Biogeosciences Discuss., 10, 15153-15180, 2013
www.biogeosciences-discuss.net/10/15153/2013/
doi:10.5194/bgd-10-15153-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Timing of sea ice retreat can alter phytoplankton community structure in the western Arctic Ocean
A. Fujiwara1,2, T. Hirawake2, K. Suzuki3, I. Imai2, and S.-I. Saitoh2
1Arctic Research Center, National Institute of Polar Research, 10-3, Midoricho, Tachikawa, Tokyo 190-8518, Japan
2Faculty/Graduate School of Fisheries Sciences, 3-1-1 Minatocho, Hakodate, Hokkaido 041-8611, Japan
3Faculty of Environmental Earth Science/Graduate School of Environmental Earth Sciences, Hokkaido 060-0810, Japan

Abstract. This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008–2010 were analyzed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years – the sea ice retreat in 2008 was 1–2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure.

Citation: Fujiwara, A., Hirawake, T., Suzuki, K., Imai, I., and Saitoh, S.-I.: Timing of sea ice retreat can alter phytoplankton community structure in the western Arctic Ocean, Biogeosciences Discuss., 10, 15153-15180, doi:10.5194/bgd-10-15153-2013, 2013.
 
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