Echosounding observations of coverage, height, PVI, and biomass of submerged macrophytes in the southern basin of Lake Biwa, Japan

Limnology ◽  
2007 ◽  
Vol 8 (2) ◽  
pp. 95-102 ◽  
Author(s):  
Hiroki Haga ◽  
Taisuke Ohtsuka ◽  
Masanari Matsuda ◽  
Minako Ashiya
Keyword(s):  
Lake Biwa ◽  
Submerged Macrophytes ◽  
Southern Basin

scholarly journals High-resolution flow simulation in Typhoon 21, 2018: massive loss of submerged macrophytes in Lake Biwa

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Nakada Satoshi ◽  
Haga Hiroki ◽  
Iwaki Maho ◽  
Mabuchi Kohji ◽  
Takamura Noriko
Keyword(s):  
High Resolution ◽  
Water Level ◽  
High Speed ◽  
Lake Biwa ◽  
Submerged Macrophytes ◽  
Circulation Model ◽  
Climate Change Scenarios ◽  
Fluid Force ◽  
Southern Basin ◽  
Massive Outflow

AbstractThe global activities of typhoons and hurricanes are gradually changing, and these storms can drastically affect lake ecosystems through the recession of submerged macrophytes that regulate the water quality in lakes. Using an echosounder, we captured the short-term, massive loss of submerged macrophytes attributed to the abnormal fluctuation of the water level induced by the approach of a catastrophic super typhoon in the southern basin of Lake Biwa, Japan. This paper investigates the physical processes responsible for the loss of vegetation using a high-resolution circulation model in Lake Biwa as a pilot study area. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The simulated results demonstrated that the fluid force driven by the gale-induced torrent uprooted submerged macrophytes during the typhoon approach and that this fluid force (rather than erosion) caused the outflow of vegetation. As a result, this uprooting attributed to the fluid force induced the massive loss of submerged macrophytes in a large area of the southern basin, which might have increased primary production and reduced the stock of fish such as bluegill in the lake. Our model can estimate the reduction in the macrophyte height within the range of − 1.3 to − 0.4 m, suggesting that fluid forces greater than the time-averaged value (1.24 × 10−4 N) were available. Flow speeds of approximately 0.8 m/s might be the critical value that induces the fluid force acting on the uprooting of the submerged macrophytes. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios.

scholarly journals High-Resolution Flow-Simulation in Typhoon 21, 2018: Massive Loss of Submerged Macrophytes in Lake Biwa

2020 ◽  
Author(s):  
Satoshi Nakada ◽  
Hiroki Haga ◽  
Maho Iwaki ◽  
Keisuke Hatano ◽  
Kohji Mabuchi ◽  
...  
Keyword(s):  
High Resolution ◽  
Water Level ◽  
Lake Biwa ◽  
Submerged Macrophytes ◽  
Circulation Model ◽  
Climate Change Scenarios ◽  
The South ◽  
Fluid Force ◽  
South Basin ◽  
Massive Outflow

Abstract Global activities of typhoons and hurricanes are gradually changing, and these storms can drastically affect lake ecosystems through the recession of submerged macrophytes that regulate the water quality in lakes. Using an echosounder, we captured the short-term, massive loss of submerged macrophytes attributed to the abnormal fluctuation of the water level induced by the approach of a catastrophic super typhoon in the south basin of Lake Biwa, Japan. This paper investigates the physical processes responsible for the loss of vegetation using a high-resolution circulation model in Lake Biwa as a pilot study area. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The simulated results demonstrate that the fluid force driven by the gale-induced torrent uprooted submerged macrophytes during the typhoon approach and that this fluid force (rather than erosion) caused the outflow of vegetation. As a result, this uprooting attributed to the fluid force induced the massive loss of submerged macrophytes in a large area of the south basin, which might have increased primary production and reduced the stock of fish such as bluegill in the lake. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios. (227 words)

scholarly journals The phytoplankton of the southern basin of Lake Biwa-ko

1960 ◽  
Vol 21 (3-4) ◽  
pp. 315-326
Author(s):  
Hisanao YAMAGUTI
Keyword(s):  
Lake Biwa ◽  
Southern Basin
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