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  • 1
    Publication Date: 2020-06-24
    Description: This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 2
    Publication Date: 2021-03-22
    Description: Sea-ice algae play a crucial role in the ecology and biogeochemistry of sea-ice zones. They not only comprise the base of sea-ice ecosystems, but also seed populations of extensive ice-edge blooms during ice melt. Ice algae must rapidly acclimate to dynamic light environments, from the low light under sea ice to high light within open waters. Recently, iron (Fe) deficiency has been reported for diatoms in eastern Antarctic pack ice. Low Fe availability reduces photosynthetic plasticity, leading to reduced ice-algal primary production. We developed a low-Fe ice tank to manipulate Fe availability in sea ice. Over 20 days in the ice tank, the Antarctic ice diatom Fragilariopsis cylindrus was incubated in artificial low-Fe sea ice ([total Fe] = 20 nM) in high light (HL) and low light (LL) conditions. Melted ice was also exposed to intense light to simulate light conditions typical for melting ice in situ. When diatoms were frozen in, the maximum photochemical quantum efficiency of photosystem II (PSII), Fv/Fm, was suppressed by freezing stress. However, the diatoms maintained photosynthetic capability throughout the ice periods with a stable Fv/Fm value and increased photoprotection through non-photochemical quenching (NPQ) via photoprotective xanthophyll cycling (XC) and increased photoprotective carotenoid levels compared to pre-freeze-up. Photoprotection was more pronounced in the HL treatment due to greater light stress. However, the functional absorption cross section of PSII, σPSII, in F. cylindrus consistently increased after freezing, especially in the LL treatment (σPSII 〉 10 nm2 PSII–1). Our study is the first to report such a large σPSII in ice diatoms at low Fe conditions. When the melted sea ice was exposed to high light, Fv/Fm was suppressed. NPQ and XC were slightly upregulated, but not to values normally observed when Fe is not limiting, which indicates reduced photosynthetic flexibility to adapt to environmental changes during ice melt under low Fe conditions. Although ice algae can optimize their photosynthesis to sea-ice environments, chronic Fe starvation led to less flexibility of photoacclimation, particularly in low light conditions. This may have detrimental consequences for ice algal production and trophic interactions in sea-ice ecosystems if the recent reduction in sea-ice extent continues.
    Electronic ISSN: 2296-7745
    Topics: Biology
    Published by Frontiers Media
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  • 3
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(5), (2019): 2943-2968, doi:10.1029/2019JC015071.
    Description: In the Southern Ocean, polynyas exhibit enhanced rates of primary productivity and represent large seasonal sinks for atmospheric CO2. Three contrasting east Antarctic polynyas were visited in late December to early January 2017: the Dalton, Mertz, and Ninnis polynyas. In the Mertz and Ninnis polynyas, phytoplankton biomass (average of 322 and 354 mg chlorophyll a (Chl a)/m2, respectively) and net community production (5.3 and 4.6 mol C/m2, respectively) were approximately 3 times those measured in the Dalton polynya (average of 122 mg Chl a/m2 and 1.8 mol C/m2). Phytoplankton communities also differed between the polynyas. Diatoms were thriving in the Mertz and Ninnis polynyas but not in the Dalton polynya, where Phaeocystis antarctica dominated. These strong regional differences were explored using physiological, biological, and physical parameters. The most likely drivers of the observed higher productivity in the Mertz and Ninnis were the relatively shallow inflow of iron‐rich modified Circumpolar Deep Water onto the shelf as well as a very large sea ice meltwater contribution. The productivity contrast between the three polynyas could not be explained by (1) the input of glacial meltwater, (2) the presence of Ice Shelf Water, or (3) stratification of the mixed layer. Our results show that physical drivers regulate the productivity of polynyas, suggesting that the response of biological productivity and carbon export to future change will vary among polynyas.
    Description: This work was cofunded by the Australian Antarctic Division research projects AAS 4131 and 4291. This project was also supported by the Australian Government Cooperative Research Centres Programme through the Antarctic Climate & Ecosystems (ACE CRC). S. Moreau and C. Genovese were supported by the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (project ID SR140300001). V. Puigcorbé and M. Roca‐Martí are grateful for the support from Pere Masque and Edith Cowan University. M.C. Arroyo was supported by the Dickhut Fellowship, administered by the Virginia Institute of Marine Science. The authors would like to thank the officers and crew of the R/V Aurora Australis for their logistic support, the CSIRO hydrochemists for their analyses of nutrient concentrations, and E. J. Yang for her microscope analysis of phytoplankton species. We also want to thank two anonymous reviewers for their very good comments on this study. The data presented in this paper are available on the Australian Antarctic Division (AAD) Data Centre at https://data.aad.gov.au/aadc/metadata/metadata_by_parameter.cfm.
    Description: 2019-09-28
    Keywords: Polynyas ; Primary productivity ; Phytoplankton biomass ; Ice shelves ; Sea ice ; Iron
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-05-27
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tison, J.-L., Maksym, T., Fraser, A. D., Corkill, M., Kimura, N., Nosaka, Y., Nomura, D., Vancoppenolle, M., Ackley, S., Stammerjohn, S., Wauthy, S., Van der Linden, F., Carnat, G., Sapart, C., de Jong, J., Fripiat, F., & Delille, B. Physical and biological properties of early winter Antarctic sea ice in the Ross Sea. Annals of Glaciology, 61(83), (2020): 241–259, https://doi.org/10.1017/aog.2020.43.
    Description: This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
    Description: S. Stammerjohn was supported by the PIPERS and LTER Programs of the U.S. National Science Foundation, ANT-1341606 (S. Stammerjohn and J. Cassano, U Colorado) and ANT-0823101 (H. Ducklow, LDEO/Columbia University), respectively. Steve Ackley (UTSA) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341717 and by NASA Grant 80NSSC19M0194 to the Center for Adv. Meas. in Extreme Environments at UTSA.Ted Maksym (WHOI) was supported by the PIPERS program of the U.S. National Science Foundation ANT-1341513. This research was supported by the Belgian F.R.S-FNRS (project ISOGGAP and IODIne, contract T.0268.16 and J.0262.17, respectively). Fanny Van der Linden, Sarah Wauthy, Gauthier Carnat, Célia Sapart and Bruno Delille are PhD students, postdoctoral researchers and research associate, respectively, of the Belgian F.R.S.-FNRS. This work was also supported by the Australian Government's Cooperative Research Centre program through the Antarctic Climate & Ecosystems Cooperative Research Centre, and by the Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). Daiki Nomura was supported by grants from the Japan Society for the Promotion of Science (#17H04715) and the National Institute for Polar Research through Project Research KP-303 (ROBOTICA) and #28-14.
    Keywords: Antarctic glaciology ; biogeochemistry ; sea ice
    Repository Name: Woods Hole Open Access Server
    Type: Article
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