Chlorophyll specific growth rate and grazing mortality rate of phytoplankton in the shelf water of the Bering Sea in summer

Chlorophyll specific growth rate and grazing mortality rate due to microzooplankton were estimated based on the dilution methods, using surface waters collected at four stations in the continental shelf area of the Bering Sea in summer. Growth rates and grazing mortality rates of phytoplankton communities were ranged between 0.06d^ and 0.56d^ and between 0.04d^ to 0.33d^, respectively. The high growth rate seems to have resulted from continuous supply of nutrients caused by gentle stratification, which is a favorable condition of the water column for phytoplankton growth. Growth and grazing mortality rates were almost the same at one station, where the most typical summer concentration of chlorophyll a was observed (less than 1μgl^), suggesting that the major grazer seems to be microzooplankton in the Bering Sea shelf in summer. On the other hand, the lowest growth rate was obtained in near St. Laurence Island, where higher chlorophyll concentrations more than several μgl^ occurred. In this water passive sinking of cells seems to become one of controlling factor of phytoplankton abundance

A simple method for estimating phytoplankton abundance using a surface seawater monitoring system off Syowa Station during austral summer

A surface seawater monitoring system was used aboard the Shirase to estimate phytoplankton abundance while the icebreaker was anchored in an ice covered area off Syowa Station during the austral summer of 1996/97. A significant positive relationship was observed between the digital output (OP) values of the chlorophyll fluorometer of the system, and chlorophyll a (Chl a) concentrations of the seawater that passed through the system. Using this relationship, OP values were converted into Chl a (Chl a OP). Throughout the present study, the Chl a OP was found to be consistent with temporal changes in Chl a observed in the field near the Shirase, with high Chl a OP values measured in relatively warm and less saline water. These findings suggest that the high Chl a may be derived from the ice-edge phytoplankton blooms that develop in stable waters associated with melting ice. Relatively simple operation without need for complicated maintenance procedures facilitates the ease with which the system can be used. The operation of the system every summer may facilitate the acquisition of data that reveal the long-term variability of phytoplankton biomass under fast ice

Successful Australia-Japan collaboration and student mentoring

第6回極域科学シンポジウム[OB] 極域生物圏11月16日（月）　統計数理研究所 セミナー室1（D305

ダイ44ジ ナンキョク チイキ カンソクタイ ナツタイ 「センヨウ カンソクセン」 コウドウ ホウコク 2003

第44次日本南極地域観測隊(JARE-44)では,南極地域観測第期5か年計画のプロジェクト研究観測を実施するため,2回目となる海洋観測のための「専用観測船」による航海を行った.JARE-44ではJARE-43の観測結果を踏まえ,生物生産過程の違いがもたらす温暖化関連ガス成分の生成除去過程や有機物の鉛直輸送過程に焦点を絞ったプロセス研究を行うこととした.本航海前には東京水産大学「海鷹丸」の観測(平成15年1月2月)が,本航海後にはJARE-44「しらせ」の観測(平成15年3月)が行われ,一連の観測により同一海域の時系列観測となった.「専用観測船」として,JARE-43と同じ,「タンガロア号」(ニュージーランド水圏大気研究所)が傭船された.2月17日,ニュージーランドウェリントン港を出航後,連続航走観測を行いながら,東経140-145度,南緯61度以南の観測海域を目指した.2月25日から3月6日の期間に,集中的な観測を行った.停船観測の終了後,ウェリントン港へ向けて航走し,3月12日にはウェリントン港外へ到達した.The second cruise for marine science was conducted as one of the projects under the five year plan Phase VI of the Japanese Antarctic Research Expeditions (JARE-43 to -47). The Research Vessel Tangaroa (National Institute of Water and Atmospheric Research, New Zealand) was chartered for the cruise. This cruise was one of the time-serial observations shared by the TS Umitaka Maru (Tokyo University of Fisheries, Japan) in January-February 2003 and icebreaker Shirase (JARE-44) in March. Our cruise focused on process studies to reveal the relationship between plankton community variations, and biogenic green house gas production/removal and vertical transport of organic matter. The RV Tangaroa departed from Wellington, New Zealand, on the 17th of February 2003. She cruised to the study area (140-145°E , 61-65°S ), while conducting continuous observations. Station observations started on 25th February (local time) and finished on 6th March. After the station observations, continuous surface water observations were conducted again between the study area and Wellington. RV Tangaroa returned to the ocean just outside the port of Wellington on 12th March

ダイ43ジ ナンキョク チイキ カンソクタイ ナツタイ 「センヨウ カンソクセン」 コウドウ ホウコク 2002

第43次日本南極地域観測隊では、観測隊史上初めて「専用観測船」を導入した集中的な海洋観測を実施した。この航海は、オーストラリア南極観測隊「オーロラ・オーストラリス号」(2001年10月～12月)、東京大学海洋研究所「白鳳丸」(2002年1月)の研究航海と連携し、本航海後の2002年3月にはJARE-43「しらせ」の観測が行われた。国際共同観測の枠組みを通して、夏期全体をカバーする時系列観測をなすものである。「専用観測船」として傭船された「タンガロア号」(ニュージーランド水圏大気研究所観測船運営会社所有、2282トン)は、2002年2月6日、オーストラリアタスマニア州ホバート港を出港した。出港後、連続航走観測(表面水温・塩分・クロロフィル蛍光観測、ADCP観測、XCTD/XBT観測、音響探査、CPR(continuous plankton recorder)観測及び大気観測)を開始し、東経140度南緯61度以南の観測海域を目指した。観測海域の最南端へは、2月12日2100(現地時間)に到達し、周辺の水深調査後、2月13日0000より停船観測を実施した。2月24日0821測点1における観測終了をもって、当初予定していた南緯61度～氷縁測点8間の断面観測は終了した。この間に、JARE-42で設置した係留系及び「白鳳丸」で設置した係留系の回収に成功した。また、3回の漂流ブイ放流・回収を含む、計画された観測項目の殆ど全てを実施することができた。断面観測終了後は、測点1～測点8間の表層観測を実施し、「白鳳丸」が実施した南緯60度、東経140度、「オーロラ・オーストラリス号」が実施した南緯57度、東経140度、及び「白鳳丸」が実施した南緯54度、東経140度での観測を実施した。これらの観測は3月2日1305に終了し、3月7日0800ホバート港へ帰港したThe first cruise for marine science started as one of projects under the Japanese Antarctic Research Expedition (JARE) from the year 43rd party. The Research Vessel Tangaroa (National Institute of Water and Atmospheric Research, NIWA, 2282 ton) was chartered for the cruise. This cruise was one of the time-serial observations shared by RMV Aurora Australis (Australian National Antarctic Research Expedition) in October-December 2001, RV Hakuho Maru (Ocean Research Institute, University of Tokyo) in January 2002, and icebreaker Shirase (JARE-43) in March. The RV Tangaroa departed from Port of Hobart (Tasmania, Australia) on 6th of February 2002. She cruised to the target area (>61°S along 140°E), conducting continuous observations (surface temperature, salinity and fluorescence, ADCP, XCTD/XBT, acoustic, continuous plankton recorder, air sampling). Station observations started from 0000 13th February (local time) from the southernmost station (Station 8, 66°26\u27S, 140°00\u27E). The transect observation between Stations 8 and 1 (61°S, 140°E) finished at 0821 24th February. During the transect observation, two moorings, which were deployed using Shirase in March 2001 (JARE-42) and RV Hakuho Maru in January 2002, were successfully recovered. Almost all observation items, including three times deployments and recoveries of drifting buoys, were performed. After the transect observation, the surface water observations were conducted again between 61°-66°26\u27S along 140°E. Station observations were conducted at several points, which were observed by RMV Aurora Australis and RV Hakuho Maru. All of the station observations were finished by 1305 2nd of March 2002, and RV Tangaroa returned to Port of Hobart at 0800 7th of March

Australia and Japan collaboration in Antarctic Science: 2nd Phase

第3回極域科学シンポジウム/第34回極域生物シンポジウム 11月26日（月） 統計数理研究所 ３階セミナー

Distribution of chlorophyll-a and sea surface temperature in the marginal ice zone (20°E-60°E) in East Antarctica determined using satellite multi-sensor remote sensing during austral summer

We investigated the distribution of chlorophyll-a (Chl-a) and sea surface temperature (SST) off the sea ice region south of 64°S in East Antarctica between 20°E and 60°E during austral summers, 1998-2002. We used satellite multi-sensor remote sensing datasets including ocean color Chl-a, SST and sea ice concentration. High concentrations of Chl-a (>0.5 mg m^(-3)) were generally observed in colder water below 0°C. Phytoplankton blooms were extended into shallow areas along the isobath. SST distribution exhibited two patterns. In the first pattern, warm water located to the north of this region associated with polynya in early spring. The second pattern was characterized by distribution of cold water throughout the study area. A shift of the Antarctic Circumpolar Current (ACC) is considered to affect this difference between SST distributions. The cold water from the Antarctic coastal current mixed with meltwater was expected to provide vertical stability of the water column for phytoplankton blooms. These results suggest that the phytoplankton blooms in this study area during austral summer can be attributed to water conditions affected by melting sea ice, movement of the ACC and sea floor topography