The submerged macrophytes in shallow eutrophic lakes can affect nutrient cycling, sediment–water interactions, water column irradiance, and phytoplankton blooms (Weisner et al. With model results predicting future warming of the tropical sea surface, the Intergovernmental Panel on Climate Change (IPCC 2007) reported that tropical cyclones will become more intense, leading to more violent winds and rainfall.Īquatic plants, particularly submerged macrophytes, play an important role in aquatic environments by positively interacting with the water quality and ecosystems of lakes. Terrestrial loadings in periods of high rainfall could enhance dissolved color, reduce irradiance, increase water turnover rates that suppress blooms, and markedly alter the ecosystems in lakes located in regions where oceanic cycles and their teleconnections result in decadal variation in rainfall (Havens et al. ( 2016a) reported the case of Lake Okeechobee and found that three hurricanes significantly reduced the coverage of submerged aquatic vegetation to one-tenth and affected water quality and plankton dynamics in open water zones. Many lakes in these regions are within the strike zones of tropical storms, and they experience high interseasonal and interannual variations in rainfall and runoff (Havens et al. For example, hurricanes Katrina and Rita eroded the freshwater marshes of the Louisiana coastal wetlands in 2005 and caused significant uprooting (Howes et al., 2010). Moreover, tropical storms disturb the community structures of aquatic plants in tropical and temperate regions (Wang et al. The global activities of tropical storms (typhoons and hurricanes), which can drastically affect wetland and lake ecosystems, are gradually changing. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios. 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 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. 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. 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. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. 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. 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. The 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.
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