第3回極域科学シンポジウム　横断セッション「南極海季節的海氷域における生物地球化学」11月26日（月） 統計数理研究所 セミナー

Endo Hisashi

Hashida Gen

Hattori Hiroshi

Iida Takahiro

Motokawa Shozo

Sasaki Hiroshi

Taguchi Satoru

National Institute of Polar Research Repository

  The effect of pCO2 on size-fractionated phytoplankton community in the Southern Ocean  Shozo Motokawa1, Hiroshi Hattori2, Gen Hashida3, Takahiro Iida3, Hisashi Endo4, Hiroshi Sasaki5 and Satoru Taguchi1 1Soka University  2Tokai University  3National Institute of Polar Research  4Hokkaido University  4Senshu University of Ishinomaki  We carried out the high pCO2 manipulation experiments in the Indian Sector of the Southern Ocean during the cruise of the TR/V Umitaka-Maru (Tokyo University of Marine Science and Technology) in the austral summer of 2011/2012. Seawater samples were collected by clean pump from 15m depth at 45oS (St. C02) and 60oS (St. C07) of 110oE, 59oS (St. D13) and 64oS (St. D07) of 140oE. The shipboard incubations were conducted under natural and high pCO2 conditions for 2 days. For high pCO2 conditions, triplicate incubation bottles (duplicate incubation at St. C02 and C07) were added with saturated pCO2 water and regulated around 750 atm of pCO2 in the bottles to compare the natural conditions. Size-fractionated pigments of phytoplankton were observed by HPLC. The relative abundance of phytoplankton biomass were estimated by size fractionated chlorophyll a (Chl a) concentration. The ratio of 19’-hexanoyloxyfucoxanthin (Hex) to Chl a (Hex:Chl a) and the ratio of Fucoxanthin (Fuco) to Chl a (Fuco:Chl a) were employed as an index of biomarker of Haptophytes and Diatoms, respectively. Decrease in Hex:Chl a under high pCO2 conditions at St. C02 and D13 suggested the increase in diatoms and the decrease in Haptophytes under high pCO2 conditions although Chl a concentrations seemed to increase without a consistent pattern in the size composition at Sts. C02 and D13 (Table I). Notable increase in Fuco:Chl a at St. D07 seemed to be related with the increase in the relative abundance in 20 - 2m size fractions. Only St. D07 did not respond to the introduction of high pCO2 in the present study. Those results suggest that nanoplankton community at St. D07, presumably diatoms in the 20 - 2m size fraction, might be competitive advantage under high pCO2 condition.  Table I. The average of Chl a concentration, Chl a composition, the ratio of Fuco to Chl a, Fuco to Chl a and Hex to Fuco at the natural condition (Control) and high pCO2 conditions (CO2) at the end of incubation.   南極海のサイズ別植物プランクトン群集に対する pCO2の影響  本川正三 1、服部寛 2、橋田元 3、飯田高大 3、遠藤寿 4、佐々木洋 5、田口哲 1 1創価大学、2東海大学、3国立極地研究所、4北海道大学、5石巻専修大学  Chl a Hex : Chl a Fuco : Chl a(mol m-3) (mol mol-1) (mol mol-1)Control 0.22 0.30 0.08 7.6 57.2 35.3CO2 0.26 0.24 0.11 14.0 50.9 35.1Control 0.70 0.17 0.66 29.9 50.8 19.3CO2 0.70 0.16 0.63 35.6 53.5 10.9Control 0.39 0.21 0.27 13.4 53.3 33.3CO2 0.44 0.17 0.36 15.8 56.8 27.4Control 0.65 0.05 0.47 28.5 62.1 9.4CO2 0.65 0.06 0.54 17.0 71.1 12.0C02C07D13D07Chl a  composition (%)>20 m 20 - 2 m <2 m

The effect of pCO2 on size-fractionated phytoplankton community in the Southern Ocean

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The effect of pCO2 on size-fractionated phytoplankton community in the Southern Ocean

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