Temporal and Spatial Flux Changes of Radiolarians in the Northwestern

ARTICLE IN PRESS

Deep-Sea Research II 52 (2005) 2240–2274 www.elsevier.com/locate/dsr2

Temporal and spatial ﬂux changes of radiolarians in the northwestern Paciﬁc Ocean during 1997–2000

Yusuke Okazakia,Ã, Kozo Takahashib, Jonaotaro Onoderab, Makio C. Hondac

aOcean Research Institute, University of Tokyo, Minamidai 1-15-1, Nakano-ku, Tokyo 164-8639, Japan bDepartment of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan cJapan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka 237-0061, Japan

Received 30 September 2003; accepted 28 July 2005 Available online 20 October 2005

Abstract

In order to examine the radiolarian fluxes and evaluate their relationship to the physical and biological environments, time-series sediment traps were deployed at three stations (Stations 50N, KNOT, and 40N) in the northwestern North Pacific from 1997 to 2000. Station 50N (501N, 1651E, 3260 m) is located in the center of Western Subarctic Gyre (WSAG); Station KNOT (441N, 1551E, 2957 m) is located toward the margin of WSAG; and Station 40N (401N, 1651E, 2986 m) is located in the Subarctic Boundary. Total radiolaria fluxes at Station 40N showed higher values than those at the other two stations, and were mainly attributed to the influence of relatively high-temperature and high-salinity subtropical gyre waters. Correlation coefficients between total mass fluxes (mainly composed of diatoms) and radiolarian fluxes at three stations were relatively low. This is primarily because of the wide vertical distribution of radiolarians and various trophic patterns corresponding to their niche. Radiolarian species were classified according to their geographic water mass and vertical distributions based on previous studies using sediment samples. As a result, seasonal changes of radiolarian fluxes in each water mass showed patterns corresponding to particular controlling factors such as physical hydrography and food conditions. Among these patterns, temporal changes in radiolarian taxonomic composition in the upper layer (0–100 m) seemed to reflect well the sea-surface temperature anomaly (SSTA) changes, affected by El Ninõ and La Ninã events, at Station 40N. Therefore, radiolarian assemblages can be used to reconstruct past SSTA changes and to understand the past El Ninõ and La Ninã teleconnection in the Kuroshio-Oyashio Extension region. r 2005 Elsevier Ltd. All rights reserved.

Keywords: Radiolaria; Sediment trap; Temporal flux variation; Western Subarctic Gyre; Subarctic Boundary; El Ninõ; La Ninã

1. Introduction change and ecological environment. Therefore, a better knowledge of the present relationship be- Microplankton shells and skeletons have been tween the ecology of microplankton and the used as various proxies to reconstruct past climate physical and biological environmental conditions will improve our understanding of both paleocea- Ã Corresponding author at: Institute of Observational Research nography and present-day oceanography. Radiolar- for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. ia are siliceous microzooplankton with high Tel.: +81 46 867 9515; fax: +81 46 867 9455. diversity that dwell in a wide range of depth zones E-mail address: [email protected] (Y. Okazaki). from the surface water down to several thousand

0967-0645/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2005.07.006 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2241 meters. Thus, they have a potential to be a proxy of 1993). However, paleoceanographic knowledge in various vertical water masses. this region is still meager mainly because of the Radiolaria are classified into two taxonomic carbonate dissolution caused by the shallow carbo- groups: Polycystina and Phaeodaria. The skeletons nate compensation depth (CCD). of polycystine radiolarians are often preserved in The northwestern Pacific Ocean is characterized the sediments, whereas phaeodarian radiolarians are by high primary production attributed to diatoms. easily dissolved in the water column because of their Therefore, the efficiency of the biological pump in skeletal constitution and thus are rarely preserved in this region is significantly high (Honda et al., 2002) the sediments (Takahashi et al., 1983). Recently, the and thus, important for the global carbon cycle. importance of the oscillation in the intermediate- There have been some previous taxon-quantitative water production rate during the Quaternary works on radiolarian flux in the subarctic North climate change has been recognized (e.g., Talley, Pacific using time-series sediment traps: the Alaskan 1999). Ganopolski et al. (1998) indicated the Gyre (Stations PAPA and C: Takahashi, 1987, expansion of the North Pacific Intermediate Water 1997), and the central subarctic Pacific (Station SA: (NPIW) formation in the north during the Last Fukumura and Takahashi, 2000). In the north- Glacial Maximum (LGM) and the oscillations in western Pacific, Bernstein et al. (1990) reported the the production of NPIW during the late Quaternary radiolarian fluxes at seven stations. However, they might have been influenced by the major climatic used free-drifting sediment traps and their sampling changes (Kennett et al., 2002). A part of the NPIW durations were only for ca. 24 h. originates in the Okhotsk Sea today (e.g., Talley, In this study we present the modern seasonal 1991; Freeland et al., 1998; Wong et al., 1998), and changes in the time-series radiolarian flux over a 2- the NPIW is distributed mainly between 300 and year period in the northwestern North Pacific and 700 m in the northwestern North Pacific (Talley, evaluate their relationships to the physical and

60°N

Bering Sea Gyre

Okhotsk KAMCHATKA Gyre East Kamchatka Current

50N 50° SAKHALIN Western Subarctic Gyre

HOKKAIDO Oyashio Current KNOT

40° 40N Subarctic Boundary

Kuroshio Extension

140°E 150° 160° 170° 180°

Fig. 1. Map showing the locations of the three sediment trap stations in the northwestern North Pacific. General circulation patterns are also shown (Map drawn by ‘‘Online Map Creation’’). ARTICLE IN PRESS 2242 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 biological environmental conditions as an impor- Monthly hydrographic data from the sea surface tant step in reconstructing the past oceanographic to 1000 m depth at each sediment trap station were conditions. obtained from the World Ocean Atlas 1994 (Levitus and Boyer, 1994), and illustrated with the Ocean 2. Materials and methods Data View software package (Fig. 2; Schlitzer, 2002). Time-series sediment traps (McLane Mark 7G- 21) with 21 collecting cups (Honjo and Doherty, 3. Oceanographic setting 1988) were deployed at approximately 3000 m depths at three stations in the northwestern North The subarctic circulation system in the North Pacific (Stations 50N, KNOT, and 40N) from Pacific has a large-scale counterclockwise surface December 1997 to May 2000 (Fig. 1; Table 1). circulation characterized by low salinity (o34.0 psu) The trapping efficiency of the Mark 7G-21 is and relatively low temperature (ca. 4–12 1C) with a approximately 1, indicating an almost 100% collec- sharp halocline (ca. 150–200 m; Favorite et al., tion efficiency in the bathypelagic zone (at depths 1976). The subarctic circulation system has four 41500 m), based on 231Pa and 230Th (Yu et al., gyres from east to west: Alaskan Gyre, Bering Sea 2001). Their recovery, maintenance and redeploy- Gyre, Western Subarctic Gyre (WSAG), and ment were carried out during the cruises of the R.V. Okhotsk Sea Gyre (OSG). The features of the Mirai, Japan Agency for Marine-Earth Science and WSAG water mass are as follows: (1) strong vertical Technology (JAMSTEC). mixing down to 150 m water depth caused by the Samples for radiolarian analyses were sieved cooling of the sea-surface water accompanied by through a stainless screen with 1 mm mesh to radiative atmospheric cooling during winter, (2) the remove larger plankton, and then split into an strong and stable stratification beneath the surface appropriate aliquot size ranging from 1/100 to layer resulting in a significant halocline, (3) the 1/132. The split samples were sieved through a sharp thermocline formation caused by heating of stainless steel screen with 63 mm mesh and filtered the sea-surface water accompanied by the rise of air through Gelmans membrane filters with a nominal temperature during summer. The most significant pore size of 0.45 mm. The filtered samples were characteristic of the WSAG is the presence of a washed with distilled water to remove salt, dried in temperature minimum (ca. 2–4 1C) subsurface layer an oven at 50 1C overnight, and then permanently (ca. 50–150 m) called the ‘‘dichothermal layer’’ mounted with Canada balsam on microslides. All (Nagata et al., 1992). The temperature maximum coarse-sized radiolarian skeletons (463 mm) on a layer below the dichothermal layer is also a microslide were counted with a light microscope and characteristic of the WSAG (Nagata et al., 1992). computed to derive radiolarian fluxes (No. radi- Below the dichothermal layer, the NPIW is defined olarians m2 day1) at each station. Species identi- as the main salinity minimum in the subtropical fication of radiolarians was performed according to North Pacific at a density of 26.7–26.8sy (ca. the taxonomy of the following works: Nigrini 300–700 m; Talley, 1993). In the WSAG, the East (1970), Renz (1976), Bjørklund (1976), Boltovskoy Kamchatka Current flows southward along the and Riedel (1987), Takahashi (1991), Abelmann Kamchatka Peninsula (Fig. 1). A part of the East (1992b), Welling (1996), Nigrini and Moore (1979), Kamchatka Current flows into the Okhotsk Sea Bjørklund et al. (1998), and Nimmergut and through the passes in the northern Kuril Islands. Abelmann (2002). Diversity indices using the The Okhotsk Sea water plays a significant role in Shannon-Wiener log-base 2 formula (H: Shannon the water-mass formation and modification of the and Weaver, 1949) were used. Subarctic Gyre such as the formation of the

Table 1 Summary information for the sediment trap samples used in this work

Trap station Latitude Longitude Water depth (m) Mooring depths (m) Sampled duration Sampled interval (day)

50N 501010N 1651020E 5570 3260 1 Dec. 97–18 May. 00 15.04, 17.38 KNOT 431580N 1551030E 5370 2957 1 Dec. 97–14 May. 00 15.04, 17.38 40N 401000N 1651000E 5483 2986 1 Dec. 97–30 Jan. 00 9.67, 15.04, 17.38 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2243

Fig. 2. Seasonal variations of mixed-layer depths and the vertical structures of temperature and salinity at three stations in the northwestern North Paciﬁc (Levitus and Boyer, 1994). Contours drawn by Ocean Data View (Schlitzer, 2002).

Oyashio Water and the NPIW (Talley, 1991; Free- Monthly hydrographic data (temperature and land et al., 1998). The Oyashio Water is formed by salinity) from the sea surface to 1000 m depth at the mixing of the East Kamchatka Current Water each sediment trap station are shown in Fig. 2. with the Okhotsk Sea Water, which comes out Hydrographic data in the surface mixed-layer depth through the passes in the southern Kuril Islands at each station also were observed during the eight (Fig. 1; Nagata et al., 1992). As a result of this cruises of the R.V. Mirai from November 1997 to mixing, the Oyashio Water has higher dissolved February 2000 (Honda et al., 2002). They compiled oxygen contents down to 500 m water depth than the oceanographic conditions at each site as follows: that of the East Kamchatka Current, attributing to Station 50N is located in the center of the WSAG the original Okhotsk Sea Water. and characterized by low temperature and high ARTICLE IN PRESS 2244 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 nutrients during winter; Station KNOT is located Phaeodarian fluxes showed a clear seasonality toward the margin of the WSAG and characterized and increased during autumn to winter throughout by high seasonal amplitudes in temperature, salinity the sampling period. The means of total polycystine and nutrients; and Station 40N is located at around and phaeodarian fluxes were 4.76 103 and the Subarctic Boundary and characterized by high 1.15 103 radiolarians m2 day1, respectively, and temperature, high salinity, and low nutrients, the mean relative abundances of total polycystine indicating the influence of the subtropical gyre and phaeodarian fluxes were 80.5% and 19.5%, (Honda et al., 2002). respectively. Both phaeodarian flux and relative abundance showed the highest values among the 4. Results three stations.

Temporal fluxes of total Radiolaria, polycystine 4.3. Station 40N Radiolaria, and phaeodarian Radiolaria during 1997–2000 are shown for Stations 50N, KNOT, Total radiolarian fluxes at Station 40N changed and 40N (Fig. 3). Temporal fluxes of total mass significantly and showed high values (412.0 (TM; total weight of particle flux) and total diatoms 103 radiolarians m2 day1) during March–May at the three stations are indicated in Fig. 4, and the and August–October in 1998. High fluxes also were annual fluxes (1998 and 1999) of radiolarians for observed during July–September in 1999, while each trap are shown together with each flux there was a period with no data from January to component (TM, total organic carbon (TOC), May because of a long sample hiatus. The aluminum (Al), and opal) in Table 2, although amplitude of radiolarian flux ranged from sampling hiatuses occurred at each site (see Fig. 3). 4.22 103 to 17.7 103 radiolarians m2 day1. Fluxes of other chemical components have been The mean total radiolarian flux was 10.0 103 radi- reported by Honda (2001) and Honda et al. (2002). olarians m2 day1, which was the highest among the three stations. 4.1. Station 50N Phaeodarian fluxes increased from July to August in 1998 and August to October in 1999. The means Total radiolarian fluxes at Station 50N showed of total polycystine and phaeodarian fluxes were high values (46.0 103 radiolarians m2 day1) 9.55 103 and 0.45 103 radiolarians m2 day1, during October–December in 1998 and 1999. On respectively. The mean relative abundance of total the other hand, high total radiolarian fluxes were polycystine and phaeodarian fluxes were 95.5% and observed during April to May in 2000. The 4.5%, respectively. The mean value of polycystine amplitude of radiolarian flux ranged from flux at Station 50N was more than twice that of the 1.92 103 to 7.24 103 radiolarians m2 day1. other two stations. On the other hand, the mean The mean total radiolarian flux was 4.34 103 radi- value of phaeodarian flux at Station 50N was the olarians m2 day1. lowest among the three stations. Phaeodarian fluxes peaked during November– December in 1998. The mean total polycystine and 4.4. Radiolarian diversity index phaeodarian fluxes were 3.67 103 and 0.68 103 radiolarians m2 day1, respectively; and the mean relative The temporal changes in the radiolarian diversity abundance of total polycystine and phaeodarian fluxes indices at all stations are shown in Fig. 3. At Station were 84.4% and 15.6%, respectively. 50N the diversity showed no significant change throughout the sampling period and the amplitude 4.2. Station KNOT ranged from 4.1 to 4.9 H. At Station KNOT, the diversity also showed no significant change through- At Station KNOT, total radiolarian fluxes out the sampling period and the amplitude ranged showed rapid oscillations but no clear seasonal from 4.2 to 4.9 H. The diversity at Station 40N trend. The amplitude of the radiolarian fluxes showed higher values (45.0 H) than that of the ranged from 3.68 103 to 10.6 103 radi- other two stations except for the period during olarians m2 day1. The mean total radiolarian flux December 1997–January 1998, when significantly was 5.91 103 radiolarians m2 day1, which was low values were observed; the amplitude ranged higher than that of Station 50N. from 3.4 to 5.7 H. ARTICLE IN PRESS

Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2245

H diversity Species 6 5 4 3 2000 2000 2000 JAM JAM JAM DFM DFM DFM 1999 1999 1999 JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN 1998 1998 1998 JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN 2000 2000 2000 JAM JAM JAM DFM DFM DFM ) at three stations in the northwestern North Paciﬁc during 1997–2000. The blank 1999 1999 1999 H JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN 1998 1998 1998 JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN 2000 2000 2000 JAM JAM JAM DFM DFM DFM H 1999 1999 1999 JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN Station 50N Station KNOT Station 40N Species diversity 1998 1998 1998 Total radiolarianTotal flux JAMO JAMO JAMO DFMJJASN DFMJJASN DFMJJASN

8 6 4 2 0 8 6 4 2 0 2 1 0

18 16 14 12 10 18 16 14 12 10

) day m radiolarians No. (X10 ) day m radiolarians No. (X10 ) day m radiolarians No. (X10

-1 -2 3 -1 -2 3 -1 -2 3

Total Phaeodaria Total Radiolaria Total Polycystina Total Phaeodaria Total vertical belts represent the sample hiatuses. Fig. 3. Temporal variations of total Radiolaria, Polycystina, Phaeodaria and diversity indices ( ARTICLE IN PRESS

2246 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

) y da m g (m ) y da m valves No. (X10

-1 -2 -1 -2 6

Total mass flux mass Total flux diatom Total 600 400 200 0 160 120 80 40 0 2000 2000 JAM JAM DFM DFM nk vertical belts represent the 1999 1999 JAMO JAMO DFMJJASN DFMJJASN 1998 1998 JAMO JAMO DFMJJASN DFMJJASN 2000 2000 JAM JAM DFM DFM 1999 1999 JAMO JAMO DFMJJASN DFMJJASN 1998 1998 JAMO JAMO DFMJJASN DFMJJASN 2000 2000 JAM JAM DFM DFM 1999 1999 JAMO JAMO DFMJJASN DFMJJASN Station 50N Station KNOT Station 40N Total radiolarianTotal flux mass flux Total radiolarianTotal flux diatom flux Total 1998 1998 JAMO JAMO DFMJJASN DFMJJASN

8 6 4 2 0 8 6 4 2 0

18 16 14 12 10 18 16 14 12 10

) day m radiolarians No. (X10 ) day m radiolarians No. (X10

-1 -2 3 -1 -2 3

Total Radiolaria Total Radiolaria Total sample hiatuses. Fig. 4. Temporal ﬂuxes of total Radiolaria, total mass, and total diatoms at three stations in the northwestern North Paciﬁc during 1997–2000. The bla ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2247

Table 2 The annual ﬂuxes of total Radiolaria, Polycystina, Phaeodaria, total mass, total organic carbon, aluminum, and opal at each trap in 1998 and 1999

TM Al Opal TOC Radiolaria Polycystina Phaeodaria (mg m2 day1) (mg m2 day1) (mg m2 day1) (mg m2 day1) ( 103 No. radiolarians m2 day1)

50N (3260 m) 1998 104.1 0.61 50.4 3.23 4.51 3.83 0.68 1999 116.5 0.61 62.5 2.89 3.81 3.16 0.65 KNOT (2957 m) 1998 157.4 1.26 77.7 6.13 6.13 5.01 1.12 1999 171.5 1.34 86.9 5.99 6.18 4.97 1.21 40N (2986 m) 1998 95.9 0.47 42.7 3.63 10.75 10.33 0.42 1999 102.8 0.33 47.3 4.18 9.91 9.38 0.52

4.5. Radiolarian species flux stations (Fig. 3). Previous studies employing plankton tows reported that radiolarian standing stocks A total of 165 radiolarian taxa were encountered in in the equatorial Pacific (Petrushevskaya, 1971; this study: 141 Polycystina (62 Spumellaria, 79 Welling et al., 1996; Yamashita et al., 2002) showed Nassellaria); and 24 Phaeodaria (Table 3). Those much higher values than those in the North Pacific species with a mean occurrence greater than 1% at (Kling, 1979; Okazaki et al., 2004). The hydro- each station are listed in Table 4. Previous studies graphic conditions at Station 40N indicated the have revealed the geographic and vertical distributions influence of the subtropical gyre with high tempera- of radiolarian taxa, and we have chosen the following ture and salinity in the upper water depths (Fig. 2). radiolarian geographic indicators (Subarctic, Transi- Therefore, radiolarian species indicative of warm tional, and Subtropical and Tropical) in the North waters were abundant in the surface and upper Pacific based on the following studies: Nigrini (1970), subsurface layers at Station 40N (Fig. 5). Radiolar- Moore (1978), Nigrini and Moore (1979),and ian production deduced from the fluxes showed a Lombari and Boden (1985) (Table 5). We also have clear difference in physical oceanographic condi- compiled the various water depth dwellers (surface tions between Station 40N and the other two (0–50 m), upper subsurface (50–100 m), lower subsur- stations. face (100–300 m), and intermediate (300–1000 m) in In addition to the physical conditions, chemical the North Pacific based on the following studies: and food conditions are also important for radi- Equatorial Pacific: Renz (1976), Welling et al. (1996) olarian production. The fluxes of all chemical and Yamashita et al. (2002);centralNorthPacific: components (TM, Al, Opal, and TOC) at Station Kling (1979); California Current region: Boltovskoy KNOT were much higher than those at other and Riedel (1987) and Kling and Boltovskoy (1995); stations in both 1998 and 1999 (Table 2; Honda, Okhotsk Sea: Nimmergut and Abelmann (2002); 2001; Honda et al., 2002). Stations KNOT and 50N Oyashio region: Okazaki et al. (2004) (Table 6). We were located in the WSAG and had similar compiled these data and illustrated the radiolarian hydrographic conditions (Fig. 2). The difference in fluxes belonging to various water masses at each trap the mean radiolarian flux levels between Stations (Fig. 5). KNOT and 50N is thought to reflect the food conditions, which can be indicated by parameters 5. Discussion such as organic matter. Diatom fluxes were closely correlated with the TM fluxes at all three stations 5.1. Radiolarian production in the northwestern (Onodera et al., 2003, 2005). On the other hand, the North Pacific correlation coefficients between radiolarian fluxes and TM fluxes were lower (Station 50N: r ¼ 0:425, The mean value of total radiolarian fluxes at Station KNOT: r ¼ 0:438, and Station 40N: Station 40N was much higher than those of other r ¼ 0:677) than these between diatom and TM ARTICLE IN PRESS 2248 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Table 3 List of 166 radiolarian taxa encountered in the sediment trap samples

Taxa Current references

Spumellaria Actinomma arcadophorum Haeckel Nigrini and Moore (1979, p. S29, Pl. 3, Fig. 4) Actinomma boreale Cleve Cortese and Bjørklund (1998, p. 151, Pl. 1, Figs. 1–18) Actinomma delicatulum (Dogiel and Reshetnyak) Welling (1996, p. 207, Pl. 2, Figs. 5–7) Actinomma leptoderma leptoderma (Jørgensen) Bjørklund (1998, p. 128, Pl. 1, Fig. 11) Actinomma leptoderma longispina Cortese and Bjørklund Cortese and Bjørklund (1998, p. 153, Pl. 2, Figs. 15–22) Actinomma medianum Nigrini Nigrini and Moore (1979, p. S31, Pl. 3, Figs. 5 and 6) Actinomma sp. 1 Abelmann (1992b, p. 378, Pl. 1, Fig. 2) Actionmma spp. Cenosphaera spp. Nigrini and Moore (1979, p. S43, Pl. 4, Figs. 3a–d) Centrocubus octostylus Haeckel Takahashi (1991, p. 64, Pl. 7, Fig. 1) Cladococcus abietinus Haeckel Takahashi (1991, p. 67, Pl. 10, Fig. 5) Cladococcus abietinus (medullary shell) Cladococcus cervicornis Haeckel Takahashi (1991, p. 67, Pl. 10, Figs. 8–10) Cladococcus cervicornis (medullary shell) Cladococcus scoparius Haeckel Takahashi (1991, p. 67, Pl. 10, Figs. 6 and 7) Cladococcus viminalis Haeckel Bjørklund (1976, p. 1131, Pl. 1, Figs. 10–12) Collosphaera confossa Takahashi Takahashi (1991, p. 56, Pl. 2, Figs. 4 and 5) Collosphaera tubelosa Haeckel Takahashi (1991, p. 55, Pl. 2, Figs. 1–3) Dictyocoryne profunda Ehrenberg Nigrini and Moore (1979, p. S87, Pl. 12, Fig. 1) Didymocyrtis tetrathalamus (Haeckel) Takahashi (1991, p. 79, Pl. 21, Figs. 2–14) Dorydruppa bensoni Takahashi Takahashi (1991, p. 78, Pl. 15, Figs. 11–14) Drymyomma elegans Jørgensen Cortese and Bjørklund (1998, p. 154, Pl. 3, Figs. 17–19) Euchitonia elegans (Ehrenberg) Takahashi (1991, p. 80, Pl. 16, Figs. 1–6) Gonosphaera primordialis Jørgensen Bjørklund (1976, p. 1143, Pl. 9, Figs. 7–10) Heliodiscus asteriscus Haeckel Nigrini and Moore (1979, p. S73, Pl. 9, Figs. 1 and 2) Hexacontium enthacanthum Jørgensen Nigrini and Moore (1979, p. S45, Pl. 5, Figs. 1a, b) Hexacontium laevigatum Haeckel Nigrini and Moore (1979, p. S47, Pl. 5, Figs. 2a, b) Hexacontium spp. Hexapyle armata (Haeckel) Welling (1996, p. 219, Pl. 12, Figs. 1 and 2) Hymeniastrum euclidis Haeckel Nigrini and Moore (1979, p. S91, Pl. 12, Fig. 3) Larcopyle butschlii Dreyer Nigrini and Moore (1979, p. S131, Pl. 17, Figs. 1a, b) Larcospira quadrangula Haeckel Takahashi (1991, p. 92, Pl. 23, Figs. 11 and 12) Lithelius minor (Jørgensen) Nigrini and Moore (1979, p. S135, Pl. 17, Figs. 3 and 4a, b) Lithelius nautiloides Popofsky Nigrini and Moore (1979, p. S137, Pl. 17, Fig. 5) Phorticium pylonium Haeckel Welling (1996, p. 220, Pl. 12, Figs. 10 and 11) Plegmosphaera lepticali Renz Renz (1976, p. 115, Pl. 1, Fig. 14) Plegmosphaera pachypila Haeckel Takahashi (1991, p. 62, Pl. 5, Figs. 7–9) Polysolenia arktios Nigrini Nigrini and Moore (1979, p. S11, Pl. 2, Fig. 1) Rhizoplegma boreale (Cleve) Bjørklund (1998, p. 128, Pl. 1, Fig. 8) Saturnalis circularis Haeckel Takahashi (1991, p.78, Pl. 15, Figs. 15–18) Siphonosphaera spp. Sphaeropyle langii Dreyer Welling (1996, p. 207, Pl. 3, Figs. 1 and 2) Spongaster tetras tetras Ehrenberg Nigrini and Moore (1979, p. S93, Pl. 13, Fig. 1) Spongodiscidae sp. Spongodiscus spp. Spongoliva ellipsoides Popofsky Renz (1976, p. 108, Pl. 1, Fig. 5) Spongopyle osculosa Dreyer Nigrini and Moore (1979, p. S115, Pl. 15, Fig. 1) Spongotrochus glacialis Popofsky Nigrini and Moore (1979, p. S115, Pl. 15, Figs. 2a–d) Spongotrochus glacialis (small) Nimmergut and Abelmann (2002, p. 469, Pl. 1, Fig. 1) Spongurus cylindricas (Haeckel) Takahashi (1991, p. 85, Pl. 17, Figs. 6–9) Spongurus pylomaticus Riedel Nigrini and Moore (1979, p. S65, Pl. 15, Figs. 3a, b) Spongurus spindalis Welling Welling (1996, p. 212, Pl. 5, Figs.4 and 5) Stylatractus spp. Nigrini and Moore (1979, p. S55, Pl. 7, Figs. 1a, b) Stylochlamydium venustum (Bailey) Ling et al. (1971, p. 711, Pl. 1, Figs. 7 and 8) Stylodictya aculeata Jørgensen Nigrini and Moore (1979, p. S101, Pl. 13, Figs. 3 and 4) Stylodictya validispina Jørgensen Nigrini and Moore (1979, p. S103, Pl. 13, Figs. 5a, b) ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2249

Table 3 (continued )

Taxa Current references

Styptosphaera spongiacea Haeckel Renz (1976, p. 116, Pl. 1, Fig. 13) Stypyosphaera ? spumacea Haeckel Nigrini and Moore (1979, p. S71, Pl. 8, Figs. 6a, b) Tetrapyle octacantha Mu¨ ller Takahashi (1991, p. 90, Pl. 23, Figs. 9 and 10) Spumellaria sp. A Spumellaria sp. B Spumellaria sp. C Nassellaria Amphiplecta acrostoma Haeckel Welling (1996, p. 231, Pl. 16, Fig. 11) Antarctissa? sp. 1 Nimmergut and Abelmann (2002, p. 488, Pl. 1, Fig. 6) Anthocyrtidium zanguebaricum (Ehrenberg) Nigrini and Moore (1979, p. N69, Pl. 25, Fig. 2) Arachnocorys umbellifera Haeckel Welling (1996, p. 227, Pl. 14, Figs.24–27) Arachnocorys pentacantha Popofsky Welling (1996, p. 227, Pl. 14, Figs.21–23) Artobotrys boreale (Cleve) Bjørklund (1998, p. 130, Pl. 2, Figs. 4 and 5) Artostrobus annulatus (Bailey) Takahashi (1991, p. 128, Pl. 38, Figs. 9 and 10) Artostrobus joergenseni Petrushevskaya Bjørklund (1998, p. 130, Pl. 2, Figs. 17–19) Botryostrobus aquilonaris (Bailey) Nigrini and Moore (1979, p. N99, Pl. 27, Fig. 1) Botryostrobus auritus/australis group (Ehrenberg) Nigrini and Moore (1979, p. N101, Pl. 27, Figs. 2a–d) Callimitra solocicribrata Takahashi Takahashi (1991, p. 100, Pl. 27, Figs. 10 and 11) Carpocanarium papillosum (Ehrenberg) Nigrini and Moore (1979, p. N27, Pl. 21, Fig. 3) Carpocanistrum spp. Nigrini and Moore (1979, p. N23, Pl. 21, Figs. 1a–c) Ceratocyrtis spp. Ceratospyris borealis Bailey Nigrini and Moore (1979, p. N9, Pl. 19, Figs. 1a–d) Cladoscenium ancoratum Haeckel Takahashi (1991, p. 94, Pl. 24, Figs. 9–14) Cladoscenium tricolpium (Haeckel) Bjørklund (1976, p. 1139, Pl. 7, Figs. 5–8) Conarachnium aff. polyacanthum (Popofsky) Takahashi (1991, p. 118, Pl. 39, Figs. 1–4) Cornutella profunda Ehrenberg Takahashi (1991, p. 113, Pl. 35, Figs. 3–9) Corocalyptra cervus (Ehrenberg) Takahashi (1991, p. 112, Pl. 33, Figs. 9–12) Cycladophora bicornis (Popofsky) Takahashi (1991, p. 122, Pl. 41, Figs. 4–6, 8–11) Cycladophora cornutoides Petrushevskaya Motoyama (1997, p. 57, Pl. 1, Figs. 1–3) Cycladophora davisiana Ehrenberg Motoyama (1997, p. 57, Pl. 1, Figs. 4–10) Cyrtopera languncula Haeckel Takahashi (1991, p. 119, Pl. 40, Figs. 3–6) Dictyophimus crisiae Ehrenberg/hirundo (Haeckel) group Welling (1996, p. 234, Pl. 19, Figs. 1–5) Dictyophimus aff. infabricatus Nigrini Takahashi (1991, p. 116, Pl. 37, Figs. 3–5) Dictyophimus macropterus (Ehrenberg) Takahashi (1991, p. 116, Pl. 39, Figs. 8–11) Dictyophimus spp. Dimelissa thoracites (Haeckel) group Welling (1996, p. 225, Pl. 14, Figs. 1–8) Eucecryphalus tricostatus (Haeckel) Takahashi (1991, p. 110, Pl. 33, Figs. 4 and 6) Eucyrtidium acuminatum (Ehrenberg) Takahashi (1991, p. 124, Pl. 42, Figs. 9, 10, 16, 17 and 20) Eucyrtidium hexagonatum Haeckel Nigrini and Moore (1979, p. N63, Pl. 24, Figs. 4a, b) Eucyrtidium spp. Hexaspyris spp. Lamprocyrtis spp. Lampromitra spp. Lipmanella spp. Litharachnium tentorium Haeckel Takahashi (1991, p. 114, Pl. 35, Figs. 14–18) Lithocampe platycephala (Ehrenberg) Bjørklund (1998, p. 130, Pl. 2, Figs. 23–25) Lithocampe sp. Nigrini and Moore (1979, p. N65, Pl. 24, Figs. 5a, b) Lithomelissa setosa Jørgensen Bjørklund (1998, p. 130, Pl. 2, Figs. 12–14) Lithomelissa spp. Lithostrobus hexagonalis Haeckel Takahashi (1991, p. 122, Pl. 41, Figs. 1–3) Lophophaena cf. capito Ehrenberg Takahashi (1991, p. 96, Pl. 25, Figs. 6–9) Lophophaena dacacantha (Haeckel) group Takahashi (1991, p. 96, Pl. 25, Figs. 2, 8 and 10) Lophophaena spp. Lophospyris pentagona pentagona (Ehrenberg) emend. Goll Takahashi (1991, p. 102, Pl. 28, Figs. 9–14) Lychnocanomma ? sp. ? Mitrocalpis araneafera Popofsky Nigrini (1970, p. 169, Pl. 3, Figs. 1 and 2) Neosemantis cladophora (Jørgensen) Takahashi (1991, p. 95, Pl. 24, Fig. 17) Neosemantis distephanus Popofsky Takahashi (1991, p. 95, Pl. 27, Fig. 12) ARTICLE IN PRESS 2250 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Table 3 (continued )

Taxa Current references

Peridium longispinum Jørgensen Bjørklund (1998, p. 130, Pl. 2, Figs. 26 and 27) Peridium spp. Peripyramis circumtexta Haeckel Takahashi (1991, p. 113, Pl. 35, Figs. 10–13) Peromelissa phalacra Haeckel Takahashi (1991, p. 97, Pl. 25, Figs. 11–15) Phormacantha spp. Phormospyris stabilis scaphipes (Haeckel) Takahashi (1991, p. 103, Pl. 29, Figs. 11, 12 and 14) Phormospyris stabilis stabilis (Goll) Takahashi (1991, p. 104, Pl. 30, Figs. 2–5) Plectacantha spp. Plectagonidium deﬂandrei Cachon and Cachon Cachon and Cachon (1969, p. 236, Pl. 39, Fig. 1) Pseudocubus obeliscus Haeckel Takahashi (1991, p. 95, Pl. 26, Fig. 1) Pseudodictyophimus bicornis (Ehrenberg) Welling (1996, p. 223, Pl. 13, Figs. 13 and 14) Pseudodictyophimus gracilipes (Bailey) Bjørklund (1998, p. 130, Pl. 2, Fig. 8) Pseudodictyophimus spp. Pterocanium korotnevi (Dogiel and Reshetnyak) Nigrini and Moore (1979, p. N39, Pl. 23, Figs. 1a, b) Pterocanium polypylum Welling (1996, p. 235, Pl. 19, Figs. 11 and 12) Pterocanium praetextum Nigrini and Moore (1979, p. N41, Pl. 23, Fig. 2) Pterocanium spp. Pterocorys zancleus (Mu¨ ller) Nigrini and Moore (1979, p. N89, Pl. 25, Figs. 11a, b) Pterocorys spp. Saccospyris antarctica Haecker Boltovskoy and Riedel (1987, Pl. 6, Fig. 17) Saccospyris conithorax Petrushevskaya Nigrini (1970, p. 172, Pl. 4, Fig. 12) Siphocampe arachnea (Ehrenberg) Abelmann (1992b, p. 382, Pl. 5, Fig. 15) Spirocyrtis subscalaris Nigrini Takahashi (1991, p. 127, Pl. 44, Figs. 3–6) Stichopilium bicorne Haeckel Nigrini and Moore (1979, p. N91, Pl. 26, Figs. 1a, b) Tetraphormis dodecaster (Haeckel) Takahashi (1991, p. 108, Pl. 32, Fig. 7) Tetraphormis rotula (Haeckel) Takahashi (1991, p. 108, Pl. 32, Figs. 1–3) Tetraplecta pinigera Haeckel Takahashi (1991, p. 93, Pl. 24, Figs. 1–5) Zygocircus productus (Hertwig) group Takahashi (1991, p. 101, Pl. 27, Figs. 13 and 14)

Phaeodaria Borgertella caudata (Wallich) Takahashi (1991, p. 148, Pl. 54, Figs. 13–17) Challengeranium diodon (Haeckel) Takahashi (1991, p. 145, Pl. 52, Figs. 11–16) Challengeron neptuni Borgert Borgert (1901, p. 31, Fig. 35) Challengeron ornithocephala (Reshetnyak) Reshetnyak (1966, p. 174, Fig. 108). Chellengeron tizardi (Murray) Takahashi (1991, p. 139, Pl. 48, Figs. 13–16). Challengeron vicina (Reshetnyak) Reshetnyak (1966, p. 174, Fig. 112) Challengeron willemoesii Haeckel Takahashi (1991, p. 138, Pl. 47, Figs. 1–14) Challengeron sp. Takahashi and Okazaki (in prep) Challengerosium avicularia Haecker Takahashi (1991, p. 140, Pl. 49, Figs. 1–13) Conchelium capsula Borgert Takahashi (1991, p. 157, Pl. 61, Figs. 1–5, 7, 8 and 10) Euphysetta elegans Borgert Takahashi (1991, p. 146, Pl. 53, Figs. 1–10) Euphysetta staurocodon Haeckel Takahashi (1991, p. 146, Pl. 53, Figs. 11–14) Hackeliana porcellana Murray Takahashi (1991, p. 154, Pl. 59, Figs. 4–13) Lirella bullata (Stadum and Ling) Takahashi (1991, p. 149, Pl. 55, Figs. 8–11) Lirella melo (Cleve) Takahashi (1991, p. 149, Pl. 55, Figs. 12–18) Porospathis holostoma (Cleve) Takahashi (1991, p. 150, Pl. 57, Figs. 1–8) Protocystis harstoni (Murray) Takahashi and Honjo (1981, p. 156, Pl. 11, Fig. 11) Protocystis murrayi (Haeckel) Takahashi (1991, p. 143, Pl. 50, Figs. 16–18) Protocystis neresi (Murray) Takahashi (1991, p. 144, Pl. 52, Figs. 6–8) Protocystis thomsoni (Murray) Takahashi (1991, p. 143, Pl. 51, Fig. 5) Protocystis tridens (Haeckel) Abelmann (1992b, p. 382, Pl. 2, Figs. 5 and 6) Protocystis tridentata Borgert Takahashi (1991, p. 142, Pl. 50, Fig. 3) Protocystis tritonis (Haeckel) Takahashi (1991, p. 133, Pl. 52, Figs. 4 and 5) Protocystis xiphodon (Haeckel) Takahashi (1991, p. 143, Pl. 52, Figs. 1–3)

ﬂuxes at all three stations. Radiolarians have a wide ing to their niche (Anderson, 1983). Therefore, a vertical distribution from the surface to deep layers detailed understanding of how radiolarian produc- and also have various trophic patterns correspond- tion relates to each niche is required. ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2251

Table 4 List of radiolarian taxa with their relative abundances greater than 1% at each station

50N % KNOT % 40N %

Pseudodictyophimus glacilipes 11.7 Challengeron vicina* 8.7 Pterocorys zancleus 6.7 Stylochlamydium venustum 7.2 Pseudodictyophimus glacilipes 7.6 Larcopyle butschlii 6.2 Ceratospyris borealis 6.8 Cycladophora davisiana 5.6 Pseudodictyophimus glacilipes 6.1 Actinomma sp. 1 5.6 Actinomma sp. 1 5.1 Stylochlamydium venustum 5.8 Challengeron vicina* 4.7 Phormacantha spp. 4.6 Plegmosphaera pachypila 3.9 Rhizoplegma boreale 4.3 Ceratospyris borealis 4.0 Spongotrochus glacialis (juvenile) 3.4 Larcopyle butschlii 3.8 Rhizoplegma boreale 3.5 Actinomma sp. 1 3.2 Borgertella caudata* 3.8 Stylochlamydium venustum 3.4 Phormacantha spp. 3.0 Cycladophora davisiana 3.4 Cladococcus cervicornis 3.2 Lamprocyrtis spp. 2.8 Phormacantha spp. 2.8 Challengeron ornithocephala* 3.0 Peridium spp. 2.4 Cycladophora cornutoides 2.3 Peridium spp. 2.9 Plectacantha spp. 2.3 Protocystis harstoni* 2.1 Borgertella caudata* 2.2 Plegmosphaera lepticali 2.3 Peridium spp. 2.1 Larcopyle butschlii 2.1 Tetrapyle octacantha 1.9 Euphysetta elegans* 1.9 Spongurus spindalis 1.8 Pseudodictyophimus spp. 1.8 Lithomelissa setosa 1.8 Lithomelissa setosa 1.5 Stypyosphaera ? spumacea 1.5 Pseudodictyophimus spp. 1.7 Plectacantha spp. 1.5 Eucecryphalus tricostatum 1.3 Stylodictya validispina 1.5 Pterocorys zancleus 1.4 Euphysetta staurocodon * 1.3 Challengeron ornithocephala* 1.4 Spongotrochus glacialis (juvenile) 1.3 Spongurus spindalis 1.2 Dorydruppa bensoni 1.4 Cladoscenium ancoratum 1.2 Lampromitra spp. 1.2 Spongurus spindalis 1.3 Dorydruppa bensoni 1.2 Cycladophora davisiana 1.1 Cladoscenium ancoratum 1.3 Protocystis harstoni * 1.1 Cycladophora bicornis 1.1 Dictyophimus crisiae /hirundo group 1.0 Spongotrochus glacialis (juvenile) 1.0 Cumulative relative abundance 74.7 67.1 60.4

The symbol asterisks denote phaeodarian taxa.

Table 5 List of radiolarian taxa characterized for three latitudinal distributions in the North Paciﬁc based on the following previous studies using surface sediment samples: Nigrini (1970), Moore (1978), Nigrini and Moore (1979) and Lombari and Boden (1985)

Subarctic species Transitional species Tropical and subtropical species

Actinomma boreale Actinomma leptoderma leptoderma Actinomma arcadophorum Polysolenia arkios Actinomma leptoderma longispina Collosphaera tubelosa Rhizoplegma boreale Actinomma medianum Dictyocoryne profunda Spongotrochus glacialis Hexacontium enthacanthum Didymocyrtis tetrathalamus Stylochlamydium venustum Hexacontium laevigatum Euchitonia elegans Stylodictya validispina Hexapyle armata Heliodiscus asteriscus Antarctissa ? sp. 1 Larcopyle butschlii Hymeniastrum euclidis Ceratospyris borealis Lithelius minor Larcospira quadrangula ? Mitrocalips araneafera Spongurus pylomaticus Siphonosphaera aff. polysiphonia Pterocanium korotnevi Stypyosphaera ? spumacea Spongaster tetras tetras Saccospyris conithorax Botryostrobus aquilonaris Tetrapyle octacantha Cycladophora bicornis Botryostrobus auritus /australis Eucyrtidium acuminatum Carpocaliarium papillosum Lophospyris pentagona pentagona Carpocanistrum spp. Pterocanium praetextum Eucyrtidium hexagonalis Pterocorys zancleus

Each water mass (Fig. 5) was deﬁned based on the radiolarian ﬂuxes in the subarctic gyre stations geographic and vertical distributions of radiolarian (Stations 50N and KNOT) showed much lower taxa (see Section 4.5). In the surface water (0–50 m), values than that of Station 40N (Fig. 5). The ARTICLE IN PRESS 2252 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Table 6 List of radiolarian taxa characterized for vertical distributions based on the following previous studies using plankton tow and pump samples in the Equatorial and North Paciﬁc: Renz (1976), Kling (1979), Welling et al. (1996), Boltovskoy and Riedel (1987), Kling and Boltovskoy (1995), Nimmergut and Abelmann (2002), Yamashita et al. (2002), and Okazaki et al. (2004)

Surface dwellers (0–50 m) Upper subusurface dwellers Lower subusurface dwellers Intermediate dwellers (50–100 m) (100–300 m) (300–1000 m)

Didymocyrtis tetrathalamus Stylochlamydium venustum Cladococcus scoparius Larcopyle butschlii Euchitonia elegans Botryostrobus auritus/australis Hymeniastrum euclidis Botryostrobus aquilonaris Heliodiscus asteriscus Carpocanarium papillosum Lithelius minor Cladoscenium ancoratum Larcospira quadrangula Eucecryphalus tricostatum Rhizoplegma boreale Cornutella profunda Spongaster tetras tetras Lithostrobus hexagonalis Spongurus cylindricus Cycladophora cornutoides Spongotrochus glacialis Pterocanium korotnevi Ceratospyris borealis Cycladophora davisiana Stylodictya validispina Pterocorys zancleus Corocalyptra cervus Dictyophimus crisiae/hirundo group Tetrapyle octacantha Stichopilium bicorne Cycladophora bicornis Lithalachnium tentorium Carpocanistrum spp. Dictyophimus aff. infablicas Peripyramis circumtexta Eucyrtidium acuminatum Lampromitra spp. Siphocampe arachnea Lipmanella spp. Phormacantha spp. Borgertella caudata* Lithomelissa setosa Pseudodictyophimus glacilipes Challengeron ornithocephala* Pterocanium praetextum Challengeron neptuni* Euphysetta staurocodon * Challengeron vicina* Lirella melo* Protocystis tridens* Protocystis thomsoni*

The symbol asterisks denote phaeodarian taxa.

hydrographic feature of the surface water of the have been caused by the difference in the fluxes of WSAG is low salinity (o34.0 psu) and relatively transitional taxa due to the difference in the low temperature (ca. 4–12 1C) (Fig. 2). These hydrographic conditions. hydrographic conditions apparently suppress the Radiolaria fluxes in the lower subsurface and radiolarian production in the surface water of the intermediate waters showed similar seasonal and WSAG. The radiolarian fluxes at each trap showed annual variations to those in the surface and upper regular seasonal cycles with peaks in spring (Fig. 5). subsurface waters. Below the euphotic zone (deeper These results suggest that the radiolarian produc- than 100 m), food availability may be important for tion in the surface layer is tightly linked to the the radiolarian flux change because the seasonal extent of the primary production. However, fluxes variability in the hydrographic conditions is smaller of tropical and subtropical radiolarians at Station than that in the upper layer (Fig. 2). Yamaguchi 40N showed significantly high values during De- et al. (2002) observed the vertical distribution cember 1999 to January 2000, although the sea- patterns of plankton organisms during 19–21 surface temperature (SST) reached a minimum at August 1998 at the same location as Station KNOT this time of year (10.5 1C; Honda et al., 2002). (441N, 1551E) and their biomass was quantified. Abundant polycystine radiolarian standing stocks They indicated that a close relationship between the were observed in the upper subsurface waters biomasses of bacteria and protozooplankton, in- (50–100 m) of the central North Pacific (Kling, cluding Radiolaria except for the 0–40 m data. 1979) and the Oyashio region (Okazaki et al., 2004). Thus, the microbial production may be responsible Kling (1979) indicated that the chlorophyll max- for the radiolarian production at subsurface water imum, which is coincident with the maximum depths, while the primary production seems to be standing stock of the polycystine radiolarians, must mainly responsible for the radiolarian production in be responsible for the polycystine radiolarian the surface waters. production in this depth zone. He also suggested Cosmopolitan taxa mainly contributed to the that algal symbionts within the radiolarians may intermediate dwelling radiolarian fluxes, whereas contribute directly to this high chlorophyll level. In latitudinal indicator taxa such as the tropical taxa our study, high radiolarian fluxes also were ob- disappeared (Fig. 5). Kling (1979) indicated that the served, especially at Station 40N (Fig. 5). This may taxa in the NPIW are characterized by their rare or ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2253

Station 50N Station KNOT Station 40N 1500 1500 Tropical & Tropical & Tropical & 1000 Subtropical Subtropical Subtropical 1000 ) 500 500

day 0 0 400 Transitional Transitional Transitional 400

200 200

Surface (0-50m) 0 0 Radiolaria flux 400 Subarctic Subarctic Subarctic 400

(No. radiolarians m (No. 200 200

0 0 1998 1999 2000 1998 1999 2000 1998 1999 2000 400 Tropical & Tropical & Tropical & 400 Subtropical Subtropical Subtropical ) 200 200

day 0 0 2000 Transitional Transitional Transitional 2000

1000 1000

0 0 Radiolaria flux 3000 Subarctic Subarctic Subarctic 3000

Upper subsurface (50-100m) 2000 2000 (No. radiolarians m (No. 1000 1000 0 0 1998 1999 2000 1998 1999 2000 1998 1999 2000 400 Tropical & Tropical & Tropical & 400 Subtropical Subtropical Subtropical ) 200 200

day 0 0 400 Transitional Transitional Transitional 400

200 200

0 0 Radiolaria flux 1000 Subarctic Subarctic Subarctic 1000 Lower subsurface Lower (100-300m) (No. radiolarians m (No.

0 0 1998 1999 2000 1998 1999 2000 1998 1999 2000 ) 2000 Total Intermediate Total Intermediate Total Intermediate 2000 day 1000 1000

0 0 1000 Cosmopolitan Cosmopolitan Cosmopolitan 1000 Radiolaria flux Intermediate (300-1000m)

0 0 (No. radiolarians m (No. 1998 1999 2000 1998 1999 2000 1998 1999 2000

Fig. 5. Temporal ﬂuxes of radiolarian groups, which were compiled based on the vertical and latitudinal distributions, at three stations in the northwestern North Paciﬁc during 1997–2000. The gray vertical belts represent the sample hiatuses.

absent occurrence in the upper few hundred meters. 5.2. Phaeodarian production in the northwestern Our previous study (Okazaki et al., 2003a) revealed North Pacific that the production of Cycladophora davisiana, one of the major intermediate dwellers, is closely related Mean values of phaeodarian fluxes were highest with the microbial biomass. TOC fluxes were the at Station KNOT and lowest at Station 40N among highest during summer to autumn when a peak in the three stations in this study. This is significantly the C. davisiana flux was observed. However, different from the results of polycystine radiolarians temporal changes in TOC fluxes did not show (Fig. 3; Table 2). Most of the phaeodarians exactly the same patterns as the intermediate encountered in this study were the lower subsurface dweller fluxes at each station (Fig. 6). Therefore, and the intermediate water dwellers (Table 6). the production of the intermediate dwellers may not Among them, Challengeron vicina and Challengeron always depend on the organic matter derived from ornithocephala, which dwell in the lower sub- microbial biomass. surface to the intermediate water, contributed high ARTICLE IN PRESS

2254 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

) y da m g m (

-1 -2 percentages to the total phaeodarian assemblages

TOC flux TOC (Station 50N: 39.3%; Station KNOT: 60.2%; and

15 10 5 0 Station 40N: 14.9%) and their ﬂuxes showed clear autumn-winter peaks at Stations KNOT and 50N (Fig. 7A). Temporal ﬂux changes in these two taxa 2000 JAM

DFM were mainly responsible for the phaeodarian seasonality in the WSAG region. Their high ﬂuxes and standing stocks were reported in the Okhotsk Sea s in the northwestern North (Dogiel and Reshetnyak, 1952; Reshetnyak, 1966; 1999 Okazaki et al., 2004), off Kamchatka in the northwestern North Paciﬁc (Dogiel and Reshetnyak, JAMO

DFMJJASN 1952), Oyashio region (Okazaki et al., 2004), and the Bering Sea (Dogiel and Reshetnyak, 1952; Matsueda, per. comm.). The geographical distributions of C. vicina and C. ornithocephala are limited 1998 to the subarctic Paciﬁc. Therefore, these taxa are

JAMO considered to be subarctic indicators, which prefer DFMJJASN to dwell in low-temperature and low-salinity waters. According to Matsueda (pers. comm.), the seasonality of C. vicina and C. ornithocephala ﬂuxes also 2000

JAM displays autumn–winter peaks in the Bering Sea DFM (Station AB: 531300N, 1771W, trap depth: 3190 m) and the subarctic Paciﬁc (Station SA: 491N, 1741W, trap depth: 4830 m) during 1994–1998. The ﬂuxes of

1999 C. vicina and C. ornithocephala at Station AB were much higher than that at Station SA (C. vicina: ca. JAMO

DFMJJASN 5.7 times; C. ornithocephala: 3.0 times), suggesting a higher productivity at Station AB than at Station SA. This is because the Bering Sea, as a semi- isolated marginal sea, is substantially more produc- 1998 tive than its pelagic counterpart in the central subarctic Paciﬁc Ocean (Takahashi et al., 2000, JAMO

DFMJJASN 2002). In our study, the mean ﬂuxes of C. vicina and C. ornithocephala at Station KNOT showed much higher values than that at Station 50N (C. vicina: ca. 2000 . The blank vertical belts represent the sample hiatuses. JAM 2.5 times; C. ornithocephala: 3.0 times). Station DFM KNOT is located toward the margin of the WSAG and characterized by higher TM and TOC ﬂuxes than at Station 50N, indicating high primary

1999 production (Table 2; Honda, 2001; Honda et al., 2002). However, ﬂuxes of both TM and TOC Honda et al. (2002) JAMO decreased during winter (Honda, 2001; Honda et DFMJJASN

and al., 2002) when the high ﬂuxes of C. vicina and C. Intermediate dweller TOC Station 50N Station KNOTornithocephala were Station 40N observed at Stations 50N and KNOT. Thus, phaeodarian production seems to be

1998 controlled not only by primary production but also by other factors such as grazing pressure and Honda (2001) JAMO

DFMJJASN microbial biomass.

0 Phaeodarian skeletons dissolve in the water

2000 1000

(No. radiolarians m radiolarians (No. ) day

-1

-2 column because of their relatively soluble skeletal Imtermediate dweller flux dweller Imtermediate composition (Takahashi et al., 1983). Gowing Pacific are from Fig. 6. Temporal fluxes of intermediate water dwelling radiolarians and TOC at three stations in northwestern North Pacific during 1997–2000. TOC(1993) fluxe indicated that several phaeodarian species ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2255

Station 50N Station KNOT Station 40N 600 (A) 400 )

-1 200 Challengeron day ornithocephara -2 0 1000

500 vicina Flux (No. radiolarians m Flux (No. Challengeron 0 1998 1999 2000 1998 1999 2000 1998 1999 2000

(B) 1200 ) -1 600 day -2 Tetrapyle octacantha

200

Flux (No. radiolarians m Flux (No. 100 Didymocyrtis tetrathalamus

0 )

-1 1998 1999 2000 1998 1999 2000 1998 1999 2000 4000 day

2000 venustum 1000 Stylochlamydium 0

Flux (No. radiolarians m Flux (No. 1998 1999 2000 1998 1999 2000 1998 1999 2000 600 (D) 400 ) -1 day

boreale 200 -2 Rhizoplegma

0 1200

600 Flux (No. radiolarians m Flux (No. borealis Ceratospyris

0 1998 1999 2000 1998 1999 2000 1998 1999 2000

Fig. 7. Temporal fluxes of major radiolarian taxa at three stations in northwestern North Pacific during 1997–2000. The blank vertical belts represent the sample hiatuses. ARTICLE IN PRESS 2256 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 with shallower depth distributions were absent in However, fluxes of both total mass and diatoms at the deep traps, whereas species with deeper dis- Station 40N showed minimum values during tributions were present in the traps deployed at December 1999–January 2000 (Honda et al., 2002; 2000 m in the North Pacific (331N, 1391W). Onodera et al., 2005). Unfortunately, there were Bernstein et al. (1990) reported significantly high sampling hiatuses during December–May in contributions of Phaeodaria in the radiolarian 1998–1999 and after February 2000. Therefore, it assemblages in the free-drifting sediment trap is difficult to judge whether or not the T. octacantha samples in the western subarctic North Pacific peak in Fig. 5 was a unique event during December (Station 18: 461N, 1651E, 400 m, 2200 m; Station 1999–January 2000. If this event occurs every winter 20: 501N, 1751E, 70 m, 100 m, 900 m). The relative around Station 40N, the occurrence of the abundances of Phaeodaria in the total Radiolaria T. octacantha peak might be directly linked to the assemblage ranged from 45.3% to 89.1% at Station amount of nutrients because of the strong vertical 18 and 82.3% to 100% at Station 20. A direct mixing in the upper 150 m of the water column comparison with our results is difficult because their (Fig. 2). sampling periods were only for ca. 24 h. However, Fluxes of Didymocyrtis tetrathalamus at Station the phaeodarian contributions in the results of 40N showed autumn peaks (Fig. 7B). On the other Bernstein et al. (1990) clearly show much higher hand, fluxes of D. tetrathalamus at Stations KNOT values than our results. In our study most of the and 50N were significantly low or barren through- encountered phaeodarian taxa dwell from the lower out the sampled time periods (Fig. 7B). D. tetra- subsurface water to the intermediate water. These thalamus also dwells mainly in the surface waters of results suggest a significant dissolution of phaeo- the North Pacific, similar to T. octacantha (central darian skeletons in the water column and rapid North Pacific: Kling (1979); California Current: changes in the species composition with depth. Kling and Boltovskoy (1995); equatorial Pacific: Welling and Pisias, 1998; Yamashita et al., 2002). 5.3. Taxa with characteristic variability in each Generally speaking, D. tetrathalamus has been water mass defined as a warm-water species based on its geographic distribution (Nigrini, 1970; Robertson, Among the tropical and subtropical radiolarians, 1975; Moore, 1978). Lombari and Boden (1985) Tetrapyle octacantha contributed significantly to the compiled the abundances of this taxon in core tops flux peak at Station 40N during December and illustrated its geographic distribution and 1999–January 2000 (Fig. 5; Fig. 7B). T. octacantha showed high abundances in the western tropical is widely distributed in the surface waters of the low Pacific, where the western Pacific warm pool exists, to mid latitudes of the North Pacific (central North a region defined as having a SST exceeding 28 1C Pacific: Kling, 1979; California Current: Kling and (Yan et al., 1992). Anderson et al. (1990) indicated Boltovskoy, 1995; equatorial Pacific: Welling and that the maximum longevity and optimal growth of Pisias, 1998; Yamashita et al., 2002). T. octacantha D. tetrathalamus occurred in a temperature range of also has been defined as a subtropical taxon based 21–27 1C. However, some individuals survived at on biogeographic studies using sediment samples temperatures as low as 10 1C based on laboratory (Lombari and Boden, 1985). In the Equatorial experiments. They suggested that D. tetrathalamus Pacific based on the plankton tow results, T. has a lower temperature tolerance than indicated by octacantha abundances generally increased from its geographical distribution. Welling et al. (1996) low values in the western Pacific warm pool with indicated that advection due to strong currents was low surface nutrient contents to high values in the the primary regulator of the abundance of D. central Equatorial Upwelling Region with high tetrathalamus, while temperature was secondary in surface nutrient contents (Yamashita et al., 2002). the Equatorial Pacific. In our study, Station 40N is This trend is similar to the geographic distribution located in the vicinity of the Subarctic Boundary, shown by Lombari and Boden (1985). Furthermore, and influenced by the Kuroshio Extension (Fig. 1). T. octacantha has been used as an indicator for The residence time of D. tetrathalamus is on the upwelling regimes in the middle and low latitudes order of 3 weeks (Welling and Pisias, 1998). The (Molina-Cruz, 1977; Abelmann and Gowing, 1997). sinking speed of particles at Station 40N was Thus, T. octacantha could be used as a high-nutrient estimated to be greater than 115 m day1 (Honda indicator of middle latitudes of the North Pacific. et al., 2002). Sinking speeds of radiolarians were ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2257 estimated to be 58–175 m day1 or greater in the 1987; Abelmann, 1992a; Nishimura et al., 1997; Gulf of Alaska (Takahashi, 1987). Considering the Nimmergut and Abelmann, 2002). Fukumura and time lags from the sea surface to the deployed trap Takahashi (2000) indicated that the seasonality of depth (3000 m), the autumn flux peaks of D. R. boreale fluxes showed a high correlation with that tetrathalamus at Station 40N may reflect the of total diatom fluxes. Neodenticula seminae con- advection of the warm Kuroshio Extension. tributed 82% in the central subarctic Pacific Stylochlamydium venustum is widely distributed in (Station SA; Takahashi et al., 2002), suggesting a the North Pacific (Robertson, 1975) and most close connection between R. boreale production and abundant in the sediment samples from the Bering the primary production. The fluxes of R. boreale in Sea (Ling et al., 1971), and also is one of the the Bering Sea (Station AB) were much higher than dominant taxa in the trap samples from the Bering those at Station SA. However, the high correlation Sea (Station AB) and the subarctic Pacific (Station between R. boreale flux and total diatom flux, within SA) (Itaki and Takahashi, 1995; Fukumura and which N. seminae contributed 79% (Takahashi et Takahashi, 2000). Robertson (1975) defined S. al., 2002), was not observed at Station AB. Dolven venustum as a subpolar species. From the plankton and Bjørklund (2001) referred to the distribution of tow studies, it is reported that S. venustum mainly R. boreale as being confined to the Nordic Seas, the dwells in the upper subsurface layers in the central North Pacific with its marginal seas, and the North Pacific (Kling, 1979) and the Oyashio region Southern Ocean, and suggested that the production (Okazaki et al., 2004). In the present study, the of R. boreale is linked to the primary production fluxes of S. venustum showed an extraordinary peak and mixing of water masses. Analogous to R. at Station 40N during December 1997–January boreale, C. borealis was also found frequently in 1998, when other radiolarian fluxes and diversity the surface sediments of the Bering Sea (Ling et al., indices had very low values (Figs. 3, 5 and 7C). 1971) and the subarctic Pacific (Nigrini, 1970). Fluxes of TM, TOC and diatoms also showed their Takahashi (1997) in his study of the eastern minima at that time (Honda, 2001; Honda et al., subarctic Pacific (Station PAPA) suggested C. 2002; Onodera et al., 2005). Sasaoka et al. (2002) borealis as a possible paleoproductivity indicator indicated a negative sea-surface temperature anom- because of the temporal flux pattern of C. borealis aly (SSTA) (up to 5 1C) at around Station 40N markedly resembled that of N. seminae, which was from summer to winter of 1997, whereas a positive the dominant diatom species. As mentioned above, SSTA (up to 5 1C) was observed from summer to the production of both R. boreale and C. borealis autumn in 1998. This low-temperature water might has been linked to diatom production, such as the have suppressed the production of warm water high N. seminae production in the subarctic Pacific. dwelling radiolarians and supported significant In our study, however, correlation coefficients (r) peaks of S. venustum during December 1997–Jan- between N. seminae flux and the fluxes of these two uary 1998. radiolarian species were unexpectedly low (N. Major taxa from the lower subsurface layers were seminae vs. R. boreale: 0.22 at Station 50N and Rhizoplegma boreale and Ceratospyris borealis 0.26 at Station KNOT; N. seminae vs. C. borealis: (Figs. 5 and 7D). The geographic distribution of 0.45 at Station 50N and 0.04 at Station KNOT). R. boreale has been reported from the high-latitude Therefore, a clear relationship between their fluxes regions: the Nordic Seas (Cleve, 1899; Swanberg and primary production could not be established at and Bjørklund, 1987; Bjørklund et al., 1998; Dolven least in the western subarctic Pacific. The possibility and Bjørklund, 2001), the Bering Sea and the of the direct influence of diatom production on the subarctic Pacific (Itaki and Takahashi, 1995; Fuku- production of R. boreale and C. borealis appears to mura and Takahashi, 2000), the Okhotsk Sea be low considering the living depth zone of these (Nimmergut and Abelmann, 2002; Okazaki et al., radiolarian taxa is below the euphotic zone. On the 2003b), and the Southern Ocean (Petrushevskaya, other hand, the influence of a common indirect 1968; Abelmann, 1992a, b; Nishimura et al., 1997). factor such as the high-nutrient condition may still R. boreale mainly dwells in the subsurface waters in exist considering from distributions of R. boreale the Okhotsk Sea (Nimmergut and Abelmann, 2002) and C. borealis, which are confined to the high- and the Oyashio region (Okazaki et al., 2004), and latitude oceans with high nutrient conditions. abundant R. boreale production was reported from Furthermore, the correlation coefficient between neritic environments (Swanberg and Bjørklund, fluxes of R. boreale and C. borealis was much higher ARTICLE IN PRESS 2258 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2000 2000 ). JAM JAM DFM DFM La Niña 1999 1999 in the surface and upper subsurface JAMO JAMO Schwing et al., 2002 DFMJJASN DFMJJASN 1998 1998 Transition JAMO JAMO El Niño DFMJJASN DFMJJASN 2000 2000 JAM JAM DFM DFM La Niña 1999 1999 JAMO JAMO DFMJJASN DFMJJASN 1998 1998 Transition JAMO JAMO El a (November 1998–early 2001) in the tropical Pacific also are shown ( Niño DFMJJASN ˜ DFMJJASN ) at three stations in northwestern North Pacific during 1997–2000. The blank vertical belts represent the sample 2000 2000 JAM JAM DFM DFM La Niña 1999 1999 Reynolds and Smith, 1994 JAMO JAMO DFMJJASN DFMJJASN Station 50N Station 40N Subarctic taxa Subarctic taxa Transitional taxa & Subtropical Tropical o (July 1997–March 1998) and La Nin ˜ 1998 1998 Transition JAMO JAMO El Niño DFMJJASN DFMJJASN

0 2 0

-2

C) 80 60 40 ( 20 (%) °

100 events Niña La

Relative abundance Relative anomaly SST IGOSS El Niño & Niño El layers (0–100 m) and IGOSS SSThiatuses. anomaly The ( durations of El Nin Fig. 8. Changes in relative abundances of three latitudinal radiolarian groups (tropical and subtropical, transitional, and subarctic) that dwell ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2259 at Station 50N (0.73) than at Station KNOT (0.21). among the three stations. During the 1997–1998 El The significant influence of coastal waters at Station Ninõ, Subarctic taxa such as S. venustum contrib- KNOT was reported based on high fluxes of uted 60–95% of total radiolarians at Station 40N aluminum (Honda, 2001) and coastal diatom taxa, (Fig. 8). On the other hand, after the 1997–1998 El especially Chaetoceros resting spores (Onodera Ninõ, the contribution of warm-water taxa in- et al., 2005) which increased during May–July in creased with increasing SST, corresponding to the 1999. During this period, Sasaoka et al. (2002) transition towards the La Ninã condition (Fig. 8). observed high chl-a around Station KNOT from The contributions of tropical and subtropical taxa the Kuril Islands based on both satellite imagery were high (up to 87%) throughout the sampled and direct observation. High R. boreale fluxes period at Station 40N when the SSTAs were positive found during spring to summer in 1999 may be (Fig. 8). Therefore, radiolarian assemblages can be an indication of neritic environmental conditions used for reconstructing the past SSTA changes and with high nutrients supplied by the coastal water also help us to understand past El Ninõ and La masses. Ninã teleconnections in the Kuroshio-Oyashio Extension region. 5.4. Climatic response in the northwestern North Pacific 6. Conclusions

In the tropical Pacific from late 1995 to early Radiolarian fluxes were observed at approxi- 2001, three major interannual climate events mately 3000 m of three sediment trap stations in occurred (Fig. 8): the 1995–1997 La Ninã (Septem- the northwestern North Pacific during December ber 1995–February 1997), 1997–1998 El Ninõ (July 1997–May 2000 and notable temporal changes are 1997–March 1998), and 1998–2001 La Ninã (No- as follows: vember 1998–early 2001) (Schwing et al., 2002). The SSTA also showed a strong variability in the 1. Total radiolarian fluxes in the Kuroshio-Oyashio northwestern North Pacific during these events Extension region (Station 40N) showed higher (Schwing et al., 2002; Sasaoka et al., 2002). During values than those in the WSAG (Stations 50N the 1997–1998 El Ninõ, significantly negative and KNOT), mainly attributed to the difference SSTAs persisted (Schwing et al., 2002; Sasaoka et in physical conditions. This trend is consistent al., 2002). During summer to autumn in 1998 with the results from earlier studies using between 331N and 551N along 1651E, a positive sediment samples. SSTA was observed. These trends were significant 2. Phaeodarian fluxes showed the highest values at around the Kuroshio-Oyashio Extension region Station KNOT, and the lowest values at Station near Station 40N (Sasaoka et al., 2002). Sasaoka 40N, among the three stations. This is signifi- et al. (2002) suggested the association with a cantly different from the results of polycystine northward shift of increased SST during La Ninã. radiolarians, which are due to the high contribu- Schneider and Miller (2001) indicated that the tions of two phaeodarian taxa (Challengeron wintertime changes of SSTA in the Kuroshio- ornithocephala and Challengeron vicina), dwelling Oyashio Extension region of the western North mainly in the lower subsurface to intermediate Pacific (along 401N, 140–1701E) increased from waters, with fluxes showing clear autumn-winter 1998 to 2000, which were correlated significantly peaks at Stations 50N and KNOT. with the observed subsurface temperature anoma- 3. Correlation coefficients between TM fluxes and lies. radiolarian fluxes at the three stations were We compiled the relative abundance changes of relatively low. This is mainly because of the the water mass indicator radiolarian taxa (see wide vertical distribution of radiolarians and Tables 5 and 6) that dwell in the surface and upper various trophic patterns within their niches. subsurface layers (0–100 m) together with the Therefore, we classified radiolarian fluxes accord- IGOSS SST anomalies (Reynolds and Smith, ing to their geographic water mass (tropical 1994) at each station (Fig. 8). In our study, the and subtropical, transitional, and subarctic) change in taxonomic composition responding to the and vertical distributions (surface, upper subsur- interannual climate changes (i.e. El Ninõ and La face, lower subsurface, and intermediate) based Ninã events) was most distinctive at Station 40N on the previous studies and discussed the ARTICLE IN PRESS 2260 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

controlling factors of radiolarian production for Matsueda of Kyushu University for providing the each group. valuable information about the phaeodarian fluxes 4. Temporal changes in radiolarian species compo- in the Bering Sea and subarctic Pacific. This sition in the upper layer (0–100 m) seemed to manuscript was significantly improved following reflect well the SSTA changes, affected by El the constructive comments provided by editor: Dr. Ninõ and La Ninã events, at Station 40N. Demetrio Boltovskoy and two referees: Dr. Stanley Therefore, radiolarian assemblages can be used A. Kling and Prof. Kjell R. Bjørklund. We thank for reconstructing the past SSTA changes and Dr. Richard W. Jordan of Yamagata University for furthermore contribute to a better understanding English editing of the manuscript. This study was of the past El Ninõ and La Ninã teleconnection funded by the following research programs of in the Kuroshio-Oyashio Extension region. MEXT: Grants-in-Aid-for Scientific Research B2 Project No. 10480128, B1 Project No. 13440152 and the GCMAPS program (H. Kawahata, PI). YO Acknowledgements received a partial fund from the Prof. Tatsuro Matsumoto Scholarship Fund. We are grateful to the captain, crew, technicians, and scientists on board the R.V. Mirai Cruises, JAMSTEC, for their efforts in collecting the Appendix A sediment trap samples. We acknowledge the technicians of Marine Works Japan Co., Ltd. for their Photographs of radiolarian taxa encountered help with laboratory works. We thank Daisuke during this study are shown in Figs. 9–14.

Fig. 9. The sample numbers correspond to those published in Honda et al. (2002).

1. Siphonosphaera spp., Station 40N, #49 2. Collosphaera tubelosa Haeckel, Station 40N, #21 3. Collosphaera confossa Takahashi, Station 40N, #1 4. Cenosphaera spp., Station 40N, #1 5. Polysolenia arktios Nigrini, Station 50N, #15 6. Hexacontium enthacanthum Jørgensen, Station 40N, #1 7. Hexacontium laevigatum Haeckel, Station 40N, #1 8. Hexacontium spp., Station 40N, #16 9. Actinomma boreale Cleve, Station 40N, #41 10. Actinomma leptoderma longispina Cortese and Bjørklund, Station 40N, #47 11. Actinomma leptoderma leptoderma (Jørgensen), Station 40N, #5 12. Actinomma delicatulum (Dogiel and Reshetnyak), Station 40N, #10 13. Sphaeropyle langii Dreyer, Station KNOT, #49 14. Actinomma sp. 1, Station 40N, #1 15. Actionmma spp., Station 40N, #6 16. Actinomma medianum Nigrini, Station 40N, #49 17. Drymyomma elegans Jørgensen, Station KNOT, #26 18. Dorydruppa bensoni Takahashi, Station 40N, #42 19. Stylatractus spp., Station 50N, #4 20. Actinomma arcadophorum, Station 40N, #46 21. Rhizoplegma boreale (Cleve), Station 50N, #54 22. Saturnalis circularis Haeckel, Station 40N, #39 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2261 ARTICLE IN PRESS 2262 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Fig. 10. Same as Fig. 9.

1. Cladococcus abietinus Haeckel, Station 40N, #6 2. Cladococcus abietinus (medullary shell), Station 40N, #6 3. Cladococcus cervicornis Haeckel, Station KNOT, #25 4. Cladococcus scoparius Haeckel, Station 40N, #24 5. Cladococcus cervicornis (medullary shell), Station KNOT, #1 6. Cladococcus viminalis Haeckel, Station 40N, #17 7. Centrocubus octostylus Haeckel, Station 40N, #17 8. Styptosphaera spongiacea Haeckel, Station 40N, #43 9. Didymocyrtis tetrathalamus (Haeckel), Station 40N, #20 10. Hexapyle armata (Haeckel), Station 40N, #15 11. Tetrapyle octacantha Muller,+ Station 40N, #20 12. Larcopyle butschlii Dreyer, Station 50N, #1 13. Heliodiscus asteriscus Haeckel, Station 40N, #10 14. Phorticium pylonium Haeckel, Station 40N, #9 15. Larcospira quadrangula Haeckel, Station 40N, #5 16. Spumellaria sp. A, Station 40N, #47 17. Gonosphaera primordialis Jørgensen, Station 40N, #1 18. Spumellaria sp. C, Station 40N, #10 19. Spumellaria sp. B, Station 50N, #1 20. Plegmosphaera lepticali Renz, Station 40N, #47 21. Plegmosphaera pachypila Haeckel, Station 40N, #42 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2263 ARTICLE IN PRESS 2264 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Fig. 11. Same as Fig. 9.

1. Stylochlamydium venustum (Bailey), Station 40N, #2 2. Stylodictya validispina Jørgensen, Station KNOT, #54 3. Stylodictya aculeata Jørgensen, Station 40N, #47 4. Spongurus cylindricas (Haeckel), Station 40N, #5 5. Spongurus pylomaticus Riedel, Station 40N, #3 6. Spongotrochus glacialis (small), Station 40N, #6 7. Spongodiscus spp., Station 40N, #37 8. Spongaster tetras tetras Ehrenberg, Station 40N, #21 9. Spongurus spindalis Welling, Station 50N, #3 10. Spongoliva ellipsoides Popofsky, Station 40N, #47 11. Spongopyle osculosa Dreyer, Station 40N, #6 12. Spongotrochus glacialis Popofsky, Station 50N, #36 13. Stypyosphaera? spumacea Haeckel, Station 40N, #10 14. Euchitonia elegans (Ehrenberg), Station 40N, #22 15. Lithelius minor (Jørgensen), Station 40N, #5 16. Lithelius nautiloides Popofsky, Station 50N, #4 17. Spongodiscidae sp., Station 40N, #5 18. Dictyocoryne profunda Ehrenberg, Station 40N, #10 19. Hymeniastrum euclidis Haeckel, Station KNOT, #12 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2265 ARTICLE IN PRESS 2266 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Fig. 12. Same as Fig. 9.

1. Peridium longispinum Jørgensen, Station 40N, #10 2. Peridium spp., Station 50N, #1 3. Phormacantha spp., Station 40N, #16 4. Plectacantha spp., Station 40N, #7 5. Pseudocubus obeliscus Haeckel, Station 40N, #20 6. Neosemantis cladophora (Jørgensen), Station 40N, #7 7. Neosemantis distephanus Popofsky, Station 40N, #5 8. Zygocircus productus (Hertwig) group, Station 40N, #5 9. Ceratospyris borealis Bailey, Station KNOT, #29 10. Mitrocalpis araneafera Popofsky, Station KNOT, #28 11. Saccospyris antarctica Haecker, Station 40N, #6 12. Saccospyris conithorax Petrushevskaya, Station 50N, #1 13. Lithomelissa setosa Jørgensen, Station 40N, #47 14. Antarctissa? sp. 1, Station 50N, #5 15. Dimelissa thoracites (Haeckel) group, Station 40N, #10 16. Peromelissa phalacra Haeckel, Station 40N, #47 17. Lophospyris pentagona pentagona (Ehrenberg) emend. Goll, Station 40N, #6 18. Arachnocorys umbellifera Haeckel, Station 40N, #1 19. Arachnocorys pentacantha Popofsky, Station 40N, #1 20. Lithomelissa spp., Station 50N, #4 21. Amphiplecta acrostoma Haeckel, Station 40N, #6 22. Lophophaena cf. capito Ehrenberg, Station 40N, #6 23. Lophophaena dacacantha (Haeckel) group, Station 50N, #4 24. Lophophaena spp., Station 40N, #6 25. Artobotrys boreale (Cleve), Station 50N, #15 26. Lithocampe platycephala (Ehrenberg), Station 50N, #49 27. Artostrobus annulatus (Bailey), Station KNOT, #48 28. Artostrobus joergenseni Petrushevskaya, Station KNOT, #48 29. Botryostrobus aquilonaris (Bailey), Station KNOT, #40 30. Botryostrobus auritus/australis group (Ehrenberg), Station 40N, #10 31. Carpocanarium papillosum (Ehrenberg), Station 40N, #10 32. Carpocanistrum spp., Station 40N, #10 33. Siphocampe arachnea (Ehrenberg), Station KNOT, #48 34. Spirocyrtis subscalaris Nigrini, Station 40N, #10 35. Cornutella profunda Ehrenberg, Station 40N, #3 36. Cyrtopera languncula Haeckel, Station KNOT, #29 37. Hexaspyris spp., Station 40N, #5 38. Cladoscenium tricolpium (Haeckel), Station 50N, #1 39. Cladoscenium ancoratum Haeckel, Station 50N, #2 40. Tetraphormis dodecaster (Haeckel), Station 40N, #1 41. Stichopilium bicorne Haeckel, Station 40N, #7 42. Lithostrobus hexagonalis Haeckel, Station 40N, #5 43. Peripyramis circumtexta Haeckel, Station 50N, #8 44. Lipmanella spp., Station 40N, #6 45. Conarachnium aff. polyacanthum (Popofsky), Station 40N, #5 46. Tetraphormis rotula (Haeckel), Station 50N, #17 47. Plectagonidium deﬂandrei Cachon and Cachon, Station 40N, #46 48. Tetraplecta pinigera Haeckel, Station 50N, #1 49. Callimitra solocicribrata Takahashi, Station 40N, #16 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2267 ARTICLE IN PRESS 2268 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Fig. 13. Same as Fig. 9.

1. Corocalyptra cervus (Ehrenberg), Station 40N, #10 2. Cycladophora bicornis (Popofsky), Station 40N, #7 3. Cycladophora cornutoides Petrushevskaya, Station 40N, #6 4. Cycladophora davisiana Ehrenberg, Station 50N, #46 5. Pseudodictyophimus gracilipes (Bailey), Station 40N, #47 6. Pseudodictyophimus bicornis (Ehrenberg), Station 40N, #10 7. Pseudodictyophimus spp., Station 40N, #16 8. Dictyophimus crisiae Ehrenberg/hirundo (Haeckel) group, Station 40N, #1 9. Dictyophimus aff. infabricatus Nigrini, Station 50N, #17 10. Dictyophimus macropterus (Ehrenberg), Station 40N, #5 11. Dictyophimus spp., Station 40N, #10 12. Eucecryphalus tricostatus (Haeckel), Station 40N, #1 13. Pterocanium polypylum, Station 40N, #10 14. Pterocanium praetextum, Station 40N, #5 15. Pterocanium korotnevi (Dogiel and Reshetnyak), Station 50N, #17 16. Pterocanium spp., Station 40N, #10 17. Lychnocanomma? sp., Station 40N, #10 18. Ceratocyrtis spp., Station 40N, #11 19. Lampromitra spp., Station 40N, #11 20. Anthocyrtidium zanguebaricum (Ehrenberg), Station 40N, #47 21. Lamprocyrtis spp., Station 40N, #16 22. Pterocorys zancleus (Muller),+ Station 40N, #1 23. Pterocorys spp., Station 40N, #5 24. Eucyrtidium acuminatum (Ehrenberg), Station 40N, #43 25. Eucyrtidium hexagonatum Haeckel, Station 40N, #5 26. Eucyrtidium spp., Station 40N, #9 27. Lithocampe sp. Station 40N, #10 28. Litharachnium tentorium Haeckel, Station KNOT, #43 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2269 ARTICLE IN PRESS 2270 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Fig. 14. Same as Fig. 9.

1. Challengeron vicina (Reshetnyak), Station KNOT, #24 2. Challengerosium avicularia Haecker, Station 40N, #6 3. Challengeron willemoesii Haeckel, Station 40N, #43 4. Chellengeron tizardi (Murray), Station KNOT, #6 5. Challengeron ornithocephala (Reshetnyak), Station KNOT, #24 6. Challengeron neptuni Borgert, Station KNOT, #15 7. Challengeranium diodon (Haeckel), Station 40N, #7 8. Challengeron sp., Station 50N, #9 9. Euphysetta staurocodon Haeckel, Station 40N, #23 10. Euphysetta elegans Borgert, Station 40N, #11 11. Protocystis harstoni (Murray), Station 50N, #1 12. Protocystis tridens (Haeckel), Station 40N, #18 13. Protocystis tridentata Borgert, Station KNOT, #40 14. Protocystis xiphodon (Haeckel), Station 40N, #47 15. Protocystis tritonis (Haeckel), Station 40N, #36 16. Protocystis murrayi (Haeckel), Station 40N, #22 17. Borgertella caudata (Wallich), Station KNOT, #3 18. Lirella bullata (Stadum and Ling), Station 50N, #44 19. Lirella melo (Cleve), Station KNOT, #43 20. Porospathis holostoma (Cleve), Station 50N, #1 21. Conchelium capsula Borgert, Station 50N, #55 22. Protocystis neresi (Murray), Station KNOT, #43 23. Protocystis thomsoni (Murray), Station 50N, #22 24. Hackeliana porcellana Murray, Station KNOT, #31 ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2271 ARTICLE IN PRESS 2272 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

References insight from 1995 to 1999 sediment trap experiment. In: Carter, E.S., Whalen, P., Noble, P.J., Crafford, A.E.J. (Eds.), Abelmann, A., 1992a. Radiolarian flux in Antarctic waters The International Association of Radiolarian Paleontologists (Drake Passage, Powell Basin, Bransfield Strait). Polar (Ninth Meeting), abstract vol. 30–31. Biology 12, 357–372. Ganopolski, A., Rahmstorf, S., Petoukhov, V., Claussen, M., Abelmann, A., 1992b. Radiolarian taxa from Southern 1998. Simulation of modern and glacial climates with a Ocean sediment traps (Atlantic sector). Polar Biology 12, coupled global model of intermediate complexity. Nature 391, 373–385. 351–356. Abelmann, A., Gowing, M.M., 1997. Spatial distribution pattern Gowing, M.M., 1993. Seasonal radiolarian flux at the VERTEX of living polycystine radiolarian taxa—baseline study for North Pacific time-series site. Deep-Sea Research I 40, paleoenvironmental reconstructions in the Southern Ocean 517–545. (Atlantic sector). Marine Micropaleontology 30, 3–28. Honda, M.C., 2001. The study of carbon cycle in the western Anderson, O.R., 1983. Radiolaria. Springer, New York 355pp. North Pacific by measurement of radiocarbon and sediment Anderson, O.R., Bryan, M., Bennett, P., 1990. Experimental and trap experiment. Ph.D. Thesis, Hokkaido University, 193pp. observational studies of radiolarian physiological ecology: 4. (in Japanese). Factors determining the distribution and survival of Didymo- Honda, M.C., Imai, K., Nojiri, Y., Hoshi, F., Sugawara, T., cyrtis tetrathalamus tetrathalamus with implications for Kusakabe, M., 2002. The biological pump in the northwestern North Pacific based on fluxes and major paleoecological interpretations. Marine Micropaleontology components of particulate matter obtained by sediment-trap 16, 155–167. experiments (1997–2000). Deep Sea Research II 49, Bernstein, R.E., Betzer, P.R., Takahashi, K., 1990. Radiolarians 5595–5625. from the western North Pacific Ocean: a latitudinal study of Honjo, S., Doherty, K.W., 1988. Large aperture time-series their distributions and fluxes. Deep-Sea Research 37, sediment traps—design objectives, construction and applica- 1677–1696. tion. Deep-Sea Research 35, 133–149. Bjørklund, K.R., 1976. Radiolaria from the Norwegian Sea, Leg Itaki, T., Takahashi, K., 1995. Preliminary results on radiolarian 38 of the Deep Sea Drilling Project. Initial Reports of the fluxes in the central subarctic Pacific and Bering Sea. In: Deep Sea Drilling Project 38, 1101–1168. Proceedings of the Hokkaido Tokai University of Science and Bjørklund, K.R., Cortese, G., Swanberg, N., Schrader, H.J., Engineering, vol. 7, pp. 37–47 (in Japanese, with English 1998. Radiolarian faunal provinces in surface sediments of the abstract). Greenland, Iceland and Norwegian (GIN) Seas. Marine Kennett, J.P., Cannariato, K.G., Hendy, I.L., Behl, R.J., 2002. Micropaleontology 35, 105–140. Methane Hydrates in Quaternary Climate Change: The Boltovskoy, D., Riedel, W.R., 1987. Polycystine Radiolaria of Clathrate Gun Hypothesis (Special Publication), vol. 54. the California Current region: seasonal and geographic AGU, Washington, DC (216pp). patterns. Marine Micropaleontology 12, 65–104. Kling, S.A., 1979. Vertical distribution of polycystine radiolar- Borgert, A., 1901. Die nordischen Tripyleen-Arten. In: Brandt, ians in the central North Pacific. Marine Micropaleontology K., Apstein, C. (Eds.), Nordisches Plankton, vol. 15, pp. 1–52. 4, 295–318. Cachon, J., Cachon, M., 1969. Revision systematique des Kling, S.A., Boltovskoy, D., 1995. Radiolarian vertical distribu- Nassellaires Plectoidea a propos de la description d’un tion patterns across the southern California Current. Deep- nouveau representant, Plectagonidium deflandrei nov. gen. Sea Research I 42, 191–231. nov. sp. Archiv fur Protistenkunde 111, S. 236–S. 251. Levitus, S., Boyer, T., 1994. World Ocean Atlas 1994, vol. 4: Cleve, P.T., 1899. Plankton collected by the Swedish expedition Temperature. NOAA Atlas NESDIS 4, US Department of to Spitzbergen in 1898. Ko¨ ngliga Svenska Vetenskaps Commerce, Washington, DC http://ingrid.ldeo.columbia.edu/ Akademiens Handlingar 32, 1–51. SOURCES/.LEVITUS94/. Cortese, G., Bjørklund, K.R., 1998. The taxonomy of boreal Ling, H.-Y., Stadum, C.J., Welch, M.L., 1971. Polycystine Atlantic Ocean Actinomma (Radiolaria). Micropaleontology Radiolaria from Bering Sea surface sediments. In: Proceed- 44, 149–160. ings of the Second Planktonic Conference, Roma, 1970, Dogiel, V.A., Reshetnyak, V.V., 1952. Material on radiolarians Tecnoscienza, Roma, pp. 705–729. of the northwestern part of the Pacific Ocean. Investigation of Lombari, G., Boden, G., 1985. Modern radiolarian global the Far East Seas of the USSR 3, 5–36. distributions. Cushman Found. Foram. Res. (Special Pub- Dolven, J.K., Bjørklund, K.R., 2001. An early Holocene peak lication No. 16A, 125. occurrence and recent distribution of Rhizoplegma boreale Molina-Cruz, A., 1977. Radiolarian assemblages and their (Radiolaria): a biomarker in the Norwegian Sea. Marine relationship to the oceanography of the subtropical south- Micropaleontology 42, 25–44. eastern Pacific. Marine Micropaleontology 2, 315–352. Favorite, F., Dodimead, A.J., Nasu, K., 1976. Oceanography of Moore Jr., T.C., 1978. The distribution of radiolarian assem- the Subarctic Pacific region, 1960–1971. Bulletin of the blages in the modern and ice-age Pacific. Marine Micro- International North Pacific Communications 33, 1–187. paleontology 3, 229–266. Freeland, H.J., Bychkov, A.S., Whitney, F., Taylor, C., Wong, Motoyama, I., 1997. Origin and evolution of Cycladophora C.S., Yurasov, G.I., 1998. WOCE section P1W in the Sea of davisiana Ehrenberg (Radiolaria) in DSDP Site 192, North- Okhotsk 1. Oceanographic data description. Journal of west Pacific. Marine Micropaleontology 30, 45–63. Geophysical Research 103, 15613–15623. Nagata, Y., Ohtani, K., Kashiwai, M., 1992. Subarctic Gyre in Fukumura, R., Takahashi, K., 2000. Radiolarian fluxes in the the North Pacific Ocean. Umi no Kenkyu 1, 75–104 Bering Sea and the central subarctic Pacific Ocean: a new (in Japanese with English abstract). ARTICLE IN PRESS Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274 2273

Nigrini, C., 1970. Radiolarian assemblages in the North Pacific Sasaoka, K., Saitoh, S., Asanuma, I., Imai, K., Honda, M.C., and their application to a study of Quaternary sediments in Nojiri, Y., Saino, T., 2002. Temporal and spatial variability of core V20–130. In: Hays, J.D. (Ed.), Geological Investigations chlorophyll-a in the western subarctic Pacific determined from of the North Pacific, Memoir vol. 126. Geological Society of satellite and ship observations from 1997 to 1999. Deep-Sea America, 1970, pp. 139–183. Research II 49, 5557–5576. Nigrini, C., Moore Jr., T.C., 1979. A Guide to Modern Schlitzer, R., 2002. Ocean Data View. http://www.awi-bremerhaven. Radiolaria. Cushman Found. Foram. Res., Special Publica- de/GEO/ODV tion No. 16, 342pp. Schneider, N., Miller, A.J., 2001. Predicting western North Nimmergut, A., Abelmann, A., 2002. Spatial and seasonal Pacific Ocean climate. Journal of Climate 14, 3997–4002. changes of radiolarian standing stocks in the Sea of Okhotsk. Schwing, F.B., Murphree, T., de Witt, L., Green, P., 2002. The Deep-Sea Research I 49, 463–493. evolution of oceanic and atmospheric anomalies in the Nishimura, A., Nakaseko, K., Okuda, Y., 1997. A new coastal Northeast Pacific during the El Ninõ and La Ninã events of water radiolarian assemblage recovered from sediment 1995–2001. Progress in Oceanography 54, 459–491. samples from the Antarctic Ocean. Marine Micropaleontol- Shannon, C.E., Weaver, W., 1949. The Mathematical Theory of ogy 30, 29–44. Communication. University of Illinois Press, Urbana (125pp). Okazaki, Y., Takahashi, K., Nakatsuka, T., Honda, M.C., Swanberg, N.R., Bjørklund, K.R., 1987. Radiolaria in the 2003a. The production scheme of Cycladophora davisiana plankton of some fjords in western and northern Norway: (Radiolaria) in the Okhotsk Sea and the northwestern North the distribution of species. Sarsia 72, 231–244. Pacific: implication for the paleoceanographic conditions during the glacials in the high latitude oceans. Geophysical Takahashi, K., 1987. Radiolarian flux and seasonality: climatic Research Letters 30 (18), 1939. and El Ninõ response in the subarctic Pacific, 1982–1984. Okazaki, Y., Takahashi, K., Yoshitani, H., Nakatsuka, T., Global Biogeochemical Cycles 1, 213–231. Ikehara, M., Wakatsuchi, M., 2003b. Radiolarians under the Takahashi, K., 1991. Radiolaria: flux, ecology, and taxonomy in seasonally sea-ice covered conditions in the Okhotsk Sea: flux the Pacific and Atlantic. In: Honjo, S. (Ed.), Ocean and their implications for paleoceanography. Marine Micro- Biocoenosis, Series 3. Woods Hole Oceanogr. Inst. Press, paleontology 49, 195–230. Woods Hole, MA (303pp). Okazaki, Y., Takahashi, K., Itaki, T., Kawasaki, Y., 2004. Takahashi, K., 1997. Siliceous microplankton fluxes in the Comparison of radiolarian vertical distributions in the eastern subarctic Pacific. Journal of Oceanography 53, Okhotsk Sea near Kuril Islands and the northwestern North 455–466. Pacific off Hokkaido Island. Marine Micropaleontology 51, Takahashi, K., Honjo, S., 1981. Vertical flux of Radiolaria: a 257–284. taxon-quantitative sediment trap study from the western Onodera, J., Takahashi, K., Honda, M.C., 2003. Diatom fluxes at tropical Atlantic. Micropaleontology 27, 140–190. Station KNOT in the western subarctic Pacific, 1997–2000. Takahashi, K., Okazaki, Y. Phaeodarian Radiolaria from the Bulletin of the Plankton Society of Japan 50, 1–15 (in Okhotsk Sea, in preparation. Japanese, with English abstract). Takahashi, K., Hurd, D.C., Honjo, S., 1983. Phaeodarian Onodera, J., Takahashi, K., Honda, M.C., 2005. Pelagic and skeletons: their role in silica transport to the deep sea. Science coastal time-series diatom fluxes and the environmental 222, 616–618. changes in the northwestern North Pacific during Takahashi, K., Fujitani, N., Yanada, N., Maita, Y., 2000. Long- 1997–2000. Deep Sea Res. II, this volume [doi:10.1016/ term biogenic particle fluxes in the Bering Sea and the central j.dsr2.2005.07.005]. subarctic Pacific Ocean, 1990–1995. Deep-Sea Research I 47, Petrushevskaya, M.G., 1968. Radiolaria of orders Spumellaria 1723–1759. and Nassellaria of the Antarctic region. In: , Biological Takahashi, K., Fujitani, N., Yanada, N., 2002. Long term Reports of the Soviet Antarctic Expedition (1955–1958), vol. monitoring of particle fluxes in the Bering Sea and the central 3. Acad. Sci. USSR, Zool. Inst. Leningrad 1–186pp. subarctic Pacific Ocean, 1990–2000. Progress in Oceanogra- Petrushevskaya, M.G., 1971. Spumellarian and nassellarian phy 55, 95–112. Radiolaria in the plankton and bottom sediments of the Talley, L.D., 1991. An Okhotsk Sea water anomaly: implications central Pacific. In: Fumnel, B.M., Riedel, W.R. (Eds.), The for ventilation in the North Pacific. Deep-Sea Research 38, Micropaleontology of Oceans, pp. 309–317. S171–S190. Renz, G.W., 1976. The distribution and ecology of radiolaria in Talley, L.D., 1993. Distribution and formation of North Pacific the central Pacific: plankton and surface sediments. Bulletin of the Scripps Institution of Oceanography 22, 267pp. Intermediate Water. Journal of the Physical Oceanography Reshetnyak, V.V., 1966. Deepwater phaeodarian radiolarians of 23, 517–537. the northwestern part of the Pacific Ocean. Fauna of the Talley, L.D., 1999. Some aspects of ocean heat transport by the USSR. Radiolaria. Acad. Nauk SSSR, Zool. Inst., No. Ser. shallow, intermediate and deep overturning circulations. In: 94, 1–208. Clark, P.U., Webb, R.S., Keigwin, L.D. (Eds.), Mechanism of Reynolds, R.W., Smith, T.M., 1994. Improved global sea surface Global Climate Change at Millennial Time Scales, Geophy- temperature analysis. Journal of Climate 7, 929–948 http:// sical Monograph Series, vol. 112. AGU, Washington, DC, ingrid.ldeo.columbia.edu/SOURCES/.IGOSS/. pp. 1–22. Robertson, J., 1975. Glacial to interglacial oceanographic Welling L.A., 1996. Environmental control of radiolarian changes in the northwest Pacific, including a continuous abundance in the central equatorial Pacific and implications record of the last 400,000 years. Ph.D. Thesis, Columbia for paleoceanographic reconstructions. Ph.D. Thesis, Oregon University, New York, 355pp. State University, Corvallis, 314pp. ARTICLE IN PRESS 2274 Y. Okazaki et al. / Deep-Sea Research II 52 (2005) 2240–2274

Welling, L.A., Pisias, N.G., 1998. Radiolarian fluxes, stocks, and communities down to the greater depths in the western North population residence times in surface waters of the central Pacific Ocean. Deep-Sea Research II 49, 5513–5529. equatorial Pacific. Deep-Sea Research I 45, 639–671. Yamashita, H., Takahashi, K., Fujitani, N., 2002. Zonal and Welling, L.A., Pisias, N.G., Johnson, E.S., White, J.R., 1996. vertical distribution of radiolarians in the western and central Distribution of polycystine radiolaria and their relation to the Equatorial Pacific in January 1999. Deep-Sea Research II 49, physical environment during the 1992 El Nino and following 2823–2862. cold event. Deep-Sea Research II 43, 1413–1434. Yan, X.H., Ho, C.R., Zheng, Q., Klemas, V., 1992. Temperature Wong, C.S., Matear, R.J., Freeland, H.J., Whitney, F.A., and size variabilities of the Western Pacific Warm Pool. Bychkov, A.S., 1998. WOCE line P1W in the Sea of Okhotsk Science 258, 1643–1645. 2. CFCs and the formation rate of intermediate water. Yu, E.F., Francois, R., Bacon, M.P., Honjo, S., Fleer, A.P., Journal of Geophysical Research 103, 15625–15642. Manganini, S.J., van der Loeff, M.M.R., Ittekkot, V., Yamaguchi, A., Watanabe, Y., Ishida, H., Harimoto, T., 2001. Trapping efficiency of bottom-tethered sediment traps Furusawa, K., Suzuki, S., Ishizaka, J., Ikeda, T., Takahashi, estimated from the intercepted fluxes of Th230 and Pa231. M.M., 2002. Structure and size distribution of plankton Deep-Sea Research I 48, 865–889.