[A-CG45] Biogeochemical linkages between the surface ocean and atmosphere

[ACG45-P01] Development of a Sensitive Method for Determination of Oxygen Consumption Rate in Aquatic Environments

*Ito Masanori¹, Urumu Tsunogai¹, Fumiko Nakagawa¹, Takashi Sambuichi¹, Yuto Watanabe¹ (1.Nagoya University Graduate School of Environmental Studies)

Keywords:Oxygen isotopes, Community respiration

Molecular oxygen (O₂), which occupied about 20% of the atmosphere, is the most common oxidizing agent and is one of the important substances characterizing the earth's surface layer environment. Depletion of O₂ in water causes environmental problems such as deterioration of water quality and blue tide. Thus, we must clarify the dynamics of dissolved O₂, such as consumption rate, especially. Traditionally the oxygen consumption rate in water columns has been determined by measuring the change in O₂ concentration during incubation of a certain period. However, the sensitivity of this method is low sensitivity so it is difficult to apply to fields in general such as the open oceans where oxygen consumption is slow.
In this study, we developed a new method to quantify the oxygen consumption rate with high sensitivity, high accuracy, and convenience by using an oxygen stable isotope (¹⁷O) as a tracer. In this method, O₂ enriched in ¹⁷O is added to a water sample sealed in a glass container and can be quantified through the change in H₂¹⁷O (Δ¹⁷O – H₂O) that can be determined precisely by the progress of respiration (oxygen consumption) during a certain incubation period. We measured the oxygen consumption rates in Ise Bay by the new method and discussed control factors for the consumption rates.