2024-03-28T11:36:01Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/798562022-11-17T02:08:08Zhdl_2115_20049hdl_2115_141Isoprene production in seawater of Funka Bay, Hokkaido, JapanOoki, AtsushiShida, RyutaOtsu, MasashiOnishi, HirojiKobayashi, NaotoIida, TakahiroNomura, DaikiSuzuki, KotaYamaoka, HideyoshiTakatsu, TetsuyaVolatile organic compound (VOC)PhytoplanktonBloomPhotosynthesisDark productionC5H8Hydrocarbon660We 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 increased isoprene 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 rates of in situ production of isoprene per unit chl-a in the surface mixed layer during 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 day^−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 rate of isoprene production under dark conditions ranged from 4% to 16% of that by photosynthesis.Journal Articleapplication/pdfhttp://hdl.handle.net/2115/79856https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/79856/1/Journal%20of%20Oceanography_2019_p1-17.pdf0916-83701573-868XJournal of Oceanography7564855012019-12enginfo:doi/10.1007/s10872-019-00517-6This is a post-peer-review, pre-copyedit version of an article published in Journal of Oceanography. The final authenticated version is available online at: https://dx.doi.org/10.1007/s10872-019-00517-6author