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Distribution and vertical fluxes of silicoflagellates, ebridians, and the endoskeletal dinoflagellate Actiniscus in the western Arctic Ocean

DOI:10.1007/s00300-015-1784-y
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Jonaotaro Onodera at Japan Agency for Marine-Earth Science Technology
Jonaotaro Onodera
Eiji Watanabe
Eiji Watanabe
Eiji Watanabe
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Shigeto Nishino at Japan Agency for Marine-Earth Science Technology
Shigeto Nishino
Naomi Harada at Japan Agency for Marine-Earth Science Technology
Naomi Harada
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Abstract and Figures

Spatial and temporal variations in major phytoplankton populations such as diatoms in the changing Arctic Ocean have been well studied, whereas only a few monitoring studies have been conducted on minor siliceous flagellates. To discern the relationship between hydrographic conditions and the spatio-temporal distribution of silicoflagellates, ebridians, and the endoskeletal dinoflagellate Actiniscus pentasterias, we analyzed seawater and bottom-tethered sediment-trap samples from the western Arctic Ocean. Silicoflagellates and ebridians were commonly observed in shelf waters around the southern Chukchi Sea in September–October during 2010 and 2013. However, one mesoscale patch with abundant silicoflagellates and ebridians was observed in the southwestern Canada Basin during September–October 2010. This offshore patch reflected an unusual occurrence of a mesoscale eddy deriving from the Alaskan Coastal Water. The active lateral transport of shelf materials by eddies was also evident in high silicoflagellate and ebridian fluxes at station Northwind Abyssal Plain (NAP) (75°N, 162°W, 1975-m water depth) in November–December during 2010 and 2011. The summer silicoflagellate flux at station NAP was mainly composed of Distephanus speculum. During the sea-ice cover period, except for July, silicoflagellates D. medianoctisol and D. octonarius were relatively abundant in the assemblage. The spike in D. speculum flux during July 2011 was observed with fecal pellets containing abundant silicoflagellates, suggesting a temporal silicoflagellate contribution to some kinds of zooplankton. The common occurrence of A. pentasterias in settling particles at station NAP during the winter may indicate their tolerance to cold water under sea ice.
Map of the study area. The black circle shows the location of the sediment trap mooring at station NAP. The arrows represent surface currents. Abbreviations of geographic areas: NR Northwind Ridge; NAP Northwind Abyssal Plain; CS the Chukchi Spur; CP Chukchi Plateau; CAP Chukchi Abyssal Plain; AMR Alpha-Mendeleev Ridge
Map of the study area. The black circle shows the location of the sediment trap mooring at station NAP. The arrows represent surface currents. Abbreviations of geographic areas: NR Northwind Ridge; NAP Northwind Abyssal Plain; CS the Chukchi Spur; CP Chukchi Plateau; CAP Chukchi Abyssal Plain; AMR Alpha-Mendeleev Ridge
… 
Horizontal gradients of a water temperature (°C), b salinity, c silicate concentration (μM), and d nitrate concentration (μM) in the first 5 m from the sea surface of the study area during cruise MR10-05 in September–October 2010
Horizontal gradients of a water temperature (°C), b salinity, c silicate concentration (μM), and d nitrate concentration (μM) in the first 5 m from the sea surface of the study area during cruise MR10-05 in September–October 2010
… 
Oceanographic data from station NAP obtained during the study period (4 October 2010 through 17 September 2012). a Short-wave radiation, b sea-ice concentration, c logged data for the depth of the moored shallow sediment trap, d water temperature at moored depth of the shallow sediment trap, and e total mass flux (<1 mm grain size) of shallow (solid line) and deep (broken line) sediment traps, and lithogenic matter flux at the shallow trap (shaded in gray) (Watanabe et al. 2014)
Oceanographic data from station NAP obtained during the study period (4 October 2010 through 17 September 2012). a Short-wave radiation, b sea-ice concentration, c logged data for the depth of the moored shallow sediment trap, d water temperature at moored depth of the shallow sediment trap, and e total mass flux (<1 mm grain size) of shallow (solid line) and deep (broken line) sediment traps, and lithogenic matter flux at the shallow trap (shaded in gray) (Watanabe et al. 2014)
… 
Vertical hydrographic profiles for the upper 150 m of the water column at station NAP and vertical distributions of silicoflagellate and ebridian skeletons around station NAP. a Water temperature (°C), salinity, and downwelling irradiance of photosynthetically active radiation (EdPAR, μmol photons m⁻² s⁻¹) on 3 October 2010; b silicate, nitrate, and chlorophyll concentrations (μM) on 3 September 2010 during cruise MR10-05; c vertical distribution of silicoflagellate skeletons (×10² number of skeletons l⁻¹) during the cruises MR10-05, MR12-E03, and MR13-06; d vertical distribution of ebridian skeletons (number of skeletons l⁻¹) on 3 September 2010 at station NAP. The data for cruise MR13-06 in c are from 56 km south of station NAP. There are no data in d for ebridians from cruises MR12-E03 or MR13-06 because their abundances were absent or were 1 skeleton l⁻¹ (Electric Supplementary Table 1)
Vertical hydrographic profiles for the upper 150 m of the water column at station NAP and vertical distributions of silicoflagellate and ebridian skeletons around station NAP. a Water temperature (°C), salinity, and downwelling irradiance of photosynthetically active radiation (EdPAR, μmol photons m⁻² s⁻¹) on 3 October 2010; b silicate, nitrate, and chlorophyll concentrations (μM) on 3 September 2010 during cruise MR10-05; c vertical distribution of silicoflagellate skeletons (×10² number of skeletons l⁻¹) during the cruises MR10-05, MR12-E03, and MR13-06; d vertical distribution of ebridian skeletons (number of skeletons l⁻¹) on 3 September 2010 at station NAP. The data for cruise MR13-06 in c are from 56 km south of station NAP. There are no data in d for ebridians from cruises MR12-E03 or MR13-06 because their abundances were absent or were 1 skeleton l⁻¹ (Electric Supplementary Table 1)
… 
Horizontal distributions of total silicoflagellates, the ebridian Ebria tripartita, and the endoskeletal dinoflagellate Actiniscus pentasterias in the sea surface waters (0 and ~4.5-m depth) during cruise MR10-05 in September–October 2010. a Total abundance of silicoflagellate skeletons (number of skeletons l⁻¹); b relative abundance (%) of D. medianoctisol and D. octonarius among total silicoflagellates (stations with fewer than 10 silicoflagellates were omitted from this plot); c abundance of ebridian skeletons (number of skeletons l⁻¹); d abundance of Actiniscus pentasterias skeletons (number of skeletons l⁻¹)
+3
Horizontal distributions of total silicoflagellates, the ebridian Ebria tripartita, and the endoskeletal dinoflagellate Actiniscus pentasterias in the sea surface waters (0 and ~4.5-m depth) during cruise MR10-05 in September–October 2010. a Total abundance of silicoflagellate skeletons (number of skeletons l⁻¹); b relative abundance (%) of D. medianoctisol and D. octonarius among total silicoflagellates (stations with fewer than 10 silicoflagellates were omitted from this plot); c abundance of ebridian skeletons (number of skeletons l⁻¹); d abundance of Actiniscus pentasterias skeletons (number of skeletons l⁻¹)
… 
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ORIGINAL PAPER
Distribution and vertical fluxes of silicoflagellates, ebridians,
and the endoskeletal dinoflagellate Actiniscus in the western Arctic
Ocean
Jonaotaro Onodera
1,2
•Eiji Watanabe
2
•Shigeto Nishino
2
•Naomi Harada
1,2
Received: 16 December 2014 / Revised: 29 June 2015 / Accepted: 22 August 2015 / Published online: 14 October 2015
ÓSpringer-Verlag Berlin Heidelberg 2015
Abstract Spatial and temporal variations in major phy-
toplankton populations such as diatoms in the changing
Arctic Ocean have been well studied, whereas only a few
monitoring studies have been conducted on minor siliceous
flagellates. To discern the relationship between hydro-
graphic conditions and the spatio-temporal distribution of
silicoflagellates, ebridians, and the endoskeletal dinoflag-
ellate Actiniscus pentasterias, we analyzed seawater and
bottom-tethered sediment-trap samples from the western
Arctic Ocean. Silicoflagellates and ebridians were com-
monly observed in shelf waters around the southern
Chukchi Sea in September–October during 2010 and 2013.
However, one mesoscale patch with abundant silicoflag-
ellates and ebridians was observed in the southwestern
Canada Basin during September–October 2010. This off-
shore patch reflected an unusual occurrence of a mesoscale
eddy deriving from the Alaskan Coastal Water. The active
lateral transport of shelf materials by eddies was also evi-
dent in high silicoflagellate and ebridian fluxes at station
Northwind Abyssal Plain (NAP) (75°N, 162°W, 1975-m
water depth) in November–December during 2010 and
2011. The summer silicoflagellate flux at station NAP was
mainly composed of Distephanus speculum. During the
sea-ice cover period, except for July, silicoflagellates D.
medianoctisol and D. octonarius were relatively abundant
in the assemblage. The spike in D. speculum flux during
July 2011 was observed with fecal pellets containing
abundant silicoflagellates, suggesting a temporal sili-
coflagellate contribution to some kinds of zooplankton. The
common occurrence of A. pentasterias in settling particles
at station NAP during the winter may indicate their toler-
ance to cold water under sea ice.
Keywords Silicoflagellate Ebridian Actiniscus
pentasterias Sinking particles Sediment trap Northwind
Abyssal Plain Chukchi Sea Arctic Ocean
Introduction
Silicoflagellates and other siliceous flagellates in sinking
particles have been studied in both low- and high-latitude
oceans (Takahashi 1987; Lange et al. 2000; Romero et al.
2002,2009; Rigual-Herna
´ndez et al. 2010; Onodera and
Takahashi 2012); however, few studies are reported from
the Arctic Ocean (Zernova et al. 2000). In the Arctic Ocean
there are snapshot records of silicoflagellate occurrences in
seawater and sea ice (Melnikov 1997; Takahashi et al.
2009). Zernova et al. (2000) reported sporadic silicoflag-
ellate occurrences in a 1-year record (from September 1995
to August 1996) of settling particle flux at station LOMO2
on the basin side of the Laptev Sea. Onodera and Taka-
hashi (2012) considered that the relative abundance of the
silicoflagellate Distephanus medianoctisol may increase in
colder waters covered with sea ice in the Arctic Ocean
compared to the subarctic North Pacific Ocean and the
Bering Sea. Matsuno et al. (2014a) showed a marked
relationship between the horizontal distribution of major
Electronic supplementary material The online version of this
article (doi:10.1007/s00300-015-1784-y) contains supplementary
material, which is available to authorized users.
&Jonaotaro Onodera
onoderaj@jamstec.go.jp
1
Research and Development Center for Global Change, Japan
Agency for Marine Earth Science and Technology,
Natsushima-cho 2-15, Yokosuka 237-0061, Japan
2
Institute of Arctic Climate and Environment Research, Japan
Agency for Marine Earth Science and Technology,
Natsushima-cho 2-15, Yokosuka 237-0061, Japan
123
Polar Biol (2016) 39:327–341
DOI 10.1007/s00300-015-1784-y
Content courtesy of Springer Nature, terms of use apply. Rights reserved.

Supplementary resource (1)

Supplementary material 1
Data
October 2015
Jonaotaro Onodera · Eiji Watanabe · Shigeto Nishino · Naomi Harada
... Fluxes and assemblages of microzooplankton, including planktic juveniles of coastal bivalvia, showed clear seasonality; the highest fluxes were observed in August-September and October-November. This seasonality is similar to the seasonal pattern of diatom (Watanabe et al., 2014), silicoflagellate, ebridian, and dinoflagellate fluxes (Onodera et al., 2015b). The bivalve larvae originate mainly from the Bering Strait to the east of the Chukchi shelf, but they rarely appear in the Canada Basin (K. ...
... This snapshot of the eddy characteristics suggests that the eddy's warm core may serve not only as transporter of heat and particles toward the cryopelagic Arctic Ocean but also as an incubator of lower-trophic-level organisms. A moored sediment trap experiment carried out from September 2010 to October 2011 at St. NAP in near the area of the eddy studied by Nishino et al. (2011b) revealed high bimodal flux peaks during the summer (July-September) and at the beginning of the polar night season (November-December) of POC (Watanabe et al., 2014), diatoms (Onodera et al., 2015a), silicoflagellates, ebridians, and dinoflagellates (Onodera et al., 2015b), micro-zooplankton with carbonate tests (K. Kimoto, JAMSTEC, unpublished data), and zooplankton swimmers (Matsuno et al., 2013). ...
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... These organisms are able to produce simple internal silica-based skeletons in the form of a network of bars [156], and use so-called undulipodium (flagellum) to propel themselves in an aquatic environment. Some species of silicoflagellates are highly specialized for cold water locations [157]. Takahashi et al. [158] reported that Distephanus medianoctisol dominates over 71 % of total silicoflagellates in the central Arctic. ...
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Time series monitoring of hydrography and marine settling particles supplies a large amount of information regarding the marine lower‐trophic ecosystem with respect to the changing Arctic Ocean. To investigate the interannual relationship between the settling particles and hydrographic conditions of the western Arctic Ocean, bottom‐tethered sediment trap moorings were deployed at the Northwind Abyssal Plain (NAP) from October 2010 to September 2014 and at the Chukchi Abyssal Plain (CAP) from October 2012 to September 2013 to the east and west of the Chukchi Borderland. The settling particles at both stations contained a significant amount of lithogenic matter, with biogenic particles being a lateral advection of shelf materials from shelf to basin. The many peaks of settling particle fluxes at NAP in 2013–2014 corresponded to the hydrographic events of passing oceanic eddies over the station, in addition to seasonal biological production. The settling particle flux at CAP remarkably increased when Pacific‐origin water advected over the northern shelf of the Chukchi Sea in March–April 2013. Additionally, abundant gelatinous matter was found at NAP and CAP in July–September 2011 and 2014 and in July–August 2013, respectively. The settling flux data of particulate organic matter and the mole ratio and stable isotope ratios of particulate organic carbon and nitrogen reflected the changes in the composition of trapped plankton assemblages under various hydrographic conditions over the course of the four years of the study.
... This species also bloomed in the temperate waters of the northern Adriatic in January in the upper 15 m layer (Cerino et al., 2017). Silicoflagellate Octactis speculum is a typical cold-water species widespread in the boreal and polar seas (Onodera et al., 2016). In the Black Sea, this is a main silicoflagellate species, which reaches its maximum biomass in winter in the upper layer (Fig. 4). ...
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... NAPt) in the Pacific sector of the Arctic Ocean (Harada, 2016). Based on the sediment trap at NAPt, seasonal changes in diatom, dinoflagellate, silicoflagellate and radiolaria fluxes ( Onodera et al., 2015Onodera et al., , 2016Ikenoue et al., 2015) are revealed. For mesozooplankton, the population structures and fluxes of large dominant copepods (C. ...
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Full-text available
  • Jan 2013
A nutrient (N), phytoplankton (P), zooplankton (Z), and detritus (D) ecosystem model coupled to an ice-ocean model was applied to the Bering and Chukchi Seas for 2007–2008. The model reasonably reproduces the seasonal cycles of sea ice, phytoplankton, and zooplankton in the Bering–Chukchi Seas. The spatial variation of the phytoplankton bloom was predominantly controlled by the retreat of sea ice and the increased gradient of the water temperature from the south to the north. The model captures the basic structure of the measured nutrients and chl-a along the Bering shelf during 4–23 July 2008, and along the Chukchi shelf during 5–12 August 2007. In summer 2008, the Green Belt bloom was not observed by either the satellite measurements or the model. The model-data comparison and analysis reveal the complexity of the lower trophic dynamics in the Bering and Chukchi Seas. The complexity is due to the nature that the physical and biological components interact at different manners in time and space, even in response to a same climate forcing, over the physically distinct geographic settings such as in the Bering and North Aleutian Slopes, deep Bering basins, Bering shelf, and Chukchi Sea. Sensitivity studies were conducted to reveal the underlying mechanisms (i.e., the bottom-up effects) of the Bering–Chukchi ecosystem in response to changes in light intensity, nutrient input from open boundaries, and air temperature. It was found that (1) a 10% increase in solar radiation or light intensity for the entire year has a small impact on the intensity and timing of the bloom in the physical–biological system since the light is not a limiting factor in the study region; (2) a 20% increase in nutrients from all the open boundaries results in an overall 7% increase in phytoplankton, with the Slope region being the largest, and the Bering shelf and Chukchi being the smallest; and (3) an increase in air temperature by 2 deg. C over the entire calculation period can result in an overall increase in phytoplankton by 11%.
Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean
Article
Full-text available
We studied time-series fluxes of diatom particles and their relationship to hydrographic variations from 4 October 2010 through 18 September 2012 using bottom-tethered sediment trap moorings deployed at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. We observed clear maxima of the diatom valve flux in November–December of both 2010 and 2011, and in August 2011. Diatoms in samples were categorized into 98 taxa. The diatom flux maxima were characterized by many resting spores in November–December and by the sea ice-associated diatom Fossula arctica in August 2011. These assemblages along with abundant clay minerals in the samples suggest a significant influence of shelf-origin materials transported by mesoscale eddies, which developed along the Chukchi Sea shelf break. In contrast, the fluxes of total mass and diatoms were reduced in summer 2012. We hypothesize that this suppression reflects the influx of oligotrophic water originating from the central Canada Basin. A physical oceanographic model demonstrated that oligotrophic surface water from the Beaufort Gyre was supplied to Station NAP from December 2011 to early half of 2012.
The Arctic sea ice ecosystem
Book
  • Jan 1997
This book is dedicated to the study of the composition, structure and dynamics of the Arctic sea ice ecosystem. It considers the permanent Arctic sea ice cover as an integral steady-state ecological system. Detailed descriptions are given of time-scale characteristics, physical and chemical ice properties, and the species composition of the sea ice bio-data. The ecological mechanisms which govern the ecosystem on both the vertical and lateral scales are discussed, including the function of microcommunities during sea ice evolution. Sections include: the past and recent sea ice environment; the characteristics of the Arctic sea ice biotope; sea ice biocenoses; and functional features of the ecosystem.
Seasonal changes in mesozooplankton swimmers collected by sediment trap moored in the western Arctic Ocean
Article
  • Nov 2015
To examine seasonal changes in the mesozooplankton community, analyses were made on the swimmer samples (>1 mm) collected by a sediment trap mooring at 184 m depth on the Northwind Abyssal Plain in the western Arctic Ocean during October 2010–September 2011. The zooplankton swimmer flux ranged from 5 to 44 ind. m−2 day−1 and was greater during July to October; copepods were the dominant taxon. Based on the zooplankton swimmer flux, cluster analysis classified samples into three groups (A, B-1 and B-2). The occurrence of each group showed clear seasonality; group A was observed during July to October, group B-1 was seen in November to January and group B-2 during March to June. The seasonal variability in population structures of four dominant copepod swimmers was clearly different between the species. Most Calanus hyperboreus were copepodid stage 6 female (C6F) throughout the year. For Metridia longa and Paraeuchaeta glacialis, C6Fs dominated during January to May, and early copepodid stages increased during June to October. Heterorhabdus norvegicus was dominated by stage C5 during November to February, and C6F/M during March to May. Since Pacific copepods (Neocalanus cristatus) occurred in significant number during August–September, possible causes are discussed.
Response of siliceous microplankton from the Santa Barbara Basin to the 1997-98 El Niño event
Article
We report on fluxes of siliceous microorganisms (diatoms, radiolarians, and silicoflagellates), organic carbon, calcium carbonate, biogenic silica, and lithogenic particles in the Santa Barbara Basin (SBB; 34°4'N, 120°02'W), offshore of California, in a sediment trap set 540 m deep. We describe changes in particle fluxes, emphasizing the period from 1996 to early 1998, and compare flux values and species composition for non-El Niño (1996) and El Niño (1997-98) conditions. The California coastal waters were strongly influenced by El Niño conditions beginning late in the summer of 1997. Terrigenous input to our sampling site, as measured by the lithogenic flux, was significantly higher during the El Niño period, presumably reflecting higher rainfall and runoff into the basin. Samples from December 1997 to February 1998 contained large amounts of detritus, Chrysophyte cysts, benthic diatoms, and estuarine benthic foraminifers, indicating that considerable material was flushed from the river mouths during large storms. Both opal and organic carbon fluxes mirrored the productivity cycle, with high fluxes during the spring-summer upwelling period and low fluxes during fall and winter. However, for the winter of 1998 organic carbon fluxes were unusually high, and coincided with a February peak in the carbonate flux and high abundance of arenaceous tintinnids. Opal fluxes decreased, and major changes in the contribution of siliceous microplankton assemblages to the biogenic opal flux were observed during El Niño conditions: (1) Diatom fluxes were an order of magnitude lower, and species richness was higher than in the 1996 non-El Niño period. (2) The flux of radiolarians was 20% lower in late 1997-early 1998 when compared to the 1993-96 period. (3) The fall-winter peak in silicoflagellate fluxes, seen annually from 1993 to 1996, was missing in 1997. In addition, major changes in species composition were observed, including a significant increase in the proportion of warm-water flora and fauna, and a decrease in the relative contribution of the siliceous microorganisms indicative of spring upwelling conditions in the SBB.
Significant populations of seven-sided Distephanus (Silicoflagellata) in the sea-ice covered environment of the central Arctic Ocean, summer 2004
Article
The Arctic Coring Expedition (ACEX) carried out in 2004 by the Integrated Ocean Drilling Program (IODP) afforded us the opportunity to obtain seawater and sea-ice samples at four different times and locations including the North Pole in the central Arctic Ocean. We performed taxonomic and census investigation on extant silicoflagellates in the samples. Of the two silicoflagellate taxa observed in the central Arctic, Distephanus medianoctisol Takahashi et al. sp. nov dominates over 71% of total silicoflagellates and Distephanus speculum (Ehrenberg) Haeckel 1887 represents only 29% or less. Significantly different silicoflagellate assemblages and skeletal morphology from the Arctic sea-ice laden areas compared to those from open oceans outside of the Arctic were observed. During the summer, silicoflagellates actively grow in the central Arctic Ocean, as evidenced by considerable population densities even compared with those of the middle latitude open oceans. Active growth is supported by the number of observed double skeletons, which are good representation of active cell divisions. Underneath the pack ice, seawater of the central Arctic receives enough sunlight under midnight Sun conditions in summer, due to the presence of ice cracks and water puddles to provide sufficient photosynthetic energy to sustain silicoflagellate populations. The documented percentage occurrences of aberrant silicoflagellates (abnormal forms) are high when compared with those from the pelagic environments. Unusual forms with greater than one apical window (also considered as aberrant) are also noted and they may have been formed due to specific environmental conditions such as low temperature, the presence of sea-ice, and low light intensity (beneath sea-ice with snow accumulation).