Oribatid mites fauna and communities structure in halophilous habitats from the Danube Delta biosphere reserve

Abstract

The halophilous habitats, commonly found in the Danube Delta Biosphere Reserve, are restrictive habitats for most edaphic microarthropods; soil with high salt content, excess moisture and deficient aeration are the main limiting environmental factors. The present study aims to investigate, both from qualitative and quantitative points of view, the oribatid mite communities in these habitats of DDBR, less approached in previous ecological research. Following the field research, representative sampling sites were selected, located in the western DDBR, north of the Razim-Sinoe lagoon complex, between Murighiol and Enisala. In terms of fauna, the small number of taxa was noticed (14 species, belonging to 12 genera and 9 families); poronotic oribatid mites are dominant both as number of species and individuals. Humerobates rostrolamellatus Grandjean, 1936, and also the genus Humerobates Sellnick, 1928 and the family Humerobatidae Grandjean, 1971 are recorded now for the first time in the Romanian fauna. Oribatid communities are simply structured, with a small number of species and low specific diversity, indicating a poor stability. In most of the investigated sites Oribatula (Zygoribatula) undulata Berlese, 1916 is the over-dominant species, holding 46-94% of all individuals. In addition, the frequency and relative abundance of the immature stages highlights the full adaptation of this species and its bio-indicator quality in relation to saline soils.