10:15 AM - 10:30 AM
[AOS12-05] Using a high-resolution marine ecosystem model predicting the combined impacts of ocean acidification and deoxygenation
Keywords:ocean acidification, deoxygenation, mitigation measures, adaptation measures, ocean model, biogeochemical model
In recent years, the impact of climate change on marine ecosystems and target fishery species has been a concern worldwide. Calcifying organisms that form calcium carbonate shells and skeletons, such as shellfish, shrimps, crabs, and sea urchins, are also susceptible to ocean acidification, which, like global warming, is primarily caused by excessive anthropogenic CO2. Furthermore, recent studies have raised concerns about the effects on marine organisms of anoxia, which is the long-term decline in dissolved oxygen (DO) concentrations in seawater, and increases in water temperature associated with global warming are one of the causes of anoxia. Thus, there is a close relationship between global warming, ocean acidification, and anoxia (Fujii et al., 2021). However, the combined effects of these concurrent phenomena on marine organisms are complex, and their sensitivity to these effects varies greatly among species and growth stages, so the full picture remains unclear. The purpose of this study is to evaluate and predict the combined effects of ocean acidification and anoxia on calcifying organisms along the coast of Japan.
The ocean model CROCO (Jullien et al., 2019), developed based on the Regional Ocean Model (ROMS) and incorporating the marine ecosystem model PISCES (Aumont and Bopp, 2006), was used to reproduce and predict physical and biochemical processes in Miyako Bay, Iwate Prefecture, Japan. The model was driven by the initial and boundary values of physical and biochemical parameters to reproduce the present and predict future physical and biochemical processes. The horizontal resolution of the model is 1.5km. The initial and boundary values of the physical parameters are taken from the Future Ocean Prediction Dataset (FORP; Nishikawa et al., 2021), particularly the historical (2000-2001) results of MRI-CGCM3, a climate prediction model developed at the Meteorological Research Institute, and the high-level reference scenario (RCP8.5 scenario) for the end of this century (2099-2100). Values of pH and aragonite saturation (Ωarag), which are indicators of ocean acidification, were estimated using CO2SYS (Pierrot et al., 2006) based on the values of temperature, salinity, total alkalinity, and dissolved inorganic carbon obtained from the simulation.
The model reproduced the observed physical and biochemical parameters in a realistic manner (Figure 1). On the other hand, the model could not reproduce the observed rapid decrease in salinity and the associated decrease in Ωarag, leaving some problems to be solved. The results of the future predictions suggest a significant impact of global warming and ocean acidification. In particular, it is feared that the value of Ωarag would approach the level dangerous for calcifying organisms (Ωarag < 1.1 (Onitsuka et al., 2018)) throughout the year. On the other hand, DO concentrations were assessed not to reach dangerous levels for marine organisms (DO < about 61 μmol kg-1; e.g., Vaquer-Sunver and Duarte (2008)) now or in the future.
The results of this study suggest the necessity to take mitigation measures for significant reduction of anthropogenic CO2. This study was conducted in an oligotrophic sea area, and the same evaluation and prediction will be conducted in more eutrophic sea areas to further assess the universality of the results.
Acknowledgements: This study was supported by Study of Biological Effects of Acidification and Hypoxia (BEACH) of the Environment Research and Technology Development Fund Grant Number JPMEERF20202007 of the Environmental Restoration and Conservation Agency of Japan and the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935498 from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.
The ocean model CROCO (Jullien et al., 2019), developed based on the Regional Ocean Model (ROMS) and incorporating the marine ecosystem model PISCES (Aumont and Bopp, 2006), was used to reproduce and predict physical and biochemical processes in Miyako Bay, Iwate Prefecture, Japan. The model was driven by the initial and boundary values of physical and biochemical parameters to reproduce the present and predict future physical and biochemical processes. The horizontal resolution of the model is 1.5km. The initial and boundary values of the physical parameters are taken from the Future Ocean Prediction Dataset (FORP; Nishikawa et al., 2021), particularly the historical (2000-2001) results of MRI-CGCM3, a climate prediction model developed at the Meteorological Research Institute, and the high-level reference scenario (RCP8.5 scenario) for the end of this century (2099-2100). Values of pH and aragonite saturation (Ωarag), which are indicators of ocean acidification, were estimated using CO2SYS (Pierrot et al., 2006) based on the values of temperature, salinity, total alkalinity, and dissolved inorganic carbon obtained from the simulation.
The model reproduced the observed physical and biochemical parameters in a realistic manner (Figure 1). On the other hand, the model could not reproduce the observed rapid decrease in salinity and the associated decrease in Ωarag, leaving some problems to be solved. The results of the future predictions suggest a significant impact of global warming and ocean acidification. In particular, it is feared that the value of Ωarag would approach the level dangerous for calcifying organisms (Ωarag < 1.1 (Onitsuka et al., 2018)) throughout the year. On the other hand, DO concentrations were assessed not to reach dangerous levels for marine organisms (DO < about 61 μmol kg-1; e.g., Vaquer-Sunver and Duarte (2008)) now or in the future.
The results of this study suggest the necessity to take mitigation measures for significant reduction of anthropogenic CO2. This study was conducted in an oligotrophic sea area, and the same evaluation and prediction will be conducted in more eutrophic sea areas to further assess the universality of the results.
Acknowledgements: This study was supported by Study of Biological Effects of Acidification and Hypoxia (BEACH) of the Environment Research and Technology Development Fund Grant Number JPMEERF20202007 of the Environmental Restoration and Conservation Agency of Japan and the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935498 from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.