Ocean Acidification State in the Highly Eutrophic Tokyo Bay, Japan: Controls on Seasonal and Interannual Variability

Yamamoto‐Kawai, Michiyo; Ito, Soichiro; Kurihara, Haruko; Kanda, Jun

doi:10.3389/fmars.2021.642041

Cited by 11 publications

(5 citation statements)

References 70 publications

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“…Similar effects of anthropogenic nutrient reduction to diminish short-term ar drawdown in coastal waters are also reported by Kessouri et al (2021). We note, however, that a certain percentage of Japanese coastal areas are now suffering due to the problem of low biological productivity derived from the decreased anthropogenic nutrient input (e.g., Yamamoto et al, 2021). We must consider the balance between the risk of ocean acidification and oligotrophication when we control anthropogenic loadings to coastal waters in the future.…”

Section: Controlling Factor Of the Amplitude Of Short-term Ph Variationsupporting

confidence: 63%

“…Historically, nutrient loading was the highest in the 1980s (∼ 2.35 × 10 5 tN yr −1 ; Nishijima, 2018). While the long-standing efforts of local communities succeeded in reducing it to the current level, significant quantities of organic nutrients still remained in the bottom sediment, creating local internal sources of nutrients in the Seto Inland Sea (e.g., Yamamoto et al, 2021). Although there is no large point source of nutrients, such as chemical plants, near the Hinase Archipelago, this area also receives nutrients from the Bizen city, which has a population of 36 000 residents.…”

Section: Hinase Archipelagomentioning

confidence: 99%

“…The ocean is witnessing a reduction in its pH due to anthropogenic CO 2 sequestration both in open oceans (e.g., Bates et al, 2014;Iida et al, 2021;Jiang et al, 2019;Lauvset et al, 2015;Takahashi et al, 2014) and coastal oceans (e.g., Carstensen and Duarte, 2019;Duarte et al, 2013;Hauri et al, 2013;Ishida et al, 2021;Ishizu et al, 2019;Yao et al, 2022). In the coastal ocean, pH shows short time variation caused by several processes such as water mass changes (e.g., Johnson et al, 2013;Ko et al, 2016;Wakita et al, 2021), coastal upwelling (e.g., Barton et al, 2012;Booth et al, 2012;Feely et al, 2008Feely et al, , 2016Vargas et al, 2015), rivers inputs (e.g., Cai et al, 2017;Fujii et al, 2021;Gomez et al, 2021;Salisbury et al, 2008;Salisbury and Jönsson, 2018), terrestrial nutrients' inputs (e.g., Cai et al, 2011;Guo et al, 2021;Kessouri et al, 2021;Provoost et al, 2010;Sunda and Cai, 2012;Wallace et al, 2014), and various coastal biological processes (e.g., Delille et al, 2009;Lowe et al, 2019;Mongin et al, 2016;Ricart et al, 2021;Yamamoto-Kawai et al, 2021). The amplitude of short-term pH variation often exceeds that of the decadal-scale long-term pH trend, and hence, blurs the signal of anthropogenic CO 2 -induced acidification of coastal seawater (e.g., …”

Section: Introductionmentioning

confidence: 99%

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Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings

Ono,

Muraoka,

Hayashi

et al. 2024

Biogeosciences

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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.

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Section: Controlling Factor Of the Amplitude Of Short-term Ph Variationsupporting

confidence: 63%

Section: Hinase Archipelagomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings

Ono,

Muraoka,

Hayashi

et al. 2024

Biogeosciences

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“…Eutrophic conditions are however still extant in many bays and estuaries, and seasonal hypoxic conditions in summer bottom 120 layers improve only slowly (Imai et al, 2006;Ando et al, 2021;Yamamoto et al, 2021). Deoxygenation and ocean acidification cause combined effects on marine organisms (Melzner et al, 2013;DePasquale et al, 2015;Gobler and Baumann, 2016;IPCC, 2018).…”

Section: Deoxygenationmentioning

confidence: 99%

Observed and projected impacts of coastal warming, acidification, and deoxygenation on Pacific oyster (Crassostrea gigas) farming: A case study in the Hinase Area, Okayama Prefecture and Shizugawa Bay, Miyagi Prefecture, Japan

Fujii

Hamanoue

Bernardo

et al. 2022

Preprint

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Abstract. Coastal warming, acidification, and deoxygenation are progressing, primarily due to the increase in anthropogenic CO2. Coastal acidification has been reported to have effects that are expected to become more severe as acidification progresses, including inhibiting formation of the shells of calcifying organisms such as shellfish. However, compared to water temperature, an indicator of coastal warming, spatiotemporal variations in acidification and deoxygenation indicators such as pH, aragonite saturation state (Ωarag), and dissolved oxygen in coastal areas of Japan have not been observed and projected. Moreover, many species of shellfish are important fisheries resources, including Pacific oyster (Crassostrea gigas). Therefore, there is concern regarding the future combined impacts of coastal warming, acidification, and deoxygenation on Pacific oyster farming, necessitating evaluation of current and future impacts to facilitate mitigation measures. We deployed continuous monitoring systems for coastal warming, acidification, and deoxygenation in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan. In Hinase, the Ωarag value was often lower than the critical level of acidification for Pacific oyster larvae, although no impact of acidification on larvae was identified by microscopy examination. Oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters. No significant future impact of surface-water deoxygenation on Pacific oysters was identified. To minimize the impacts of coastal warming and acidification on Pacific oyster and related local industries, cutting CO2 emissions is mandatory, but adaptation measures such as regulation of freshwater and organic matter inflow from rivers and changes in the form of oyster farming practiced locally might also be required.

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“…With the increase of CO 2 in atmosphere, it is expected that ocean acidification would be enhanced in the near future via more sequestration of CO 2 and stratification induced by global warming (Guo et al, 2022). To date, most studies of acidification focused geographically on coastal seas and shelf regions (Yamamoto-Kawai et al, 2021) because these areas are often subjected to enhanced acidification resulting from eutrophication-associated hypoxia (Cai et al, 2011;Song et al, 2020). With extensive investigations, the driving forcing and mechanisms of acidification in shallow seas are well understood (Guo et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Slow-sinking particulate organic carbon and its attenuation in the mesopelagic water of the South China Sea

2022

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Coastal acidification has been widely investigated in terms of its rationale and ecological effects in the last decade. However, the driving mechanism for acidification in open seawater, especially in mesopelagic water, is still poorly understood. Here, the sinking velocity and flux attenuation of particulate organic carbon (POC) were examined based upon the radioactive 210Po-210Pb tracer to reveal the remineralization of POC in the mesopelagic zone in the northeastern South China Sea (SCS). Overall, the profiles of 210Po followed those of 210Pb, lending support to the particle sinking controlled top-down deficits of 210Po. Using an inverse model, the sinking velocity of particles, for the first time in the SCS, was estimated to vary from 3 to 34 m d-1 with the mean value of 15 ± 9 m d-1, indicating that the slow sinking particles largely contribute to the POC flux in the SCS. Beneath the euphotic zone, a consistent descending of the sinking speed implied continuous remineralization of sinking POC in the twilight zone. A preliminary estimate revealed that 1.9-5.4 mmol-C m-2 d-1 remineralized back to carbon dioxide within 100-500 m, representing about 70% of the exported autochthonous POC from the euphotic zone. In 100-1000 m, 2.4-6.6 mmol-C m-2 d-1 (i.e., 84%) remineralized. Thus, the upper twilight zone (i.e., 100-500 m) is the dominant layer of POC remineralization, and POC-induced acidification could be unneglectable there. These results provided insights into the POC-induced acidification mechanism in the mesopelagic water, especially in the upper mesopelagic layer.

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Ocean Acidification State in the Highly Eutrophic Tokyo Bay, Japan: Controls on Seasonal and Interannual Variability

Cited by 11 publications

References 70 publications

Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings

Short-term variation in pH in seawaters around coastal areas of Japan: characteristics and forcings

Observed and projected impacts of coastal warming, acidification, and deoxygenation on Pacific oyster (Crassostrea gigas) farming: A case study in the Hinase Area, Okayama Prefecture and Shizugawa Bay, Miyagi Prefecture, Japan

Slow-sinking particulate organic carbon and its attenuation in the mesopelagic water of the South China Sea

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