Marine Ecological Studies in the
Subarctic to Subtropical North
Pacific
A mini-symposium to mark the 2005 port
call of the T/S Oshoro Maru to Honolulu

Program and Abstracts

8 August 2005
University of Hawai’i
Marine Science Building

1

PROGRAM
09:00-09:05

Opening remarks
Chris Helm, Office of International Education, University of Hawaii

09:05-09:15

Welcoming remarks
Lorenz Maagard, Chairman, Department of Oceanography, Universityof Hawai’i at Manoa
Samuel Pooley, Science Center Director, Pacific Islands Fisheries
Center, NOAA

09:15-09:20

Symposium logisitics
Evan Howell (Pacific Islands Fisheries Science Center, NOAA)

09:20-09:32

John Bower (Hokkaido University)
A short history of the Oshoro Maru in the North Pacific

SESSION 1: Iron and Aerosols (Chair: Atsushi Yamaguchi)
09:32-09:44

Kenshi Kuma (Hokkaido University)
Iron in the northwestern North Pacific Ocean

09:44-09:56

Chris Measures (University of Hawai’i at Manoa)
Dust deposition to the surface waters of the North Pacific Ocean inferredfrom surface water dissolved Al concentrations

09:56-10:08

Eriko Shimizu, J. Zhang, M. Arisawa and W. Yuan (Toyama University)
Aerosol geochemistry and nutrient deposition in the North Pacific

10:08-10:20

Yohei Shinozuka (University of Hawai’i at Manoa)
Can new satellite capabilities be used to infer cloud condensation nuclei?
-- An empirical assessment based on in-situ airborne data

10:20-10:40

BREAK

SESSION 2: Nekton (Chair: Keiko Sekiguchi)
10:40-10:52

Jeff Polovina, Itaru Uchida, George Balazs, Evan A. Howell, Denise
Parker and Peter Dutton (Pacific Islands Fisheries Science Center,
NOAA)
The Kuroshio Extension Bifurcation Region: A pelagic hotspot forjuvenile loggerhead sea turtles

10:52-11:04

Lareina Yee and Keiko Sekiguchi (University of Hawai’i at Hilo)
Results of a cetacean sighting survey during the T/S Oshoro Maru North
Pacific cruise in 20052

11:04-11:16

Evan Howell, Donald R. Hawn and Jeffrey J. Polovina (Pacific Islands
Fisheries Science Center, NOAA)
Vertical and horizontal distribution of bigeye tuna (Thunnus obesus) in
the northeastern subtropical gyre during summer

11:16-11:28

John Bower (Hokkaido University)
Squid studies aboard the Oshoro Maru

SESSION 3: Self-introduction of students (Chair: John Bower)
11:28-11:45

1. Yujiro Aota
2. Mitsuru Chigira
3. Ryohei Fukui
4. Kei Hirose
5. Shinichi Kado
6. Hitoshi Kaneko
7. Saori Kitayama
8. Eri Manabe
9. Yosuke Sagawa
10. Kenichi Sato
11. Meguru Takashima

11:45-13:00

LUNCH

SESSION 4: Plankton (Chair: Hiroji Onishi)
13:00-13:12

Bob Bidigare (University of Hawai’i at Manoa)
Influence of climate forcing on plankton community structure in thesubtropical North Pacific Ocean

13:12-13:24

Saho Kitatsuji and Tsutomu Ikeda (Hokkaido University)
Long-term changes (1984-1994) in phytoplankton communities inOshoro Bay, northeastern Japan Sea

13:24-13:36

Cecilia C.S. Hannides* and Michael Landry (*University of Hawai’i at Manoa)
Spatial and temporal variability in mesozooplankton community
structure in the subtropical North Pacific

13:36-13:48

Atsushi Yamaguchi (Hokkaido University)
East-west comparison in zooplankton community structures along 165oE
and 165oW in the North Pacific Ocean

13:48-14:00

Ken Kato and Naonobu Shiga (Hokkaido University)
Summer distribution and community structure of appendicularia in thenorthwestern North Pacific3

SESSION 5: Remote Sensing (Chair: Evan Howell)
14:00-14:12

Takahiro Iida*, Jia Wang, Meibing Jin and Seiichi Saitoh (*Hokkaido University)
The springtime plankton dynamics affected by wind forcing and solar
radiation on the Bering Sea shelf

14:12-14:24

Kazushige Oishi (Hokkaido University)
Temporal and spatial variability of chlorophyll a concentration aroundFutaoi Island in the Sea of Japan - A comparison of satellite ocean color
data and in-situ ship observation data

14:24-14:36

Cedric Chavanne (University of Hawai’i at Manoa)
HF-radar remote sensing of the ocean surface currents in the lee of Oahu,
Hawaii

14:36-14:48

Toshiyuki Konishi (Hokkaido University)
Prediction of Pacific saury fishing grounds based on SST and SSC
variability derived from satellite remote sensing data

14:48-15:10

BREAK

SESSION 6: Acoustics, Nutrients and Hydrography (Chair: Kenshi Kuma)
15:10-15:22

Reka Domokos (Pacific Islands Fisheries Science Center)
Distribution and abundance estimates of micronekton and tuna using two
frequency echosounder in the tropical and subtropical Pacific

15:22-15:34

Takaaki Tatsuta, Kouji Iida and Toru Mukai (Hokkaido University)
Relationship between SV and zooplankton in the North Pacific

15:34-15:46

TaeKeun Rho (Hokkaido University)
Nutrient dynamics and productivity in the Bering Sea during 1997-2001

15:46-15:58

Fernando Santiago-Mandujano (University of Hawai’i at Manoa)
Long-term hydrographic observations in the subtropical North Pacificduring the Hawaii Ocean Times-series

15:58-16:10

Hiroji Onishi (Hokkaido University)
Temperature inversion in the Gulf of Alaska

16:10-16:15

Closing remarks
Kenshi Kuma

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ABSTRACTS
Influence of climate forcing on plankton community structure in thesubtropical North Pacific Ocean
Bob Bidigare
University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI 96822. E-mail: bidigare@hawaii.edu

Potential biological responses to basin-scale climate forcing in the Subtropical North
Pacific Ocean are assessed based on temporal variations in phytoplankton community
structure observed at Station ALOHA (1990-2004) and the output of a Regional Ocean
Modeling System (ROMS) model. Phytoplankton populations were monitored monthly
during this period using taxon-specific pigment analyses. These analyses revealed
distinct temporal patterns, with highest pelagophyte abundance during the periods 19901995 and 1998-2004. For other key groups, such as the haptophytes and cyanobacteria,
there appears to be a recent post-1998 enhancement in their biomass relative to theprevious period of observation. An Ocean General Circulation Model, based on theterrain-following vertical coordinate primitive equation ROMS model, was used tosimulate hydrographic dynamics at Station ALOHA. A comparison of model simulation
with TAO observations has shown that the model can realistically reproduce the lowfrequency (seasonal-to-interannual) variability. The ROMS simulation during 19902004 will be first compared against the HOT physical measurements and then used tohelp interpret the observed changes in phytoplankton community structure at Station
ALOHA.

Squid studies aboard the Oshoro MaruJohn Bower
Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan. E-mail:akaika@fish.hokudai.ac.jp

The cephalopods, commonly the octopuses, squids and cuttlefishes, comprise a welldefined class of Mollusca. Much of what we know about these animals comes frominshore species, which are those most available to study and easiest to maintain in tanks.
The offshore fauna, which comprises both epipelagic and deep-sea species, is far lesswell known. My talk will briefly describe some of our research aboard the Oshoro Maruon the offshore fauna, including the red flying squid (Ommastrephes bartramii) andseveral gonatid species.

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HF-radar remote sensing of the ocean surface currents in the lee of
Oahu, Hawaii
Cedric Chavanne
University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI 96822. E-mail: cedric@hawaii.edu

Two high-frequency radars were deployed on the west shore of Oahu, Hawaii, from
September 2002 to May 2003, as a component of the Hawaii Ocean Mixing Experiment(HOME). Surface currents were obtained every 20 to 30 minutes during the 9-month
period, up to 100 km offshore with a spatial resolution of 2 km.
The 9-month average circulation reveals the Hawaiian Lee Current, flowing
northwestward along the western side of the Hawaiian archipelago. The variability isdominated by 10-day oscillations of 50 cm/s amplitude, mesoscale eddies spun-up at
Barbers Point, and semi-diurnal tidal currents of 10-20 cm/s amplitude. A study ofisland retention vs. dispersal of reef larvae is on-going.

Distribution and abundance estimates of micronekton and tuna using
two frequency echosounder in the tropical and subtropical Pacific
Reka Domokos
Pacific Islands Fisheries Science Center, NMFS, 2570 Dole Street, Honolulu, Hawaii 96822-2396. Email: reka@soest.hawaii.edu

Active acoustics measurements at 38kHz and 120kHz frequencies were used as part of an effort toadvance our knowledge regarding the oceanographic characteristics of the American Samoa
fishing grounds and to better understand how these characteristics affect the local longline fisheryand their target species, albacore tuna. For this project, shipboard acoustics data were collected
March-April, 2004, on board the Oscar Sette to study the spatial and temporal distribution andrelative abundance of forage for albacore, the micronekton scattering layer. Results werecompared with depth records from tagged tuna, satellite altimetry data, and CTD profiles. Tagged
albacore spend most of their time between 150-250 m depth --- with depths between 150-300m
during the day and 0-200m during the night --- corresponding to relatively high biomass asestimated from acoustic backscatter and to strong temperature and salinity gradients. Further,horizontal distribution of relatively high biomass corresponds to that of lower dissolved oxygenand higher chloropigments.
Another project involving active acoustics is designed to develop an efficient method for long-termmonitoring of tuna biomass at Cross Seamount within the Hawaiian EEZ, as well as to study theeffects of the physical environment of seamounts on bigeye and its forage, the micronekton
scattering layer. Shipboard active acoustic measurements at 38kHz and 120kHz frequencies werecollected over Cross and Finch seamounts during the month of April, 2005, as part of a6preliminary investigation. Future plans include a cruise back to Cross Seamount in the spring of2007 to complete the first acoustic survey for bigeye tuna biomass estimation.

Spatial and temporal variability in mesozooplankton community
structure in the subtropical North PacificCecilia C.S. Hannides1 and Michael Landry2
1

Department of Oceanography, University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI, 96822.
E-mail: sheridan@hawaii.edu
2
Scripps Institution of Oceanography, University of California, San Diego, 9500 Gillman Drive, La Jolla,
CA, 92093

Recent evidence from the Hawaii Ocean Time-series (HOT) program indicates thatmesozooplankton biomass has increased in the North Pacific over the past decade. Thisobservation challenges the classic view of a time-invariant, “climax state” zooplankton
community in the region. To understand this shift in perspective we explore differences
between current (HOT) and early (CLIMAX) long-term sampling studies in thesubtropical gyre. We focus on change in zooplankton species composition over space
and time. Decadal change in the zooplankton community is finally linked to physicalchanges in the upper water column of the subtropical North Pacific.

Vertical and horizontal distribution of bigeye tuna (Thunnus obesus) in
the northeastern subtropical gyre during summer
Evan Howell, Donald R. Hawn and Jeffrey J. Polovina
Pacific Islands Fisheries Science Center, NMFS, 2570 Dole Street, Honolulu, Hawaii 96822-2396. Email: evan.howell@noaa.gov

Popup satellite archival tags were deployed on 6 bigeye tuna (Thunnus obesus) inAugust of 2003. These tags were deployed from a commercial vessel operating as partof the Hawaii Longline fishery during normal fishing conditions at 150ºW, 30ºN. Thesetags had times at liberty ranging from 19 to 74 days before release from the animal andsurface transmission of data to Service ARGOS satellites. Vertical depth andtemperature data from these tags show a strong diurnal pattern with a bimodal
surface/depth distribution during the daytime while over 80% of the nighttime wasspent at the surface. Geolocations were estimated using a Kalman Filter state-spacemodel and light and surface temperature values measured by the archival tag. The
horizontal distributions of these 6 bigeye tunas show a highly resident pattern, with over
71% of the total time at liberty spent in the box 145ºW-154ºW, 27ºN-32ºN. Fishery datafrom the Hawaii Longline Logbook program shows that this region is an area of highhistorical bigeye catch and effort in the summer months of recent years. Satellite
altimetry and sea surface temperature data show that this region is situated on thenortheastern gradient of the subtropical gyre, a region with high eddy activity. These7

temporal and spatial conditions appear to creating a preferential habitat for bigeye tuna,
resulting in a shift from migratory to residential behavior in summer months in thisregion resulting in high interaction with the Hawaii Longline fishery

The springtime plankton dynamics affected by wind forcing and solar
radiation on the Bering Sea shelf
Takahiro Iida1, Jia Wang2, Meibing Jin2 and Seiichi Saitoh1
1- Laboratory of Marine Environment and Resource Sensing, Graduate School of Fisheries Sciences,
Hokkaido University, 3-1-1, Minato, Hakodate, Hokkaido, 041-8611, Japan. E-mail:tiida@salmon.fish.hokudai.ac.jp
2- International Arctic Research Center, 930 Koyukuk Drive, PO Box 757335, University of Alaska
Fairbanks, Fairbanks, Alaska 99775-7335

Interannual and seasonal variability of surface phytoplankton are examined in the
Bering Sea using Empirical Orthogonal Function (EOF) analysis of Sea-viewing Wide
Field-of-view Sensor (SeaWiFS) datasets from 1998 to 2002. The results of EOF
analysis on normalized monthly fields in spring (April-June) after temporal and spatial
monthly means were removed showed that phytoplankton concentrations varied inspring. The spatial EOF showed different phases occurred on the eastern shelf and thewestern Bering Sea shelf. This suggests the timing and magnitude of the spring bloom
has an east–west dipole mode in the Bering Sea. The east-west dipole of the spring
bloom is linked by ocean surface wind and solar radiation in connection with theposition and strength of the Aleutian low. The Aleutian low located in the western
Bering Sea, winds blow in the western Bering Sea, the solar radiation is stronger in theeastern Bering Sea.
To quantify phytoplankton variability in relation to wind and solar radiance, we
simulated the phytoplankton dynamics using a vertical one-dimensional NPZD
ecosystem model. The phytoplankton bloom period varied from late April to late May
in relation to wind-driven water column convection in the eastern and western Bering
Sea. Large phytoplankton blooms occurred when the mixing layer depth was shallow,
the winds were weak, and the solar radiance was strong. These results show that thetiming and distribution of the phytoplankton bloom changed with the Aleutian low
system.

Summer distribution and community structure of appendiculariansin the northwestern North PacificKen Kato and Naonobu Shiga
Biological Oceanography Laboratory, Hokkaido University. E-mail: ken-kato@fish.hokudai.ac.jp

8Appendicularians live within a complex mucus structure known as ‘house’. They feed
efficiently on food ranging from nanoplankton to bacteria by filtering ambient waterwith mucus filters, and transfer energy directly to higher trophic levels in the marine
ecosystem. Since appendicularians are fragile organisms, there have been few studies on
their distribution compared with other zooplankton taxa. In the present study, we
examined the horizontal and vertical distribution of appendicularians in thenorthwestern North Pacific.
Samplings were conducted by vertical hauls (0-150 m depth) with a NORPAC net(mesh size 0.33 mm) along 155oE (35oѸ 44oN) in the northwestern North Pacific during
MayѸ July of 2001, 2002 and 2003. Based on hydrographic conditions, this region canbe divided into three domains (subarctic domain: SA, transition domain: TD,
subtropical domain: ST). The number of sampling stations ranged from 6 to 14 eachyear. To determine the vertical distribution, simultaneous horizontal tows with MTD(Motoda) nets (mesh size 0.33 mm) were made at 20- to 50-m depth intervals between 0
and 200 m depth at 44oN, 42o30’N, 39o30’N and 38oN in 2003. All the samples were
preserved with borax-buffered formalin, and appendicularians were identified under astereomicroscope.
A total of 15 species were identified. Species number was greater in the southern region(SA: 4, TD: 12, ST: 14 species). In the SA (north of ca. 42oN), the cold-water species
Oikopleura labradoriensis was most abundant, followed by Fritillaria borealis f. typica.
O. labradoriensis showed a bimodal vertical distribution with peaks at 0 and 50 m depth.
In the TD (ca. 40Ѹ 42oN), O. labradoriensis and O. longicauda (warm water species)
were dominant. The vertical distributions of the two species differed slightly; O.
longicauda dominated near the surface, while O. labradoriensis dominated below 50 m
depth. The neritic species O. dioica was also collected at a few stations in the TD,
presumably due to transport by the Kuroshio. In the ST (south of ca. 40oN), many warm
water appendicularians were collected. O. longicauda was dominant at most stations,followed by O. fusiformis. Smaller F. pellucida predominated (79.6 inds. m-3) at thesurface in the ST. The horizontal and vertical distributions of appendicularians areprimarily governed by surface currents and will reflect the difference in their optimum
temperature ranges, even within the same hydrographic domain in the oceanic North
Pacific.

Long-term changes (1984-1994) in phytoplankton communities inOshoro Bay, northeastern Japan Sea
Saho Kitatsuji and Tsutomu Ikeda
Plankton Laboratory, Graduate School of Fisheries Sciences, Hokkaido University. E-mail:kit@fish.hokudai.ac.jp

Phytoplankton samples collected at bi-weekly or monthly intervals in 1984-1994 (11years) in Oshoro Bay, northeastern Japan Sea, were analyzed to look for a signal fromthe 1989/1990 regime shift, which caused a sudden increase of sea surface temperature

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(SST) throughout the Sea of Japan. Phytoplankton were collected with a conical net(110 µm mesh aperture) towed through the surface layer from the center of the semiclosed bay to its mouth and preserved in 10% neutralized formalin-seawater. As
environmental parameters, SST, transparency and specific gravity (a measure ofsalinity) were measured at each sampling station. Day-length data were obtained fromthe Japan Meteorological Agency homepage. In the laboratory, phytoplankton cells
larger than 100 µm were counted and identified to species. Of the time-series data of
1984-1994, a signal of the 1989/1990 regime shift was detected in monthly SST
anomalies, but not in monthly specific gravity and transparency anomalies. During the
11 years, phytoplankton abundance (cells ml-1) was high during the late 1980’s and the
1990’s, and was negatively correlated with SST. It is interpreted that low phytoplankton(cell size >100 µm) abundance during high SST years was due to possible nutrient
depletion caused by an earlier bloom of smaller phytoplankton. It has been observedthat small phytoplankton blooms occur in early summer during years of high SST.
Phytoplankton community structure (species composition) was not affected by the
1989/1990 regime shift. An anomalous feature seen in phytoplankton community
structure was the predominance of Pseudo-nitzschia sp. in the summer 1992 since
centric diatoms were the dominant phytoplankton component in the summer of all otheryears. A combination of low nutrients and short day-length in spring-summer 1992 is
considered to be a special condition to which Pseudo-nitzschia sp. is better adapted thanthe other diatoms.

Prediction of Pacific saury fishing grounds based on SST and SSC
variability derived from satellite remote sensing data
Toshiyuki Konishi, Hidetada Kiyofuji and Sei-Ichi Saitoh
Laboratory of Marine Environment and Resource Sensing, Graduate School of Fisheries Sciences,
Hokkaido University, 3-1-1, Minato, Hakodate, Hokkaido, 041-8611, Japan. E-mail:konishi@salmon.fish.hokudai.ac.jp

Pacific saury, Cololabis saria, is one of most important commercial fishes exploited in
the Northwest Pacific Ocean, especially in the waters around the central Kurile Islands,
southeastern Hokkaido Island and northeastern Honshu Island. We investigated thetemporal and spatial variability of sea surface temperature (SST) and chlorophyll-aconcentration on the formation of saury fishing grounds, and estimated the daily saury
fishing grounds. During 2000-2002, we analyzed these fishing grounds based on the
distribution of fishing fleet lights from Defense Meteorological Satellite
Program/Operational Linescan System (DMSP/OLS) night time images, sea surface
temperature (SST) from NOAA/AVHRR data, and chlorophyll-a from
Orbview2/SeaWiFS images. We found that the fishing grounds formed on the range of
11.8-18.0oC and 0.4-2.4 mg chl-a/m3 off southeastern Hokkaido, 12.5-18.8oC and 0.21.4mg/m3 off the Sanriku coast and 16.0-19.8oC and 0.3-0.8mg/m3 off the Jyoban coast.
These results show a relatively good agreement with the daily saury fishing grounds
detected by DMSP/OLS. In this study, we estimated the optimal environmental

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conditions for the formation of saury fishing grounds, which may help fisherman to findgood fishing grounds in the future.

Iron in the northwestern North Pacific Ocean
Kenshi Kuma
Graduate School of Fisheries Sciences/ Graduate School of Environmental Science,
Hokkaido University, Kita 13-Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0813 JAPANTel & Fax: +81-11-706-5314. E-mail: kuma@fish.hokudai.ac.jp

Iron is an essential micronutrient for phytoplankton growth, as an important componentof such biochemical processes as photosynthetic and respiratory electron transport,
nitrate and nitrite reduction and chlorophyll synthesis. Although iron is an element ofgreat biological and geochemical importance, its oceanic chemistry, such as inorganic
speciation and organic complexes, is very complex and not yet fully understood.
Recently, a number of studies pointed out that the Fe(III) complexation with naturalorganic ligands is possible in oceanic waters, but the detailed distribution, origin andchemical identity of organic ligands are largely unknown. Here I present the basic
concept of bioavailable iron species in seawater and iron chemistry in seawater such as
ferric iron hydroxide solubility and iron-organic complexation in seawater. Finally, I
present the detailed vertical distributions of iron (Fe(III) hydroxide solubility, dissolved
and dissolvable Fe concentrations) which are strongly related to the concentration andaffinity of natural Fe(III)-complexing organic ligands in seawater in the northwestern
North Pacific Ocean showing the iron source such as upwelling, vertical water mixing
during winter and atmospheric input.

Dust deposition to the surface waters of the North Pacific Ocean
inferred from surface water dissolved Al concentrations
Chris Measures
University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI 96822. E-mail: chrism@soest.hawaii.edu

Surface water dissolved Al concentrations determined during two cruises in the northwestern and central Pacific have been used to calculate mineral dust deposition to thesurface waters of these regions. Along 30˚N, calculated mean mineral deposition rates
range from ~ 1 gm m-2 yr-1 in the subtropical gyre near Japan to less than 0.1 gm m-2 yr-1
near the US west coast. A region of relatively enhanced deposition was seen to the northwest of the Hawaiian Islands, between 155 and 145˚W. In the north west Pacific, themixed water region and the sub-arctic gyre west of 170˚E show deposition values that
range from <0.1 to 0.6 gm m-2 yr-1. These values are more than one order of magnitude
lower than those predicted for this region by the GESAMP model (Duce et al., 1991)
and are surprisingly low given the very large transport of dust from the Gobi desert overthis part of the ocean. The high altitude of the dust transport across this region, above

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the marine boundary layer, is thought to be responsible for the relatively low mineraldeposition rate. However, the low deposition rate of mineral aerosol material to thesurface waters of this region is consistent with their High Nutrient Low Chlorophyll
status, since this would suggest that only small amounts of Fe are added to the nutrientrich surface waters by aerosol deposition.
[Duce et al. Global Biogeochemical Cycles, 5, 193-259, 1991.]

Temporal and spatial variability of chlorophyll a concentration aroundFutaoi Island in the Sea of Japan - A comparison of satellite ocean
color data and in-situ ship observation data
Kazushige Oishi
Laboratory of Marine Environment and Resource Sensing, Graduate School of Fisheries Sciences,
Hokkaido University, 3-1-1, Minato, Hakodate, Hokkaido, 041-8611, Japan. E-mail: ooishi@salmon.fish.hokudai.ac.jp

A large fishing ground for chub mackerel and Japanese sardine occurs in the Sea ofJapan around Futaoi Island, where the Tsushima Current, which is high in nutrients andchlorophyll, flows eastward and mixes with coastal water. To better understand thespatial and temporal variations of chlorophyll distribution in this area, we observed
chlorophyll concentrations using satellite ocean color data and in-situ ship observation
data. We measured in situ chlorophyll concentration during 29 July 29, 4-5 August, 8
October, and 25 November 2004 using a MODIS (Moderate Resolution Image
Spectroradiometer) for satellite chlorophyll estimation. Chlorophyll concentrations weregenerally higher near the coast than in offshore waters. This difference was larger inautumn and winter than in summer. In situ chlorophyll concentrations showed a peak at
20-25 m depths. The correlation coefficient between satellite and in situ observations
was 0.82, and the slope was 0.58. During autumn, a chlorophyll front occurred in the
coastal area and may have resulted from nutrients supplied by the Tsushima Current.

Temperature inversion in the Gulf of Alaska
Hiroji Onishi
Hokkaido University, Graduate School of Fisheries Science, Division of Marine Bioresource andEnvironmental Science. E-mail: onishi@fish.hokudai.ac.jp. http://a-stream3.fish.hokudai.ac.jp

Temperature inversions are generally observed in the subarctic North Pacific (e.g.,
Favorite et al., 1976). They are thought to be formed mainly by wintertime cooling fromthe surface, preserving the memory of wintertime atmospheric conditions. After theformation, temperature inversions gradually weaken as the season progresses due tosurface heating and vertical mixing.

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Using hydrographic data from the Oshoro Maru monitoring along 145oW every summer
during 1994-2002 and Argo profiling floats during 2001-2004, I will study theformation and fluctuation of temperature inversions in the Gulf of Alaska focusing on
their distributions and interannual variation. The Argo project started in 2000 to monitor
the temperature and salinity in the world oceans in 10-day cycles using 3000 profiling
floats (The Argo Science Team, 2001).
A distribution map of temperature inversions of all Argo data indicates a distinctive
feature separating three areas in the Gulf of Alaska. In the central area of the Alaskan
gyre centered at about 53oN, 152oW, large temperature inversions were seldom recordedin all years. Contrarily, in the Alaskan Stream area north of the Alaskan gyre, large(>0.3oC) temperature inversions were often observed. In the Alaska Current east of the
Alaskan gyre, small temperature inversions including non-inversions and large
temperature inversions were observed together side by side at the same time. In this area,
warm mesoscale eddies generated from coastal areas in the eastern Gulf of Alaska areoften observed (e.g., Crawford 2002). These eddies carry mesothermal structures in thisarea. From Oshoro Maru data along 145oW, which is just east of the center of the
Alaskan gyre, the frequency of temperature inversions and degree of temperature
minimum also showed large interannual variations.

The Kuroshio Extension Bifurcation Region: A pelagic hotspot forjuvenile loggerhead sea turtles
Jeffrey J. Polovina1, Itaru Uchida2, George Balazs1, Evan A. Howell1, Denise Parker3
and Peter Dutton4
1-Pacific Islands Fisheries Science Center, NMFS, 2570 Dole Street, Honolulu, Hawaii 96822-2396. Email: jeffrey.polovina@noaa.gov
2-Port of Nagoya Public Aquarium, Minato-ku, Nagoya, Japan
3-Joint Institute for Marine and Atmospheric Research, University of Hawaii, Honolulu, HI, U.S.A.
4-Southwest Fisheries Science Center, NOAA, 8604 La Jolla Shores Dr., La Jolla, CA 92037, U.S.A.

Satellite telemetry of 43 juvenile loggerhead sea turtles (Caretta caretta) in the western
North Pacific together with satellite-remotely sensed oceanographic data identified theKuroshio Extension Bifurcation Region (KEBR) as a forage hotspot for these turtles. In
the KEBR juvenile loggerheads resided in Kuroshio Extension Current (KEC) meanders
and the associated anti-cyclonic (warm core) and cyclonic (cold core) eddies during thefall, winter, and spring when the KEC water contains high surface chlorophyll. Turtles
often remained at a specific feature for several months. However, in the summer when
the KEC waters become vertically stratified and surface chlorophyll levels are low, theturtles moved north up to 600 km from the main axis of KEC to the Transition Zone
Chlorophyll Front (TZCF).
In some instances, the loggerheads swam against geostrophic currents, and seasonally
all turtles moved north and south across the strong zonal flow. Loggerhead turtles
traveling westward in the KEBR had their directed westward movement reduced 50%
by the opposing current, while those traveling eastward exhibited an increase in directed13zonal movement. It appears, therefore, that these relatively weak-swimming juvenile
loggerheads are not passive drifters in a major ocean current but are able to move east,
west, north, and south through this very energetic and complex habitat.
These results indicate that oceanic regions, specifically the KEBR, represent an
important juvenile forage habitat for this threatened species. Interannual and decadalchanges in productivity of the KEBR may be important to the species’ population
dynamics. Further, conservation efforts should focus on identifying and reducing threats
to the survival of loggerhead turtles in the KEBR.

Nutrient dynamics and productivity in the Bering Sea during 1997-2001
TaeKeun Rho*, Terry E. Whitledge and Dean Stockwell
Institute of Marine Science, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks,
Fairbanks, AK 99775* Current address: Marine Environment and Remote Sensing, Hokkaido University, Hakodate, Hokkaido,
JapanࠊE-mail: tkrho@salmon.fish.hokudai.ac.jp

During the late 1990s and early 2000s, the southeastern Bering Sea experienced large
physical and biological changes. In this region, there were also changes in the nutrient
dynamics, and high ammonium concentrations were observed over the southeastern
Bering Sea shelf in early spring. In this study, we investigated interactions between
ammonium and nitrate, especially ammonium inhibition of nitrate uptake rates during
the early summer of 2000. Ambient nitrate concentrations in the ammonium treatment
were not utilized until the ambient ammonium concentration fell below 7 µM. Absolutenitrate uptake rates in the ammonium treatments decreased when ammonium
concentrations were greater than 7 µM. Carbon uptake rates increased both in the nitrate
and ammonium addition bottles. During 1997-2001, high summer production over the
inner shelf may have been supported by the supply of ammonium during 1997-2001.

Long-term hydrographic observations in the subtropical North Pacificduring the Hawaii Ocean Times-series
Fernando Santiago-Mandujano
Department of Oceanography, University of Hawai’i, 1000 Pope Rd., Honolulu, HI 96822. E-mail:santiago@soest.hawaii.edu

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Aerosol geochemistry and nutrient deposition in the North Pacific
Eriko Shimizu, J. Zhang, M. Arisawa and W. Yuan
Faculty of Science, Toyama University, Toyama, Japan. E-mail: m052115@ems.toyama-u.ac.jp

In the present study, we measured the phytoplankton cell-number, chlorophyll a, andnutrients in sea surface water between 35-50oN along 165oE in July 2003. In the subarctic
and transition regions, the surface water was characterized by high nutrients and low
chlorophyll a concentration, which suggests that these regions were iron limited.
Estimations of nutrient consumption showed that the consumption of silicon andphosphorus were high in these regions. Near 40oN, the sea surface water was characterized
by low nutrients and high chlorophyll a concentration, which suggests that sufficient iron
was supplied to this area. To clarify the origin of iron near 40oN, we calculated the backtrajectories of air currents 3000 m above 40oN, 165oE using a model. The model showedthat more than half of back trajectories at 40oN, 165oE originated in the Gobi desert.
Thus we hypothesize that iron was supplied to the North Pacific by aerosol deposition.
We also found that aluminum and opal fluxes measured in a sediment trap at St. KNOT
(44oN, 155oE) were highly correlated with dust events in the desert. To determine theeffect of continental dust, in August 2004, we collected both aerosols and sea surface
water samples over the North Pacific and measured the major water-soluble ions andnutrients in each. NO3- concentrations at the sea surface showed that the Japanese coast
was a nitrate-limited area. Our estimation showed that the aerosols supplied 24 µmol m2
day-1 NO3- flux to the Japanese coast. We are now measuring major nutrients,
microelement nutrients and acidity in aerosols to clarify the importance of aerosols as asource of iron to the ocean.

Can new satellite capabilities be used to infer cloud condensation
nuclei? -- An empirical assessment based on in-situ airborne data
Yohei Shinozuka
University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, HI 96822. E-mail: yohei@hawaii.edu

The goal of this proposed research is to identify the satellite capabilities needed to infercloud condensation nuclei (CCN). The current satellite algorithms (e.g., Kaufman et al.,[1997]) derive the concentration of small particles, which contribute little to theobserved radiances, based on their association with larger optically effective particles
defined in several aerosol models. It is, however, not clear how well these models
reflect the actual aerosol physical, chemical and optical properties. During extensive
airborne campaigns in diverse regions over the globe, we measured aerosols derivingfrom urban pollution, biomass burning, desert outflow and ocean surface. By evaluating
their properties, we will constrain the degree to which satellites will be able toeffectively retrieve the CCN concentration in various air masses. We expect this effort
to provide guidance as to when, where and how satellite platforms might best be used toaddress this objective.

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Relationship between SV and zooplankton in the North PacificTakaaki Tatsuta, Kouji Iida, Toru Mukai
Faculty of Fisheries, Hokkaido University. E-mail: tatsuta@echo.fish.hokudai.ac.jp

In recent years, acoustic technology has been extensively used to estimate zooplankton
abundance. Zooplankton generally form a sound scattering layer and aggregate near thesurface at night by diel vertical migration. In this study, we compared the volume
backscattering strength (SV) measured using a scientific echo sounder (actual SV) with
the SV calculated from an acoustic scattering model (calculated SV) and verified theacoustic characteristics of the zooplankton sound scattering layer (SSL). We carried out
surveys along 165oE and 165oW during June-August of 2003 and 2004. Acoustic data
were collected with a scientific echo sounder (Simrad EK60), and zooplankton samples
were collected at night with oblique hauls of bongo nets (2003) and horizontal hauls of
an ORI net (2004). We sorted the zooplankton and measured the live body density,
sound speed, number of individuals, wet weight, and body length of each zooplankton.
On the basis of these data, we determined the calculated SV using the high-pass fluid
sphere model described by Johnson (1977). Echograms and the SV were greatest at low
frequencies in low latitude areas. The zooplankton samples comprised mainly copepods,
so only copepods were used in the acoustic scattering model. Comparison of the actual
SV with the calculated SV showed a weak correlation at high frequencies in highlatitude areas, and no correlation in low latitude areas. This was thought to be due to thelow efficiency of the nets used to collect zooplankton and micronekton and the low
accuracy of the acoustic scattering model.

East-west comparison in zooplankton community structure in thesubarctic Pacific during summers of 2003 and 2004
Atsushi Yamaguchi, Yuu Yokoi, Naonobu Shiga and Tsutomu Ikeda
Marine Biology Laboratory, Hokkaido University. E-mail: a-yama@fish.hokudai.ac.jp

Recently, east-west differences in phytoplankton community in the subarctic Pacifichave been well reported; they show that a large spring phytoplankton bloom occurs in
the west, while little or no bloom occurs in the east. However, little information isavailable on east-west differences in zooplankton community structure. In the present
study, we evaluated east-west differences in zooplankton community structure and bodysize in the subarctic Pacific. Zooplankton samples were collected with vertical hauls ofa NORPAC net at 0-150 m depth at 7 stations (2003) and 9 stations (2004) between
36oN to 50oN along 165oE, and 7 (2003) and 11 stations (2004) along 165˚W during
June-August of 2003 and 2004. After wet-weight measurement, zooplankton were
sorted, counted with major taxa and species identification were done for the dominant
copepod Neocalanus cristatus copepodid 5 stage (C5), N. plumchrus C5, Eucalanus
bungii C4 to C6F, Metridia pacifica C6F, the hydrozoa Aglantha digitale, and the16chaetognatha Sagitta elegans. Body size measurements were also made for eachspecimen. Integrated mean temperature between 0 and 150 m was lower in the west
(165˚E) than at the same latitude in the east (165˚W). In both 2003 and 2004, theabundance of A. digitale was greater in the east; in 2004, its abundance was 60 times
greater in the east (U-test: p<0.001). The copepod E. bungii showed the opposite
pattern; its abundance was 3 times greater in the west (p<0.05). Body sizes of A.
digitale and S. elegans showed a bimodal distribution throughout the region in both
years, which suggests the presence of several generations in the study period. Body
sizes of most copepod species were larger in the west, which reflect the lower
temperature in this region. Differences in marine ecosystem structure and generation
length will be discussed as possible causes of the dominance of A. digitale in the eastand E. bungii in the west.

Results of a cetacean sighting survey during the T/S Oshoro Maru
North Pacific cruise in 2005
Lareina Yee and Keiko Sekiguchi**

University of Hawai’i at Hilo, 200 W. Kawili Street, Hilo, HI 96720. E-mail: ksekiguc@hawaii.edu

The cetacean sighting survey was conducted along the second and third legs of the T/SOshoro Maru North Pacific cruise 2005. Leg 2 was in the eastern Bering Sea above the
Aleutians Islands and Leg 3 was en route from Dutch Harbor to Honolulu, Hawaii alongthe 165oW longitude line. One or two observers scanned the sea on the upper bridge
during full effort surveys using a 7x50 Fujinon binocular while communicated withanother who had the responsibility of recording data gathered on the bridge. The survey
was conducted daily for 12 days beginning about 1 hour after sunrise weather
permitting alongside with other marine research conducted on the vessel. A total of 79
hours and 29 minutes was performed during full effort status during Leg 2 covering a
distance of 549.7 nautical miles. On Leg 3, a duration of 172 hours and 45 minutes wasused during full effort surveying covering a distance of 1312.75 nautical miles. In total,full effort cetacean sighting survey had covered a distance of 1862.45 nautical miles in
252 hours and 14 minutes. On the Bering Sea voyage, a total of 170 cetaceans was
sighted in 63 schools: 3 harbor porpoise in 2 groups, 88 Dall’s porpoise in 19 groups, 19
fin whales in 12 groups, 4 sei whales in 2 groups, 24 humpback whales in 11 groups, 13
killer whales in two groups, 3 minke whales and 1 sperm whale and 15 unidentified
cetaceans in 10 groups. On Leg 3, a total of 232 cetaceans in 40 groups was sighted:
109 Pacific white-sided dolphin in 5 groups, 56 Dall’s porpoise in 14 groups, 16
humpback whales in 6 groups, 8 killer whales in 1 group, 1 northern right whale dolphin,
1 fin whale, 1 sei whale, 1 Ziphiidae and 31 unidentified cetaceans in 2 groups. Mostsightings were associated near the edge of the continental shelf in the Bering Sea and incolder waters along the 165oW longitude line.

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List of speakers
Hokkaido University
Yujiro Aota
John Bower
Mitsuru Chigira
Ryohei Fukui
Kei Hirose
Takahiro Iida
Shinichi Kado
Hitoshi Kaneko
Ken Katou
Saho Kitatsuji
Saori Kitayama
Toshiyuki Konishi
Kenshi Kuma
Eri Manabe
Kazushige Oishi
Hiroji Onishi
TaeKeun Rho
Yosuke Sagawa
Kenichi Sato
Takaaki Tatsuta
Atsushi Yamaguchi
Pacific Islands Fisheries Science Center, NOAA
Reka Domokos
Evan Howell
Jeff Polovina
Toyama University
Eriko Shimizu
Meguru Takashima
University of Hawai’i at Hilo
Lareina Yee
University of Hawai’i at Manoa
Bob Bidigare
Cedric Chavanne
Cecilia C.S. Hannides
Chris Measures
Fernando Santiago-Mandujano
Yohei Shinozuka

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