Appearance Characteristics of Coccolithphores in Suruga Bay

Hagiwara, Naoki; Senga, Yasuhiro; Niki, Masato; Sugimoto, Takashige

doi:10.2208/kaigan.67.i_871

Cited by 2 publications

(4 citation statements)

References 2 publications

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“…5). Although coccolithophore blooms have been reported in various areas around Japan (Kai et al 1999, Imoto 2007, Kanzaki 2007, Hagiwara et al 2011, Fujishiro et al 2014, Sugimoto 2020, no such media or research articles had been published in Sagami Bay since the reports about the previous bloom in 1995 (e.g., Yamada 1997, Ogura & Sato 2001.…”

Section: Bloom Occurrencementioning

confidence: 99%

“…7). Coccolithophores are typically found in the oceanic waters on the Pacific side of Japan (Hagiwara et al 2011). Tokyo Bay is a semi-enclosed bay that is frequently influenced by the outer ocean through the mouth of the bay (Suzuki 2010).…”

Section: Bloom Movements and Biogeochemical Estimationsmentioning

confidence: 99%

“…Therefore, one of the key environmental conditions to sustain/expand the coccolithophore bloom in Sagami Bay in May 2020 was the relatively high concentrations of nitrate and nitrite. Off-shore of Suruga Bay, it was reported that G. huxleyi abundance increased when nitrate was resupplied by snowmelt water and precipitation after silica and nitrate were depleted due to a diatom bloom (Hagiwara et al 2011). In the Barents Sea, G. huxleyi blooms were observed every summer from 2014 to 2018, and it was reported that diatoms almost completely disappeared during the coccolithophore blooms (Silkin et al 2020).…”

Section: Bloom Sustainment In Sagami Baymentioning

confidence: 99%

“…oceanica blooms occurred when water temperature, chloride ion concentrations, and solar radiation were high, and pH, dissolved oxygen, and wind speed were low (Fujishiro et al 2014). In Suruga Bay, a G. huxleyi bloom was reported in 2007, and occurred when diatom growth depleted silicates and nitrates, and nitrate was resupplied by snowmelt water and rainfall (Hagiwara et al 2011). Thus, as with many episodic phytoplankton blooms, coccolithophore blooms are caused by multiple interacting conditions rather than a single factor (Iida et al 2012, Hopkins et al 2015, Vostokov et al 2022, and it is often not clear which environmental factors trigger extensive blooms.…”

Section: Introductionmentioning

confidence: 99%

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Observation of a coccolithophore <i>Gephyrocapsa oceanica</i> bloom in the temperate coastal waters of Sagami Bay, Japan

Yano,

Takayama,

Shimode

et al. 2024

Plankton Benthos Res

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In mid-May 2020, a coccolithophore bloom of Gephyrocapsa oceanica Kamptner, 1943 was observed in Sagami Bay, Japan, possibly for the first time in 25 years. This species is a common yet elusive taxon in the waters around Japan, but there has only been one report of a bloom observation in Sagami Bay in 1995. The G. oceanica bloom in 2020 was observed by the combined approach of the JAXA ocean color remote sensing satellite "Shikisai" and field surveys. The true-color RGB images from the satellite showed the initial bloom in Tokyo Bay appears to have advected into Sagami Bay on May 5. On May 15, ad hoc field sampling was conducted based on visual confirmation from the shore. Nitrate, nitrite and phosphate concentrations at the sea surface were 3.28 µM, 0.11 µM and 0.29 µM, respectively, and higher than the median of May from 1997 to 2019. Chlorophyll a concentration was 2.23 µg L −1 at the sea surface, and cell density was 5.3 × 10 3 cells mL −1 . The large bloom appears to have reached the western shorelines of the bay, and dispersed counterclockwise within the bay. The bloom reached an estimated 1119.02 km 2 surface expression on May 17, and completely disappeared by May 24. Further, the median value of 19′-hexanoyloxyfucoxanthin (a signature pigment of haptophytes, including coccolithophores) concentration has been increasing from 2017 to 2020, and the coastal area of Sagami Bay may have changed to a region favorable for haptophytes.

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Section: Bloom Occurrencementioning

confidence: 99%

Section: Bloom Movements and Biogeochemical Estimationsmentioning

confidence: 99%

Section: Bloom Sustainment In Sagami Baymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observation of a coccolithophore <i>Gephyrocapsa oceanica</i> bloom in the temperate coastal waters of Sagami Bay, Japan

Yano,

Takayama,

Shimode

et al. 2024

Plankton Benthos Res

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Seasonal dynamics of seawater CO2 system at a coastal site near the southern tip of Izu Peninsula, Japan

et al. 2020

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To elucidate how variables of the seawater CO2 system in surface waters have been changing seasonally and the mechanisms responsible for these changes in the area off the south coast of central Honshu Island, Japan, we made time-series measurements of total dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic macronutrient and chlorophyll a concentrations as well as temperature and salinity at a near-shore station off Shimoda city near the southern tip of the Izu Peninsula over 19 months from November 2011 to June 2013. The oceanographic setting in our study site is characterized by seasonal stratification, low salinity in summer, and well-mixed water column in winter. A large bloom of phytoplankton developed in spring, thereafter nutrients were depleted within the mixed layer in summer. DIC exhibited large seasonal variations and ranged from 1967 µmol kg −1 in summer to 2073 µmol kg −1 in winter when normalized to a salinity of 35, because of biological production in the spring and summer and vertical mixing in autumn and winter, as shown by multiple regression analysis in which variations of normalized DIC (nDIC) are estimated from variations in temperature (13.3 to 25.5 °C) and chlorophyll concentrations (0.27-3.9 μg l -1 ). We observed a decrease of TA due to dilution by precipitation and river runoff in summer and a trend of salinity-normalized TA increase over time. The saturation state of the calcium carbonate mineral aragonite Ωarg varied seasonally from 2.40 in winter to 3.58 in summer. The Ωarg in the present study was calculated using DIC, TA, temperature and salinity, and we applied sensitivity analysis for these parameters. Ωarg was predominantly controlled by the large variations of DIC. The combination of these results from the station off Shimoda and from an offshore station at 34°N, 137°E to the west allow us to predict Ωarg with high precision for temporal and spatial variations. It suggests that in winter, there is a meridional gradient of Ωarg in the region off the 3 southern coast of central Honshu Island, with considerably lower Ωarg in the coastal zone.

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Appearance Characteristics of Coccolithphores in Suruga Bay

Cited by 2 publications

References 2 publications

Observation of a coccolithophore <i>Gephyrocapsa oceanica</i> bloom in the temperate coastal waters of Sagami Bay, Japan

Observation of a coccolithophore <i>Gephyrocapsa oceanica</i> bloom in the temperate coastal waters of Sagami Bay, Japan

Seasonal dynamics of seawater CO2 system at a coastal site near the southern tip of Izu Peninsula, Japan

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