Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings
-
Published:2024-01-15
Issue:1
Volume:21
Page:177-199
-
ISSN:1726-4189
-
Container-title:Biogeosciences
-
language:en
-
Short-container-title:Biogeosciences
Author:
Ono TsuneoORCID, Muraoka Daisuke, Hayashi MasahiroORCID, Yorifuji MakikoORCID, Dazai Akihiro, Omoto Shigeyuki, Tanaka Takehiro, Okamura Tomohiro, Onitsuka Goh, Sudo Kenji, Fujii Masahiko, Hamanoue Ryuji, Wakita MasahideORCID
Abstract
Abstract. The pH of coastal seawater varies based on several local forcings, such as water circulation, terrestrial inputs, and biological processes, and these forcings are changing along with global climate change. Understanding the mechanism of pH variation in each coastal area is thus important for a realistic future projection that considers changes in these forcings. From 2020 to 2021, we performed parallel year-round observations of pH and related ocean parameters at five stations around the Japanese coast (Miyako Bay, Shizugawa Bay, Kashiwazaki Coast, Hinase Archipelago, and Ohno Strait) to understand the characteristics of short-term pH variations and their forcings. Annual variability (∼ 1 standard deviation) of pH and aragonite saturation state (Ωar) were 0.05–0.09 and 0.25–0.29, respectively, for three areas with low anthropogenic pressures (Miyako Bay, Kashiwazaki Coast, and Shizugawa Bay), while it increased to 0.16–0.21 and 0.52–0.58, respectively, in two areas with medium anthropogenic pressures (Hinase Archipelago and Ohno Strait in Seto Inland Sea). Statistical assessment of temporal variability at various timescales revealed that most of the annual variabilities in both pH and Ωar were derived by short-term variation at a timescale of <10 d, rather than seasonal-scale variation. Our analyses further illustrated that most of the short-term pH variation was caused by biological processes, while both thermodynamic and biological processes equally contributed to the temporal variation in Ωar. The observed results showed that short-term acidification with Ωar < 1.5 occurred occasionally in Miyako and Shizugawa bays, while it occurred frequently in the Hinase Archipelago and Ohno Strait. Most of such short-term acidified events were related to short-term low-salinity events. Our analyses showed that the amplitude of short-term pH variation was linearly correlated with that of short-term salinity variation, and its regression coefficient at the time of high freshwater input was positively correlated with the nutrient concentration of the main river that flows into the coastal area.
Funder
Environmental Restoration and Conservation Agency Nippon Foundation
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Reference95 articles.
1. Abo, K. and Onitsuka, G.: Characteristics of currents induced by heavy rainfall in Hiroshima Bay in July 2018, Proceedings of the Japan Society of Civil Engineers, Ser. B, 75, 1051–1056, 2019 (in Japanese). 2. Barcelona, A., Oldham, C., Colomer, J., Garcia-Orellana, J., and Serra, T.: Particle capture by seagrass canopies under an oscillatory flow, Coast. Eng., 169, 103972, https://doi.org/10.1016/j.coastaleng.2021.103972, 2021. 3. Barton, A., Hales, B., Waldbusser, G. G., Langdon, C., and Feely, R. A.: The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: Implications for near-term ocean acidification effects, Limnol. Oceanogr., 57, 698–710, https://doi.org/10.4319/lo.2012.57.3.0698, 2012. 4. Bates, N. R., Astor, Y. M., Church, M. J., Currie, K., Dore, J. E., González-Dávila, M., Lorenzoni, L., Muller-Karger, F., Olafsson, J., and Santana-Casiano, J. M.: A time-series view of changing surface ocean chemistry due to ocean uptake of anthropogenic CO2 and ocean acidification, Oceanography, 27, 126–141, https://doi.org/10.5670/oceanog.2014.16, 2014. 5. Baumann, H. and Smith, E. M.: Quantifying metabolically driven pH and oxygen fluctuations in US nearshore habitats at diel to interannual timescales, Estuar. Coast., 41, 1102–1117, https://doi.org/10.1007/s12237-017-0321-3, 2018.
|
|