Seasonal variation of volatile organic iodine compounds in the water column of Funka Bay, Hokkaido, Japan

Shimizu, Yasuko; Ooki, Atsushi; Onishi, Hideaki; Takatsu, Tetsuya; Tanaka, Seiji; Inagaki, Yuta; Suzuki, Kota; Kobayashi, Naoto; Kamei, Yoshihiko; Kuma, Kenshi

doi:10.1007/s10874-016-9352-6

Cited by 8 publications

(3 citation statements)

References 45 publications

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“…Our methods for Funka Bay observations and seawater measurements have been recently reported (Shimizu et al 2017). Seawater samples were collected in 2-L Niskin bottles attached to a rosette multisampler along with a CTD probe and a photosynthetically-active-radiation (PAR) sensor.…”

Section: Shipboard Observations and Seawater Samplingmentioning

confidence: 99%

Isoprene production in seawater of Funka Bay, Hokkaido, Japan

et al. 2019

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We carried out shipboard observations in Funka Bay, Hokkaido, Japan, monthly or bimonthly from December 2015 to November 2016. We measured vertical profiles of isoprene, chlorophyll-a (chl-a), and other parameters from surface to bottom layer (about 95 m) near the center of the bay. We found substantial increases in isoprene concentration in the surface mixed layer from February to March during the peak of the spring diatom bloom, in the bottom layer from March to April after the peak of the bloom, and in the subsurface layer (below the surface mixed layer) in summer from July to August, where there were also substantial chl-a concentration maxima. We attribute the isoprene increases in the surface and subsurface layers to photosynthetic production of isoprene by the dominant phytoplankton in the spring bloom and in summer, and that in the bottom layer to dark production of isoprene by diatom aggregates that settled from the surface euphotic zone. We also measured isoprene production in laboratory incubation experiments. The in-situ production rates of isoprene per unit chl-a in the surface mixed layer in the spring bloom, in the dark bottom layer during the bloom, and in the subsurface layer in summer (0.82, 0.03-0.13, and 7.38 pmol (μg chl-a)-1 d-1 , respectively) were consistent with our incubation results. We believe that this is the first report focused on dark production of isoprene by diatoms; the production rate of isoprene under the dark condition ranged from 4% up to 16% of that by photosynthesis.

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Section: Shipboard Observations and Seawater Samplingmentioning

confidence: 99%

Isoprene production in seawater of Funka Bay, Hokkaido, Japan

et al. 2019

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“…The sampling depths were 0, 5, 10, 20, 30, 40, 50, 60, 65, 70, 75, 80, 85, and 95 m (1 m above the seafloor). Observations in Funka Bay have been reported elsewhere (Shimizu et al 2017).…”

Section: Shipboard Observationsmentioning

confidence: 93%

Nutrient consumption by diatoms in the dark subsurface layer of Funka Bay, Hokkaido, Japan

Umezawa

Tozawa

Nosaka

et al. 2022

Preprint

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Abstract. We conducted time-series observations in Funka Bay, Hokkaido, Japan, from 15 February to 14 April 2019. The diatom spring bloom peaked on 4 March and started declining on 15 March. Funka Bay winter water remained below 30-m depth, which was below the surface mixed-layer and dark-zone depths on both dates. At depths of 30–50 m, concentrations of NO3–, PO43–, and Si(OH)4 decreased by half between these dates even in darkness. Incubation experiments using the diatom Thalassiosira nordenskioeldii showed that this diatom could consume nutrients in darkness at substantial rates. We conclude that the nutrient reduction in the subsurface layer (30–50 m) could be explained by dark consumption by diatoms that had been growing in the surface waters and then sank to the subsurface layer. We believe that this is the first study to present observational evidence for the consumption of the main nutrients by diatoms in the dark subsurface layer during the spring bloom. Nutrient consumption in this layer might have a substantial influence on the primary production during and after the spring bloom.

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“…From repetitive observations in the bay, it is possible to collect seawater samples originating from the same water mass at different times (when the water remains in the bay during the observation period) and then examine the temporal changes in the biogeochemical parameters within the same water mass. For example, temporal changes in nutrients (Kudo and Matsunaga, 1999;Kudo et al, 2000), D-Fe (Hioki et al, 2015), volatile organic iodine (Shimizu et al, 2017), and isoprene (Ooki et al, 2019(Ooki et al, , 2022 have been examined in relation to primary production in the bay.…”

Section: Introductionmentioning

confidence: 99%

Significant nutrient consumption in the dark subsurface layer during a diatom bloom: a case study on Funka Bay, Hokkaido, Japan

Umezawa

Tozawa²,

Nosaka³

et al. 2023

Biogeosciences

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Abstract. We conducted repetitive observations in Funka Bay, Hokkaido, Japan, on 15 February, 4 and 15 March, and 14 April 2019. The diatom spring bloom peaked on 4 March and started declining on 15 March. Funka Bay winter water remained below 30 m depth, which was below the surface mixed-layer and dark-layer depth (0.1 % of the surface photosynthetically active radiation, PAR, depth) on 4 and 15 March. In the subsurface layer at depths of 30–50 m, concentrations of NO3-, PO43-, and Si(OH)4 decreased by half between these dates, even in the dark. Incubation experiments using the diatom Thalassiosira nordenskioeldii showed that this diatom could consume added nutrients in the dark at substantial rates after pre-culturing to deplete nutrients. Incubation experiments using natural seawater collected in the growing phase of the bloom on 8 March 2022 also showed that nutrient-depleted phytoplankton could consume added nutrients in the dark. We excluded three physical process – water mixing, diffusive transport, and subduction – as possible main reasons for the decrease in nutrients in the subsurface layer. We conclude that the nutrient reduction in the subsurface layer (30–50 m) between 4 and 15 March 2019 could be explained by nutrient consumption by diatoms in the dark in that layer.

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Seasonal variation of volatile organic iodine compounds in the water column of Funka Bay, Hokkaido, Japan

Cited by 8 publications

References 45 publications

Isoprene production in seawater of Funka Bay, Hokkaido, Japan

Isoprene production in seawater of Funka Bay, Hokkaido, Japan

Nutrient consumption by diatoms in the dark subsurface layer of Funka Bay, Hokkaido, Japan

Significant nutrient consumption in the dark subsurface layer during a diatom bloom: a case study on Funka Bay, Hokkaido, Japan

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