The use of bdelloids in reference to rotifer biocoenotic indices as an indicator of the ecological state of small field water bodies: The effect of macrophytes, shading and trophic state of water

Species identification of many rotifers is very difficult due to e.g. body contraction in the preserved material. In the case of bdelloids, it is even more problematic as they can only be determined when alive. Therefore, a necessity for developing a method of using the class Bdelloidea for environmental analyses arose, so I examined them as a whole group. This is an approach that reduces extensive, time-consuming and particularly difficult taxonomic identification of certain species. The occurrence of bdelloids against various rotifer community indices in a mosaic of habitats of 220 small water bodies in an agricultural landscape was subjected to both abiotic and biotic factors so as to measure the extent of their reaction and the possibility of their usage in the assessment of environmental conditions. Despite their preference for forest ponds, bdelloids were also a very common and abundant element of field aquatic ecosystems. Due to their specific sensitivity bdelloids serve as a valuable ecological indicator which can be used for environmental assessment of habitat quality in small water bodies in the agricultural landscape and also for monitoring appropriate conservation actions for ponds. Bdelloids are typically macrophyte-associated organisms, selectively choosing Phragmites stands, a transitional area between aquatic and terrestrial ecosystems. Their response to the environment was similar to the littoral fraction and rotifer diversity indices, which were found to be in opposition to the eutrophic community associated with the open water area in large-surfaced fish ponds. Moreover, the increase in bdelloids in ponds of low human impact supports their potential for the diagnosis of natural ponds of low transformation level. Their preference towards ponds with an increasing layer of nymphaeids and pleustophytes also supports their role in diagnosing good-quality waters as floating-leaved macrophytes are known to improve water quality. It is recommended that bdelloids as a group can be used for the determination of the level of heterogeneity (connected with macrophyte occurrence) and the level of shade (generated by macrophyte cover) as well as the water quality state of small water bodies.