AUTHOR=Endo Masanori , Zhao Yue , Nakamura Wataru , Sasaki Jun TITLE=A practical pCO2 estimation and carbonate dynamics at an event of hypoxic water upwelling in Tokyo Bay JOURNAL=Frontiers in Marine Science VOLUME=9 YEAR=2023 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1016199 DOI=10.3389/fmars.2022.1016199 ISSN=2296-7745 ABSTRACT=
Urban bays have been considered to have a high CO2 absorption function due to the high nutrient load and resultant primary production. It is expected to enhance the function by promoting a blue carbon policy co-beneficial with strengthening ecosystem services such as fisheries. Estimates of CO2 absorption in urban bays have been based mostly on fragmentary information from shipboard observations, and an evaluation based on continuous observation of water quality is necessary considering the large spatiotemporal variability of such bay environment. In particular, Tokyo Bay has a specific feature of water pollution problem of hypoxia and anoxia leading to emitting high CO2. Bottom hypoxic and anoxic waters develop from early summer to autumn in the central part of the bay and enclosed areas such as navigation channels and borrow pits. It is known that pCO2 becomes very high in these waters, and their upwelling (called blue tide in the bay from the discoloration of the sea surface) is thought to cause high CO2 emissions; however, the actual situation is unknown. We developed a practical method for continuous estimation of pCO2 by appropriately combining continuous observation of water quality using sensors and measurements of carbonate parameters by water sampling. The results show that a highly reproducible and practical method for continuous estimation of pCO2 was possible by combining