Seasonality of the Physical and Biogeochemical Hydrography in the Inflow to the Arctic Ocean Through Fram Strait

Randelhoff, Achim; Reigstad, Marit; Chierici, Melissa; Sundfjord, Arild; Ivanov, Vladimir; Cape, Matthias; Vernet, María; Tremblay, Jean‐Éric; Bratbak, Gunnar; Kristiansen, Svein

doi:10.3389/fmars.2018.00224

Cited by 73 publications

(96 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In May 2014, the Atlantic water (3.5-5.0 • C) reached up to the surface between 6 and 8 • E. In the western end of transect D, colder, lower-salinity surface waters were observed west of 5 • E, closer to the sea ice edge. In August 2014, a fresher (salinity < 34) surface layer extended over most of transect D, with surface temperatures ranging from 7.5 • C in the east to 1 • C west of 4 • E (Randelhoff et al, 2018).…”

Section: The Study Sitesmentioning

confidence: 99%

“…The Fram Strait is already one of the most productive areas of the Arctic (Slagstad et al, 2011) and is likely become a regional hotspot with increased primary production due to efficient transport of nutrients and the increased light availability in the ice-free water column (Randelhoff et al, 2018). However, microzooplankton remain little studied in this polar region.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Microzooplankton Distribution and Dynamics in the Eastern Fram Strait and the Arctic Ocean in May and August 2014

2019

View full text Add to dashboard Cite

Microzooplankton community structure, distribution, growth, and herbivory were examined in the eastern Fram Strait and Arctic Ocean shelf affected by the Atlantic water inflow in May (during the spring bloom) and August (post-bloom, summer stratification) 2014. In May, integrated microzooplankton biomass in the upper 100 m ranged from 0.16 g C m −2 above the slope to 2.3 g C m −2 within the West Spitsbergen Current (0.71 g C m −2 on average), where it peaked in the mixed layer at 206 µg C L −1 . This is the highest volumetric microzooplankton biomass recorded so far in the Arctic. It primarily consisted of mixotrophic oligotrich ciliates from the genus Strombidium, which were dominant in the spring and formed a surface bloom (79 × 10 3 cells L −1 ). The heterotrophic dinoflagellates Gyrodinium and Protoperidinium were abundant at the diatom-dominated stations in the ice-covered waters during both seasons. In the summer, a more diverse community included a large proportion of heterotrophic and mixotrophic dinoflagellates, tintinnids, and other ciliates. Microzooplankton biomass increased to the average of 1.27 g C m −2 . At the ice-covered and open water stations in the Yermak shelf and deep basin, microzooplankton grew at 0.04 to 0.38 d −1 ; their species-specific growth rates were up to 1.79 d −1 . Microzooplankton herbivory on average removed 72% (in two experiments > 100%) of daily primary production with the exception of samples dominated by Phaeocystis pouchetii colonies. The results indicate that microzooplankton play a significant role in the carbon cycle in this Atlantic-influenced polar system.

show abstract

Section: The Study Sitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microzooplankton Distribution and Dynamics in the Eastern Fram Strait and the Arctic Ocean in May and August 2014

2019

View full text Add to dashboard Cite

show abstract

“…Three 24 h process stations were sampled in May, corresponding to early, peak, and decline phase of an algal bloom, and three stations in August, representing post bloom stages (Figure 1 and Table 1). Sampling stations were located to intercept the core of the warm Atlantic water inflow, which enters the Arctic Ocean with the West Spitsbergen Current east and north of Svalbard (Randelhoff et al, 2018). Vertical profiles of temperature, salinity and fluorescence were mapped with a rosette oceanographic profiler (CTD, Seabird SBE 911 plus).…”

Section: Spatial Coverage and Water Column Profilesmentioning

confidence: 99%

“…Scale bar in km. Depths of the mixed layer (d ML ) and photic zone (Z eu ) at each station according to Randelhoff et al (2018). Mixed layer is defined as the depth where MSS-90L microstructure sonde measured potential density (σ θ) crosses 20% of the density difference between a surface layer density (3-5 m), and deeper (reference depth interval 50-60 m).…”

Section: Carbon Poolsmentioning

confidence: 99%

Food Web Functions and Interactions During Spring and Summer in the Arctic Water Inflow Region: Investigated Through Inverse Modeling

et al. 2019

Self Cite

View full text Add to dashboard Cite

We used inverse modeling to reconstruct major planktonic food web carbon flows in the Atlantic Water inflow, east and north of Svalbard during spring (18-25 May) and summer (9-13 August), 2014. The model was based on three intensively sampled stations during both periods, corresponding to early, peak, and decline phases of a Phaeocystis and diatom dominated bloom (May), and flagellates dominated post bloom stages (August). The food web carbon flows were driven by primary production (290-2,850 mg C m −2 d −1 ), which was channeled through a network of planktonic compartments, and ultimately respired (180-1200 mg C m 2 d −1 ), settled out of the euphotic zone as organic particles (145-530 mg C m −2 d −1 ), or accumulated in the water column in various organic pools. The accumulation of dissolved organic carbon was intense (1070 mg C m −2 d −1 ) during the early bloom stage, slowed down during the bloom peak (400 mg C m −2 d −1 ), and remained low during the rest of the season. The heterotrophic bacteria responded swiftly to the massive release of new DOC by high but decreasing carbon assimilation rates (from 534 to 330 mg C m −2 d −1 ) in May. The net bacterial production was low during the early and peak bloom (26-31 mg C m −2 d −1 ) but increased in the late and post bloom phases (>50 mg C m −2 d −1 ). The heterotrophic nanoflagellates did not respond predictably to the different bloom phases, with relatively modest carbon uptake, 30-170 mg C m 2 d −1 . In contrast, microzooplankton increased food intake from 160 to 380 mg C m 2 d −1 during the buildup and decline phases, and highly variable carbon intake 46-624 mg C m 2 d −1 , during post bloom phases. Mesozooplankton had an initially high but decreasing carbon uptake in May (220-48 mg C m −2 d −1 ), followed by highly variable carbon Frontiers in Marine Science | www.frontiersin.org 1 May 2019 | Volume 6 | Article 244Olli et al.Arctic Food Web Carbon Flow consumption during the post bloom stages (40-190 mg C m −2 d −1 ). Both, micro-and mesozooplankton shifted from almost pure herbivory (92-97% of total food intake) during the early bloom phase to an herbivorous, detritovorous and carnivorous mixed diet as the season progressed. Our results indicate a temporal decoupling between the microbial and zooplankton dominated heterotrophic carbon flows during the course of the bloom in a highly productive Atlantic gateway to the Arctic Ocean.

show abstract

“…The salient point is this: as the Atlantic Water is cooled on its way north, it loses stability, potentially leading to wintertime convection (Ivanov et al, 2016) and efficient vertical mixing. The result is that the surface layer nutrient reservoirs are replenished long before the end of winter (Randelhoff et al, 2015); increased wintertime upwelling will not bring more nutrients (Randelhoff and Sundfjord, 2017, published dataset; see also Randelhoff et al 2018); see panel (b) for location. Salinity is plotted on the colour scale, and temperature is marked (in • C) on the black isolines inside the plot.…”

Section: Ocean Bottom Sea Surfacementioning

confidence: 99%

Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

Randelhoff

Sundfjord

2018

Ocean Sci.

Self Cite

View full text Add to dashboard Cite

Abstract. The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of "the new Arctic". It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

show abstract

Seasonality of the Physical and Biogeochemical Hydrography in the Inflow to the Arctic Ocean Through Fram Strait

Cited by 73 publications

References 41 publications

Microzooplankton Distribution and Dynamics in the Eastern Fram Strait and the Arctic Ocean in May and August 2014

Microzooplankton Distribution and Dynamics in the Eastern Fram Strait and the Arctic Ocean in May and August 2014

Food Web Functions and Interactions During Spring and Summer in the Arctic Water Inflow Region: Investigated Through Inverse Modeling

Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

Contact Info

Product

Resources

About