Numerical Simulation for Seasonal and Inter-Annual Change of Dissolved Oxygen in Lake Biwa, Japan

Abstract

The dynamics of dissolved oxygen in lake is a fundamental issue of comprehending the water environmental habitats of aquatic organisms. In recent years, the decrease in dissolved oxygen has been observed at the bottom of the northern part of Lake Biwa, Japan. In recent years, eutrophication and global warming caused the decrease in the dissolved oxygen in the deep layer. Under these circumstances, in order to preserve the ecosystem of Lake Biwa and to provide water resources, the environmental changes in Lake Biwa should be accurately grasped. In our present study, a water quality model considering the flow field from hydrodynamic model was developed in order to grasp the concentration of phytoplankton, zooplankton, nitrogen, phosphorus, dissolved oxygen and chemical oxygen demand in Lake Biwa. Numerical simulation was carried out for 3 years from 2007 to 2009. Comparisons of the simulations with the observations showed that the seasonal and interannual change of dissolved oxygen was well reproduced. The dissolved oxygen decreased during decomposing the organic matter by bacteria in the bottom layer with little oxygen supply from the atmosphere and the photosynthesis from the phytoplankton under the thermocline from spring to autumn. The simulation confirmed that in each year, the dissolved oxygen was supplied in all layers by the overturning in winter.

Assessing the impact of climate change on dissolved oxygen using a flow field ecosystem model that takes into account the anaerobic and aerobic environment of bottom sediments

“…The one-dimensional model employed for long-term analysis was constructed based on the three-dimensional water quality model of Lake Biwa as developed by Koue et al (2020). To facilitate a comprehensive examination of inorganic nutrient dynamics and dissolved oxygen consumption, inorganic nitrogen was segregated into state variables representing "ammonia-form nitrogen," "nitrite-form nitrogen," and "nitrate-form nitrogen."…”

Sentinel responses of Arctic freshwater systems to climate: linkages, evidence, and a roadmap for future research

“…Models are being developed to better understand oxygen dynamics and the linkages with climatic drivers (Couture et al 2015;Golosov et al 2012;Koue et al 2020). Because of logistical difficulties, what little aquatic biogeochemical data exist from remote areas of the Arctic comes mostly from midsummer sampling during the short, ice-free period.…”

Oxygen Depletion in Arctic Lakes: Circumpolar Trends, Biogeochemical Processes, and Implications of Climate Change

“…The deployment of instruments continuously measuring oxygen at high frequency has contributed to rapid progress regarding our understanding of annual oxygen dynamics in northern lakes (e.g., Bégin et al., 2021; Cortés & MacIntyre, 2020; Huang et al., 2021). Measures over multiple years are especially valuable for the identification of the linkages between climate and interannual variability in oxygen‐related processes (Bégin et al., 2021; Koue et al., 2020). As temperatures continue to increase with concomitant effects on the duration of winter limnological conditions and stratification regimes during summer, many questions remain unanswered regarding the rates and controls of under‐ice biogeochemical processes.…”