(Radiolaria) in the Western Arctic Ocean: Environmental Indices in a Warming Arctic T

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 3 , K. Kimoto 3 , J. Onodera 4 16646 16645 , S. B. Kruglikova 2 , K. R. Bjørklund 3 1,2,3,* This discussion paper is/has beenPlease under refer review to for the the corresponding journal final Biogeosciences paper (BG). in BG if available. Department of Earth and Planetary Sciences, Graduate School ofNatural Sciences, History Kyushu Museum, Department of Geology, University of Oslo, P.O. BoxResearch 1172 and Blindern, Development Center for Global Change, JAMSTEC, Natsushima-cho 2-15, ShirshovP.P. Institute of Oceanology, Russian Academy of Sciences, Nakhimovsky Prospect now at: Central Laboratory, Marine Ecology Research Institute, 300 Iwawada, Onjuku-machi, Received: 4 October 2014 – Accepted: 10Correspondence November to: 2014 T. – Ikenoue Published: ([email protected]) 3 December 2014 Published by Copernicus Publications on behalf of the European Geosciences Union. and N. Harada 1 University, 6-10-1 Hakozaki, Higashi-ku,2 Fukuoka 812-8581, Japan 0318 Oslo, Norway 3 Yokosuka, 237-0061, Japan 4 36, 117883 Moscow,* Russia Isumi-gun, Chiba 299-5105 Japan Flux variations and vertical distributions of microzooplankton (Radiolaria) in the western Arctic Ocean: environmental indices in a warming Arctic T. Ikenoue Biogeosciences Discuss., 11, 16645–16701, 2014 www.biogeosciences-discuss.net/11/16645/2014/ doi:10.5194/bgd-11-16645-2014 © Author(s) 2014. CC Attribution 3.0 License. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | was Amphimelissa setosa 16648 16647 , a warm Atlantic water species, in net samples, W, bottom depth 1975 m) in the western Arctic Ocean during 0 absorption is an important carbon sink in the area without sea-ice ecting the productivity, distribution, and composition of radiolarian 00 2 ff ◦ Ceratocyrtis histricosus N, 162 0 00 ◦ Particle flux play important roles in the carbon export (Francois et al., 2002). With The biological CO the samples collected by sedimentet trap al. in the (2010) Canadamagnitude found Basin and smaller that Chukchi than annual Rise, that Honjo an average in important of epipelagic role sinking areas forobserved particle where carbon a flux the export massive was particle to algalice three flux greater biomass edge orders represented depths. beneath in of However, fully thecover Arrigo increased consolidated Chukchi light et transmission Sea pack under al. the ice duringet ice (2012) and far the al. allowed blooming (2013) from summer, of also algae. and the Boetius Arctic reported suggested Ocean that was that the widely a algal depositedit biomass thinning at is released the inferred ice from that sea biomass the floorthe of melting in zooplankton Arctic ice the also Ocean, summer in changed as of seasonally the now a under 2012. result the recognized Therefore, sea-ice of as in the a2004). variable key The sea-ice seasonal component conditions. and of Microzooplankton interannual changesthe are pelagic of sea food microzooplankton ice communities webs regions, within however, (e.g., are Calbet still poorly and understood. Landry, ocean circulation (Proshutinskyenhanced et recently al., due 2002). toThe The the biological decreasing Beaufort pump sea-ice is Gyre reduced (Shimada withinoutside has et the the Beaufort al., been Gyre, Beaufort 2006; and Gyre become conversely, Yang, it (Nishino 2009). is et enhanced al., 2011). in the Arctic Ocean (Bates etboth al., enhance 2006; and Bates reduce the and biological Mathis,circulation pump 2009). (Nishino in Melting et the of Arctic sea-ice al., Ocean, can 2011).Basin depending The on in ocean Beaufort the Arctic High, Ocean, athe drives high Beaufort the pressure Gyre sea-ice over and (Fig. the the 1). Canada water In masses the anticyclonically, Canada as Basin, the Beaufort Gyre governs the upper western Arctic Ocean ofMarkus the et Pacific al., side 2009). (Shimada InBering the et Strait western al., contributes Arctic 2006; to Ocean,formation Comiso both during the et winter sea-ice warm (Shimada al., pacific melt et water 2008; in al., through 2006; summer the Itoh and et an al., inhibition 2013). of sea-ice Abstract The vertical distribution of radiolarianston was investigated sampler using (100–0, a vertical 250–100,size) multiple 500–250 plank- at and the 1000–500 mber Northwind water 2013. depths, Abyssal To 62 µm investigate Plainsea-ice mesh seasonal and and variations water southwestern in masses,NAP Canada time the (75 series Basin flux sediment in of trap radiolarians Septem- system in was relation moored at to Station indicating that it has extendedflux its was habitat comparable into the to Pacific that Winter Water. in The the radiolarian North Pacific Oceans. dominant during the openwith water well-grown and ice the algae, beginningdeep ice and vertical fauna the mixing. and end During with the ofwater sea-ice alternation ice tolerant cover Actinommidae cover of season, was seasons stable however, dominant oligotrophic andand water and the masses cold- its productivity and of species radiolariaincrease was diversity lower of was solar greater, which radiationphytoplankton species that might under the induce be sea-ice. the associated Thesewas a indicated growth with major that of factor the the a dynamics algae seasonal fauna. of on sea-ice the ice and the other 1 Introduction In recent years, summerglobal sea-ice climate extent in change the (Stroevereached Arctic et the Ocean al., minimum decreases 2007, extent rapidlyservation 2012). in (NSIDC, due 2012). The September to The sea-ice 2012 most in remarkable since sea-ice the the decrease Arctic beginning was observed Ocean of in satellite the ob- October 2010–September 2012. We showed characteristicsolarian of taxa fourteen related abundant to radi- theWe vertical found hydrographic the structure in the western Arctic Ocean. 5 5 20 25 15 10 10 15 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | C) and saltier (near 35 psu) ◦ 16649 16650 C) and originates from Pacific water that is modified in ◦ 1.7 − and is characterized by very low salinities (less than 28 psu). ect of sea ice reduction on marine ecosystems in the Arctic ff ff The deep water is divided into Atlantic Water (AW), Canada Basin Deep Water This is the first extensive study of the seasonal and interannual flux changes of radio- The radiolarian assemblages in the western Arctic Ocean has been studied mainly The abundance of microzooplankton radiolaria in a region is related to temperature, To understand the e relation to the environmentaltration, conditions and (temperature, downward salinity, shortwave depth, radiation). sea-ice concen- 2 Oceanographic setting The hydrography in the(e.g., western Aagaard Arctic et al., Ocean 1985; hascolumn McLaughlin been et can al., discussed be 2011) in and dividedterized several the into upper studies by 1000 five low m distinct of temperaturesubdivided the water and water into masses. low three The salinity layers,(PSW), water surface i.e. Pacific (Aagaard water Winter Surface et is Water Mixed (PWW). al., charac- ice Layer The 1981) melt (SML), SML and and (0–25 Pacific river m) can SummerThe runo is be PSW Water formed (25–100 in m) and summer PWW bythe (100–250 sea- Pacific m) are Ocean cold via halocline theand layers enters Bering originating the from Sea. Canada The Basin through PSWand the flows Barnes, Bering 1961) along Strait (Fig. and the 1). Barrow Alaskan Canyon Thethe (Coachman coastal PSW 1990s, is area 28–32 relatively psu warmer in andThe the less PSW saline 2000s, (30–32 is according psu further to in cooler Jackson classified et and into al., warmer more 2011) and salinefrom than less the Pacific Bering saline PWW. water Sea Alaskan that coastalThe water Alaskan is water (Coachman coastal and modified water et is in al.,northwards carried the along by 1975), the a Chukchi which Northwind current and along Ridge originateice the Bering by cover the Alaskan Seas and coast, Beaufort decay and during gyreature (Shimada spread depending summer. minimum on et (of the al., rates about 2001). of The PWW is characterized by a temper- (CBDW). AW (250–900 m) is warmer (near or below 1 the Chukchi and Bering Seasis during also winter (Coachman characterized and by Barnes,from a 1961). the The shelf nutrient PWW sediments maximum (Jones and and Anderson, its 1986). source is regenerated nutrients larians in the western Arcticvariations Ocean. We in present the radiolarian western depthtrap distributions Arctic and material, Ocean flux based respectively. We on plankton discuss tow their samples seasonality and and sediment species associations in surface sediment samples mainly overand the Atlantic Kruglikova, side 2003). ofdistribution the However, of Arctic the living Ocean knowledge radiolarians (Bjørklund are ofof still radiolarians the limited, has and geographical not the been seasonal andsea-ice studied and coverage. the in annual changes the depth western Arctic Ocean because of seasonal based on the samples collected1963; by Tibbs, plankton 1967), net and in tow the at Beaufort the Sea ice-floe in stations summer of (Hülseman 2000 (Itaki et al., 2003) or the changes and radiolarian abundancesvation based on on radiolarian a fluxes fifteenare in year also long the related time-series central to obser- Takahashi, subarctic 2007; the Pacific. Boltovskoy vertical Radiolarian et hydrographic al., assemblages proportion structure 2010), therefore might (e.g., variations be Kling, in useful 1979;depth their environmental abundance Ishitani interval proxies and and related for waterprosperity to and mass the decline exchanges of recent at sea-ice, climate each influx of change water (e.g., mass from ocean other circulation regions). change, salinity, productivity and nutrientCortese availability and (Anderson, Bjørklund, 1983; 1997;at Cortese Bjørklund genus et et and al., al., family 2003). levels 1998; their Not radiolarians distribution only represent at patterns various species oceanographic andstudies, conditions level compositions Ikenoue but by (Kruglikova et also et al. al., (2012a, 2010, b) 2011). found a In close recent relationship between water mass ex- Ocean, we studied productivity, distribution, composition,radiolarians, and biological which regime are of living onesiliceous of skeletons, the based commonest on micro-zooplankton the plankton groups tow that samples secrete and sediment trap samples. 5 5 10 15 20 25 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ® C) ◦ ) at 1 − C) at about ◦ 1.6 − C) at about 400 m ◦ ) was towed from 4 layers 2 ) around the boundary of the PWW and AW, 1 16651 16652 − W; Station 56 in southwestern Canada Basin, 0 ). C) at about 50 m and show a rapid decrease with 3 54 ◦ ◦ − magnification. Phaeodaria have not been recognized as N, 161 × 0 32 ◦ WSD-10). The split samples were fixed with 99.5 % ethanol for or 400 TM × W) (Fig. 1 and Table 1) in September 2013. Hydrographical data 0 59 ◦ N, 159 0 C) with a maximum value (1.6 48 ◦ ◦ The samples collected by VMPS were split with a Motoda box splitter and a ro- 1 200 m. Highest temperatures are found in the AW (near or below 1 screen with 45 µm meshmembrane size. filters Remains with on a thesalted nominal screen with pore were distilled size filtered water ofon through and 0.45 Gelman dried, microslides. µm. then Radiolarian The permanently filtered taxamicroscope mounted samples at were with were 200 identified Canada de- Balsam andRadiolaria counted but as with Cercozoa a in compound recent light studies using molecular biology (Cavalier-Smith with a gradual decreaseSML, below increasing 500 m. rapidly Salinity witha showed depth gradual low from increase values 28–32 of psu (25–28 salinitythe psu) in from PWW/AW in the 32 boundary. Dissolved the PSW. to oxygen In 35 showed psu, the maximum while value PWW there (405 there is µmolkg a is slight decrease below tary splitter (McLane radiolarian studies. Plankton samplesbetween were living stained and dead with specimens. Rose-Bengal The split to samples discriminate were sieved through a stainless 73 net. and Chao, 2003; Nikolaevcomplications et we al., dealt 2004; with Adl theing phaeodarians et to as al., the one 2005; classical of taxonomy the YuasaWe et (Anderson radiolarian determined groups et al., accord- that al., 2005). 2002; specimens Tothis Takahashi avoid and to were avoid Anderson, “living”, false 2002). staining if byon their other a organisms protoplasm slide such were was as identified bacterialstanding stained and growth). stocks counted, clearly, All (No. and specimens specimens their m individual numbers were converted to 3.2 Hydrographic profiles Profiles of temperature, salinity,tions and 32 dissolved (Northwind oxygen Abyssal downber Plain) to 2013 and are 1000 m 56 from depth Nishino (southwestern32, (2013) at Canada temperature and Basin) sta- showed shown in in sharpdepth Septem- Fig. with decrease 2a a from and b, sharp the− respectively. increase At surface Station at and the downincreasing base to depth. of about The SML. 25 PWW m The is PSW the is coldest generally water cold (minimum (about value (temperature, salinity) down to 1000 ma water CTD depth observation with were the simultaneously plankton obtainedthe sampling. from net The volume was of seawater estimated filtered using through a flow meter mounted in the mouth ring of the plankton (100–0, 250–100, 500–250,wind and Abyssal Plain, 1000–500 m) 74 at 2 stations (Station 32 in North- the boundary of the SMLand and PWW, minimum PWW, rapid value decrease (270 µmolkgand with slight increasing increase depth below the in boundary thedissolved of PSW oxygen the show PWW almost and AW. similar Temperature,for salinity, values and in at the both Station SMLStation 32 and 56. and PSW. In Station In the 56 PSW, the a except and temperature SML, a peak salinity at little Station at deeper, 32 compared Station was to about 32 Station one was 56. degree slightly higher, lower than at water mass located beneath theis AW formed and has by the the samemass brine salinity sinking as over formation the the on continental AW. The the margin CBDW into shelves, the which deep makes basins cold (Aagaard et and3 al., saline 1985). water Materials and methods 3.1 Plankton tow samples Plankton tow samples wereVMPS collected (mesh by vertical size: multiple 62 µm, plankton sampler open (VMPS). mouth area: 0.25 m intermediate water than the surfaceOcean, waters, which via is the originating Norwegian from Sea. the North The Atlantic CBDW (below 900 m) is a cold (lower than 0 5 5 15 20 25 10 15 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 N, (1) (2) − 0 00 day ◦ 2 and R/V − the aperture magnification is the order of S × i or 400 45 µm) fraction of each × < 45µm) fractions are filtered Sir Wilfrid Laurier < the aliquot size, V the sampling interval (day). Diversity indices 100 aliquot size of the samples to make mi- 45 µm) and the fine ( / C) were monitored every hour (sensor type: 16653 16654 ◦ 45 µm) and fine ( D > > er (pH 7.6–7.8) and 5 % formalin was added as ff 0.28 is the contribution of species and + ), and (hexametaphosphate, surfactant) solution was added P 2 ® ered formalin seawater before the sediment trap was deployed. ff , Nichiyu Giken Kogyo, Co. Ltd.) rotated at 10–15 day intervals 2 i P WSD-10). At first, we used 1 2 is the counted number of radiolarians, V/S/D is the diversity index, · TM W, bottom depth 1975 m) during 4 October 2010–28 September 2011 and dur- log i N 0 H N P of Japan Agency for Marine–Earth Science and Technology. The sample cups = 00 − ◦ = We made slides of both the coarse ( The samples were first sieved through 1 mm mesh to remove larger particles, which As supplemental environmental data, the moored sediment trap depth and the (45 µm mesh size). Both the coarse ( to disaggregate the sample. The treated samples are then sieved through a screen 162 sion of particles from(Ewing and the Connary, nepheloid 1970). layer, Recoveriesout reaching and on redeployments about the of 400 Canadian the mMirai Coast traps above were Guard the carried Ship seafloor were I/B filled with (ice 5 % breaker) bu are not relevant for(McLane the present study.croslides The for samples microscope were workcase split (species of with identification). low a Weprotoplasm, radiolarian rotary made 20 specimen mL additional splitter of numbers. slidesa 10 In 100 % in mL order pyrex hydrogen beaker, and peroxide to heated (notaction solution remove boiling) was on are organic completed, a added hot Calgon matter plate to for and one the hour. After samples this re- in through Gelman membrane filterswith with distilled a water. The nominalin edge pore wet of size condition each of and filteredsamples 0.45 mounted samples µm are on are and added glass cut Xylene, desalted slides and according on permanently to a mounted slide slide with size warmer. Canadasample. The balsam. For dried the filters enumeration of and radiolarianof taxa radiolarian in skeletons this larger than study, we 45amined counted µm encountered all under on specimens an a Olympus slide. Each compound sample light was microscope ex- at 200 where area of the sediment trapusing (0.5 m the Shannon–Weaver log-basecalculated for 2 total formula radiolarians (Shannon andH Weaver, 1949) were ing 4 October 2011–18designed September to 2012 set the (Fig.This collecting 1; depth instrument Table of 2). at the approximately The moored 600 mooring m sediment above system traps the was was chosen sea in floor. order to avoid possible inclu- 3.3 Sediment trap samples Particle flux samplesmouth area were 0.5 collected m moored at by 184 m aSeptember (4 2012) sediment October and 2010–28 trap 1300 September mtober 2011)–260 (SMD26 (4 2011–18 m September October (4 S-6000, 2012) 2010–28 October at September open 2011–18 Station 2011)–1360 m NAP (4 (Northwind Oc- Abyssal Plain, 75 This seawater was collected fromand was 1000 m membrane filtered water (0.45 depth mmmixed pore in with size). the The sodium southern seawater in Canada boratea the Basin, preservative. as sample cups a was bu was calculated from our count data usingFlux the following formula: for species identification and counting. The radiolarian flux (No. specimens m where species. water temperature (accuracy of ST-26S-T). Moored traping depth for the the seconddepth). upper year Especially, trap during (about was July–Augustto 260 m in lowered about 2012, depth) by the 300 about thantion m moored 80 NAP during (Fig. m trap during the depth dur- S1). thedata was first set mooring Time-series (http://iridl.ldeo.columbia.edu/SOURCES/.IGOSS/.nmc/.Reyn_SmithOIv2/, lowered year cf. period data were (aboutReynolds of et calculated 180 al., m from sea-ice 2002). the concentration sea-ice around concentration Sta- 5 5 25 15 10 20 15 10 25 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | was was were (1 %) in the (5 %), (4 %), Acti- Tholospyris A. setosa juvenile (22 %) Actinomma bo- were absent in A. setosa sp. A was absent and . Actinomma boreale Spongotrochus glacialis and Actinomma leptodermum lepto- Pseudodictyophimus clevei Joergensenium Amphimelissa setosa Pseudodictyophimus clevei were mainly distributed in the 0–250 m Actinomma l. leptodermum Actinomma leptodermum leptodermum 16655 16656 (58 %) and Tripodiscium gephyristes juvenile (6 %), sp. A (6 %), spp. (56 %). In the 100–250 m depth, Actinomma leptodermum leptodermum (29 %) were dominant, and Pseudodictyophimus clevei, was rare. Amphimelissa setosa Actinomma sp. A (4 %) were common (Fig. 3b). Actinommidae spp. juvenile Joergensenium sp. A, Amphimelissa setosa Amphimelissa setosa S. glacialis certainly is not a Spyridae at all. This species has been accepted as (6 %), , but we cannot separate between the two. Joergensenium Amphimelissa setosa At Station 32, Joergensenium Adult and juvenile of Actinommidae spp. juvenile forms and nommidae spp. juvenile forms (3 %),were and common (Fig. 3a).and At Station 56 the Actinommidae spp. juvenile forms (38 %) rare in the 0–100 mdeeper depth layers at Station 32 (0.4 %) but commonabundant at in Station the 56 100–250 m (1.4 %). depth In at both stations. dermum We selected fourteen abundant radiolarian taxato to the show vertical species characteristics hydrographic related structure in the western Arctic Ocean (Fig. 4). 4.1.2 Vertical distribution of radiolarian species and environment and forms are juvenile forms of reale depth at both stations. In(70 the and 0–100 m 28 %, depth, respectively) Adultfollowing at and the Station juvenile juvenile 32, stages and werethe at dominant dominant Station species 56 at (23 both and100–250 stations. m 7 At %, depth Station interval respectively) 32, was the lowerthe abundance than abundance of in in the the 0–100 100–250 m m depth, depth whereas was at almost Station the 56, 0–100 same m as depth in the at 0–100(56 m Station %) depth. 32, were but abundantboth both, at stations especially Station (8 and Actinommidae 56. 4 spp. %, Both56), respectively juvenile and were at decreased forms Station common abundance 32; in in 14 and the the 7 250–500 100–250 %, m m respectively depth. at depth Station at Station 56 at eachradiolarians depth decreased interval with in increasingThe the abundance water upper of depth 500 dead m, at radiolariansexcept where both also for the decreased stations 100–250 with abundance m (Fig. water ofradiolarians depth 2a depth was living at at and generally both higher b). Station stations thanthe 32 living 0–100 (Fig. m radiolarians depth at 2a at both0–100 and m stations Station b). depth except 32. interval, for The The in increasedthen abundance living slightly with radiolarian of decreased depth diversity below dead and 500 index m the was depth maximum low at at in both stations. about the 400 m, and A total ofPhaeodaria) 43 were radiolarian identified taxa inindividuals (12 for the each Spumellaria, plankton radiolarian 3 taxa tow are Entactinria, samples in Tables 26 (Table S1 3).4.1.1 (Station Nassellaria, The 32) and and numbers S2 Standing 2 of (Station stocks 56). and diversities ofThe radiolaria abundance of living radiolarians at Station 32 was about two times as large as at 4 Results 4.1 Radiolarians collected by plankton tows were dominant, and a Spyridae by mostthat workers, is but typical with forsition a the and closer Spyridae. have We view have now thisPlagiacanthidae. therefore an species Based tried understanding has on to no that our evaluateclude sagittal microscope this its that and ring this species taxonomic species literature po- better can studies be belongs we named in at the present family con- gephyristes 3.4 Taxonomic note The species described by Hülsemann (1963) under the name of 5 5 20 15 10 25 10 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 1 > − − 0.52) day day ). The − 3) than 2 2 1 ) during − − − , Plagia- 1 = > − r day 2 day − 2 was widely dis- − (range, 0–33 %; av- ) than those during was rare and mainly 1 − Amphimelissa setosa juvenile was slightly in- Actinomma leptodermum day 2 were most abundant below were also observed during Pseudodictyophimus clevei − ) and around the end of sea-ice were dominant throughout the 800 specimensm (Fig. 5). The fluxes were high 1 occurred in very low numbers at − (Fig. 5). The highest fluxes were A. setosa < 1 − 1 − day 2 day Actinomma boreale − Actinomma boreale 2 day Tripodiscium gephyristes − 2 − Pseudodictyophimus plathycephalus 16657 16658 4000 specimensm were dominant during June–July and August– > Cycladophora davisiana Tripodiscium gephyristes Amphimelissa setosa , 0.91) (Fig. 6). ). The fluxes were higher during the open water season 1 = − distributed throughout surface to 1000 m depth, but was ), while, extremely low (0–80 specimensm 5000 specimensm 1 A. setosa r was mainly distributed in the 250–500 m depth, and occurred − > day 2 2) (Fig. 5). The diversity indices were negative correlated with day − 2 < − Pseudodictyophimus g. gracilipes (range, 0–14.6 %; average, 4 %), Species composition varied seasonally. Adult and juvenile Ceratocyrtis histricosus Adult and juvenile stages of 10 000 specimensm the sea-ice cover season (December–June, mostly erage, 4 %) were dominant. Relatively high percentages of cover season (July–August in 2011, the total radiolarian fluxes ( were most dominant (90 %)end during of the sea-ice sea-ice cover free season. season, Thelater juvenile and season, and the respectively adult (Fig. beginning forms 7). and were Duringmidae the abundant the in spp. sea-ice earlier juvenile cover and season, forms however,leptodermum Actinom- (range, 0–51 %; average, 18 %), the sea-ice cover season. 4.2.2 Radiolarian flux and diversity inTotal the radiolarian lower trap flux inwith the an lower annual trap mean varied of from 4828 0 specimensm to 22 733 specimensm with an annual mean of 2823 specimensm diversity of radiolarians, however, was highopen during water the season sea-ice ( cover season ( Pseudodictyophimus gracilipes 10 000 specimensm Total radiolarian flux in the upper trap varied from 114 to 14 677 specimensm in the 0–100 m depthPseudodictyophimus but abundant clevei in the 100–250 mrare at depth Station and 32 rare except in for deeper in the depths. 100–250 m. 500 m depth at both stations. 4.2 Radiolaria collected by sediment trap A total ofPhaeodaria) 51 were radiolarian identified taxa inNAP the (15 during upper 4 Spumellaria, October and 2010–18 3 lowercounted September sediment Entactinria, 2012 in (Table each trap 3). 31 sample The samples number Nassellaria, ranged0 at of from to and Station radiolarians 8 2672 specimens to 2 in 1100fewer the specimens than lower in 100 trap the (Tables specimens S3 (2 upper andthe samples trap, S4). species in and There upper recognized from were trap, in 15 13 samples our samples with sample in materials lower are trap). shown4.2.1 Most in of Plates 1–9. Radiolarian flux and diversity in the upper trap during October–November both in 2010 and 2011 and during March in 2011 ( (August–October in 2011, canthidae gen. et sp. in det., and observed during the beginning of> sea-ice cover season (November in 2010 and 2011, May–September in 2012. Diversity did notMay–July change 2011, greatly, and and increased slightly in during indices April 2012 were when weakly the(Fig. and radiolarian 6). fluxes negative were correlated low. with The diversity the radiolarian fluxes ( September, respectively. The relative abundancecreased of in 2012 in comparison to 2010 and 2011. sampling periods (range, 66–92 %;venile average, and 82 %). adult During forms July–September 2011, of ju- also in the 100–250 m depth at both stations. distributed in the 100–250 m depth at both stations. tributed below 100 m depthat at all Station depth 56, layers. whileboth at stations Station through 32 the this upper species 1000 m. was scarce 5 5 10 25 15 15 20 10 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Cer- mor- C) and ◦ nity to the , and 1.7 ffi − erent structure ff Actinomma Actinomma georgii , but di nity to the Atlantic fauna, ffi morphogroup B (57 speci- sp. A in the PWW (Table S6). ected by the inflowing Pacific ff A. boreale Stylochlamydium venustum Actinomma Joergensenium sp. A might be new species endemic for the 16660 16659 Joergensenium sp. A (1401 specimens) observed in the western Arctic Ocean and its juvenile stages were found in a shallow cold-water in both are absent in the western Arctic Ocean. In our results the radiolarian , and suggested the endemism hypotheses for these two species as morphogroup A (58 specimens), Joergensenium Ocean A. turidae the always-changing quality ofwater. the water masses as a 5.3 Vertical distribution of species and5.3.1 hydrographic structure PSW and PWW association Amphimelissa setosa stations 32 and 56.100 m) Specifically, at they Station were 32 morewarmer than abundant temperature Station than in 56. Station the At 56; Station SML indicating 32, that and these cold PSW two but (0– water moderate masses warm, exhibited and well and a result that radiolariansthe had Arctic Ocean been and rapidlyspeciation that evolving within the under the central the family Arcticsuggesting stressful Actinommidae. Basin that Our conditions local might speciation results in be took mightin the place support center the not only this of western in an hypothesis Arctic thestill ongoing central undescribed Ocean. Arctic Actinomma This basin, species, but is veryof also similar demonstrated the to by medullary theJoergensenium, shells. occurrence one Also of or within a twoian the new undescribed species radiolarian speciation and species in group are thisthis Entactinaria, area found. can is in be The still controlled not reason the by understood the forlikova genus but harsh et we radiolar- environmental can al., stress only (Allen 2009). speculate and The that Gilooly, extremely 2006; Krug- cold water masses under the sea-ice ( western Arctic. Kruglikova et al. (2009) described two new species Actinomma Actinommidae and high standing stock of mens), phogroup A and B and in our study have not beenPacific reported and in in other the areas North in Atlantic. the Although Arctic we Ocean, could nor not in conclude the yet, North atospyris borealis fauna in the western Arctic Ocean were characterized by a wide diversity of the family 5 Discussion 5.1 Comparison between Arctic and NorthBiogenic Pacific particle Oceans flux into the deepductivity sea of in shell-bearing the microplankton, Canada which Basin playprocess was an (Honjo low important et due role to al., in the 2010). biological low However, pump per we pro- observed trap, high 22 733: radiolarian lower fluxes (14the trap) 677: at beginning up- Station and NAP the during end(2823: the upper of open trap, sea-ice water 4823: cover season lower seasoneas and trap) in in around were 2011–2012. the comparable The to North annualstudy those Pacific means mainly observed Ocean consisted in of (Fig. several radiolarians ar- 8,diolarians and Table and diatoms, S5). therefore diatoms The siliceous might skeletons biogenicArctic. play of opal Relatively ra- important collected high role in to fluxsubstantial this export part of biogenic of radiolarians the silica in POC to flux. arctic the deep microplankton5.2 might contribute to Characteristic and ongoing speciation of radiolarians in the westernRadiolarian Arctic fauna in the westernand Arctic the Ocean family had Cannobotryidae a and closeOcean. Actinommidae a were Petrushevskaya dominant (1979) in the pointedknown western out Arctic from that the the ArcticNorwegian arctic-boreal Ocean Sea radiolarian basins polycystine species had radiolariancluded been that fauna. the originated Bjørklund modern from radiolarian and fauna the Kruglikova in early the (2003) Arctic Postglacial con- Ocean had a close a Norwegian Sea radiolarian fauna. Inflowpart of of radiolarians the with Pacific watersradiolarian Ocean from species is the in northern the probably North negligible Pacific since such the as most abundant and typical 5 5 20 25 10 15 25 10 20 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | A. as sp. were were were is asso- A. setosa A. setosa sp. A were erent water ff P. clevei S. glacialis Spongotrochus Spongotrochus dominated (60– . inhabited surface , Actinomma bore- Joergensenium might prefer cold wa- and A. l. leptodermum Actinomma boreale, Joergensenium P.clevei was lower than Actinommidae Actinomma l. leptodermum sp. A has not yet been described , and showed a similar vertical distribution Amphimelissa setosa sp. A and A. boreale Spongotrochus glacialis . at both stations, and mainly occurred in the Actinomma l. leptodermum Actinomma l. leptodermum 16661 16662 preferred cold but warmer water than PWW. Small Joergensenium Actinomma l. leptodermum in recent years in the western Arctic Ocean, as we . is a species interpreted as being introduced from the A. boreale Joergensenium might therefore be bound to the euphotic zone where was not reported in the PWW from the plankton samples in Pseudodictyophimus clevei Spongotrochus glacialis occurred commonly in the upper AW (250–500 m) and rarely in A. l. leptodermum C. histricosus A. l. leptodermum sp. A, erences of their growth stages due to the sampling period might be ff Amphimelissa setosa A. l. leptodermum C. histricosus Ceratocyrtis histricosus C) with low turbulence. The depth distribution of ◦ were mainly distributed in the PSW and PWW and preferred di preferred warmer water than PWW. is associated with warm (Atlantic) water, whereas 1.7 − had been reported as a group (e.g. Samtleben et al., 1995), due to identification Actinommidae spp. juvenile forms, 5.3.2 PWW association Joergensenium from recent radiolarian assemblages, so can be suggested that mainly distributed in the PWW. ter ( restricted to the PWW (100–250 m) and the upper AW (250–500 m), but more flexible and widely distributed. A might occur only oncator the for Pacific the side PWW of layer.spp. the Standing juvenile Arctic stocks forms Ocean of and andPWW. might In serve as the an surfaceboreale indi- sediments of theciated Greenland, with Iceland the and cold(Bjørklund East Norwegian et Greenland Seas, al., Current 1998). andor Other the environmental seasonal factors warm di such Norwegianrelated as Current to salinity, water the food standing availability, stocks of mixed water mass weremass more such favorable as for PWW this (100–250 m). species The than vertical the and geographic perennial distribution cold of water 5.3.3 Upper AW association Ceratocyrtis histricosus the PWW. has been described in several previous studies. Norwegian Sea, most likely duringing the through early the Holocene Arctic by the Oceanin warm the (Kruglikova, Atlantic 1999). Canada water This Basin drift- during speciesthermore, the has 1950s not and been 1960s observed the (Hülseman Chukchi 1963; and Tibbs, Beaufort 1967). Seasthat Fur- in the occurrence 2000 of (Itaki etfound, al., was 2003). related Itaki to et theet al. recent al. (2003) warming indicated (2011), of the the Arctic mean water. temperature According of to the McLaughlin PWW within the Canada Basin increased 80 %) the radiolarian assemblageChukchi through Sea the and upper the 500 mwater Beaufort of (Itaki Sea the et and water al., column soprefers in 2003). well-mixed, can cold the Matul be and an and saline indicator surface/subsurface Abelmann waters. of (2005) cold also Arctic suggested surface that a subsurface dweller with abundance maximumSea, in associated the 50–100 with m the interval phytoplankton in production. the Okhotsk glacialis as Actinommidae spp. juvenile formsglacialis and water also in the Okhotsk(Nimmergut Sea and and Abelmann, well adapted 2002). to Okazaki low et temperatures al. and (2004) low salinities also reported problems, particularly of the juveniletwo stages, but species the following adult Cortese stages can and be Bjørklund separated (1998). into ale phytoplankton prevails. masses from absent in the water massesthese of water SML and masses PSW at atcolder Station Station and 56. 32, more but At homogeneous they Stationjuvenile than were forms 56, abundant at and in SML Station and 32;spumellarians PSW indicating might water that be masses Actinommidae herbivorous were spp. forms (Anderson, 1983) and so Actinommidae spp. juvenile 5 5 15 10 20 25 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | is oc- Cy- adult have a three P. g. gracilipes erence in the radi- ff , in the western Arctic ) was dominant during A. setosa Amphimelissa setosa C. histricosus Pseudodictyophimus g. gracilipes juvenile occurred in the end of sea- also have their flux peaks during the be- Actinomma boreale and its juveniles were correlated well with , 16664 16663 A. setosa , Plagiacanthidae gen. et sp. in det., and adult occurred in the beginning of sea-ice season A. setosa A. setosa did not show any specific vertical distribution, and its standing were abundant in the cold and oxygenated lower AW at both Pseudodictyophimus clevei prefer water masses near the summer ice edge for reproduction and C) from 2003 to 2007 and then remained constant until 2010. Thus, erent between Station 32 and Station 56 whereas temperature, salinity, ◦ Actinomma l. leptodermum ff into the PWW. and phaeopigments along the ice edge in summer in the Greenland Sea. a 0.05 ∼ P. g. gracilipes A. setosa From the upper trap, a flux peak of Bjørklund et al. (2012) reported 98 tropical-subtropical radiolarian taxa in the area the ice-cover season (Fig.olarian 5). species These in might the explainsea Arctic the sediments Ocean. (Iceland, regional Barrents, Cannobotryidae di and Chukchi wassummer Seas) dominant but where Actinommidae in sea-ice was disappeared Arctic dominant in marginal the insen, the and central Arctic Makarov Ocean Basins) (Nansen,the where Amund- year the (Bjørklund sea and surfacegrown was Kruglikova, ice covered 2003). algae, by ice The fauna sea-ice summer (Hornerand throughout favorable et ice alternation al., between edge 1992; stable accompanies Michel waterthe masses et well- nutrients and al., are deep 2002; brought vertical Assmy to mixing et where (1992) the al., surface found 2013) (Harrison that and Cota, abundance 1991). of Swanberg and Eide Thus growth. 5.4 Seasonal and annual radiolarian flux 5.4.1 Radiolarian fauna and seasonal sea-iceSeasonal concentration radiolarian fluxes at Stationof NAP a were characterized few by specieschanges the and high in the dominance the changesand of sea-ice its their concentration. juvenile ratios Cannobotryidae forms) inbeginning was and the ( the dominant upper end during trap ofjuvenile the with ice-cover forms, seasons, open-water the while season seasonal Actinommidae (Actinommidae and spp. around the chlorophyll ice season, and that(Fig. of 7). The time interval of these peaks might indicate that ginning of sea-ice season (November–December)prefer (Fig. 7). to These live two under speciesstages seem cold to of water Actinommidae mass were with dominant sea-ice formation. during On the the ice-cover contrary, season juvenile (Fig. 5). There- months life cycle. slightly ( the recent warming of theC. histricosus PWW and AW might induce the expansion of the habitat of stocks were low. curred at 0–50 m in theresults, Chukchi Sea and 25–50 m in the Beaufort Sea. However, in our north of Svalbard in the easternof Arctic warm Ocean. They Atlantic stated thatfauna. water there We are that always did pulses do notern observe reach Arctic any the Ocean. tropical Arctic However,annual and it changes Ocean, subtropical in is transporting the radiolarian necessary radiolarian taxa warmer fauna, to in including water conduct the continuous west- monitoring of the 5.3.4 Lower AW association Pseudodictyophimus plathycephalus Ocean. cladophora davisiana stations. However, their distributionwere slightly patterns di in PWWand dissolved and oxygen have upper similartherefore values AW reflect at water both not stations. masses only Their hydrographicwidely standing conditions. stocks distributed might in thelatitudes world and ocean, at and greateret known depth al., to at 2008). inhabit Itaki low et the latitudes al. surface (Ishitani (2003) layer and reported at that Takahashi, high 2007; the maximum Ishitani depth of 5 5 10 15 20 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) ected ff in the upper Amphimelissa Actinomma boreale sp. A were probably , and Actinommidae have were most abundant in the to the basins (Proshutinsky et al., erence in ocean circulation ff Joergensenium ff Tripodiscium gephyristes , 90 %) in our area. Such high dominance and > ( 16665 16666 A. l. leptodermum Amphimelissa setosa Actinomma l. leptodermum A. setosa Spongotrochus glacialis ect of the deeper mooring depth of the trap after October 2011 , ff Ceratocyrtis histricosus , which have small and delicate siliceous skeleton, might respond to primary ect the radiolarian fluxes at least until September 2012. McLaughlin et al. (2011) ff erent nutritional niches. This study showed that the productivity of radiolarian was low but diversity was high Actinomma boreale ff trap showed increase in their fluxestemperature from May at to September the in summer upper 2012. trap The water depth also increased during the same period (Figs. 7 and S1), we therefore interpretedand warm their upper increase AW and to underdue be PWW, to rather related than their to a preference the decrease of in mixing the sea of warm ice nutrient upper concentrations AW. 5.4.2 Radiolarian fauna and between yearIntensification di of geostrophic currentsbeen on reported the in recent periphery years (Nishinois of et caused Beaufort al., by Gyre 2011; increasing McPhee, (Fig. 2013). volumetion 1) This of of intensification has water arctic from summer sea-ice melt sea-ice associated and with the the river reduc- runo depth interval of 0–100 mwe at interpreted Station that 56 in coldto the and southwestern Station oligotrophic Canada water NAP Basin. in into Therefore, the a the Canada Northwind Basin Abyssal beganreported to Plain that the spread from position of Decemberthe the 2011 center area of and under the continued the Beaufortyears. Gyre influence Moreover, shifted high-resolution of westwards pan-Arctic and the Ocean that gyreBeaufort model spread results Gyre northwards also expanded showed and with thatthe westwards shifting the in Chukchi of recent Borderland itstion in center in 2012 from the surface the compared 100 Canada m within layer Basin 2011 2011, switched (E. northwestward interior and Watanabe, to to personal southwestward thecurrents in communication, on ocean December 2014). the current Thus, Beaufort recent direc- Gyre intensification associated of with sea-ice reduction would have a 2009; Yamamoto-Kawai et al., 2008).tion during The summer total (July–September) radiolarian in 2012traps flux than showed and in lower 2011 especially in produc- in thelower both flux the upper during and lower summer lower trap of(Actinommidae (Fig. 2012 spp. (Fig. 5). juvenile 7). Most forms, Onthat of the might other radiolarian hand, be taxa fluxes adapteding also of to December Actinommidae showed 2011–September the 2012 coldActinommidae than and spp. during oligotrophic juvenile December water forms 2010–September showed 2011. and higher values dur- more abundant at depths lowerOn than the the other first hand, upper trap depth (about 180 m) (Fig. 3a). (Figs. 7 and S1). This might be caused by their vertical distribution patterns, as they are set in the Okhotsk Seasea-ice showed covered low diversity the during surface the (Okazakiduring winter et to al., the spring 2003). summer when The seasonal seasonterized maximum total around by radiolarian high the flux dominance sea-iceof of edge single species and does thethe not open radiolarian occur assemblage water and in issetosa major the charac- nine Okhotsk taxa Sea contributed (Okazakiproduction more et more than al., directly 2003). 60 %have and to more rapidly robust and skeleton. Therefore, di develop earlier than Actinommidae, which related to food supplyfluxes to of the these PWW threemight species during be in the the due sea-ice upper to free trap an season. in e Relatively summer higher 2012 than in summer 2011 under the sea-ice (Figs. 5 and 6). In contrast, radiolarian fauna in the sediment trap fore, we interpreted that Actinommidaewater were masses. tolerant Itaki to and oligotrophic Bjørklund,could and 2007 reproduce stratified as reported cold well that as the adulttons stage juvenile since from stage they Japan Actinommids found conjoined Sea Actinommidaeforms sediments. skele- increased Furthermore, towards the the fluxincreasing end of of of Actinommidae downward the spp. shortwave juvenile sea-iceActinommidae radiation cover spp. (Figs. season juvenile 5 and forms accompanied andplankton feeds under with 7). on the This sea-ice. algae might growing indicate on that the ice or other phyto- 5 5 25 20 10 15 25 15 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − , Pla- 90 %) during Sir Wil- , which > 1 − Cycladophora A. setosa Pseudodictyophimus , cient biological pump in Ceratocyrtis histricosus, ffi ) in the lower trap was high was the most dominant ( cers and crews of the CCGS ffi Pseudodictyophimus plathycephalus , during July–August 2011, and 73 m day 1 16668 16667 − Cycladophora davisiana Amphimelissa setosa Pseudodictyophimus g. gracilipes , Plagiacanthidae gen. et sp. in det., and (JAMSTEC), operated by GODI, R/V, Humfrey Melling (IOS, Canada), We are grateful to the captain, o Mirai ) or intermediate to deep water distribution ( , R.V. Pseudodictyophimus g. gracilipes ) might be attributed to the reproduction of these species in a depth be- Higher abundance in the lower trap rather than the upper trap in species having, Radiolarian fluxes in the lower trap were generally higher than that in the upper trap plathycephalus a wide vertical distribution ( the lower trap in spiteWe of speculated their high that abundance the inin disappearance the the of upper lower trap fluxes trap since of might December be Actinommidae 2011. due spp. to juvenile lack forms of aggregate formation. Tripodiscium gephyristes davisiana tween the upper andand lower deep traps. The dwellers seasonal indwellers changes the ( in lower the trap fluxes would of reflect intermediate the food supply. Flux of deep water the surface water mass conditions andOcean. the biological pump system in the western Arctic 5.4.3 Vertical and lateral Transport Flux peaks of totalcomparison radiolarians to the in upper theradiolarian trap lower (Fig. particle trap 5). are flux Therefore, the delayed between sinking by these speed about of depths two the were weeks aggregated averaged in to 74 m day during July–August in 2011.from This the would primary probably production indicatedepths, during that giving the decomposing nutrition sea-ice material species free to in season the the was lower deep transported trapperiod water also to with peaks radiolarian a great during heavy fauna. ice Marchflux cover Most in and peak 2011, of a which during low the corresponded downward March shortwave to radiolarian in radiation. the In 2011 addition, was the made up of more than 80 % of frid Laurier November–December 2010, 86 mduring day November 2011. Watanabe et al.eddies (2014) using simulated a movement of high-resolution coldtotal pan-Arctic and mass warm Ocean flux model, during and October–Decembering 2010 suggested sediment at that samples, Station the was NAP, aspump high mainly we by determined an due us- anti-cyclonic to coldresuspended the eddy. bottom enhancement Shelf-break sediments eddies of composed induce thepump of the (O’Brien marine old lateral et biological transport carbon, al., of andeddy 2013; enhance was Watanabe the observed et biological from al.,corresponding 2014). a period Actually, cooling (Fig. the S1). and passage a of deepening the of cold the moored trap depth in the giacanthidae gen. et sp. in det., were surface water species although thein peaks the around upper the trap. same Therefore, period thesome were flux lateral not peaks found during advection March at in amaterials 2011 depth would into lower be the than derived upper from 180 m water or column. a re-suspension of shelf bottom The Supplement related to thisdoi:10.5194/bgd-11-16645-2014-supplement. article is available online at Acknowledgements. the Canada Basin. In the southwesternof Canada dead Basin radiolarian (Station 56), specimens high (Fig. standing 2) stock might indicate an ine except for during May–September in 2012 (Fig.trap 5). during The extremely May–September low in fluxes intion. 2012 the The might lower aggregate be formation, which due helpssuppressed to rapid by sinking a influx of decrease of biogenic oligotrophic of particles, surface would aggregate water be forma- originating from the Beaufort Gyre in during this periodand and after the the cold radiolarian eddymass species passage. variations Therefore composition the with cold sea was eddy icediversity, not in formation in addition would changed 2010. to enhance seasonal before the water high radiolarian flux, but not the Canada Basin. 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A.: The role of the Beaufort Gyre in Arc- Reynolds, R. W., Rayner, N. A., Smith, T. M., Stokes,Riedel, D. C., W. R.: and Subclass Wang, radiolaria, W.: An in: improved The in Fossil Record, situ editedSaha, by: Harland, S., W. Moorthi, B. et S., al., Geol. Pan, H. L., Wu, X. R., Wang, J. D., Nadiga, S., Tripp, P., Kistler, R., Samtleben, C., Schäfer, P., Andruleit, H., Baumann, A.,Shannon, C. Baumann, E. and K. Weaver, W.: The H., Mathematical Kohly, Theory of A., Communication, University of Popofsky, A.: Die Radiolarien der Antarktis (mit Ausnahme der Tripyleen), in: Deutsche Proshutinsky, A., Krishfield, R., Timmermans, M. L., Toole, J., Carmack, E., McLaughlin, F., Petrushevskaya, M. G.: Radiolyarii Nassellaria v planktone Mirovogo Okeana, Issledovaniya Okazaki, Y., Takahashi, K., Onodera, J., and Honda, M. C.: Temporal and spatial fluxPetrushevskaya, changes M. G.: Radiolarians of orders Spumellaria and Nassellaria of the Antarctic re- Müller, J.: Über die Thalassicollen, PolycystinenNikolaev, und S. Acanthometren I., des Berney, Mittelmeeres, C., Ab- Fahrni, J., Bolivar, I.,Nimmergut, A. Polet, and Abelmann, S., A.: Mylnikov, Spatial and A. seasonal changes P., ofNishino, Aleshin, radiolarian S., standing V. Kikuchi, stocks V., T., Yamamoto-Kawai, M., Kawaguchi, Y., Hirawake, T., and Itoh, M.: En- Nishino, S.: R/V NSIDC (National Snow and Ice Data Center): Arctic sea ice extent settlesO’Brien, M. at C., record Melling, H., seasonal Pedersen, T. F., and Macdonald, R. W.: TheOkazaki, role of Y., Takahashi, eddies K., on particle Yoshitani, H., Nakatsuka, T., Ikehara, M., and Wakatsuchi, M.: Ra- Okazaki, Y., Takahashi, K., Itaki, T., and Kawasaki, Y.: Comparison of radiolarian vertical distri- 5 5 15 10 20 25 30 30 25 10 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O, and nutrients, J. Geo- 18 δ 16678 16677 Res., 114, C00A14, doi:10.1029/2008JC005084, 2009. Radiolaria based onEur. the J. 18s Protistol., 41, rDNA 287–298, sequences 2005. of the Spumellarida and the Nassellarida, phys. Res., 113, C01007, doi:10.1029/2006JC003858, 2008. ature maximum waters inLett., the 28, western 3441–3444, Canadian 2001. Basin of the Arctic Ocean,mermann, Geophys. Res. S.,reduction and of Proshutinsky,,doi:10.1029/2005GL025624 sea A.: 2006. ice Pacific cover Ocean in inflow:faster than the influence forecast, Geophys. Res. 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Enhanced implications for role paleoceanographic ofCorvallis, 314 reconstructions, eddies pp., Ph.D. 1996. in thesis, the Oregon State Univ., water budget of the Canada Basin, Arctic Ocean, from salinity, Yang, J.: Seasonal and interannual variability of downwelling inYuasa, the T., Takahashi, Beaufort O., Honda, Sea, D., J. and Geophys. Mayama, S.: Phylogenetic analyses of the polycystine Shimada, K., Carmack, E. C., Hatakeyama, K., and Takizawa, T.: Varieties of shallowShimada, temper- K., Kamoshida, T., Itoh, M., Nishino, S.,Stroeve, Carmack, J., Holland, E., M. M., McLaughlin, Meier, W., F., Scambos,Stroeve, Zim- T., J. and C., Serreze, Serreze, M.: M. Arctic C., sea Holland, ice M. decline: M., Kay, J. E.,Swanberg, Malanik, N. R. J., and and Eide, Barrett, L. A. K.: P.: The TheTakahashi, K.: radiolarian Radiolaria: fauna flux, ecology, at and taxonomy the in the ice Pacific edge and Atlantic, in in:, the Ocean Bio- Greenland Sea Takahashi, K. and Anderson, O. R.: Class Phaeodaria, in: The Second Illustrated Guide toTakahashi, K. the and Honjo, S.: Vertical flux of Radiolaria: a taxon-quantitative sedimentTibbs, trap J. study F.: On some planktonic Protozoa takenWatanabe, from E., the Onodera, track J., of Harada, Drift Station N., Arlis Honda, I, M. 1960– C.,Welling, Kimoto, L. K., A.: Environmental Kikuchi, control T., of Nishino, radiolarian abundance S., in the central equatorialYamamoto-Kawai, Pacific M., McLaughlin, F. A., Carmack, E. C., Nishino, S., and Shimada, K.: Fresh- 5 5 10 15 25 20 30 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (days) ) S.S. (count) S.S. (count) S.S. (count) 3 Cruise MR13-06. 16680 16679 Mirai (m) interval* depth sampling duration time interval water mass size radiolarian radiolarian radiolarian 01:22 100–25001:10 500–1000 27.217:34 79.3 100–25017:22 1/4 500–1000 23.8 1/2 96 (654) 81.8 12 (462) 1/2 116 (790) 1/2 17 265 212 (665) (3156) (1444) 480 25 (5711) (1034) 29 (1127) 745 (8867) 83 (3381) 108 (4415) (UTC) (m) (m WW 1975 1975 184 (upper), 1300 (lower) 260 (upper), 1360 (lower) 10–15 10–15 4 Oct 2010–28 Sep 2011 4 Oct 2011–18 Sep 2012 0 0 00 00 ◦ ◦ W 01:24 0–100W 17:36 20.4 0–100 1/4 15.8 247 (1257) 75 (381) 1/4 322 (1638) 499 (1968) 677 (2671) 1176 (4639) 0 0 54 59 ◦ ◦ NN 162 162 0 0 N, 161 N, 159 00 00 0 0 ◦ ◦ 32 48 ◦ ◦ Logistic and sample information for the vertical plankton tows for radiolarian standing Locations, mooring depths, standard sampling interval, and sampled duration of sedi- Date 9 Sep 2013Date 27 Sep 2013 01:18 250–500 17:30 39.7 250–500 1/2 40.8 11 (215) 1/2 20 (397) 55 (1125) 31 (612) 276 (5627) 331 (6752) Station IDStation 32 74 Station 56 73 Sampling Depth Flow Aliquot Living Dead Total Trap station Latitude Longitude WaterNAP10t Mooring depth (m) 75 Standard Sampled NAP11t 75 * Details of the exact durations for each sample are shown in Tables S3 and S4. Table 2. ment trap station in the western Arctic Ocean. stock (S. S.) at two stations during R/V Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | References References 16682 16681 , Bernstein (1934) Bjørklund and Kruglikova (2003), Plate V, Figs. 11–13 , Cortese and Bjørklund (1998) Cortese and Bjørklund (1998), Plate 2, Figs. 15–22 , Ehrenberg (1861) Bjørklund and Kruglikova (2003), Plate V, Figs. 16–19 , Popofsky (1908) Petrushevskaya (1967), Fig. 74, I–IV bicornis multispinus longispinum , Ehrenberg (1873) Bjørklund et al. (1998), Plate II, Figs. 23–25 , Ehrenberg (1862) Bjørklund et al. (1998), Plate II, Figs. 1 and 6 , Ehrenberg (1854) Petrushevskaya (1967), Fig. 59, I–III , Petrushevskaya (1967) Petrushevskaya (1971), Fig. 92, VIII–IX , Bailey (1856) Bjørklund et al. (1998), Plate II, Figs. 7 and 8 , Bailey (1856) Bjørklund et al. (2014), Plate 9, Figs. 1–4 , Ehrenberg (1873) Bjørklund et al. (2014), Plate 9, Figs. 10 and 11 , Cleve (1899), juvenile Bjørklund et al. (1998), Plate II, Figs. 30–33 , Ehrenberg (1854) Petrushevskaya (1967), Fig. 62, I–II, Fig. 58, VIII , Jørgensen (1900) Cortese and Bjørklund (1998), Plate 2, Figs. 1–14 , Murray (1885) Takahashi and Honjo (1981), Plate 11, Fig. 11 juvenile , Haeckel (1887) Bjørklund and Kruglikova (2003), Plate V, Figs. 1–5 . furcaspiculata ff , Bailey (1856); , Bailey (1856); , Cleve (1899) Bjørklund et al. (2014), Plate 11, Figs. 5 and 6 , Burridge, Bjørklund and Kruglikova (2013) Burridge et al. (2013), Plate 6, Figs. 7–15, Plate 7, Figs. 3–15 , Jørgensen (1900) Dolven et al. (2014), Plate 1, Figs. 1–4 ? Jørgensen (1905) , Haeckel (1887) Petrushevskaya (1971), Fig. 32, IV, V , Jørgensen (1900) Bjørklund et al. (2014), Plate 9, Figs. 5–7 , Haeckel (1862) Welling (1996), Plate 14, Figs. 24–27 , Haeckel (1887) Bjørklund (1976), Plate 7, Figs. 5–8 , Jørgensen (1900); , Hülsemann (1963) Bjørklund et al. (1998), Plate II, Figs. 20 and 21 ? , Popofsky (1908) Bjørklund et al. (1998), Plate I, Fig. 3 , Jørgensen (1905) Petrushevskaya (1971), Figs. 52, II–IV ? Jørgensen (1900) Bjørklund et al. (1998), Plate II, Figs. 26 and 27 , Jørgensen (1900) Dolven et al. (2014), Plate 1, Figs. 5–7 , Cleve (1899) Bjørklund et al. (2014), Plate 9, Figs. 15–17 , Jørgensen (1900) Dolven et al. (2014), Plate 6, Figs. 20–24 , Cleve (1899) Dumitrica (2013), Plate 1, Figs. 1–9 , Jørgensen (1905) Dolven et al. (2014), Plate 7, Figs. 7–9 spp. juvenile forms , Haeckel (1881) Petrushevskaya (1971), Fig. 31, I–III , Petrushevskaya (1971) Petrushevskaya (1971), Fig. 57, I , Haeckel (1887) Takahashi (1991), Plate. 24, Figs. 1–5 , Cleve (1899) Cortese and Bjørklund (1998), Plate 1, Figs. 1–18 , Cleve (1899) Bjørklund et al. (2014), Plate 8, Figs. 1–2 , Kruglikova and Bjørklund (2009) Kruglikova et al. (2009), Plate 5, Figs. 1–35, Plate 6, Figs. 1–28 Eucyrtidiidae, Ehrenberg (1847); emend. PetrushevskayaArtostrobus (1971) annulatus Artostrobus joergenseni *Cornutella stylophaena *Cornutella longiseta Cycladophora davisiana Lithocampe platycephala Lithocampe a Sethoconus tabulatus Cannobotryidae, Haeckel (1881); emend. RiedelAmphimelissa (1967) setosa Amphimelissa setosa Phaeodaria, Haeckel (1879) Lirella melo Protocystis harstoni All taxa are found in the trap, and * refer to taxa found in trap only. sp. A sp. B morphogroup B morphogroup B juvenile morphogroup A sp. Continued. List of 51 radiolarian taxa encountered in the plankton tow and sediment trap samples. Pseudodictyophimus gracilipes Actinomma leptodermum longispinum Actinommidae spp. juvenile forms Actinomma turidae Actinomma Actinomma *Drymyomma elegans *Actinomma friedrichdreyeri Arachnosphaera dichotoma Litheliidae, Haeckel (1862) * Streblacantha circumtexta Spongodiscidae, Haeckel (1862) Spongotrochus glacialis Stylodictya Entactinaria, Kozur and Mostler (1982) Cleveiplegma boreale Joergensenium Joergensenium Nassellaria, Ehrenberg (1875) Sethophormididae, Haeckel (1881); emend. PetrushevskayaEnneaphormis (1971) rotula Enneaphormis enneastrum Protoscenium simplex Plagiacanthidae, Hertwig (1879); emend. Petrushevskaya*Arachnocorys (1971) umbellifera Ceratocyrtis histricosus Ceratocyrtis galeus *Cladoscenium tricolpium Cladoscenium tricolpium Lophophaena clevei Phormacantha hystrix *Peridium longispinum Plectacantha oikiskos Pseudodictyophimus clevei Pseudodictyophimus gracilipes gracilipes Pseudodictyophimus Pseudiodictyophimus gracilipes Pseudodictyophimus plathycephalus Tetraplecta pinigera Tripodiscium gephyristes Plagiacanthidae gen. et sp. in det. Radiolaria, Müller (1858) Polycystina, Ehrenberg (1838); emend. RiedelSpumellaria, (1967) Ehrenberg (1875) Actinommidae, Haeckel (1862); emend. RiedelActinomma (1967) boreale Actinomma leptodermum leptodermum Actinomma Actinomma leptodermum Table 3. Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent , and ff

(a) 120W 5 5

4 4 70N 3 3 (H) (H) 2 2 Diversity Diversity 1 1

0 0 130 SML PSW PWW AW CBDW SML PSW PWW AW CBDW

450 450

0N 8 350 350 Oxygen Oxygen (μmol/kg) (μmol/kg)

2000 140 250 250 35 3000 35

0 30 30 Salinity Salinity Canada Basin Beaufort Gyre 25 25 2 150 2 16684 16683 1 1 St. 32 0 0 (℃) (℃) 1 − −1 St. NAP Temperature Temperature 2 Alaska − −2 Northwind Abyssal Plain (Station 32) Southwestern Canada Basin (Station 56) St. 56

160 600 600 2000 −3 −3 400 400 100 Live Live 200 200 200 0 0 Bering Strait 200 200 Standing stock 400 Standing stock 400 Total Radiolaria Total Radiolaria Dead Dead (No. specimens m ) (No. specimens m )

170 600 600 800 800 0 0

100 200 300 400 500 600 700 800 900 100 200 300 400 500 600 700 800 900

1000 1000

m depth Water m Siberia depth Water ） （ ） （ (b) (a) Fig. 2

180 The depth distributions of total dead and living radiolarians at stations 32 Map of the Chukchi and Beaufort Seas showing the locations of sediment trap (solid in comparison to vertical profiles of temperature, salinity, dissolved oxygen (Nishino, Fig. 1 (b) water masses are identified SurfaceWinter Mixed Water Layer (PWW), (SML), Atlantic Pacific Water Summer (AW), Water and (PSW), Canada Pacific Basin Deep Water (CBDW). Figure 2. 56 2013), and living radiolarian diversity index (Shannon and Weaver, 1949). Also the di triangle) and plankton towsBeaufort (solid Gyre circles). and Gray the arrows inflow of indicate Pacific the water cyclonic through circulation the Bering of Strait, the respectively. Figure 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and 56 (south- (a) 25 8 38% 8 25 20 6 Actinommidae spp. juvenile forms 20 6 15 15 4 4 10 29% 10 2 5 2 5 Cycladophora davisiana Cycladophora davisiana Pseudodictyophimus clevei 0 Pseudodictyophimus clevei 0 0 0 30 10 10 30 8 (Station 56) 8 20 20 6 6 4 4 10 10 2 2 6% Other taxa Plagiacanthidae gen. et sp. in det. Plagiacanthidae gen. et sp. in det. Southwestern Canada Basin Southwestern Canada 0 Joergensenium sp. A 0 0 0 Joergensenium sp. A 6% 8 2 2 8 6 -3 6 -3 (b) 1 4 1 4 2 2 Spongotrochus glacialis Spongotrochus glacialis 0 Pseudodictyophimus plathycephalus 0 0 0 Pseudodictyophimus plathycephalus 2 2 50 50 40 40 30 30 Actinomma l. leptodermum 1 1 20 20 Actinomma l. leptodermum Actinomma l. leptodermum 10 10 gracilipes gracilipes 0 0 0 0 Pseudodictyophimus g. Pseudodictyophimus g. 3 3 300 300 16686 16685 2 2 200 200 1 1 100 100 Standing stock (No. specimens m ) Standing stock (No. specimens m ) Tripodiscium gephyristes Tripodiscium gephyristes Northwind Abyssal Plain (Station 32) Southwestern Canada Basin (Station 56) Actinommidae spp. juvenile forms Actinommidae spp. juvenile forms 0 0 0 0 80 2 2 80 60 58% 60 40 1 1 40 Amphimelissa setosa Ceratocyrtis histricosus 20 Ceratocyrtis histricosus 20 Amphimelissa setosa juvenile Amphimelissa setosa juvenile 0 0 0 0 1.6 200 200 1.6 150 150 0.8 0.8 100 100 . 50 50 (Station 32) Actinomma boreale Actinomma boreale 0 0 Amphimelissa setosa 0 0 Amphimelissa setosa 0 0 0 0

(b)

100 200 300 400 500 600 700 800 900

100 200 300 400 500 600 700 800 900 1000

100 200 300 400 500 600 700 800 900

22% 100 200 300 400 500 600 700 800 900 1000

1000 1000

Water depth depth Water m Water depth depth Water m

Water depth depth Water m ) ( Water depth depth Water m ) (

) ( ) Northwind Abyssal Plain ( (a) (b) Fig. 4 (a) Pseudodictyophimus clevei . (b) Amphimelissa setosa juvenile Compositions of living radiolarian assemblages in plankton samples through the The depth distributions of fourteen living radiolarians in plankton samples at stations Joergensenium sp. A and 56 (a) Fig. 3 Figure 4. 32 Figure 3. upper 1000 m of thewestern water columns Canada at basin) stations 32 (Northwind Abyssal Plain) Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and lower 25 −1 −2 (a) 20 r = 0.52 15 3

y = -0.18 ln(x) + 2.349 Sea ice concentration (%) concentration ice Sea (x 10 No. specimens m d )

10

100 80 60 40 20 0

Diversity (H) Diversity Diversity (H) Diversity Total radiolarian fluxes with the 3 2 1 0 4 3 2 1 0 4 * S S S * * A * A A (d) * * 5 J * J J * * Barren * Other taxa J J J NAP Lower trap Actinommidae spp. juvenile forms Pseudodictyophimus clevei * Other taxa * M M M * A A A Total Radiolaria flux Diversity (H) barren Diversity (H) M M M * Total Radiolaria flux 0 F F F Total Radiolaria flux Sea ice concentration Diversity (H)

J 2012 J J 5 3 2 1 0 4 2012 2012 D (H) Diversity D D gephyristes N N N (b) O O O S S S Radiolarian faunal compositions in lower trap at Amphimelissa setosa juvenile Tripodiscium Actinomma boreale A Amphimelissa setosa juvenile A A 20 −1 16688 16687 J J J (e) J J J −2 M M M A A A Station NAP Lower trap (1300-1360 m) Station NAP Upper trap (180-260 m) Station NAP M M M Radiolarian faunal compositions in upper trap at Station F F F 15 J 2011 J J 2011 2011 D D D (b) Amphimelissa setosa N Amphimelissa setosa Pseudodictyophimus g. gracilipes N N Actinomma l. leptodermum O 2010 O O 2010 * 2010 r = 0.91 0 5 0 0 5 0 0 80 60 40 20 25 20 15 10

25 20 15 10 80 60 40 20

100

100

400 300 200 100 ) d m specimens No. 10 (x

(W m ) m (W

(x 10 No. specimens m d ) d m specimens No. 10 (x 3 − − 1 3 2

− 2 − − 1 3 2

(%)

(%)

Shortwave Radiation Shortwave Relative abundance Relative Total Radiolaria flux Radiolaria Total Relative abundance Relative Total Radiolaria flux Radiolaria Total 10 (c) (b) (d) (a) (e) Fig. 5 y = -0.66 ln(x) + 2.566 (x 10 No. specimens m d ) 5 NAP Upper trap 0 Total radiolarian fluxes with diversity index and sea-ice concentration in upper trap Total Radiolaria flux

5 3 2 1 0 4 Diversity (H) Diversity Scatter plots of diversity indices and total radiolarian fluxes at upper Downward short wave radiation at the surface of sea-ice and ocean (after sea-ice (a) . In these plots, samples with fewer than 100 specimens were excluded. Fig. 6 (c) (b) trap Figure 6. Figure 5. (a) at Station NAP. 2concentration samples data with are fewer than from.IGOSS/.nmc/.Reyn_SmithOIv2/). 100 Reynolds specimens et are al.NAP. marked (2002) with (http://iridl.ldeo.columbia.edu/SOURCES/ asterisk. Sea-ice opening) around Station NAP from Nationalcast Centers System for Environmental Reanalysis Prediction-Climate (NCEP-CFSR) Fore- (Saha et al., 2010). Station NAP. Barren area, no samples due to trap failure. Shannon–Weaver diversity index in the100 lower specimens trap are at marked Station with NAP. 13 asterisk. samples with fewer than

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Sea ice concentration (%) concentration ice Sea S S A A 80 60 40 20 0 100 J J J S J S S M A A M A J A J A J J M NAP Upper NAP Lower J NAP Upper NAP Lower J M gracilipes M F M M F A A A 2012 J J 2012 M M M D NAP Upper NAP Lower D F F NAP Upper NAP Lower F N N J NAP Upper NAP Lower 2012 J 2012 J 2012 sp. A O O D D D S S N N N A O A O O J J S S S J A J A A J M J J M J A J A J M M M M M A Joergensenium F A A F g. Pseudodictyophimus g. Ceratocyrtis histricosus M M J 2011 M J 2011 F Plagiacanthidae gen. et sp. in det. F F D Actinomma boreale Actinomma l. leptodermum Actinomma l. leptodermum forms Actinommidae spp. juvenile D J 2011 Sea ice concentration J 2011 J 2011 N N D D D O 2010 O 2010 N N N O 0 2010 0 0 O O 2010 0 2010 50 50 50 50 250 200 150 100 250 200 150 100 150 100 150 100 0 0 0 0 0 0 50 80 60 40 20 50 80 60 40 20 700 600 500 400 300 200 100 700 600 500 400 300 200 100 150 100 150 100 S S 80 60 40 20 0 S 100 A A A S S S J J J A A A J J J 16690 16689 J J J M M M J J J A A A M M M M NAP Upper NAP Lower A NAP Upper NAP Lower NAP Upper NAP Lower A A M M F M M F M F NAP Upper NAP Lower juvenile F J F 2012 F J 2012 J 2012 NAP Upper NAP Lower J J 2012 J 2012 2012 D D D NAP Upper NAP Lower D D D N N N N N N O O O O O O S S S S S S A A A A A A J J J J J J J J J J J J M M M M M M A A A A A A Spongotrochus glacialis M M Cycladophora davisiana M Tripodiscium gephyristes M Pseudodictyophimus clevei M M Amphimelissa setosa Amphimelissa setosa F F F F F F J 2011 J 2011 J Sea ice concentration J 2011 2011 J 2011 J 2011 D D Pseudodictyophimus plathycephalus D D D D N N N N N N O 2010 O O 2010 2010 O 2010 O O 2010 2010 0 0 0 0 0 0 50 50 0 0 0 0 0 0 150 100 300 200 100 300 200 100 150 100

50 50 50 50 50 50 5000 5000

200 150 100 150 100 150 100 200 150 100

150 100

150 100

25000 20000 15000 10000 25000 20000 15000 10000

Flux Flux (No. specimens m d ) d m specimens (No. Flux (No. specimens m d ) d m specimens (No. (No. specimens m d ) d m specimens (No. Flux Flux (No. specimens m d ) d m specimens (No. Flux (No. specimens m d ) d m specimens (No. (No. specimens m d ) d m specimens (No.

2 − 1 − 2 − 1 − 2 − 1 − 2 − 1 − 2 − 1 − 2 − 1 − Fig. 7 Fig. 7 (continued) Continued. Two year fluxes of major radiolarian taxa at Station NAP during the sampling period. Figure 7. Figure 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (Cortese N Actinomma 0 same speci- 4 morphogroup T O same specimen. sp. in det., same KN longispinum K2 same specimen. NAP10t Actinomma N 0 Actinomma leptodermum lep- 5 Actinomma morphogroup A, same specimen. juvenile, same specimen. NAP10t SA Actinomma boreale, Actinomma leptodermum leptodermum, AB (Jørgensen, 1900) sp. in det., same specimen. NAP10t Deep r e 6 same specimen. NAP10t Shallow #24. 5–10. w Actinomma M o l r morphogroup A. 11, 12. e 16692 16691 6 p Actinomma leptodermum leptodermum, M p u (Jørgensen, 1900). 5, 6. r Actinomma e 4 maximum 75 percentile average median 25 percentile minimum w M o l (Cleve, 1899). 1, 2. r e Actinomma 4 p M p Actinomma leptodermum longispinum, u r Actinomma boreale, e Actinomma leptodermum AP sp. in det., same specimen. NAP10t Deep #12. 25–26. w o N l r e p Actinomma leptodermum longispinum AP p N u 0 Actinomma boreale .0 .5 .0 .5 .0 .5 .0 Actinomma

0.5 1 1 2 2 3 3 4

100 µm for all figures. same specimen. NAP10t Deep #12. 7, 8. Total Radiolaria flux Radiolaria Total (x 10 No. specimens m d ) d m specimens No. 10 (x

Box plot of total radiolarian fluxes at Station NAP and previous studied areas in the −1 −2 4 = 1–4. Fig. 8 (Kruglikova and Bjørklund, 2009), same specimen. NAP10t Deep #22. Scale bar todermum, same specimen. NAP10t Deep #12. 9, 10. turidae Actinomma leptodermum leptodermum NAP10t Shallow #23. 3, 4. men. NAP10t Deep #12. 11–14. A, same specimen. NAP10tNAP10t Deep Deep #4. #4. 15–18. 13,and Bjørklund, 14. 1998). 15, 16. Deep #12. 17,Deep 18. #12. 19–24.specimen. Actinommidae NAP10t spp. Deep juvenile #12.#12. forms. 21, 23, 19, 22. 24. 20. Plate 1. Figure 8. North Pacific Ocean. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ? ? juvenile same spec- (Popofsky, 1908). same specimen. NAP11t Streblacantha circumtexta Arachnosphaera dichotoma, morphogroup B, same specimen. Streblacantha circumtexta Spongotrochus glacialis, Spongotrochus glacialis Actinomma (Cleve, 1899), same specimen. NAP11t Deep 16693 16694 sp. NAP10t Shallow #16. (Jørgensen, 1900). 1, 2. ? (Jørgensen, 1905). 5, 6. Arachnosphaera dichotoma, morphogroup B juvenile, same specimen. NAP10t Deep (Jørgensen, 1900), same specimen. NAP10t Deep #14. 7– Stylodictya (Burridge, Bjørklund and Kruglikova, 2013), same specimen. . NAP10t Shallow #24. 10, 11. morphogroup B. 1, 2. Cleveiplegma boreale Actinomma Streblacantha circumtexta Actinomma Arachnosphaera dichotoma 100 µm for all figures. 100 µm for all figures. Drymyomma elegans = = 1–4. 1–4. Actinomma friedrichdreyeri Spongotrochus glacialis Deep #4. 5–8. juvenile form, sameform, specimen same NAP10t specimen. Deep NAP10t9. #12. Shallow #23. 7, 9–11. 8. same specimen. NAP11t Deep #5. 3, 4. Plate 3. imen. NAP10t Shallow #22. 12. #12. Scale bar Scale bar NAP11t Deep #4. 10–11. 9. #15. 5, 6. Plate 2. NAP10t Deep #4. 3, 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , Proto- Arach- (Cleve, same specimen. , same specimen. , same specimen. Enneaphormis ro- Phormacantha hystrix Ceratocyrtis histricosus, same specimen. NAP10t Enneaphormis enneastrum Protoscenium simplex sp. A, same specimen. NAP10t Ceratocyrtis galeus, Phormacantha hystrix Cladoscenium tricolpium ?, same specimen. NAP10t Deep #14. 17– , same specimen. NAP10t Deep #12. 23, 24, Joergensenium Ceratocyrtis histricosus, , same specimen. NAP10t Deep #4. 11–12. 16696 16695 same specimen. NAP10t Deep #12. 15, 16. (Jørgensen, 1905). 1, 2, 3. (Cleve, 1899). 7, 8. sp. A, juvenile forms of 1–3, same specimen. NAP11t Deep spp. 1, 2, 3. Phormacantha hystrix (Jørgensen, 1900). 19, 20. sp. B, same specimen. NAP11t Deep #9. 8–9. Cladoscenium tricolpium , same specimen. NAP10t Deep #12. 26, 27. (Haeckel, 1887). 13, 14. (Petrushevskaya, 1971), same specimen. NAP10t Shallow #14. 19– Ceratocyrtis galeus (Haeckel, 1862), same specimen apical view. NAP10t Deep #4. 13–16. Protoscenium simplex, same specimen. NAP10t Deep #12. Ceratocyrtis galeus Joergensenium Ceratocyrtis histricosus Joergensenium 100 µm for all figures. 100 µm for all figures. = = Joergensenium 1–6. 1–7. (Haeckel, 1881), same specimen. NAP11t Deep #4. 10–11. Lophophaena clevei Phormacantha hystrix Phormacantha hystrix Plate 5. same specimen. NAP10t Deep #12.Deep 4, #12. 5, 7–10. 6. NAP10t Deep #6. 9, 10. NAP10t Deep #12. 21, 22. 25. same specimen. NAP10t Deep #12. Scale bar (Haeckel, 1887), same specimen. NAP10t Deep #12. 12–16. Deep #12. 4, 5. tula 1899). 12, 13, 14. scenium simplex, Scale bar nocorys umbellifera NAP10t Deep #6. 15,18. 16. 27. Plate 4. #4. 6, 7. Cladoscenium tricolpium Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in (Bai- , same in det., ?, same Pseudo- Tetraplecta in det., juve- , same spec- same specimen. , same specimen. (Bernstein, 1934) 1, 2. Pseudodictyophimus Pseudodictyophimus plathy- Pseudodictyophimus Peridium longispinum same specimen. NAP10t Deep , same specimen. NAP10t Deep Pseudodictyophimus multispinus ?, same specimen. NAP11t Deep Pseudiodictyophimus gracilipes Pseudodictyophimus clevei (Bailey, 1856), same specimen. NAP10t same specimen. NAP10t Deep #12. 11, 12. Pseudiodictyophimus gracilipes bicornis (Bailey, 1856) 16698 16697 , same specimen. NAP10t Shallow #2. 3. spp. juvenile forms. 14, 15. same specimen. NAP11t Deep #4. 13–14. Pseudodictyophimus plathycephalus, NAP11t Shallow #2. 4–12. Peridium longispinum Pseudiodictyophimus gracilipes bicornis ? (Jørgensen, 1900). 1, 2. Pseudodictyophimus clevei (Jørgensen, 1905), same specimen. NAP10t Deep #12. 7–11. (Jørgensen, 1900). 7, 8, 9. Pseudodictyophimus plathycephalus, Pseudodictyophimus (Ehrenberg, 1861). 20, 21. Peridium longispinum Pseudodictyophimus gracilipes Pseudodictyophimus gracilipes gracilipes 100 µm for all figures. 100 µm for all figures. Pseudodictyophimus plathycephalus, bicornis (Haeckel, 1887). 4, 5, 6. = = 1–4. Plectacantha oikiskos (Haeckel, 1887), same specimen. NAP10t Deep #12. 1–3. NAP10t Deep #12. 7,#12. 8. 9, 10. Pseudodictyophimus plathycephalus, pinigera Scale bar Plate 7. dictyophimus gracilipes multispinus. cephalus Pseudodictyophimus gracilipes multispinus #4. 5–6. Pseudodictyophimus clevei Plate 6. specimen. NAP11t Deep #4. 3, 4. imen. NAP10t Deep #12.#12. 10, 12–13. 11. Deep #12. 14–19. det., juvenile forms samejuvenile specimen. forms, NAP10t same Deep specimen. NAP10t #12. Deep 16, #12. 17. 18, 19. nile forms same specimen. NAP10t Deep #12. 20–23. NAP11t Deep #4. Scale bar ley, 1856) specimen. NAP11t Deep #4. 22, 23. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , Tripodis- Artostrobus joer- , same specimen. Artostrobus annula- Artostrobus joergenseni Tripodiscium gephyristes , same specimen. NAP10t , same specimen. NAP10t Deep #12. Artostrobus joergenseni , same specimen. NAP10t Deep #12. 21, 22. 16700 16699 Tripodiscium gephyristes , same specimen. NAP10t Deep #12. 9, 10. (Hülsemann, 1963). 1, 2. Artostrobus joergenseni , same specimen. NAP10t Deep #12. 27, 28. Artostrobus annulatus , same specimen. NAP10t Deep #12. 23–30. Tripodiscium gephyristes , same specimen. NAP10t Deep #12. 11–18. Plagiacanthidae gen. et sp. in Tripodiscium gephyristes 100 µm for all figures. = 1–10. , same specimen. NAP10t Deep #12. 29, 30. Artostrobus joergenseni (Bailey, 1856). 19, 20. det. 11, 12. Plagiacanthidae13, gen. 14. et Plagiacanthidae sp. gen.giacanthidae in et gen. det. sp. et juvenile, in sp. samegen. in det., specimen. et det., same NAP10t sp. same specimen. Deep specimen. in NAP10t #12. NAP10t det. Deep Deep juvenile, #12. #12. same 15, 17, specimen. 16. 18. NAP10t Pla- Plagiacanthidae Deep #12. 19–22. cium gephyristes tus Artostrobus annulatus (Petrushevskaya, 1967). 23, 24. Deep #12. 6, 7, 8. 25, 26. Plate 8. same specimen. NAP10t Deep #12. 3, 4, 5 genseni NAP10t Deep #12. Scale bar Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , , Cy- Am- Pro- , same , same speci- Amphimelissa juvenile, same (Popofsky, 1908). Amphimelissa se- , same specimen, . NAP11t Deep #14. Sethoconus tabulatus (Ehrenberg, 1873). 12. , NAP11t Deep #4. 6, 7. Cycladophora davisiana (Cleve, 1899). 22, 23. Amphimelissa setosa , same specimen. NAP10t Deep . furcaspiculata juvenile, same specimen. NAP11t juvenile. 34, 35. ff Sethoconus tabulatus Amphimelissa setosa Amphimelissa setosa , same specimen. NAP10t Deep #12. 18, Lithocampe platycephala Lithocampe a Lithocampe platycephala Cycladophora davisiana Amphimelissa setosa 16701 Amphimelissa setosa Amphimelissa setosa (Ehrenberg, 1854), same specimen. NAP10t Deep #12. Amphimelissa setosa , same specimen. NAP11t Deep #4. 30, 31. Sethoconus tabulatus (Cleve, 1899), same specimen. NAP10t Deep #14. 42–43. (Ehrenberg, 1873). 14, 15. (Ehrenberg, 1854), same specimen. NAP10t Deep #12. 5–9. , same specimen. NAP10t Deep #12. 20, 21. . NAP10t Deep #13. 13. , same specimen. NAP10t Deep #12. 8, 9. (Ehrenberg, 1862). 5. Lirella melo , same specimen. NAP10t Deep #12. 24, 25. (Murray, 1885), same specimen. NAP10t Deep #18. Cornutella stylophaena Amphimelissa setosa 100 µm for all figures. = 1, 2. Sethoconus tabulatus , same specimen. NAP10t Deep #12. 32, 33. Cornutella longiseta juvenile, same specimen. NAP11t Deep #14. 36, 37. Sethoconus tabulatus setosa apical view. NAP11t Deep #4.tosa 34–39. specimen. NAP10t Deep #12. 38,Deep 39. #14. 40–41. tocystis harstoni Scale bar #12. 28, 29. phimelissa setosa specimen. NAP10t Deep #12. 26, 27. same specimen. NAP10t Deep #12. 22–33. men. NAP10t Deep #12. 16, 17. 19. Lithocampe platycephala 14–21. same specimen. NAP10t Deep #12. 12–13. cladophora davisiana Cycladophora davisiana same specimen. NAP10t Deep #12. 10–11. Plate 9. 3, 4.