Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean

Abstract. The primary production and zooplankton life cycles in the Southern Ocean synchronize with seasonal sea ice melting, during which particulate organic carbon (POC) and nitrogen (PN), including ice algae, are supplied from sea ice into the water column. To understand carbon flow through food webs in this productive marginal ice zones, it is necessary to determine the quantity and quality of organic carbon and nitrogen in sea ice. However, knowledge regarding brash sea ice is scarce, even though it is the predominant form at the Antarctic ice edge. In this study, 102 sea-ice samples were collected from the Indian sector (20–160°E) during summer to clarify variations in isotopic baselines and the potential contribution of sea ice-derived carbon and nitrogen to the water column. The δ13C and δ15N values of sea-ice particulate matter were −24.5±3.2‰ and +1.6±2.2‰ (mean±standard deviation), respectively, showing greater variability compared to those in seawater (−28.8±1.0‰ for δ13C and −0.5±1.4‰ for δ15N). We identified correlations of δ13C and δ15N with organic matter and nutrient concentrations and their ratios (e.g., silicate:nitrate), indicating that nutrient consumption and organic matter decomposition influenced those isotopic characteristics in sea ice. Using freshwater flux from sea ice melt and the measured sea-ice POC concentrations, this supply was estimated to be 4.6±0.3 Tg C year−1, equivalent to >14% of primary production in the marginal ice zone of the studied region. These results suggest that the carbon supply from sea ice is a crucial factor supporting ecosystems in the seasonal sea ice zone.

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Publication Details

Journal
Biogeosciences
Published
2026-10-26
DOI
https://doi.org/10.5194/bg-23-7505-2026
Primary Topic
Marine and coastal ecosystems
Type
article
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article

Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean

Michiyo Yamamoto‐Kawai, Naho Horimoto‐Miyazaki, Κay I. Ohshima, Aiko Tachibana et al.
Biogeosciences
Marine and coastal ecosystems
article

Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean

Michiyo Yamamoto‐Kawai, Naho Horimoto‐Miyazaki, Κay I. Ohshima, Aiko Tachibana, Keigo D. Takahashi, Masato Moteki, Takeshi Tamura, Kohei Mizobata, Natsumi Nojiro, Noriaki Kimura, Norio Kurosawa, Masato Ito, Kazuki Nakata, Masayoshi Sano, Ryo Matsuda, Ryosuke Makabe, Mizuki Komatsu, Shigeru Aoki, Daiki Nomura, Shintaro Takao
article en

Abstract

Abstract. The primary production and zooplankton life cycles in the Southern Ocean synchronize with seasonal sea ice melting, during which particulate organic carbon (POC) and nitrogen (PN), including ice algae, are supplied from sea ice into the water column. To understand carbon flow through food webs in this productive marginal ice zones, it is necessary to determine the quantity and quality of organic carbon and nitrogen in sea ice. However, knowledge regarding brash sea ice is scarce, even though it is the predominant form at the Antarctic ice edge. In this study, 102 sea-ice samples were collected from the Indian sector (20–160°E) during summer to clarify variations in isotopic baselines and the potential contribution of sea ice-derived carbon and nitrogen to the water column. The δ13C and δ15N values of sea-ice particulate matter were −24.5±3.2‰ and +1.6±2.2‰ (mean±standard deviation), respectively, showing greater variability compared to those in seawater (−28.8±1.0‰ for δ13C and −0.5±1.4‰ for δ15N). We identified correlations of δ13C and δ15N with organic matter and nutrient concentrations and their ratios (e.g., silicate:nitrate), indicating that nutrient consumption and organic matter decomposition influenced those isotopic characteristics in sea ice. Using freshwater flux from sea ice melt and the measured sea-ice POC concentrations, this supply was estimated to be 4.6±0.3 Tg C year−1, equivalent to >14% of primary production in the marginal ice zone of the studied region. These results suggest that the carbon supply from sea ice is a crucial factor supporting ecosystems in the seasonal sea ice zone.

BiogeosciencesVol. 23(20)
Pontificia Universidad Católica de Valparaíso (CL), Japan Agency for Marine-Earth Science and Technology (JP), National Institute for Environmental Studies (JP), The Graduate University for Advanced Studies, SOKENDAI (JP), University of Kochi (JP), Hokkaido University (JP), Japan Society for the Promotion of Science (JP), Japan Aerospace Exploration Agency (JP), National Institute of Polar Research (JP), Soka University (JP), Japan Fisheries Research and Education Agency (JP), Hokkaido University Arctic Research Center (JP), Institute of Low Temperature Science, Hokkaido University (JP), Earth Observation Research Center (JP), Tokyo University of Marine Science and Technology (JP), The University of Tokyo (JP), Kōchi University (JP)
University of Tokyo, Hokkaido University, National Institute of Polar Research, Japan Society for the Promotion of Science, Core Research for Evolutional Science and Technology
Life below water, Climate action
Openalex Percentile: Top 70%
Marine and coastal ecosystems
DOIOpen Access PDFOpenAlex
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