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Water pollution is one of the most serious aquatic environmental problems worldwide. In China, recent agricultural and industrial development has resulted in rapid changes in aquatic ecosystems. Here, we reveal the effects of water pollution on the phylogenetic community structure of aquatic macrophytes in the Tiaoxi River, China.We placed a rectangular plot at 47 sites within the Tiaoxi River from the mouth of the river to 88.5 km upstream, in which we recorded species abundance and measured 22 physico‐chemical variables. Bayesian phylogeny using the rbcL and matK gene sequences was employed to quantify phylogenetic α‐ and β‐diversity, and test the phylogenetic signal in four growth forms: emergent, floating‐leaved, free‐floating, and submerged. Within communities, water contamination and phytoplankton abundance decreased species richness and phylogenetic diversity, which resulted in phylogenetic clustering; species within communities were more closely related to each other than expected. Between communities, differences in geographical distance and phytoplankton abundance resulted in phylogenetic dissimilarity among plots. Aquatic macrophytes showed phylogenetic signals in which related species responded more similarly to disturbance. Thus, the observed patterns could be explained by environmental filtering and suggested that water pollution by human activity has added more filters to the existing environmental filters that drive the species assembly of macrophyte communities. [ABSTRACT FROM AUTHOR]

Selecting sites for river restoration projects or performing ex post evaluation must be done in ecoregions with comparable biological integrity. Moreover, to evaluate the integrity of a river ecosystem that varies from the headwater to downstream regions, adjustments of the ecoregion according to the longitudinal change in biota must be made. We defined regions where biota are identical according to the direction of change along the stream path as “segment-based ecoregions.” We delineated segment-based ecoregions using fish fauna data for two ecoregions in Japan: the northeast Kyushu, and south Kyushu. The northeast Kyushu ecoregion was divided into three segment-based ecoregions, and south Kyushu ecoregion into five segment-based ecoregions. Classifying fish fauna within the same ecoregion enables classification by differences in the longitudinal change in the stream path rather than by differences in watersheds. Specific topographic regions such as the amphitheater areas of the south Kyushu ecoregion was classified as independent segment-based ecoregions. We further defined indicator fish species for each segment-based ecoregion. Indicator fish species reflected the fish fauna of each ecoregion in the midstream area, such as migratory Gobiidae of the south Kyushu ecoregion. Applying the segment-based ecoregion concept helps compare the biological integrity of fish fauna depending on a common environmental type between watersheds. [ABSTRACT FROM AUTHOR]

Throughout Japan, numerous restoration projects and efforts to conserve the river environment are underway. However, in spite of such efforts, effective measures to conserve the river ecosystem or post-evaluation of restoration projects remain insufficient due to a lack of environmental indicators. In many European countries and the United States, a number of biological indicators have been developed and adapted. However, it appears to be difficult to directly apply these indicators to Japan, because its biota is finely classified according to its many islands and peninsulas. The ultimate goal of this study is to comprehensively evaluate indicators of aquatic biodiversity from both physical and biological aspects. We divided the Kyushu region in Japan into several ecoregions as a preliminary step to establish an indicator. We delineated the ecoregions of the Kyushu region using the fish fauna data of 21 rivers within the Kyushu region. Presence-absence (0/1) data for each fish species were used to run a two-way indicator species analysis (TWINSPAN analysis). As a result, the Kyushu region was divided into four ecoregions (A: northwest Kyushu, B1: northeast Kyushu, B2: south Kyushu, and C: Amami-Oshima Island). Each ecoregion was characterized by the following fish species: (A) Cyprinidae, in particular Acheilognathinae, is abundant; (B1) Gobiidae is abundant, while Cyprinidae such as Tanakia limbata (not confirmed in B2) are also present; (B2) Gobiidae is abundant, while Rhingobius sp. DA and Rhingobius sp. CO (not confirmed in B1) are present. These results indicate that the fish fauna of the Kyushu region is finely delineated, and that an assessment standard for biological integrity should be established, based on differences in fish fauna. [ABSTRACT FROM AUTHOR]

Riverine floodplains play many important roles in river ecosystems. However, many floodplains have suffered degradation or loss of ecological function due to excessive river improvements or through changes in agricultural systems. As a result, many floodplain restoration projects are being conducted worldwide. One of the many methods being implemented to restore floodplain vegetation is flood water seed dispersal. In this technique, precisely estimating the effect of seed dispersal by flood water is important in order to achieve successful floodplain revegetation. Here, we focus our attention on sediment transport by flood water into the Azamenose Swamp, a restored floodplain. We attempt to estimate the function of seed deposition in the restored floodplain and explain how the seeds are deposited in the floodplain by flood water. The result suggests that the restored floodplain functions as a more appropriate deposition site for seeds than the riverbanks of the main river. It was also found that the distance from the inflow site and the weight of the sediment were related to seed deposition. [ABSTRACT FROM AUTHOR]