Accurate environmental bioindication in floodplains in spite of an extreme flood event

The ecological reaction of species on environmental factors can differ both, temporally and geographically. Therefore, bioindicator systems must be shown to remain accurate at different places and points of time. Extreme events pose challenges for testing this robustness, which has not yet been explored systematically. The unique opportunity of the extreme flooding of the river Elbe in August 2002 was used for such a test. The bioindicator system for mean groundwater depth during the vegetation period and annual duration of inundation in floodplains studied here was developed with data collected in 1999. Data from 2003 were used to analyse the dependence of the bioindication results on the humidity of the study plots and taxonomic group (plants, molluscs and carabid beetles). For the duration of inundation, the accuracy of bioindication in 2003 was similar to that in 1999, except for the medium‐humid and dry plots using molluscs as indicators. For groundwater depth, the accuracy of bioindication in 2003 was similar to that of the reference year except in the dry plots with significantly lower accuracy for all species groups. With a few exceptions, the bioindicator system is shown to be robust and to remain accurate in spite of an extreme flood event. In conclusion, the relevance of extreme events for the robustness of bioindicator systems differs between the indicated parameters and taxonomic groups. The results stress the need to take into account the limits of the working range and the occurrence of extreme events, when testing and applying bioindicator systems. Copyright © 2009 John Wiley & Sons, Ltd.     

青岛沿海潮间带三个采集点软体动物种类组成及分布

对青岛沿海潮间带3个采集点软体动物进行了初步的调查,经整理鉴定,共获得标本51种,隶属于3纲、23科;对软体动物的生态分布进行了分析。     

Water mollusc communities and bioindication of lower salzach floodplain waters

The lower Salzach River lost its natural river dynamics as a result of channelization, which caused its bed to deepen, its groundwater table to be lowered, and its floodplains to gradually dry out. These changes of the floodplain have lead to a loss of natural biotopes with their biocoenoses. By using water mollusc communities as bioindicators these losses are detectable at a landscape level. A numerical analysis of a water mollusc survey in 1989 defined six water mollusc communities identifying six water-body types: three flowing (streams, ditches, and rivers) and three standing (young former meanders, large deep groundwater-influenced backwaters and small shallow groundwater-influenced backwaters) within the lower Salzach valley. These communities and water-body types are interpreted using results from water mollusc communities of other floodplain systems and by comparison with earlier water mollusc surveys in the lower Salzach valley. Then predictions are made on the future fate of the investigated floodplain water. Finally the investigated water bodies are evaluated for nature conservation in the face of plans to impound the lower Salzach River.     

HYDROLOGICAL GRADIENT AND SPECIES TRAITS EXPLAIN GASTROPOD DIVERSITY IN FLOODPLAIN GRASSLANDS

Floodplains are characterized by high spatial and temporal heterogeneity. Despite low active mobility, Central European floodplain gastropod communities show a high species diversity. They are supposed to have developed a large range of resistance and/or resilience strategies to survive in the highly variable and frequently disturbed floodplain habitats. Relating gastropod diversity and species traits to hydrological conditions, we tested how different groundwater and flood regimes affect gastropod diversity and identified the main species traits favouring their survival in highly dynamic floodplain grasslands. Species richness, species diversity and functional diversity peaked at intermediate flood disturbance and moisture levels. Harsher environmental conditions in either dryer or frequently flooded habitats restricted the gastropod communities to a few specialized species. Morphological and life‐history traits showed significant variations along the hydrological gradient. Shell character and mode of reproduction proved to be important functional determinants for gastropod community composition. Species with strongly calcified shells, which limit the risk of injuries in case of dislodgment, were more often found in flood prone sites. Uniparental reproduction dominated in the driest as well as in highly flood‐disturbed habitats, providing reproductive assurance where harsh environmental conditions may reduce the number of potential mates. Intermediate disturbance and moisture levels favoured local gastropod diversity whereas dryer or highly flood‐disturbed habitats sheltered specialized species. Therefore, the maintenance of areas with different disturbance and moisture levels is of major importance in favouring taxonomical and functional mollusc diversity across the whole floodplain. Copyright © 2011 John Wiley & Sons, Ltd.