Summer and fall distribution of phytoplankton in relation to environmental variables in Labrador fjords, with special emphasis on Phaeocystis pouchetii

Simo-Matchim, Armelle-Galine; Gosselin, Michel; Poulin, Michel; Ardyna, Mathieu; Lessard, Sylvie

doi:10.3354/meps12125

Cited by 20 publications

(12 citation statements)

References 92 publications

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“…4 a). None of the top autumn OTUs were diatoms, consistent with diatoms being limited by low autumn light availability and non-diatoms dominating under lower light conditions 21 . Autumn Chl a concentrations remained low in the surface and SCM, suggesting that the dinoflagellates were not overly reliant on photosynthesis.…”

Section: Discussionmentioning

confidence: 68%

A decadal perspective on north water microbial eukaryotes as Arctic Ocean sentinels

Freyria

Joli

Lovejoy

2021

Sci Rep

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The North Water region, between Greenland and Ellesmere Island, with high populations of marine birds and mammals, is an Arctic icon. Due to climate related changes, seasonal patterns in water column primary production are changing but the implications for the planktonic microbial eukaryote communities that support the ecosystem are unknown. Here we report microbial community phenology in samples collected over 12 years (2005–2018) from July to October and analysed using high throughput 18S rRNA V4 amplicon sequencing. Community composition was tied to seasonality with summer communities more variable than distinct October communities. In summer, sentinel pan-Arctic species, including a diatom in the Chaetoceros socialis-gelidus complex and the picochlorophyte Micromonas polaris dominated phytoplankton and were summer specialists. In autumn, uncultured undescribed open water dinoflagellates were favored, and their ubiquity suggests they are sentinels of arctic autumn conditions. Despite the input of nutrients into surface waters, autumn chlorophyll concentrations remained low, refuting projected scenarios that longer ice-free seasons are synonymous with high autumn production and a diatom dominated bloom. Overall, the summer sentinel microbial taxa are persisting, and a subset oceanic dinoflagellate should be monitored for possible ecosystem shifts as later autumn ice formation becomes prevalent elsewhere.

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Section: Discussionmentioning

confidence: 68%

A decadal perspective on north water microbial eukaryotes as Arctic Ocean sentinels

Freyria

Joli

Lovejoy

2021

Sci Rep

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“…Based on this novel pan-Arctic compilation, two main types of Arctic phytoplankton blooms were identified (occurring under both sea-ice-covered and sea-ice-free conditions; Figure 8), those dominated by diatoms and those dominated by the haptophyte Phaeocystis pouchetii (Figures 8 and 9). Phaeocystis pouchetii blooms have long been observed in the European Arctic sector (Smith et al, 1991;Schoemann et al, 2005) but have only recently been observed in Labrador fjords (Simo-Matchim et al, 2017) and Baffin Bay. Amongst these blooms, only one has been designated as an UIB (Assmy et al, 2017).…”

Section: Changing Nutriscapes and Icescapes Shape Phytoplankton Assemmentioning

confidence: 99%

Environmental drivers of under-ice phytoplankton bloom dynamics in the Arctic Ocean

Ardyna

Mundy

Mills

et al. 2020

Elementa: Science of the Anthropocene

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The decline of sea-ice thickness, area, and volume due to the transition from multi-year to first-year sea ice has improved the under-ice light environment for pelagic Arctic ecosystems. One unexpected and direct consequence of this transition, the proliferation of under-ice phytoplankton blooms (UIBs), challenges the paradigm that waters beneath the ice pack harbor little planktonic life. Little is known about the diversity and spatial distribution of UIBs in the Arctic Ocean, or the environmental drivers behind their timing, magnitude, and taxonomic composition. Here, we compiled a unique and comprehensive dataset from seven major research projects in the Arctic Ocean (11 expeditions, covering the spring sea-ice-covered period to summer ice-free conditions) to identify the environmental drivers responsible for initiating and shaping the magnitude and assemblage structure of UIBs. The temporal dynamics behind UIB formation are related to the ways that snow and sea-ice conditions impact the under-ice light field. In particular, the onset of snowmelt significantly increased under-ice light availability (>0.1–0.2 mol photons m–2 d–1), marking the concomitant termination of the sea-ice algal bloom and initiation of UIBs. At the pan-Arctic scale, bloom magnitude (expressed as maximum chlorophyll a concentration) was predicted best by winter water Si(OH)4 and PO43– concentrations, as well as Si(OH)4:NO3– and PO43–:NO3– drawdown ratios, but not NO3– concentration. Two main phytoplankton assemblages dominated UIBs (diatoms or Phaeocystis), driven primarily by the winter nitrate:silicate (NO3–:Si(OH)4) ratio and the under-ice light climate. Phaeocystis co-dominated in low Si(OH)4 (i.e., NO3:Si(OH)4 molar ratios >1) waters, while diatoms contributed the bulk of UIB biomass when Si(OH)4 was high (i.e., NO3:Si(OH)4 molar ratios <1). The implications of such differences in UIB composition could have important ramifications for Arctic biogeochemical cycles, and ultimately impact carbon flow to higher trophic levels and the deep ocean.

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“…The later station, located near the West Greenland coast, was also characterized by the presence of palmelloid colonial cells of Phaeocystis pouchetii, reaching 9 % of total cell count (0.5 × 10 6 cells L −1 ). Although the success and geographical range of Phaeocystis in the Northern Hemisphere are still poorly understood (Lovejoy et al, 2002;Schoemann et al, 2005;Tremblay et al, 2012), particularly in the Canadian Arctic, the codominance of species of Phaeocystis has been shown to occur in the waters of the West Greenland Current (Fragoso et al, 2017) and Labrador fjords (Simo-Matchim et al, 2017).…”

Section: The Myi Edge In Nares Strait and The Adjacent North Watermentioning

confidence: 99%

“…tion exposure with heightened DMS production as a defense strategy against light-associated oxidative stress (Sunda et al, 2002;Toole and Siegel, 2004;Vallina and Simó, 2017;Galí and Simó, 2010). The fresher water lens may also have indirectly stimulated DMS production through the possible enhancement of DMSP d availability and its bacterial conversion into DMS, following an osmosis-related excretion of cellular DMSP (Stefels, 2000;Van Bergeijk et al, 2003;Niki et al, 2007). Although biological processes cannot be completely ruled out, the strength of the association between DMS and salinity near the FYI edge suggests that physical drivers most strongly shaped DMS dynamics in Barrow Strait.…”

Section: Synthesismentioning

confidence: 99%

Phytoplankton and dimethylsulfide dynamics at two contrasting Arctic ice edges

et al. 2020

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Abstract. Arctic sea ice is retreating and thinning and its rate of decline has steepened in the last decades. While phytoplankton blooms are known to seasonally propagate along the ice edge as it recedes from spring to summer, the substitution of thick multiyear ice (MYI) with thinner, ponded first-year ice (FYI) represents an unequal exchange when considering the roles sea ice plays in the ecology and climate of the Arctic. Consequences of this shifting sea ice on the phenology of phytoplankton and the associated cycling of the climate-relevant gas dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) remain ill constrained. In July–August 2014, two contrasting ice edges in the Canadian High Arctic were explored: a FYI-dominated ice edge in Barrow Strait and a MYI-dominated ice edge in Nares Strait. Our results reveal two distinct planktonic systems and associated DMS dynamics in connection to these diverging ice types. The surface waters exiting the ponded FYI in Barrow Strait were characterized by moderate chlorophyll a (Chl a, <2.1 µg L−1) as well as high DMSP (115 nmol L−1) and DMS (12 nmol L−1), suggesting that a bloom had already started to develop under the markedly melt-pond-covered (ca. 40 %) FYI. Heightened DMS concentrations at the FYI edge were strongly related to ice-associated seeding of DMS in surface waters and haline-driven stratification linked to ice melt (Spearman's rank correlation between DMS and salinity, rs=-0.91, p<0.001, n=20). However, surface waters exiting the MYI edge at the head of Nares Strait were characterized by low concentrations of Chl a (<0.5 µg L−1), DMSP (<16 nmol L−1), and DMS (<0.4 nmol L−1), despite the nutrient-replete conditions characterizing the surface waters. The increase in autotrophic biomass and methylated sulfur compounds took place several kilometers (ca. 100 km) away from the MYI edge, suggesting the requisite for ice-free, light-sufficient conditions for a phytoplankton bloom to fully develop and for sulfur compound dynamics to follow and expand. In light of the ongoing and projected climate-driven changes to Arctic sea ice, results from this study suggest that the early onset of autotrophic blooms under thinner, melt-pond-covered ice may have vast implications for the timing and magnitude of DMS pulses in the Arctic.

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Summer and fall distribution of phytoplankton in relation to environmental variables in Labrador fjords, with special emphasis on Phaeocystis pouchetii

Cited by 20 publications

References 92 publications

A decadal perspective on north water microbial eukaryotes as Arctic Ocean sentinels

A decadal perspective on north water microbial eukaryotes as Arctic Ocean sentinels

Environmental drivers of under-ice phytoplankton bloom dynamics in the Arctic Ocean

Phytoplankton and dimethylsulfide dynamics at two contrasting Arctic ice edges

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