Distribution and microhabitats of freshwater mussels in waterbodies in the terrestrialized floodplains of a lowland river
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Even when anthropogenically altered, river floodplains continue to contribute to biodiversity. This study examined the distribution of freshwater mussels in relation to environmental factors in waterbodies in the terrestrialized floodplain of a lowland river. Mussels were captured, and environmental measurements were taken in November of 2013 and 2014 in quadrats established in three floodplain waterbodies (FWBs), which were isolated from the main river channel. Among the three FWBs, mussel abundance was highest in a shallow FWB (depth range 18–45 cm) that had intermediate conditions of mud depth and fine sediment rate. Mussel abundance showed a hump-shaped relationship with water depth (the peak 45–50 cm) and mud depth (the peak 8–12 cm). Mussel abundance was also negatively related to the abundance of benthic litter. Litter abundance was positively related to branch abundance and the presence of tree cover, and negatively related to the distance to tree cover, indicating that benthic litter was derived from riparian trees. Our results indicate that relatively shallow (≤ 50 cm) FWBs with moderately accumulated mud, which are not scoured even during flooding, appear to be suitable habitats for mussels. Moreover, it is possible that riparian trees negatively impact mussel distribution in FWBs. Possible short-term measures for improving mussel habitat in FWBs may include the elimination of riparian trees and benthic litter.
KeywordsFloodplain pond Backwater Unionid mussels Microhabitat Riparian litter
We thank our colleagues, H. Takaoka and T. Fujimori, and M. Kume from Gifu Keizai University for their assistance with fieldwork, M. Sueyoshi for his helpful comments about statistical analysis, and Editage (http://www.editage.jp) for English language editing. We also appreciate two anonymous reviewers for their constructive and helpful comments.
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