4:30 PM - 4:45 PM
[ACG38-10] An integrated land-ocean-benthic and pelagic ecosystem model for assessing terrestrial impacts on the Shiraho fringing reef, Ishigaki Island
Keywords:coral reef, integrated land-ocean-benthic and pelagic ecosystem model, numerical simulation, terrestrial impacts
Terrestrial loads, such as nutrients and sediment runoff, may have negative impacts on coral reef ecosystems (e.g., Fabricius, 2005). However, it is not well known how the terrestrial load spreads into coral reef areas and affects coral reef ecosystems because water quality parameters, such as nutrients, are invisible and highly variable in space and time.
In this study, we developed an integrated land-ocean-benthic and pelagic ecosystem model for the Shiraho fringing reef area in Ishigaki Island to understand the actual situation of dispersion of terrestrial load into the area and to assess the impact of terrestrial loads on the coral reef ecosystem. The details of the model system are as follows. First, to estimate the terrestrial loads, we used the Soil and Water Assessment Tool Plus (SWAT+) watershed model to calculate the freshwater, red soil, and nutrient runoff from the Todoroki River that flows into the Shiraho reef. A coupling framework of the ocean model ROMS and the wave model SWAN based on the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System (Warner et al., 2010) was used to investigate the dispersion of terrestrial loads around the reef area. The ocean model of the finest resolution reached a 50 m mesh size by downscaling from global and regional ocean analysis/reanalysis products by a multi-nesting approach. The model successfully reproduced the spatiotemporal patterns of wave, flow, and other physical environments in the Shiraho reef area with high resolution and accuracy. Furthermore, the land-ocean model is coupled with the newly developed pelagic low-trophic ecosystem model and benthic ecosystem model, such as the coral polyp model (Nakamura et al., 2013; 2018), seagrass model, macroalgae model, and sediment model. The model successfully reproduced spatiotemporal patterns of nutrients, turbidity, and other water quality parameters. Therefore, the integrated model is an useful tool to assess terrestrial impacts on coral reef ecosystems.
In this study, we developed an integrated land-ocean-benthic and pelagic ecosystem model for the Shiraho fringing reef area in Ishigaki Island to understand the actual situation of dispersion of terrestrial load into the area and to assess the impact of terrestrial loads on the coral reef ecosystem. The details of the model system are as follows. First, to estimate the terrestrial loads, we used the Soil and Water Assessment Tool Plus (SWAT+) watershed model to calculate the freshwater, red soil, and nutrient runoff from the Todoroki River that flows into the Shiraho reef. A coupling framework of the ocean model ROMS and the wave model SWAN based on the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System (Warner et al., 2010) was used to investigate the dispersion of terrestrial loads around the reef area. The ocean model of the finest resolution reached a 50 m mesh size by downscaling from global and regional ocean analysis/reanalysis products by a multi-nesting approach. The model successfully reproduced the spatiotemporal patterns of wave, flow, and other physical environments in the Shiraho reef area with high resolution and accuracy. Furthermore, the land-ocean model is coupled with the newly developed pelagic low-trophic ecosystem model and benthic ecosystem model, such as the coral polyp model (Nakamura et al., 2013; 2018), seagrass model, macroalgae model, and sediment model. The model successfully reproduced spatiotemporal patterns of nutrients, turbidity, and other water quality parameters. Therefore, the integrated model is an useful tool to assess terrestrial impacts on coral reef ecosystems.