Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean
- 1Hokkaido University (Sapporo, Japan)
- 2Japan Society for the Promotion of Science (Tokyo, Japan)
- 3Pontificia Universidad Católica de Valparaíso (Valparaíso, Chile)
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 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 δ ¹³ C and δ ¹⁵ N values of all sea-ice particulate matter samples were -24.6±3.2 ‰ and +1.5±2.2 ‰ (mean ± standard deviation), respectively, showing greater variability compared to those in seawater (-28.8±1.0 ‰ for δ ¹³ C and -0.5±1.4 ‰ for δ ¹⁵ N). We identified correlations of δ ¹³ C and δ ¹⁵ N with organic matter and nutrient concentrations and their ratios (e.g., silicate : nitrate), suggesting 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, the POC supply was estimated to be 4.1±0.3 Tg C yr ⁻¹ , equivalent to 14.7±2.8 % of primary production in the marginal ice zone of the studied region. This result suggests that sea ice melt provides significant portion of organic matters potentially supporting Antarctic ecosystems in the seasonal sea ice zone, which could be traced by difference of sea-ice and seawater stable isotope compositions.
Versions
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BibTeX
@article{takahashi2026biogeochemical,
title = {{Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean}},
author = {Keigo D. Takahashi and Ryosuke Makabe and Masayoshi Sano and Kazuki Nakata and Noriaki Kimura and Daiki Nomura and Michiyo Yamamoto-Kawai and Ryo Matsuda and Natsumi Nojiro and Masato Ito and Shintaro Takao and Naho Horimoto-Miyazaki and Aiko Tachibana and Norio Kurosawa and Takeshi Tamura and Mizuki Komatsu and Kay I. Ohshima and Kohei Mizobata and Shigeru Aoki and Masato Moteki},
journal = {Biogeosciences},
year = {2026},
month = oct,
doi = {10.5194/bg-23-7505-2026},
url = {https://bg.copernicus.org/articles/23/7505/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Biogeochemical controls on the concentrations and stable isotope compositions of sea-ice particulate organic matters in the Southern Ocean
AU - Keigo D. Takahashi
AU - Ryosuke Makabe
AU - Masayoshi Sano
AU - Kazuki Nakata
AU - Noriaki Kimura
AU - Daiki Nomura
AU - Michiyo Yamamoto-Kawai
AU - Ryo Matsuda
AU - Natsumi Nojiro
AU - Masato Ito
AU - Shintaro Takao
AU - Naho Horimoto-Miyazaki
AU - Aiko Tachibana
AU - Norio Kurosawa
AU - Takeshi Tamura
AU - Mizuki Komatsu
AU - Kay I. Ohshima
AU - Kohei Mizobata
AU - Shigeru Aoki
AU - Masato Moteki
PY - 2026
DA - 2026/10/26
JO - Biogeosciences
DO - 10.5194/bg-23-7505-2026
UR - https://bg.copernicus.org/articles/23/7505/2026/
AB - 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 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 δ ¹³ C and δ ¹⁵ N values of all sea-ice particulate matter samples were -24.6±3.2 ‰ and +1.5±2.2 ‰ (mean ± standard deviation), respectively, showing greater variability compared to those in seawater (-28.8±1.0 ‰ for δ ¹³ C and -0.5±1.4 ‰ for δ ¹⁵ N). We identified correlations of δ ¹³ C and δ ¹⁵ N with organic matter and nutrient concentrations and their ratios (e.g., silicate : nitrate), suggesting 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, the POC supply was estimated to be 4.1±0.3 Tg C yr ⁻¹ , equivalent to 14.7±2.8 % of primary production in the marginal ice zone of the studied region. This result suggests that sea ice melt provides significant portion of organic matters potentially supporting Antarctic ecosystems in the seasonal sea ice zone, which could be traced by difference of sea-ice and seawater stable isotope compositions.
SN - 1726-4189
SN - 1726-4170
ER -