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4. Light absorption and albedo reduction by pigmented microalgae on snow and ice.

Author

Chevrollier, Lou-Anne, Cook, Joseph M., Halbach, Laura, Jakobsen, Hans, Benning, Liane G., Anesio, Alexandre M., and Tranter, Martyn

Subjects
ALBEDO, LIGHT absorption, ALGAL cells, MICROALGAE, RADIATIVE transfer, ALGAL blooms, ICE sheets
Abstract

Pigmented microalgae inhabiting snow and ice environments lower the albedo of glacier and ice-sheet surfaces, significantly enhancing surface melt. Our ability to accurately predict their role in glacier and ice-sheet surface mass balance is limited by the current lack of empirical data to constrain their representation in predictive models. Here we present new empirical optical properties for snow and ice algae and incorporate them in a radiative transfer model to investigate their impact on snow and ice surface albedo. We found ice algal cells to be more efficient absorbers than snow algal cells, but their blooms had comparable impact on surface albedo due to the different photic conditions of their habitats. We then used the model to reconstruct the effect of ice algae on bare ice albedo spectra collected at our field site in southern Greenland, where blooms dropped the albedo locally by between 3 and 43%, equivalent to 1–10 L m $^{-2}$ d $^{-1}$ of melted ice. Using the newly parametrized model, future studies could investigate biological albedo reduction and algal quantification from remote hyperspectral and multispectral imagery. [ABSTRACT FROM AUTHOR]

Published
2023
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5. Tidewater Glaciers and Bedrock Characteristics Control the Phytoplankton Growth Environment in a Fjord in the Arctic

Author

Halbach, Laura, primary, Vihtakari, Mikko, additional, Duarte, Pedro, additional, Everett, Alistair, additional, Granskog, Mats A., additional, Hop, Haakon, additional, Kauko, Hanna M., additional, Kristiansen, Svein, additional, Myhre, Per I., additional, Pavlov, Alexey K., additional, Pramanik, Ankit, additional, Tatarek, Agnieszka, additional, Torsvik, Tomas, additional, Wiktor, Józef M., additional, Wold, Anette, additional, Wulff, Angela, additional, Steen, Harald, additional, and Assmy, Philipp, additional

Published
2019
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6. Feeding activity of larval and juvenile Antarctic krill Euphausia superba in open water, the marginal ice zone and pack ice region in late winter in the Scotia Sea and the northern Weddell Sea

Author

Halbach, Laura

Abstract

A successful larval overwintering is a major factor determining population sizes of Antarctic krill, Euphausia superba (hereafter krill). A high population recruitment success of krill was linked to years with more extensive sea ice in the previous winter. However, the benefit of the winter sea ice cover for a successful larval development during winter remains unclear. The aim of the present study was to test the hypothesis that larval krill in pack ice regions are in better condition in terms of food supply and feeding activity than larvae from OW regions. Therefore, the condition of larval krill (furcilia (F) III–VI as well as juveniles) was investigated in open water (OW), the marginal ice zone (MIZ1+2) and the pack ice region (Ice Camp1+2) during late winter, in relation to Chlorophyll a (Chl a) and particulate organic carbon (POC) concentrations in the water column and in the sea ice. In addition, differences in the dietary intake of larval krill during the day and night were examined. Overall, krill larvae from pack ice regions were not in better condition than in OW. Although, krill larvae caught at Ice Camp1 had the largest body lengths (mean 15.69 mm) and highest dry weights (mean 4.59 mg), only the body lengths showed significant differences with larval krill from OW and stage composition was similar (few F6 and mostly juveniles). Larval krill of Ice Camp2 had the smallest body lengths (mean 7.96 mm) and dry weights (mean 0.50 mg) while stage composition ranged from F3-F6. The high amount of available food sources within the sea ice (Ice Camp1: 21.78 μg L-1 Chl a and 400.55 μg L-1 POC; Ice Camp2: 12.68 μg L-1 Chl a and 330.2 μg L-1 POC) was used only to a small extent by krill larvae, which is reflected by their lowest feeding activities and relatively empty stomachs. At Ice Camp2, larval krill was observed performing diel vertical migration (DVM). During the day larval krill was closely associated with the sea ice, whereas during the night they descended into the upper 20 m of the water column. Stomach content analyses showed that larval krill consumed diatoms and dinoflagellate primary during the day, while zooplankton and detritus predominated in the diet during the night. In pack ice regions where food abundance in the sea ice is patchy, the DVM could serve as a strategy to exploit potentially new feeding grounds.

Published
2015

7. The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

Author

Meyer, Bettina, Freier, Ulrich, Grimm, Volker, Groeneveld, Jürgen, Hunt, Brian P. V., Kerwath, Sven, King, Rob, Klaas, Christine, Pakhomov, Evgeny, Meiners, Klaus M., Melbourne-Thomas, Jessica, Murphy, Eugene J., Thorpe, Sally E., Stammerjohn, Sharon, Wolf-Gladrow, Dieter, Auerswald, Lutz, Götz, Albrecht, Halbach, Laura, Jarman, Simon, Kawaguchi, So, Krumpen, Thomas, Nehrke, Gernot, Ricker, Robert, Sumner, Michael, Teschke, Mathias, Trebilco, Rowan, Yilmaz, Noyan I., Meyer, Bettina, Freier, Ulrich, Grimm, Volker, Groeneveld, Jürgen, Hunt, Brian P. V., Kerwath, Sven, King, Rob, Klaas, Christine, Pakhomov, Evgeny, Meiners, Klaus M., Melbourne-Thomas, Jessica, Murphy, Eugene J., Thorpe, Sally E., Stammerjohn, Sharon, Wolf-Gladrow, Dieter, Auerswald, Lutz, Götz, Albrecht, Halbach, Laura, Jarman, Simon, Kawaguchi, So, Krumpen, Thomas, Nehrke, Gernot, Ricker, Robert, Sumner, Michael, Teschke, Mathias, Trebilco, Rowan, and Yilmaz, Noyan I.

Abstract

A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

Published
2017

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