from a historical situation minimally influenced by human activities. 4. Data from 408 sites from 14 investigation areas were used. Ten of the 14 areas were ranked in class II ('good ecological status') within the five-tiered system, which is the level of ecological status targeted in the directive. One area corresponds to the reference condition (class I, 'high ecological status'), and three areas do not meet the quality objective (class III, 'moderate ecological status'). A total of 49 species were found along the whole section, which represents 82% of the river-type-specific reference list. Copyright Π2003 John Wiley & Sons, Ltd.