Summary Degradation of floodplains continues with an increasing number of floodplain lakes disconnected from the fluvial dynamics of rivers. Limited understanding is available as to how historical geomorphic formation processes (i.e. geomorphic legacy) determine contemporary ecosystem structure and function. We tested the hypothesis that geomorphic legacy mediates morphometry and results in heterogeneity of macrophyte distributions in disconnected floodplain lakes. The distribution of macrophyte cover was examined in relation to environmental factors, including water nutrient level, morphometry of lakes and patch shelter level across and among three types of lakes along the Ishikari River, Japan. Artificial lakes (isolated by channelisation), natural oxbow lakes and marsh lakes have been disconnected for more than 40 years from natural flood pulses because of dyke construction. The presence of macrophytes (in 5 × 5 m areas) was predicted well by a combination of local water depth and bed slope. Lake average depth, higher values indicating lakes that are more deeply incised with a steeper‐sloped littoral zone, had the strongest and most negative influence on total macrophyte cover across lakes. Cover was least in artificial lakes because of greater average depth. Predicted area of macrophyte cover was significantly less than occupied by actual cover in artificial lakes compared with other lake types. Macrophyte cover in artificial lakes was particularly vulnerable to external factors such as waves and wind. This study underscored the significance of geomorphic legacy in explaining a large proportion of heterogeneity of total macrophyte cover in the study lakes. Artificial lakes did not have the macrophyte habitat quality of natural lakes. When lake morphometry needs to be altered, local conditions as well as patch‐scale properties should be carefully examined in the light of the geomorphic legacy left by dynamic river–floodplain interactions.
22Although both patch area and shape are key factors driving biodiversity in fragmented 23 terrestrial landscapes, researchers have had limited and mixed success in documenting 24 the effects of these two factors on aquatic ecosystems. Here we examined the effects of 25 lake area and shape on macrophyte species richness in a lowland floodplain by 26 considering the differences in lake types, i.e. marsh, oxbow and man-made lakes. We Also, marsh lakes had positive species-area relationships while man-made lakes had 35 negative relationships. Our results suggest the opposing shape complexity and 36 species-area relationships of these two contrasting lake types are the result of the 37 interactions between lake area and shape. These results indicate that different lake types 38 result in variations in their conservation value for preserving macrophyte diversity. We 39 suggest that small complex-shaped patches (especially oxbow lakes), which are often 40 given the lowest conservation priority in terrestrial ecosystems, cannot be disregarded 41 when conserving macrophyte biodiversity in aquatic ecosystems. 42Keywords: area-shape interaction, edge effect, floodplain lake, macrophyte assemblages,
18Increasing threats posed by overfishing and dams to wild migratory fish make understanding their 19 migration patterns essential. Telemetry is a useful technique for elucidating salmon behaviour, but the recovery 20 periods before fish can be safely released after the attachment of telemetry devices have not yet been 21 established. Reported recovery times vary widely, from 2 h to 13 d. We examined how anaesthesia and surgery 22 to attach external electromyogram (EMG) transmitters affected chum salmon (Oncorhynchus keta) recovery 23 based on three physiological parameters. Fish subjected to anaesthesia plus EMG transmitter attachment 24 (EMG group), anaesthesia only (AO group), and no handling (control) were placed in a swim tunnel. Critical 25 swimming speed (U crit ), oxygen consumption (MO 2 ), and muscle activity (EMG values) were assessed 0, 1, 6, 26 12, 24, and 30 h after treatment. The MO 2 in the EMG and AO groups was higher than in the control group 1 27 h after treatment, but the U crit and EMG values were not significantly different from the control group at any 28 other sampling time. We concluded that chum salmon had fully recovered their swimming ability by 1 h after 29 treatment and could be safely released into the natural environment. 30 31
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