Author(s): Hikari Matsuda; Yui Shinozaki; Naoki Shirakawa
Linked Author(s):
Keywords: Environmental flow; Disturbance; Algae; Biomass; Global model
Abstract: This study is one of the first attempts to assess global environmental flow requirements (EFR), taking into account the effect of disturbance. Shinozaki et al. (2018) proposed the global fluvial biomass model to estimate EFR based on the primary productivity and aquatic plant biomass. Though, like other global models, the model output is a monthly basis and does not consider extreme flow events or disturbance. However, disturbance such as floods plays a critical role in maintaining the functions and diversity of river ecosystems. Therefore, we improved the model by considering disturbance as an increase in shear stress that causes loss of plant biomass. In this model, daily river flow and the river gradient determine the timing and frequency of disturbance. According to Biggs (1996), where the river gradient is steeper than 0.5%, five times the preceding 14 days mean flow was set as the disturbance threshold and 2.5 times in other areas, which causes a 100% loss of plant biomass. The total global amount of aquatic plant biomass was estimated to be 1.06×108t. For verifying the model results, we compared calculated biomass with observed values in 15 rivers around the world. We confirmed that the results followed the trend of seasonal fluctuations, and 70% of calculated values fell within the range of the observation sites.
Year: 2020