Interannual variability in euthecosomatous pteropods (Limacina spp.) in the Indian sector of the Southern Ocean during austral summer

Abstract

Euthecosomatous pteropods with carbonate (aragonite) shells living in polar waters are thought to be very sensitive to ocean acidification resulting from increased anthropogenic CO2 uptake. To assess the impacts of ocean acidification on pteropods, we investigated pteropod abundance and shell size at three sites located between 55 and 64°S on the 110°E meridian in the Indian sector of the Southern Ocean during austral summer from 1987 to 2008 with the Japanese Antarctic Research Expedition (JARE) monitoring projects. The pteropod community was dominated by Limacina spp. with a shell size of ＜400 μm, and there was a distinct interannual variation ranging 2.2–2767.7 ind. m－3. No significant decrease in pH was detected in various water layers above 400 m depth at three sites (55°S, 60°S and 64°S) during the study period, and no marked decrease both in abundance and shell size have been observed in these waters for at least 20 years. Though ocean acidification in the Southern Ocean will be in progress, the effects on shelled pteropods are not yet evident.

Keywords

• Pteropods
• shell size
• ocean acidification